Historic Reconstruction of the Ecology of the Rio Grande/Río Bravo Channel and Floodplain in the Chihuahuan Desert

Report prepared for Chihuahuan Desert Program, World Wildlife Fund

14 June 2000

by: Nancy G. Stotz

Downloadable versions of this report will be made available at World Wildlife Fund’s website, www.worldwildlife.org. Updates to this report and lists of supplemental sources of information may also be found there.

For additional information about this report, contact the author: Nancy Stotz Desert Scribes [email protected] (505) 521-8087

For information about WWF’s Chihuahuan Desert Conservation Program, contact: Jennifer Atchley Chihuahuan Desert Program Officer 100 E. Hadley Las Cruces, NM 88001 [email protected] (505) 525-9537

Second Printing: February 2001

ii Table of Contents

Acknowledgments……………………………………………………………………………………. iv Summary……………………………………………………………………………………………… v Introduction: Justification and Scope ……………….……………………………………………….. vii Literature Cited ……………………………………………………………………………… viii Chapter 1: Geographic and Historic Overview ……...………………………………………………. 1 Belen and Socorro Valleys………………….……………………………………………….. 1 Engle and Las Palomas Valleys…………….……………………………………………….. 2 Mesilla and El Paso Valleys……………….………………………………………………… 3 Forgotten Reach and Presidio Valley…..……………………………………………………. 5 Big Bend and the Lower Canyons………..………………………………………………….. 5 Literature Cited………………………………………………………………………………. 6 Chapter 2: Historic Ecosystem Descriptions ……..………………………………………………….. 9 Channel Morphology and Location………………………………………………………….. 9 Flooding and Flow Regimes………....………………………………………………………. 11 Flow Data…………………………………………………………………………... 12 Extent of Flooding………………………………………………………………….. 16 Channel Width and Depth………………………………………………………….. 17 Surface Flow Disruptions………………………………………………………….. 18 Still-Water Features and Water Table……………………………………………………….. 20 Floodplain Vegetation ………………………………………………………………………. 23 Cottonwood-Willow Stands………………………………………………………... 24 Mesquite and Screwbean…………………………………………………………… 27 Grasses and Other Plants…………………………………………………………… 28 Qualitative Descriptions of Changes in Vegetation………………………………………..… 30 Quantifying Changes in Vegetation …………………………………………………………. 33 Areal Extent………………………………………………………………………… 33 Plant Densities and Size-class Distributions……………………………………….. 35 Fauna ………………………………………………………………………………………… 38 Literature Cited………………………………………………………………………………. 42 Chapter 3: Fishes of the Desert Rio Grande………………………………………………………….. 51 Species Accounts…………………………………………………………………………….. 56 Literature Cited………………………………………………………………………………. 68 Chapter 4: Herpetofauna of the Desert Rio Grande………………………………………………….. 73 Species Accounts…………………………………………………………………………….. 80 Literature Cited………………………………………………………………………………. 95 Chapter 5: Mammals of the Desert Rio Grande……………………………………………………… 97 Species Accounts…………………………………………………………………………….. 103 Literature Cited………………………………………………………………………………. 117 Chapter 6: Birds of the Desert Rio Grande…….…………………………………………………….. 121 Species Accounts…………………………………………………………………………….. 139 Literature Cited………………………………………………………………………………. 145 Appendix A: Extracting Data from Township and Range Line Surveys..…………………………… 149 Literature Cited………………………………………………………………………………. 151 Appendix B: Threatened and Endangered Vertebrates of the Desert Rio Grande…………………… 153 Literature Cited………………………………………………………………………………. 158 Maps………………………………………………………………………………………………….. 159

iii

Acknowledgments

This project would have been impossible without the guidance, input, and connections of Jennifer Atchley, World Wildlife Fund, Chihuahuan Desert Program Officer.

Teri Neville, of the New Mexico Natural Heritage Program, provided an invaluable service by producing the maps for this report.

General discussions with a number of individuals (Neal Ackerly, Dennis Daily, Benjamin Everitt, Tony Garcia, Diana Hadley, Austin Hoover, Mike Landis, Robert Mallouf, Tim McKimmie, John Peterson, Carole Purchase, and Raymond Skiles) helped to identify potential sources of information.

The El Paso office of the International Boundary and Water Commission provided access to a wide variety of resources; Manny Rubio, Jim Robinson, David Maruffo, and the staff in the Technical Library were particularly generous with their time, expertise, and equipment.

Gary Esslinger gave us permission to access the Elephant Butte Irrigation District Archives held by the Hobson-Huntsinger Archives at the New Mexico State University Library.

Several other individuals and institutions provided access to and copies of maps: John Kennedy (Water Resources Research Institute, Las Cruces, NM), Scott Cutler (Centennial Museum, University of Texas at El Paso), Robert Skiles (Texas General Land Office), and Richard Smith (National Archives and Records Administration).

John Sproul (Center for Environmental Resource Management, University of Texas at El Paso) provided copies of several bird lists, including an unpublished draft of the forthcoming eighth edition of the El Paso area list.

Thom Maestes (Las Cruces District, Bureau of Land Management) introduced me to the protocol for Government Land Office Surveys so I could interpret the information contained in the surveyors’ field notes.

Several individuals provided valuable feedback on drafts of portions of this document: John Schmidt (hydrology); Chris Hoagstrom, W.L. Minckley, and David Propst (Chapter 3); Paul Hyder (Chapter 4); John Karges (Chapter 5); and Ray Meyer and Bill Howe (Chapter 6). In addition to his thoughtful review, Chris Hoagstrom generously provided photocopies of a large collection of papers and unpublished reports.

iv Summary

The Chihuahuan Desert straddles an international border and encompasses some 630,000 square kilometers of the southwestern United States and north-central Mexico. As the only major through-flowing stream in this desert, the Rio Grande represents a critical component of the region’s biodiversity. The desert Rio Grande traverses about 1270 kilometers of the Chihuahuan Desert between the mouths of the Rio Puerco in New Mexico and the Devil’s River in Texas. The Río Conchos, the Pecos River and the Devils River are the only major perennial tributaries that reach the desert Rio Grande, and all meet the river in the lower half of its Chihuahuan Desert course. Thus, the waters of the desert Rio Grande have always been a precious resource for populations—both human and non-human—living in this arid region.

As a result of centuries of intensive human settlement, agriculture, and industry within the river’s watershed, the natural environment has been impacted immensely. For the second time in less than a decade, American Rivers has placed the Rio Grande among the 10 most endangered rivers of the United States, and a World Wildlife Fund-sponsored symposium identified the river as a priority site for conservation and restoration. In order to assist policy-makers, land-managers, and property owners with restoration efforts along the Rio Grande through the Chihuahuan Desert, the primary goal of this report is to compile information about what natural environments used to exist along and within the river. In terms of environmental change, the late-nineteenth and early twentieth centuries were among the most significant periods in the river’s history: agricultural development and dam construction impacted river flows and floodplain habitats directly and land-use changes elsewhere in the river’s watershed impacted run-off and sedimentation patterns.

For centuries, the waters of the Rio Grande have been used for agricultural pursuits. In the thirteenth and fourteenth centuries, agricultural societies existed along several parts of the desert Rio Grande; they appear to have engaged in flood-water farming that utilized overbank flooding or diverted sheetflow after rainfall for irrigation instead of using ditch irrigation from the main channel of the Rio Grande. Ditch irrigation became more widespread following the establishment of missions and settlements in the sixteenth and seventeenth centuries; although along some portions of the desert Rio Grande (such as in the Mesilla and Presidio valleys) large-scale ditch irrigation did not occur prior to the nineteenth century. Late in the nineteenth century, extensive agricultural development in southern Colorado and northern New Mexico usurped most of the river’s water, resulting in flow disruptions downstream and precipitating the construction of Elephant Butte Reservoir (completed in 1916) to store water for agriculture downstream.

Under the natural flow regimes that existed prior to the dam’s construction, the environment along the desert Rio Grande was dynamic and patchy, with organisms adapted to spatial and temporal heterogeneity. This heterogeneity was driven by the river’s flows, which exhibited within- and between-year variability. Above the mouth of the Río Conchos, flows peaked in late spring or early summer when snow melted in the upper reaches of the river’s watershed; below the Río Conchos, peak flows tended to occur in late summer or fall, resulting from summer precipitation in Mexico. In many years, overbank flooding occurred during periods of peak flow. The river exhibited a meandering course through the valley reaches, and because meanders naturally migrate along a channel, small-scale changes in channel location and shape were common. In addition, large-scale channel migration also occurred, sometimes from one side of the river valley to the other. However, in at least one reach of the desert Rio Grande, such large-scale channel shifts appear to have resulted from returns to previously established river channels instead of the creation of a new channel. Meander cut-offs and channel migration also helped to create and maintain numerous backwaters including oxbows, marshes, and sloughs. These non-river aquatic habitats may have been important refugia for aquatic organisms when portions of the river went dry; prior to extensive agricultural development, flow disruptions along limited stretches of the river occurred quite infrequently, and seem to have only occurred during extended droughts.

The natural vegetation of the river bottom responded to the variable flow regime and exhibited a patchy, dynamic distribution. Flood-tolerant seepwillows occurred along the river’s edge, and cottonwoods and willows, largely dependent upon sediments and moisture deposited by floods for sexual reproduction, grew in discontinuous stands near the river. Farther from the active channel, large expanses of shrubby growth

v dominated by screwbean and honey mesquite occurred. Salt grass often grew in association with screwbean, and elsewhere, patches of arrowweed could be found. Marshes and sloughs were typified by aquatic and emergent vegetation such as pondweed, cattails, sedges, and rushes. Nineteenth-century surveys and descriptions suggest that cottonwood stands may have occupied roughly a quarter to a third of the area in river valleys, with shrubby and more open growth covering larger expanses, and marsh and slough habitats limited to a small area (perhaps 5% or less of the river valleys).

Under natural flow regimes, these plant communities would not have been static; flood events, meander migration, and large-scale channel shifts all could remove existing vegetation and allow for the establishment of new patches. The dynamic eqilibrium of this system allowed for a diversity of plant communities and stands of many different ages. Animals living along the desert Rio Grande could thus occupy a wide variety of terrestrial and aquatic habitats. Accordingly, vertebrate diversity is high along the river: as many as 44 native fishes, 95 amphibian and reptiles, 95 mammals, and 345 birds occur (or previously occurred) along the desert Rio Grande.

Accounts from the mid-nineteenth century and earlier describe the abundance of certain types of animals, particularly game species. In the waters of the Rio Grande and the surrounding ponds and sloughs, fish were abundant, and waterfowl provided a ready source of meat for travelers. Large animals including deer, turkeys, bears, wolves, and mountain sheep occurred along some reaches of the river; all but the deer have been extirpated by human activities along the river. Some local extirpations occurred relatively early—for instance, beaver populations along the river declined severely during the 1820s due to overharvesting by fur trappers—but many followed the extensive settlement, water diversions, and other modifications of the natural environment that intensified in the late-nineteenth century. For example, bears and turkeys were eliminated from the Socorro Valley sometime after 1850, and at least 15 native fishes have been extirpated from all or part of their range along the desert Rio Grande, many during the mid-twentieth century. The conversion of natural habitats to agriculture and urban areas, the introduction of exotic species, water diversions, flow regulation, dam and levee construction, channel straightening and dredging, and numerous other changes have taken place along the desert Rio Grande and all have impacted the organisms of the riparian landscape immensely. The dynamics of the river system and the ecosystems that depend on it have been changed, reducing the natural heterogeneity of the system and severing connections between the patches within it.

Introduction: Justification and Scope

Along much of the river, restoration is necessary because centuries of intensive settlement, agriculture, and industry along the river’s shores have impacted its natural environments immensely. The environments are so degraded that American Rivers placed the Rio Grande on its list of the ten most endangered rivers of the United States in 1993 and again in 2000 (Bartlett 1995: 27, American Rivers 2000). In order to assist policy-makers, land-managers, and property owners with restoration efforts along the Rio Grande through the Chihuahuan Desert, the primary goal of this report is to compile information about what natural environments used to exist along and within the river.

In his introduction to The Explorers’ Texas, Weniger (1984: vii) explains …that an ever increasing proportion of our people cannot, as they gaze across the fields and the cities, conceive of the original, natural Texas any more than one can, from opening a milk carton, imagine milking a cow or, from eating a package of potato chips, picture himself digging in a hill of potatoes…. There is reason to think that this ignorance of environmental history might be as dangerous as any blindness. With no knowledge of what was originally in Texas, we doubt that these environmental orphans can be in any position, no matter how much ecology they study, to make valid decisions about the fate of water forests, prairies and rivers we have left…. Weniger (1984: vii) further justifies his compilation of early historic descriptions of Texas by observing that “the early historical period’s environment has been almost completely unstudied.” Unfortunately, though he provides an eloquent call for such research and compiles a remarkable amount of information about the pre-1860 environment in Texas, Weniger’s two-volume set only includes a handful of pages devoted to the Rio Grande through the Chihuahuan Desert (pp. 148-154). Although excellent historic compilations exist for the Middle Rio Grande in northern and central New Mexico (e.g.: Crawford et al. 1993, Scurlock 1998), no comprehensive document focusing on the river through the Chihuahuan Desert exists, and it is hoped that this report will begin to fill that gap.

In terms of environmental change, the late-nineteenth and early twentieth centuries were among the most significant periods in the river’s history. Along the upper portions of the Rio Grande, agricultural development reached a peak in the late-nineteenth century, and “by 1880, every piece of irrigable land along the length of the Rio Grande [in New Mexico] was under development” (Harris 1995: 9). As this agriculture was irrigated by water from the Rio Grande, the river’s flows were significantly reduced during this period. In fact, it was this reduction in flow to downstream users that necessitated the construction of Elephant Butte Dam in southern New Mexico (completed in 1916). While providing a dependable supply of irrigation water to farmers in southern New Mexico, west Texas, and northern Chihuahua, this dam also represented a critical date for much of the Rio Grande in the Chihuahuan Desert. The river’s natural flooding cycle and sedimentation patterns were disrupted, affecting not only the aquatic environment but also many terrestrial communities dependent upon these physical processes.

As such, this report focuses largely on information about environments along the Rio Grande recorded prior to dam construction. The earliest accounts come from Spanish expeditions beginning in the sixteenth century; however, descriptions are more abundant from later periods, particularly the mid-nineteenth century, when military expeditions of the Mexican-American War; railroad, wagon-road, and boundary

1 Although the title of this report recognizes the alternate name, Río Bravo, given to this river in Mexico, for brevity’s sake, throughout this document the name Rio Grande will be used.

vii surveys; and the journals of 49-ers heading for California all recorded aspects of the environment encountered along the Rio Grande. While most of this information is narrative in form—qualitative descriptions of aquatic features, natural vegetation, and wildlife—some quantitative information from maps, survey notes, and flow records is also presented. In addition, some modern data have also been included to illustrate the magnitude of environmental change in the last 100 to 150 years.

Because this report is designed to provide all stakeholders involved in river restoration with a baseline, descriptive document that could be of use in the development of specific restoration goals for particular reaches of the river, information is typically presented with geographic identifiers so descriptions and data can be located along the river. Furthermore, this compilation is more comprehensive than selective (meaning that it includes as many different accounts of a particular feature of the river as practical, instead of picking just one example of how someone described it) to provide a catalog of descriptions from a variety of locations. In order to synthesize the compiled information, the significance of many of the observations has been interpreted in light of more recent ecological studies to try and describe some of the natural processes which must have been occurring along the river prior to the significant changes of the late-nineteenth and early twentieth century.

The information in this report is presented in three main sections—Geographic and Historic Overview (Chapter 1), Historic Ecosystem Descriptions (Chapter 2), and Species Lists (Chapters 3-6). The first section provides an introduction to geographic reference points used throughout the report as well as a very selective discussion of human history as it relates to settlement patterns and environmental change in the region. The second section provides both qualitative and quantitative descriptions of the river and areas around it, moving from the hydrologic regime of the river (flows, floods, and ground- and surface-water features) to the biological elements (vegetation and fauna) and their relations to the hydrologic regime. The third and final section of the report summarizes the past and present occurrence of vertebrate species along specific sections of the desert Rio Grande. The lists of occurrence are supplemented by species accounts detailing habitat requirements and population changes through time for particular species.

Literature Cited

American Rivers. 2000. America’s most endangered rivers of 2000. Available at http://www.amrivers.org/00endangered.html.

Bartlett, R.C. 1995. Saving the best of Texas: a partnership approach to conservation. Austin: University of Texas Press.

Crawford, C.S., A.C. Cully, R. Leutheuser, M.S. Sifuentes, L.H. White, J.P. Wilber. 1993. Middle Rio Grande ecosystem: Bosque Biological Management Plan. Albuquerque: U.S. Fish and Wildlife Service.

Harris, L.G. 1995. The developers: controlling the lower Rio Grande 1890-1980. In Proceedings of the 40th Annual New Mexico Water Conference, Reaching the Limits: Stretching the Resources of the lower Rio Grande, ed. C.T. Ortega Klett, pp. 7-12. Las Cruces, NM: New Mexico Water Resources Research Institute.

Scurlock, D. 1998. From the rio to the sierra: an environmental history of the Middle Rio Grande Basin. Rocky Mountain Research Station General Technical Report RMRS-GTR-5. Ft. Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Weniger, D. 1984. The Explorers’ Texas. Austin: Eakin Press.

viii

Chapter 1: Geographic and Historic Overview

The desert Rio Grande traverses about 1270 kilometers of the Chihuahuan Desert between the mouths of the Rio Puerco in New Mexico and the Devil’s River in Texas (Map 1). The river’s path alternates between a series of open, level valleys and narrows or canyons where geologic features restrict the river’s path. Through the desert, only a handful of perennial tributaries contribute water to the desert Rio Grande. The Rio Puerco has not been a perennial stream during the historic period, as its flow has ceased during dry seasons and drought periods (Scurlock 1998: 195), but it provides a significant input of both water and sediments to the desert Rio Grande. The Río Conchos, the Pecos River and the Devils River are the only major perennial rivers that reach the desert Rio Grande, and all meet the river in the lower half of its Chihuahuan Desert course. Thus, above the mouth of the Río Conchos, most of the water in the desert Rio Grande ultimately comes from snowmelt in the upper reaches of the river’s watershed in northern New Mexico and southern Colorado. The following section traces this water’s course through the desert, and briefly describes human history and events having a significant impact on the river, focusing on settlement patterns and agricultural development in the valley reaches.

Belen and Socorro Valleys The mouth of the Rio Puerco is about 18 kilometers upriver from the southern end of the Belen Valley in central New Mexico (Map 1a). At this confluence, the valley is about 4.5 kilometers wide, with approximately 4400 hectares occupying the valley floor between the confluence and the 0.5-kilometer long San Acacia Gorge (lengths and area estimated from USGS 7.5-minute quads). The walls of this gorge, which marks the end of the Belen Valley, are about 75 meters high (Lee 1907: 14). Between the San Acacia Gorge and the narrows at San Marcial, the river flows through the 64-kilometer long Socorro Valley (Map 1a), containing about 24,000 hectares of floodplain (Lee 1907: 14). At San Marcial, the river forces its way through a narrow gap in a basalt flow for a distance of about 2 kilometers.

The Belen and Socorro valleys are both within the stretch of the river described as the “Middle Rio Grande”; the desert Rio Grande accounts for the southernmost 38% of the length of the Middle Rio Grande (100 of 260 km total; Crawford et al. 1993: 8). The valleys of the Middle Rio Grande have been continuously occupied by agricultural societies since at least 1350 AD, when human populations and agricultural development grew to a point where they probably began to have a significant influence on the environment along the river through activities such as land clearing and water diversions for agriculture (Crawford et al. 1993: 23). The Pueblo cultures flourished in these valleys, living in sedentary villages, composed of multi-story, multi-family houses; in 1581, Gallegos documented 11 pueblos, containing a total of 425 two-story houses between San Marcial and the Rio Puerco (Gallegos 1927: 45-46).

When Europeans first reached the Middle Rio Grande in 1540 as a part of Coronado’s expedition, it is estimated that about 10,000 hectares of land were under cultivation in the valleys along the Middle Rio Grande (Crawford et al. 1993: 23), though the land may not have been watered by irrigation ditches. Ackerly (1996: 5-6) argues that the first clear records of irrigation ditches watering such fields were documented by members of the Espejo expedition in 1583. Similarly, Wozniak (1987: 7-15) suggests that floodwater farming (relying on overbank flows and surface run-off following rainfall) was probably the most important agricultural practice during the initial period of contact with the Spanish, and he reviews evidence suggesting that the few early irrigation ditches that were used did not tap mainstem river flows, but that they instead diverted side flows during flood events, as well as diverting waters from marshes and tributaries entering the river valley.

Ditch irrigation became more widespread following the establishment of permanent Spanish settlements in the seventeenth century (Ackerly 1996: 8-9). Agricultural development along the Middle Rio Grande reached a peak around 1880, when about 50,000 hectares were being cultivated (Crawford et al. 1993: 24). This peak was followed by a sudden decline in actively cultivated lands, precipitated by two factors: the sudden increase in irrigated agriculture upriver, which reduced river flows coming into the Middle Rio

1—Geographic and Historic Overview

Grande Valley, and the lack of drainage mechanisms for excess irrigation water, which resulted in increased salinity, rising water tables, and flooding of cultivated lands in the valley (Crawford et al. 1993: 24).

By 1821, about 40,000 people lived along the Rio Grande between Taos and Socorro (Weber 1982: 5), although most of the European settlement was concentrated in cities such as Albuquerque and Santa Fe, upstream from the desert Rio Grande. However, even the activities of these remote settlers had immense impacts upon the desert Rio Grande. One example of these influences is the introduction of huge herds of sheep to the watershed, which affected the flow of water and sediments into the river. As Horgan (1954: 364) explains, …by the middle of the eighteenth century there were millions of sheep grazing on the sparse slopes of the watershed. Between two hundred thousand and five hundred thousand sheep were driven every year to Mexico for sale. The grasses struggled for life in ordinary years and in dry years barely showed. The colonials looked at their hills and shook their heads. It was all very much like Spain, a condition of the natural life that seemed impossible to govern. The tilted lands were growing more and more barren, the torrents—when it did rain—swept faster and cut deeper, the earth ran into the tributaries and into the river, piling up silt on the river floor, the river spilled over its old banks and made swamps on good farm land, and a man could only bow his head and invoke patience.

Under Spanish and Mexican rule, the market for such livestock was to the south, and a significant trade route, the Camino Real or Chihuahua Trail, developed along much of the desert Rio Grande downriver as far as El Paso. Thus, large numbers of people and livestock traveled along the desert Rio Grande. For instance, in 1807, in a span of 4 days, Zebulon Pike encountered at least three large caravans—the first including 15,000 sheep and 300 men; the second, 50 men and 200 horses; and the third, another 200 horses—along the northern reaches of the desert Rio Grande (Jackson 1966: 407-8).

Engle and Las Palomas Valleys A few segments of the desert Rio Grande—Engle Valley, Las Palomas Valley, and Selden Canyon—were rarely seen by travelers along this route. The main branch of the trail left the river valley to avoid the lengthy westward bend of the river where it traversed this rugged series of canyons and narrow valleys and instead crossed the Jornada del Muerto, an open plain to the east.

The Engle Valley began at the narrows of San Marcial (Map 1a). This 64-kilometer valley varied in width from about 245 meters to 3.2 kilometers (Lee 1907: 15); the eastern side of this valley was defined by a series of steep mountains. Upon entering this valley in the mid-nineteenth century, Emory (1976: 54) noted: “The valley of the Del Norte, as we advance [southward], loses what little capacity for agriculture it possessed. The river commenses [sic] to gather its feeble force into the smallest compass to work its way around the western base of Fra Cristobal mountain.” After 1916, almost 15,600 hectares were flooded, turning this valley into Elephant Butte Reservoir (Lee 1907: 14, Fugate and Fugate 1989: 54). The largest dam in the United States at the time of its construction, Elephant Butte was designed to provide a dependable source of irrigation water for the Las Palomas, Mesilla, and El Paso valleys downriver; its construction was necessitated by the extensive agricultural development in northern New Mexico and southern Colorado at the end of the nineteenth century, which was appropriating most (and during some drought periods, all) of the river’s flow during the growing season.

The dam for this reservoir was built in Elephant Butte Canyon, which also defines the northern end of Las Palomas Valley (Map 1b). This valley, about 80 kilometers long, contained more than 10,500 hectares of bottom land in 1907 (Lee 1907: 15). About 4700 hectares near the northern end of this valley were flooded with the creation of Caballo Reservoir in 1938, built largely as a flood control mechanism. Like the Engle Valley, the eastern edge of parts of Las Palomas Valley were defined by steep mountains, such as the Caballo Mountains; Cooke’s 1846 description of this area noted that “For the last eighteen miles [29 kilometers] we have found fine river bottoms interrupted by points of bluff, on this [the west] side chiefly, for a mountain rises abruptly beyond [to the east]. They are more than a mile [1.6 kilometers] wide…” (Bieber 1938: 97).

2—Geographic and Historic Overview

In spite of these “fine river bottoms” the agricultural Pueblo cultures did not extend any farther south than the Socorro Valley (Everitt 1977: 22, Ackerly 1996: 5), and ditch-irrigated agriculture did not develop in this valley until European settlers arrived. This valley’s relative isolation (off of the Camino Real) seems to have resulted in slower rates of settlement and agricultural development. Ackerly (1996: 75) cites an 1898 compilation showing that the only irrigation canals along the upper reaches of the desert Rio Grande were in the Engle Valley and above; however, in 1853, Bartlett (1965: 217-218) described a new settlement in Las Palomas Valley, where “virgin soil” was being plowed and irrigated, and an 1857 survey of Ft. Thorn (near modern Hatch) mapped an acequia within the boundaries of the military reserve (Garrettson 1857: T19S, R4W plat). By 1905, only about 2025 hectares were under cultivation in Sierra County (Frost and Walker 1906: 267), which would include parts of both the Engle and Las Palomas valleys.

Mesilla and El Paso Valleys Las Palomas Valley ends downstream of modern Rincon at the beginning of Selden Canyon, a 29- kilometer stretch of the river, where occasional patches of bottom land total about 3200 hectares in extent (Lee 1907: 15). Below Selden Canyon, the final valley in the state of New Mexico is the Mesilla Valley (Map 1b), about 80 kilometers in length and up to 13 kilometers wide, and containing about 60,000 hectares (Lee 1907: 15). Although the Camino Real reentered the desert Rio Grande’s floodplain at the northern end of the Mesilla Valley, European settlement of this large valley was also relatively slow, perhaps because of the threat of raids by non-agricultural, nomadic tribes (Baldwin 1938: 315). The Doña Ana Bend Colony, established in 1843, was the first successful European settlement in the valley (Baldwin 1938: 316), soon followed by towns like Las Cruces and La Mesilla (established in 1849 and 1853, respectively). Settlers immediately established irrigated agriculture. For instance, in 1849, camped near Las Cruces, Eccleston (1950: 160) observed a cornfield “3 leagues [12 kilometers] long” and surveyors crossed acequias (irrigation canals) 6 times while establishing township and range boundaries near Las Cruces and Mesilla in 1857 (Garrettson 1857). By 1905 the population of Doña Ana County (concentrated in the Mesilla Valley) was 13,000, and 16,000 hectares were ditch-irrigated and under cultivation (Frost and Walker 1907: 161, 163). As of 1981, about 34,000 hectares of the Mesilla Valley could be supplied with irrigation water via 89 kilometers of main canals (Ackerly 1996: 74-5).

The Mesilla Valley ends at the constriction referred to as El Paso Canyon (Lee 1907: 15) a narrows about 5 km long (IBC 1903: 285). Extending from this canyon to about Ft. Quitman, Texas is the El Paso Valley (Map 1c), 136 km in length, up to 16 km in width, and including at least 57,000 hectares of land (IBC 1903: 296; IBWC 1978: 2, Emory 1987, Vol. 1, pt 1: 90).

Both the Mesilla and El Paso valleys have had a long history of human occupation. Though Paleoindian sites are relatively rare, archeological evidence indicates that the greater El Paso area (which includes the Mesilla Valley) was probably inhabited by “small, mobile bands subsisting predominantly on large game supplemented with the utilization of wild plant resources” between about 10,000 and 6,000 BC (Peterson et al. 1994: 55). Archaic period occupations began around 6,000 BC and by 1000 or 2000 BC, plant domestication was probably underway (Peterson et al. 1994: 58, 61). As agriculture became more significant, larger sites which may have served as year-round base-camps developed along the Rio Grande (Peterson et al. 1994: 60); however, in this area, non-agricultural food resources remained more important than in other cultures to the north (Peterson et al. 1994: 60). Mesilla Phase (pithouse) occupations began around the year AD 1, typified by increasingly sedentary and agricultural society, including some villages along the river (Peterson et al. 1994: 64). The Doña Ana phase, dating from about AD 1100, marks the beginning of a transition toward Pueblo cultures, with even larger settlements and agricultural fields (Peterson et al. 1994: 65-66). Though agriculture was clearly practiced during this period, “there is no archeological evidence of prehistoric irrigation facilities on the floodplain of the Rio Grande near El Paso” and agriculture probably depended upon the diversion of sheetwash runoff following rainstorms (Ackerly 1994: 118).

Around AD 1400 many settlements in the El Paso area appear to have been abandoned; whether this resulted from widespread migration or a shift back to a more nomadic, non-agricultural society is not clear (Peterson et al. 1994: 69-70). At the time of early European contact, as chronicled by the Rodriguez and Espejo expeditions of 1581 and 1582, no permanent farming settlements existed in these valleys (Everitt 1977: 22, Ackerly 1996: 5), although camps utilized by Mansos and Sumas were sometimes encountered

3—Geographic and Historic Overview

(Peterson et al. 1994: 71-72). The first permanent mission for the Mansos (Guadalupe Mission, in modern Juarez) was established in 1659, and ditch irrigation was evidently introduced to the area at this time by the Spanish (Ackerly 1994: 118). Ditch irrigation became more prominent following the Pueblo Revolt of 1680 (Ackerly 1994: 118). Following the influx of refugees from the revolt in northern New Mexico, officials in the El Paso area requested assistance and land for the creation of irrigation canals (Ackerly 1996: 9). Portions of the upper and central El Paso Valley have thus been under cultivation for centuries. In 1934, an El Paso Herald-Post report described a four-acre tract near Ysleta “which had been in continuous cultivation by the Roman Catholic Church since 1682” (Hammons 1942: 26). Intensive settlement in El Paso Valley below San Elizario did not occur until after 1881 (Ackerly 1994: 119).

The ditch irrigation which developed in the El Paso Valley, using water from the mainstem of the river, required irrigation structures to direct river water into ditches. In 1773, an El Paso Valley resident described a diversion dam as follows: The upkeep of the dam is obligatory upon all. It is made of wattles, as the terrain of the river does not permit any other kind of fabrication, to say nothing of the trouble caused by its excessive floods and freshets, for it not seldom happened that after a dam had been built of stones, fagots, and stakes it was necessary to tear it down to prevent inundation of the town. (Hackett 1902: 507) Other sources described the eighteenth-century diversion structures as large baskets woven of willow wands which were filled with small rocks and placed into specific parts of the river channel during the irrigation season (Horgan 1954: 347). Irrigated agriculture also required land-leveling, as described by Edwards in 1846, in the El Paso Valley: I saw some Mexicans grading, or rather leveling, a hill that was at least one hundred feet [high], with a base according to the height. They had a hoe and spades, and would dig with these while some others were engaged in packing the dirt into a neighboring gully. Two men worked in shafts of poles with rawhide between, which they packed the dirt on….They have graded a number of hillocks in this way, which they are compelled to do in order to irrigate the soil. (Bieber 1936: 246)

Though the Camino Real headed south toward the city of Chihuahua and away from the desert Rio Grande near El Paso, some other routes from the east converged within the El Paso Valley. For instance, during the Gold Rush of 1849, two emigrant roads were established which passed through the El Paso Valley (Martin 1925: 129). After 1849, [t]he whole Rio Grande Valley, from Santa Fe to El Paso, was the half-way place on the overland trip where the emigrants coming via Missouri, Arkansas and Texas expected to lay in new supplies. Most parties rested for three to four weeks to build up the animals for the balance of the journey, and consequently, there was congestion at El Paso, Santa Fe, and every little village between the two places. (Martin 1925: 300-301) Many of these parties were quite large, such as one reported to contain 800 Americans and 300 Mexicans travelling in 300 wagons with 4000 cattle and 300 mules; at least 4000 emigrants (and all of their livestock) were reported camping in the vicinity of El Paso in 1849 (Martin 1925: 301). Because of the huge influx of travelers, Mexican residents were concerned that their food supplies might run out, resulting in a famine (Martin 1925: 301). Some examples of the effects such travelers had on native plants are discussed later in this report, in the section on qualitative descriptions of changes in floodplain vegetation.

The El Paso Valley ends near Ft. Quitman, Texas. In addition to representing a geographic boundary created the Quitman Mountains, this location also represents a significant management boundary for the floodplain of the Rio Grande. Upstream of this point, two International Boundary Water Commission (IBWC) projects initiated in the 1930s—the Rio Grande Canalization Project (between Caballo Dam and El Paso) and the Rio Grande Rectification Project (El Paso to Ft. Quitman)—were established to facilitate water delivery to Mexico (as required under the Treaty of 1906) and to stabilize the river’s location along the international boundary. To accomplish these goals, the river was channelized, largely confined to a floodway defined by levees, and a program of vegetation removal was initiated (IBWC 1978: 11-12). In addition, in the El Paso Valley, the river’s path was straightened, reducing the length of its path from about 250 to 138 kilometers (IBWC 1978: 5).

4—Geographic and Historic Overview

Forgotten Reach and Presidio Valley Between Ft. Quitman and Candelaria is a 130-kilometer stretch of canyons alternating with small valleys (Maps 1c and 1d), totaling about 12000 hectares of river bottom (measured from maps in IBWC 1978); this area is sometimes described as “the forgotten river” because it is remote and often overlooked. Many archeological sites dated from 1220 to about 1450 AD have been found through this reach; they appear to be associated with trade and wild-food gathering, with no evidence of agricultural activity (Kelley 1990: 38). A similar culture existed in this area during the early Spanish period. During a 1683 journey along this stretch of the Rio Grande, Mendoza recorded a number of “rancherias” belonging to members of the Suma nation; he suggested that their main food was roasted yucca roots and made no mention of agriculture along this stretch (Mendoza 1952: 321-324).

The Presidio Valley (Map 1d) begins just upstream of Candelaria, Texas and is about 88 kilometers long, containing about 20000 hectares of river bottom [measured from maps in IBWC 1978]. The Presidio Valley is narrower than the El Paso Valley, averaging only a mile wide (Kelley 1992: 119), and reaching its maximum width below the mouth of the Río Conchos, where it ranges “from one to three miles wide on each side of the river” (Emory 1987, vol. I, pt. 1: 80). Entering the Presidio Valley near Presidio, Texas and Ojinaga, Chihuahua, the Río Conchos is the first perennial tributary that provides year-round water into the desert reach of the Rio Grande.

Moving downriver from the El Paso Valley, a sedentary, agricultural society became established in the Presidio Valley between 1200-1300 AD (Kelley 1992: 139); Kelley (1952: 362, 383) argues that the expansion of agricultural societies from the north may have been made possible by a shift to a slightly wetter climate. As in the El Paso area, these farmers practiced floodwater and rainwater irrigation, not ditch irrigation (Kelly 1952: 383). And as happened elsewhere in the region, many of these villages appear to have been abandoned in the 1400s (Kelley 1990: 39), a shift Kelley (1952: 362-3) again ascribes to climate change, this time to a drier climate. By the time of early contact with the Spanish in the mid- to late 1500s, a few farming villages were concentrated in the part of the valley below the mouth of the Río Conchos and along the lower reaches of the Río Conchos (Kelley 1952: 366). In 1684, Mendoza (1952: 325) reported that farms belonging to the Julimes nation in the Presidio Valley cultivated corn and wheat. In 1747 and 1748, cultivated crops mentioned in Spanish documents included corn, wheat, pumpkins, and legumes (Ydoiaga 1992: 27, 41, 50, 60, 82).

The first Spanish missions were established in the vicinity of La Junta de los Rios (the confluence of the Río Conchos and Rio Grande) in the late 1600s (Jones 1991: 47). Under Spanish rule, the area was host to at least 6 missions and 3 military presidios (Jones 1991: 49, 52). Even after the arrival of the Spanish, such settlements largely depended upon overbank flooding to irrigate their fields; early attempts at ditch irrigation from the two rivers prior to 1747 evidently failed due to the shifting location of river banks, and sandy beaches and soil (Ydoiaga 1992: 41, 46, 80). Thus widespread ditch-irrigated agriculture developed much later in the Presidio Valley than in the El Paso, Socorro, and Belen valleys upriver, and even during the mid-nineteenth century, “floodwater farming seems to have been the ordinary method of cultivating crops above the confluence” (Everitt 1977: 22). Wooden structures known as burro dams were first used to divert flows of the two rivers around La Junta into irrigation canals around 1860 (Madrid 1996: 24) and irrigation ditches were observed at a Mexican military outpost near the northern end of the valley in 1857 (Emory 1987, vol. I, pt. 1: 89). A ditch was built on the American side of the river as early as 1872 (Everitt 1977: 22), and by 1910, the American side of the upper portion of the Presidio Valley contained at least 4 irrigation ditches with about 790 hectares under cultivation (Everitt 1977: 23).

In addition to agricultural development, the river valley and channel in the La Junta area have been directly impacted by international concerns. As in the Mesilla and El Paso valleys, the IBWC has been involved in managing the Rio Grande in the Presidio Valley. In the mid-1970s a channel relocation project was completed along 13.4 kilometers of the Rio Grande near the mouth of the Río Conchos, including levee construction and vegetation clearing (IBWC 1978: 13).

Big Bend and the Lower Canyons Below the Presidio Valley, the desert Rio Grande encounters few open valleys and is largely constrained in narrow canyon reaches (Map 1e). Three large canyons occur in the Big Bend region: Santa Elena,

5—Geographic and Historic Overview

Mariscal, and Boquillas Canyons (115, 203, and 260 river kilometers below the mouth of the Conchos, respectively). Narrow valleys with limited floodplains occur between the canyons; for instance, in 1852, Chandler described the valley below Santa Elena Canyon as “susceptible of cultivation; the bottom land is, however, limited by an elevated bank of gravel (Emory 1987, vol. I, pt. 1: 83). The rugged, remote character of this area limited population growth and agricultural development in this area, although mining and ranching operations did impact the environment along the river (see section on Qualitative Descriptions of Vegetation Change in Chapter 2).

Below the Stillwell Valley, which is located downstream of Boquillas Canyon, the river maintains a rugged path through a succession of canyons. This area below Big Bend is commonly referred to as the “lower canyons” (Wauer 1977:165). Michler’s 1856 survey of this area noted that through this area the river’s bed is narrow, and hemmed in by continuous and perfect walls of natural masonry, varying from 50 to 300 feet in height; the breadth of the river being extremely contracted, these structures, seen from our boats, look stupendous as they rise perpendicularly from the water. It is not unfrequently the case that we travel for miles without being able to find a spot on which to land. (Emory 1987, vol. 1, pt. 1: 77)

At the downstream end of the lower canyons of the desert Rio Grande, Michler noted that the “thirty miles above the mouth of the Pecos is one continued rapid” and the river varied from 25-800 feet wide (Emory 1987, vol. I, pt. 1: 78). Near the mouth of the Pecos (about 550 river kilometers below the mouth of the Río Conchos), the river appeared less rugged, with more and more floodplain appearing along its edge (Emory 1987, vol. I, pt. 1: 79).

About 70 kilometers below the mouth of the Pecos, the Devils River met the Rio Grande, in “[a] spectacular canyon [containing] typical vega [shrubs and trees of a riparian forest]” (Gehlbach 1981:66). This canyon, and the limited floodplains above it, no longer exist. Completed in 1969, Amistad Reservoir was created by a dam constructed just below the mouth of the Devils River and flooded a 119-kilometer length of the Rio Grande; the waters of Amistad Reservoir reach 40 kilometers up the Devils River, 23 kilometers up the Pecos River, and 48 kilometers up the Rio Grande above the mouth of the Pecos (U.S. Dept of Interior 1999).

Literature Cited

Ackerly, N.W. 1994. Historic and modern irrigation systems. In El Valle Bajo: the culture history of the Lower Rio Grande Valley of El Paso, Volume 1: Culture and Environment in the Lower Valley, ed. J.A. Peterson and D.O. Brown, pp. 118-129. Prepared for the El Paso County Lower Valley Water District Authority. El Paso: Archaeological Research, Inc/ Austin: Hicks and Company.

Ackerly, N.W. 1996. A review of the historic significance and management recommendations for preserving New Mexico’s acequia systems. Santa Fe: Historic Preservation Division.

Baldwin, P.M. 1938. A short history of the Mesilla Valley. New Mexico Historical Review 13: 314-324.

Bartlett, J.R. 1965. Personal narrative of explorations and incidents in Texas, New Mexico, California, Sonora, and Chihuahua, connected with the United States and Mexican Boundary Commission, during the years 1850, 1851, 1852, and 1853. Volume I. Chicago: Rio Grande Press. [Reprint of 1854 publication.]

Bieber, R.P., ed. 1936. Marching with the Army of the West, 1846-1848. Glendale, CA: Arthur H. Clark Co.

Bieber, R.P., ed. 1938. Exploring southwestern trails, 1846-1854. Glendale, CA: Arthur H. Clark Co.

Crawford, C.S., A.C. Cully, R. Leutheuser, M.S. Sifuentes, L.H. White, J.P. Wilber. 1993. Middle Rio Grande ecosystem: Bosque Biological Management Plan. Albuquerque: U.S. Fish and Wildlife Service.

6—Geographic and Historic Overview

Eccleston, R. 1950. Overland to California on the Southwestern Trail, 1849: Diary of Robert Eccleston, eds. G.P. Hammond and E.H. Howes. Berkeley: University of California Press.

Emory, W.H. 1976. The United States conquest of California. New York: Arno Press. [Reprint of: Notes of a military reconnaissance, from Fort Leavenworth, in Missouri, to San Diego, in California, including part of the Arkansas, Del Norte, and Gila Rivers. 30th Congress, 1st Session, Executive Document No. 41 (1848).]

Emory, W. H. 1987. Report on the United States and Mexican Boundary Survey, made under the direction of the Secretary of the Interior, 2 volumes. Austin: Texas State Historical Association. [Reprints of 34th Congress, 1st Session, House Executive Document 135 (1857) and 34th Congress, 1st Session, House Executive Document 108 (1859).]

Everitt, B.L. 1977. Historical background. In A preliminary appraisal of cultural and historical resources found along the Rio Grande between Fort Quitman and Haciendita, TX, ed. C.A. Johnson, pp. 21- 25. Publications in Anthropology, No. 5. El Paso Centennial Museum, University of Texas at El Paso.

Frost, M. and P.A.F. Walker, eds. 1906. The land of sunshine. Santa Fe: New Mexico Bureau of Immigration of the Territory of New Mexico/ New Mexico Printing Co.

Fugate, F.L. and R.B. Fugate. 1989. Roadside history of New Mexico. Missoula, MT: Mountain Press Publishing.

Gallegos, H. 1927. The Gallegos relation of the Rodriguez expedition to New Mexico. trans. and eds. G.P. Hammond and A. Rey. Historical Society of New Mexico, Publications in History, Volume IV, December 1927. Santa Fe: El Palacio Press.

Garrettson, J.W. 1857. Government Land Office Survey field notes. Microfiche, available at Las Cruces District Office, Bureau of Land Management, Las Cruces, NM.

Gehlbach, F. R. 1981. Mountain islands and desert seas: a natural history of the U.S.-Mexican Borderlands. College Station: Texas A&M University Press.

Hackett, C.W., ed. 1902. Historical documents relating to New Mexico, Nueva Vizcaya, and Approaches thereto, to 1773, Volume III. Collected by A.F.A. Bandelier and F.R. Bandelier. Washington D.C.: Carnegie Institution.

Hammons, N.L. 1942. A history of El Paso County, Texas to 1900. MA Thesis, Texas Western College, El Paso.

Horgan, P. 1954. Great River: the Rio Grande in North American history, 2 volumes. New York: Rhinehart and Co.

International Boundary Commission. 1903. Equitable distribution of the waters of the Rio Grande. Proceedings of the International (Water) Boundary Commission, United States and Mexico, Treaties of 1884 and 1889, Volume 2. Washington, D.C.: Department of State.

International Boundary and Water Commission. 1978. Final Environmental Statement: Rio Grande Boundary Preservation, Hudspeth and Presidio Counties, Texas.

Jackson, D., ed. 1966. The journals of Zebulon Montgomery Pike, with letters and related documents. Norman: University of Oklahoma Press.

7—Geographic and Historic Overview

Jones, O.L. 1991. Settlements and settlers at La Junta de los Rios, 1759-1822. Journal of Big Bend Studies 3: 43-70.

Kelley, J.C. 1952. Factors involved in the abandonment of certain peripheral southwestern settlements. American Anthropologist 54: 356-387.

Kelley, J.C. 1990. The Rio Conchos Drainage: History, Archaeology, Significance. Journal of Big Bend Studies 2: 29-41.

Kelley, J. C. 1992. The historic Indian pueblos of La Junta del los Rios. In The Native American and Spanish Colonial Experience in the Greater Southwest, Volume II, Introduction to the Research, ed. D.H. Snow, 117-193. New York: Garland Publishing. [Reprint of 2-part article from New Mexico Historical Review 27(4): 257-295 and 28(1): 21-51.]

Lee, W.T. 1907. Water resources of the Rio Grande Valley in New Mexico and their development. Water-supply Irrigation Paper No. 188. Washington, D.C.: Department of the Interior, U.S. Geological Survey.

Madrid, E.R. 1996. Native American and mestizo farming at La Junta de los Rios. Journal of Big Bend Studies 8: 15-31.

Martin, M.E. 1925. California emigrant roads through Texas. Southwestern Historical Quarterly 28: 287- 301.

Mendoza, J. 1952. Itinerary of Juan Dominguez de Mendoza,1684. In Spanish exploration in the southwest, 1542-1706, ed. H.E. Bolton, 320-325. New York: Charles Scribner and Sons.

Peterson, J.A., A.C. Earls, T. Myers, and H.C. Morrow. 1994. A cultural perspective on the Lower Valley. In El Valle Bajo: the culture history of the Lower Rio Grande Valley of El Paso, Volume 1: Culture and Environment in the Lower Valley, ed. J.A. Peterson and D.O. Brown, pp. 55-117. Prepared for the El Paso County Lower Valley Water District Authority. El Paso: Archaeological Research, Inc/ Austin: Hicks and Company.

U.S. Department of the Interior. 1999. Amistad: Amistad National Recreation Area, Texas [map and brochure]. Government Printing Office: U.S. Department of the Interior, National Park Service.

Wauer, R.H. 1977. Significance of Rio Grande riparian systems upon the avifauna. In Importance, preservation and management of riparian habitat: a symposium, coord. R.R. Johnson and D.A. Jones, pp.165-174. USDA, Forest Service, General Technical Report RM-43. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station.

Weber, D.J. 1982. The Mexican frontier, 1821-1846: the American Southwest under Mexico. Albuquerque: University of New Mexico Press.

Wozniak, F.E. 1987. Irrigation in the Rio Grande Valley, New Mexico: a study of the development of irrigation systems before 1945. Amarillo, TX: Southwest Regional Office, Bureau of Reclamation.

Ydoiaga, J. 1992. Expedition to La Junta de los Rios, 1747-1748, Captain Commander Joseph de Ydoiaga’s Report to the Viceroy of New Spain. trans. E.R. Madrid. Office of the State Archeologist, Special Report 33. Austin: Texas Historical Commission.

8—Geographic and Historic Overview

Chapter 2: Historic Ecosystem Descriptions

Prior to the significant human impacts of the late-nineteenth and early twentieth centuries, the riparian landscape of the desert Rio Grande was likely a system in dynamic equilibrium, in terms of both geomorphic and biological processes. In terms of geomorphology, “dynamic equilibrium” can refer to a system’s energy balance (Bullard and Wells 1992: 28): if the energy input to a river system changes (such as changes in the volume of water or sediments entering it), then the form of the system (such as the channel gradient or shape) changes to keep the entire system in balance. In terms of biological processes, the dynamic landforms created by a river system result in a heterogeneous landscape; the “dynamic equilibrium” of such landscapes maintains stability on relatively large spatial and temporal scales by allowing for change and variability on smaller scales (White 1979: 231, 252). Although the early explorers and settlers were not concerned about how organisms adapted to such dynamic landscapes, their descriptions of the riparian environment allow us to glimpse some of these geomorphic and biological processes in action, and they allow us to infer how hydrologic, geomorphic, and biological processes interacted within the riparian landscape.

Channel Morphology and Location Hydrologic processes are driven by the flow of water and sediments through the riparian landscape. Though sediment levels likely increased dramatically in the late-nineteenth century (Sublette et al. 1990: 9, Scurlock 1998: 188), even some of the earliest accounts mentioned the river’s turbidity. In December 1582, heading northward along the river near the mouth of the Río Conchos, a chronicler of the Espejo expedition noted “This Rio del Norte we named El Rio Turbio because it is exceedingly muddy…” (Luxan 1929: 64). In the same area, Ydoiaga (1992: 27) in 1747 reported that inhabitants of the La Junta region referred to the Rio Grande above the mouth of the Conchos as the “Rio Puerco,” meaning “dirty river” (Madrid in Ydoiaga 1992: 27). Mid-nineteenth-century descriptions also contain references to high sediment loads. Bartlett (1965: 187) described the river near El Paso as “muddy and sluggish except during freshets.” Also near El Paso, in 1846, Ruxton (1973: 168) described the Rio Grande as “a small turbid stream, with water of a muddy red.” Upon reaching the river in the southern end of the El Paso Valley in 1849, Eccleston (1950: 125) observed that “[t]he water looks much like that of the Pecos, fully as muddy, but not so brackish.…” Several years later (1857), in the same general area, Humphrey “…was much disappointed in finding the stream so small in the first place (being only a hundred yards wide) and so muddy in the second….” (Lesley 1949: 67).

Heavy sediment loads in the upper reaches of the desert Rio Grande were probably deposited along the river. As is explained in the Middle Rio Grande Ecosystem: Bosque Biological Management Plan, for thousands of years, the Middle Rio Grande has most likely been an aggrading system, in which tributaries carry more sediments into the floodplain than the river can carry out (Crawford et al. 1993: 16). However, periodic avulsion events, when the river would move from its aggraded channel into a lower elevation part of the valley allowed the river to maintain its state of “dynamic equilibrium” (Crawford et al. 1993: 19).

Farther down the desert Rio Grande, the situation is somewhat different, as valley-wide aggradation may have ended about a thousand years ago. Prior to the historic period, from about 2500 to 1000 years ago, the floodplain soils of at least one reach of the El Paso Valley (in the vicinity of San Elizario) formed, resulting from the deposition of suspended sediments from relatively frequent, large floods (Hall 1994: 18). These floods probably were created by high levels of runoff and sheet erosion from the more arid parts of the river’s watershed in central and southern New Mexico (Hall 1994: 19). Hall (1994: 24, 26) argues that this period of floodplain formation (aggradation) ended about 1000 years ago, probably because of a shift to a drier climate, and that “no significant” or only “minimal” deposition has occurred since then. Scurlock (1999: 86) describes the historic period river in the El Paso area as a “degrading stream.”

In addition to the impact of the volume of sediment and water flowing through a system, the gradient of a river can influence rates of aggradation and degradation. In the extensive valley reaches of the desert Rio

9—Historic Ecosystem Descriptions

Grande, elevation change along the river is quite gradual. For instance, along the New Mexico portion of the desert Rio Grande, the river descends about 5 feet per mile, whereas in northern New Mexico, the river’s gradient is greater than 10 feet per mile (Campbell and Dick-Peddie 1964: 492). Between Ft. Quitman and Presidio, Texas, the river descends about 4.3 feet per mile (IBWC 1978: 8). Such a low gradient may allow the river to appear slow and calm, as noted by some early travelers. In 1582, a member of Espejo’s party noted that near the mouth of the Río Conchos, the Rio Grande “flows so quietly that it does not make any noise in spite of being very large in some places” (Luxan 1929: 64).

Low-gradient flow in wide valleys may also be characterized by a meandering path. In general terms, for thousands of years, the Middle Rio Grande has had a “braided, slightly sinuous channel that broadly meandered laterally within the 2-6 km (1-4 mi) wide floodplain” (Crawford et al. 1993: 27). In the historic period, the extent of meandering can be documented from early descriptions and maps. For instance, in the El Paso Valley of the mid-nineteenth century, an observer noted that “[f]rom San Elceario up to El Paso, [the] distance by the sinuosities of the river [is] thirty miles, but by air-line…only twenty miles….” (Emory 1987, vol. I, pt. 1: 90-91).

An even more sinuous river existed in the Mesilla Valley in 1844, when one segment of the river channel was surveyed as the boundaries of the Doña Ana Bend Civil Colony and Brazito Grant. As depicted on a later map (US Reclamation Service 1914; see Map 2), this segment was about 34 kilometers long, measured as a straight line distance from one end to the other. Following the meanders of the river, the distance was almost twice as long, about 65 km. By 1912, the river’s path through the Mesilla Valley was much straighter, and it took only about 40 km to cover the 34 straight-line kilometers. The significant reduction in meandering and apparent widening of the channel in the Mesilla Valley during the late- nineteenth and early twentieth centuries (which also occurred in the El Paso and upper Presidio Valleys; Everitt 1993: 230, 236) may have been due, at least in part, to an increase in sediment levels and a reduction in flows, which affected the river’s ability to carry sediments. During this period, increasing sediment load, and to a lesser extent, a reduction in flows, led to a wider and shallower channel along portions of the Middle Rio Grande (Crawford et al. 1993: 20). Channel avulsion, in the form of meander cutoffs, can be a secondary result of sediments accumulating in a channel, because the cross-sectional area of the channel eventually reaches a point at which it can no longer accommodate even a moderate flood (Everitt 1993: 236).

In addition to following a natural meandering path, the desert Rio Grande changed channels frequently. Small-scale shifts in channel location are a natural feature of a meandering channel because the hydraulics of the channel are such that meanders tend to migrate laterally (away from the convex side of the curve) and downstream, creating point-bar deposits inside the curve (Malanson 1993: 33-34). Meander cutoffs can also form, creating islands or oxbow lakes; cutoffs can be produced when a faster moving upstream meander overtakes a slower moving meander downstream (Malanson 1993: 34). Such small-scale changes may have been responsible for some of travelers’ complaints about changes in river crossings. In the mid- nineteenth century, Bartlett (1965: 187, 167) noted that “The ford [near El Paso] changes more or less every season” and that “The river [at El Paso] had to be forded by daylight, in consequence of the frequent changes in the channels and bars.” Similarly, in 1846, Ruxton (1973: 168) warned that because of the river’s “…constantly shifting quicksands and bars, [the river near El Paso] is always difficult, and often dangerous to cross with loaded wagons.”

However, large-scale changes in channel position also occurred. As illustrated on the Mesilla Valley map (Map 2), below Las Cruces, the 1844 channel was about 6.4 kilometers east of the channel recorded in 1903; included in this change is a channel shift which occurred between 1862 and 1865 and moved the river from the east side of Mesilla to the west. Flooding in August of 1862 left Mesilla surrounded by water on both sides (Couchman 1990: 155) and as the river tried to establish a new channel, between 1862 and 1865, “the head of the Mesilla ditch had to be changed 13 times” (Yeo cited in Wozniak 1987: 115). In 1865, the river finally cut a new channel beginning at a point weakened by a ditch head (Baldwin 1938: 320).

In addition, another large-scale channel shift occurred in the lower Mesilla Valley below Anthony sometime between 1903 and 1912, when the river shifted about 4.8 kilometers, from the west edge of the

10—Historic Ecosystem Descriptions

valley to the east side, near modern Canutillo (Map 2). The location of the main flow of the Rio Grande in this area had been variable in this area in prior years as well. In the late 1850s, Anson Mills surveyed the area around Canutillo, and noted that the river was near mid-valley at that point, and moving westward (Mills 1918: 261). He spoke with long-term residents of the area, who informed him that in 1821, the river had run along the eastern bluff; in the 1850s this abandoned channel was still evident (Mills 1918: 261). In 1857, dry channels near the eastern edge of the valley were also noted by surveyors to the north, south of modern Mesquite (Garrettson 1857, see Map 2). In the late 1850s, Mills (1918: 261) also noted a less obvious abandoned channel along the western edge of the valley across from Canutillo, the general location of the active river channel in 1888 (Mills 1918: 261) and 1903 (Map 2).

A complex network of channels also existed in the vicinity of modern Socorro and San Elizario in the El Paso Valley, as depicted on 1852-3 Boundary Survey maps (Map 3). Two old channels (the “Rio Viejo del Bracito,” closest to the eastern edge of the valley and the “Rio Viejo de San Elizario,” between the old Bracito channel and the 1852 channel) appear to have been abandoned sometime between 1827 and 1831 (Ackerly 1994: 119, Peterson 1994a: 9, Peterson et al. 1994: 103). Though such channel shifts create the impression of a highly mobile river channel, detailed analysis of the stratigraphy of floodplain deposits in this reach suggest that the location of these three channels has been stable for about 2500 years and that the historic records of channel shifts in this area “probably reflect shifts in routes of main streamflow into previously existing channels rather than erosion of a new channel” (Hall 1994: 24, 26). Historic descriptions also mention the river’s tendency to return to pre-existing channels. For instance, a 1773 description of life in the El Paso Valley noted that “They guard against the danger that the river may return to its old course by making deep ditches through which it may flow in such an event” (Hackett 1902: 508). Though Hall argues that large-scale channel migration across the floodplain did not occur in this reach, that does not mean that the small-scale changes associated with a meandering channel did not occur. Hall (1994: 12) estimates that each channel’s meander belt, within which such changes occurred, was probably about 2000 feet (600 meters) wide.

Flooding and Flow Regimes As the examples above illustrate, channel shifts generally occur during or as a result of floods when sediment deposition and high flows can resculpt the river’s path. In his Environmental History of the Middle Rio Grande Basin, Scurlock catalogs at least 82 floods (defined as events with a flow greater than 10,000 cfs) that occurred along the river above El Paso between 1591-1942 (1998: 32); of these, 51 occurred along the desert Rio Grande between the Rio Puerco and El Paso, 34 of them after 1846 (Scurlock 1998: 33-38). In a later publication, Scurlock summarizes the 1665-1942 flood history of the Rio Grande from Mesilla, New Mexico through Fabens, Texas: at least 72 floods have been documented along this reach, 51 of these after 1846 (Scurlock 1999: 89). A combination of a more complete historical record and environmental change (discussed below) probably resulted in the apparent increase in flood frequency after 1846.

Scurlock (1998: 32) ascribes these floods to three distinct causes: spring floods (April-June) resulting from heavy snowmelt, widespread summer flooding resulting from extensive summer rains in years with a significant spring flood, and local summer flooding (July-September) resulting from localized but heavy thunderstorms. In addition to the timing difference, spring and summer floods have different flow characteristics: snowmelt floods tend to build to their peak flow relatively slowly, whereas rainstorms result in flashier pulses of water that create sharp, short peaks in flow (Lagasse 1981: 29, Poff et al. 1997: 771). For an illustration of a sudden summer rise, consider Hill’s (1901: 167-8) description of his party’s departure from a pile of rocky debris blocking the river in Santa Elena Canyon: Having finally succeeded in crossing the obstruction early one morning, we transported our baggage to the boats preparatory to leaving. Before the boats were loaded a tremendous roaring sound like a distant thunder was heard up the canyon, and we saw what we most dreaded was happening—the river was rising. A big flood of the ordinary kind would have veneered the dangerous rocks with water and our prospects for escape would have been small. We hastily piled our baggage into the boats and sprang aboard. It was either stay and starve or go and chance it.

11—Historic Ecosystem Descriptions

Fortunately, this particular rise proved to be a small one, just sufficient to give the desired impetus to our craft….

As Scurlock’s categories of flood causes suggest, the river had a variable flow through the year, with relatively low flows during the winter and early spring, and maximum flows in late spring or summer. Bartlett (1965: 187) described how these variable flows influenced El Paso Valley agriculture in the mid- nineteenth century: “In February and March there is always enough for the first irrigation. In April and May the quantity is much diminished; and if the rise, expected to take place the middle of May, fails, there is not enough to irrigate properly all the fields prepared for it.” According to Kelley (1986: 119), increasing settlement, especially after the U.S. Civil War, changed the seasonal pattern of river flows associated with snowmelt: …as settlement grew, timber was stripped from the lower elevations. The denuding of timber allowed winter snows to melt prematurely, and their waters went into winter flow, being lost to the summer season. Prior to heavy settlement, the snows remained packed until the spring thaw.

Flow Data. The first systematic measurements of river flow did not begin until 1889, when the IBWC began to establish gaging stations.2 Thus, these data document flows after significant agricultural development had occurred along the upper Rio Grande and after logging had modified the snowmelt dynamics in the river’s watershed. Nevertheless, as Figure 2-1 shows, a late-spring flood still typified the annual flow cycle of the desert Rio Grande above the mouth of the Río Conchos.

A comparison of Figures 2-1a and 1b reveals two important differences. First, the peak flood at El Paso and the Upper Presidio gage appears to have shifted from May to June, and secondly, the figures illustrate the substantial decrease in discharge during this period. Whereas the average May discharge at El Paso between 1889 and 1895 was over 420 million cubic meters, in the years that followed it was closer to 260 million, and even the upriver discharge at San Marcial was only about 405 million cubic meters from 1895- 1914. Everitt (1998: 661) suggests that the changes at Presidio may have been caused by climatic factors and increasing diversions upriver. Agricultural diversions were significant: Kelley (1986: 119) estimates that between 1890 and 1893, more than half the summer discharge that should have reached San Marcial was lost to irrigation above that point. Below San Marcial, irrigation also reduced flows. IBWC data from 1896-1901 compiled by Kelley (1986: 116) shows that without irrigation, 14% of the San Marcial flow would have been lost to seepage and evaporation by the time the river reached El Paso (versus 38% lost when irrigation is included) and 35% of the San Marcial flow would have been lost naturally by the Upper Presidio gauge (versus 74% lost with irrigation).

The construction of Elephant Butte Dam brought an end to the late-spring/early summer flood along the Rio Grande between the dam and the mouth of the Río Conchos (Figure 2-2). As all the water in the reservoir belongs to the irrigation project (which ends in the El Paso Valley), “the flow reaching Presidio since 1915 consists of irrigation drainage, local storm runoff, and occasionally a ‘spill’ or surplus from upriver” (Everitt 1996: 661). Between 1916 and 1950, total annual flows through the Presidio Valley above the Río Conchos declined gradually (except for a high water period in the early 1940s); from 1951- 1969, winter flows were so low the river became “hydrographically disjunct” when flow events recorded at the Ft. Quitman gage never reached the Upper Presidio gage (Everitt 1993: 228-9).

2 The gaging stations along the desert Rio Grande were established at different times. Thus, in the figures that follow, the time spans covered by various gages differ.

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Figure 2-1. Average monthly discharge of the desert Rio Grande 1889-1915. “Upper Presidio” gage is located above the mouth of the Río Conchos. Data from Neel (1926: 204-209) and IBWC (1956: 7, 13). a). 1889-1894

450 400 El Paso 350 Upper Presidio 300 250 200 150 100 Mean Total Discharge

(millions of cubic meters) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

b). 1895-1915

450 400 San Marcial 350 El Paso 300 Upper Presidio 250 200 150 100 Mean Total Discharge

(millions of cubic meters) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

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Figure 2-2. Average monthly run-off of the desert Rio Grande for the ten years following construction of Elephant Butte Dam (1916-1925). “Upper Presidio” gage is located above the mouth of the Río Conchos. Data from Neel (1926: 209-212) and IBWC (1956: 7, 14).

500 450 San Marcial 400 El Paso 350 Upper Presidio 300 250 200 150 100 Mean Total Discharge

(millions of cubic meters) 50 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Elimination of the spring flood in downstream reaches was not the only effect of the closure of Elephant Butte Dam. Because of the scouring effects of the clear water released from the dam, in Las Palomas Valley, and to a lesser extent, in the Mesilla Valley, the river bed degraded, becoming about 0.6 m deeper in the first 15 years after the dam’s completion (Lagasse 1981: 32). Farther downstream, however, in the Presidio Valley, the overall reduction in flow along the river caused it to aggrade and decreased the width and depth of the channel through time, reducing the river’s capacity for carrying water and increasing flood frequency (Everitt 1998: 662). From 1 to 4 meters of sediments collected in the Presidio Valley between 1916 and 1977 (Johnson 1977: 10).

Below the mouth of the Río Conchos, the annual cycle of river discharge was substantially different from the reaches above, due to precipitation patterns in the watershed of this major tributary. While illustrating a shift to a late-summer peak below the Río Conchos, Figure 2-3a probably under-represents the magnitude of the earlier snow-melt peak that would have come down the Rio Grande from the mountains of Colorado and New Mexico under natural conditions; flow estimates compiled by Kelley (1986: 116, 118) suggest that without agricultural diversions above the Presidio Valley, summer flows at the Upper Presidio gage might have been 2 to 4 times the volume of those measured at the end of the nineteenth century. In addition to the shift toward a late-summer peak, the input from small tributaries and the Pecos and Devils rivers (which both empty into the Rio Grande below Langtry) allow the desert Rio Grande to gain water through Big Bend and the Lower Canyons (Figure 2-3b).

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Figure 2-3. Average monthly discharge of the desert Rio Grande 1896-1912. “Lower Presidio” gage is located just below the mouth of the Río Conchos. Data from IBWC (1956: 13, 17, 21-22, 28). a). 1896-1899

700 Upper Presidio 600 Lower Presidio 500

400

300

200

Mean Total Discharge 100 (millions of cubic meters) 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

b). 1900-1912

900 800 Lower Presidio 700 Langtry 600 Del Rio 500 400 300 200 Mean Total Discharge

(millions of cubic meters) 100 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Because the input from the Río Conchos is so significant to the Rio Grande through the Big Bend region and below, it is worth examining the effect of a series of dams which have been built within its watershed. Figure 2-4 illustrates the annual discharge cycle of the Río Conchos at a gage just above its confluence with the Rio Grande, following the completion of various dams along its length: La Boquilla Reservoir, with a capacity (about 3000 million cubic meters) slightly greater than Elephant Butte Reservoir, completed in 1913 and located 400 km upriver from the gauge; Francisco I. Madero Reservoir, with a capacity of about 350 million m3, completed in 1947 and located about 310 km upriver; and Luis L. Leon Reservoir, also with a capacity of about 350 million m3, completed in 1967 and located 180 km upriver (IBWC 1997: 16, 83).

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Figure 2-4. Average monthly discharge of the Río Conchos just above its confluence with the Rio Grande, 1896-1997. Data from IBWC (1956: 15-16 and 1956-1997: 16-18).

600 1896-1913 500 1914-1947 400 1948-1967 1968-1997 300

200

Mean Total Discharge 100 (millions of cubic meters) 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

As Figure 2-4 illustrates, in the past century, dam construction has not modified the general timing of peak flows on this river as drastically as Elephant Butte affected the Rio Grande above the Conchos; on the Río Conchos, a late-summer peak still occurs, though the total volume of flows has been reduced substantially. According to Madrid (1996: 20), completion of the Luis Leon Flood Control Dam has reduced overbank flooding to the point that traditional flood-water farming is no longer possible along the Rio Grande below the mouth of the Río Conchos.

Extent of Flooding. While illustrating general flow patterns, multi-year averages of total monthly flows as presented above mask other important characteristics of the hydrologic regime such as the duration and magnitude of overbank flooding at particular locations. Though such specific details from the mid- nineteenth century and before are rare, flooding was such a dominant feature of the river that early descriptions of the river did not have to be recording specific flood events to make mention of it: evidence of flooding could be recognized even during non-flood seasons. Although Espejo’s 1582-3 expedition traveled during the winter, a period of relatively low flow, Luxan (1929: 64) observed that the river near the mouth of the Río Conchos “…is three leagues in the widest part when it becomes swollen.” More than 150 years later, in 1747, residents of a village in this same area cited the potential for “destruction by annual floods” as one of the reasons they chose to build their village on higher ground above the floodplain (Kelley 1992: 120). A century later (in 1846) and more than 300 kilometers farther upriver, Ruxton (1973: 168) learned that “…in the season of the rains [the river in the El Paso area] is swollen to six times its present breadth, and frequently overflows its banks.” During cadastral surveys of township and range lines in New Mexico, surveyors noted that “trees show marks of overflow off 15 to 20 inches [38-51 cm]” near the river’s edge in Las Palomas Valley (Garrettson 1857: T17S R4W, Section 31), and while working northwest of Las Cruces, they observed “marks on cottonwood trees” approximately 0.8 km (half a mile) from the river indicating floodwaters about 0.6 m (2 feet) deep (Garrettson 1857: T22S R1E, Section 33). Even the floodplain soil held a record of flood history, as Parry observed in the El Paso Valley in 1854: “The body of the soil is sandy, but acquires a somewhat compact texture from the deposition of river slime, and is further enriched by the decaying vegetation that luxuriates on its moist bottoms…” (Emory 1987, vol. I, pt. 2: 7).

Such floods could make travel difficult, as Bartlett (1965: 217) observed when he entered Las Palomas Valley in 1851: “From the water marks on the trees, the river rises about four feet above its banks,

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inundating the bottom lands to the base of the hills which border them, and rendering the valley impassable.” Even when the whole valley was not inundated, travelers were sometimes delayed by high waters; seventeenth-century wagon trains sometimes had to wait for weeks to cross the river at El Paso in early summer or fall, but not at other times of year (Peterson et al. 1994: 73). In June 1849, Brockway reported that his journey to California was delayed at Doña Ana, where he waited several days for river to go down enough to cross (Brockway 1850). Similarly, in September 1855, Garrettson declined to run a survey line across Selden Canyon because: “This line will cross the river…three times in less than a mile and a half. The river is now high and we cannot cross it. I know of no crossing nearer than that at Mesilla, a distance of 25 miles below….I cannot continue this line further at present” (Garrettson 1855: T20S R1W, Section 32). To pave the way for later travelers, Hutton considered the potential effects of flooding when building a wagon road north of Mesilla in 1857: ….the line here follows up the valley for six (6) miles through a low, rich bottom, thickly studded with cornfields and intersected by numerous ascequias [sic] or irrigating canals. To avoid the injurious effects of rain and the frequent overflowing of the ascequias on the heavy loam portions of this route, it was found necessary for about three (3) miles to isolate the road bed by ditches on either side, and to raise the surface by the material thus excavated; also to construct bridges over five of the ascequias….These bridges were of the simplest description, having from eight to ten feet span, and consisting of cottonwood logs (obtained along the river bank) as stringers, and similar smaller ones as cross pieces, the whole being covered with a layer of earth eight inches deep. (Hutton 1859: 81)

Flooding associated with acequia overflow and soils saturated with irrigation water is only one example of how human activities may have influenced the floods of the desert Rio Grande. The frequency of floods apparently increased during the nineteenth and early twentieth centuries because the river channel became shallower as aggradation increased (Crawford et al. 1993: 20). Aggradation of the channel resulted from two factors: increased sediment loads coming off the heavily logged and grazed watershed and increased water diversions for agriculture, which reduced flows and made it more difficult for sediments to be carried away by the river (Sublette et al. 1990: 9, Scurlock 1998: 32, 188).

Channel Width and Depth. Heavy sediment loads entering the Rio Grande in the late-nineteenth century were associated with entrenchment, or deepening of the channel (i.e.: arroyo cutting) in the tributaries feeding the river. For instance, Sublette et al. (1990: 11) point to 1885 as the date that an 8.5 m deep arroyo began to form along part of the Rio Puerco, and a different “new channel” first noted along the Rio Puerco in 1899 was about 6 meters deep just seven years later (Scurlock 1998: 196). The relatively flat floodplain of the desert Rio Grande makes it somewhat immune to such deep channel formation, although along the outside edge of a meander corner, a cutbank forms, creating a steep bank on one side of the river. In addition, there are some description of fairly steep-walled channels along the river in valley reaches. For instance, in the El Paso Valley, Mendoza (1952: 321) wrote, in 1683 that “Below this cottonwood is found the watering place for the horse herd, there being no other, because the river has such high and steep banks. I crossed it with difficulty on the said day….” A mid-nineteenth-century traveler described similar deep channels in the El Paso Valley about 5 days travel below San Elizario: “The river, which we saw some miles back, was a little beyond with steep banks from 4 to 6 feet high” (Eccleston 1950: 125). Five days later, probably within 10 miles of San Elizario, the same traveler wrote, “Our road today lay along what is called Old River, an old bed, partially dry, of the Rio Grande. Part of the road would have been extremely dangerous to have driven at night. It sometime touched close to a perpendicular bank of some 10 or 15 feet” (Eccleston 1950: 130).

Given its dynamic flow regime and natural tendency to flood, it should come as no surprise that the river’s width and depth were highly variable. In the mid-nineteenth century, some accounts included estimates of the river’s width at various locations. Bartlett (1965: 187) recorded a relatively broad river, in the early 1850s, “[t]he river near [El Paso] varies in width from 300 to 600 feet [91.5-183 m].” A width within that range was noted by surveyors who observed that the river was “about 6 chains” (121 m) wide, perpendicular to its bank, in the Las Palomas Valley in August 1877 (McBroom and Shaw 1877: T17S R5W, Section 36). In October 1878, other surveyors measured channel widths of 142 and 112 meters, at Palomas and Ft. Selden, respectively (Wheeler cited in Ackerly 1998: 30). At the low end of Bartlett’s range, in July 1857 Humphrey noted that the river in the El Paso valley was 100 yards (91.5 m) wide

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(Lesley 1949: 67). A slightly narrower river was recorded about 5-days travel below San Elizario, in September 1849 “[t]he river was 50 to 100 yards [46-91.5 m] wide in some places, having two channels, and between islands of sand” (Eccleston 1950: 125). Still narrower records come from the winter of 1846. In November, near Valverde, Abert (1962: 127) recognized that the river’s flow was probably unusually low: “The river here is full of sand bars. At one place we plucked a reed, ‘arundo phragmites,’ and without difficulty threw it across the river, which at that place was not more than 50 feet (15.25 m) wide to the bar, but the water is now very low.” In December of 1846, Emory (1976: 55) observed that near Fra Cristobal Mountain, “[a] cross section of [the river] at this point is 118 feet (36 m) wide, with a mean depth of 14 inches [35.6 cm], flowing over large round pebbles, making it, at this point, unsuitable fo [sic] navigation with any kind of boats.”

Emory’s observation of a 14-inch depth is shallower than other depths recorded. In October 1878, surveyors measured depths of .64m and .67m at Palomas and Ft. Selden, respectively (Wheeler cited in Ackerly 1998: 30). When crossing one channel of the river to the island where San Elizario was located, Whiting, in April 1849, observed, “[t]he water was not more than three feet [0.92 m] at the most, and we readily crossed” (Bieber 1938: 303). Bartlett’s 1854 description (1965: 187) of the river’s minimum depth near El Paso was similar: “It is easily forded at El Paso, and probably for two thirds its length, the greatest depth of the water where it is crossed being from only two to three feet [0.61-0.92 m]. Still there are places, even near El Paso, where it is much deeper.” In a naturally meandering river, water depth varies along a reach at a given point in time, because deeper pools form at meander corners and shallower riffles occur at the inflection point where the river briefly straightens out before entering the next meander corner.

Surface Flow Disruptions. In a few instances, water depth was not a problem at fords, since the river had gone dry. For instance, Emory (1987, vol. I, pt. 1: 50) wrote, “I was informed, on good authority, that in the summer of 1851, a man drove a gang of mules along the bed of the river from the Presidio del Norte to El Paso. The bed was dry for nearly the whole distance….” It should be noted that such a drying of the river was a relatively extraordinary occurrence; in this case it was evidently caused by drought coupled with agricultural demands in the El Paso Valley. As Bartlett (1965: 187-8) explains, …during the summers of 1851 and ’52, there were [no spring floods]. The river not only did not swell or overflow its banks, but in the former year it became quite dry near El Paso, all the water being transferred to the acequias….In 1851 many large tracts of land near El Paso, which were planted in the spring, and through which irrigating canals were dug at great cost, produced nothing…at San Eleazario, twenty-five miles below El Paso,…the summer of 1852 was the first one in five years when there had been sufficient [water] to irrigate all the land of that vicinity…. In his compilation of historic droughts in New Mexico, Scurlock (1998: 40) identifies the years 1845-1847, 1849, and 1851-1853 as drought periods.

A handful of other examples of the river going dry are described in various sources; almost all match up with known drought periods. For instance, Pedro de Castadeña (1984: 341), a member of Coronado’s 1540-1542 expedition in northern New Mexico reported that a captain explored down the Rio Grande until he reached a point where “the river sank into the earth”; Bandelier (1976: 24) speculates this location may have been near modern Mesilla, and Scurlock (1998: 24) identifies 1542 as a drought year based on tree ring data. When summarizing the December 1683 journey of Fray Nicolas Lopez from El Paso to the mouth of the Conchos, Horgan (1954: 299) explains “The river fell lower and lower as they went until toward the end of their journey there was almost no water in it. But where the Conchos entered from Mexico the river sprang back to life again with renewed flow from the great tributary…”; Scurlock (1998: 40) lists the years 1681-1686 as a drought period. Follett (quoted in Ackerly 1998: 27-8) describes drying of the river in southern and central New Mexico in 1860 (or 1861), 1879, and 1889; all these dates fall within drought periods lasting from two to four years (Scurlock 1998: 40). Two other observations of a dry river above El Paso catalogued by Ackerly (1998: 27, 28)—in 1752 and 1894—followed 4 and 2 years of drought, respectively (Scurlock 1998: 40).

Significant periods during which the river dried up entirely began to intensify after the agricultural development of the San Luis Valley in Colorado at the end of the nineteenth century. During his pastoral visit to the Mesilla and El Paso valleys in 1902, Bishop Granjon lamented the effects of a consistently dry river on local agriculture: for instance, in El Paso, he observed: “The valley of the Rio Grande below

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Ciudad Juarez was previously rich and prosperous. For a number of years, because of a lack of water, cultivation has had to be abandoned, and the countryside presents a desolate aspect” (Granjon 1986: 105). In the 25 years from 1889-1914, the IBWC flow gage at Presidio recorded 34 months with zero flow in the river (Everitt 1998: 660). Much of the impetus for the creation of Elephant Butte Dam was provided by the need to store water during periods of heavy flow in order to make it available for agriculture at other times.

What has yet to be established is how regularly the river dried up, particularly before agricultural development usurped most of its flow. Some indirect evidence exists for consistently low flows in the stretch of the Rio Grande just above its junction with the Río Conchos. Early explorers in the region of La Junta de los Rios (the meeting of the rivers) encountered several settlements of indigenous people; as both Everitt (1977: 21) and Kelley (1992: 122) observe, almost all of these settlements were located either at the mouth of the Conchos, or downstream of its junction with the Rio Grande. Because of the location of its watershed, the Río Conchos has a more consistent flow, and Kelley suggests that these agricultural settlements may have been limited to certain areas by the rivers’ flows: “Hence, the flow of the Río Conchos is vital to irrigated farming in the area. Significantly, all the major La Junta pueblos of the historic period were located either on the Río Conchos or on the Rio Grande at and below the junction” (Kelley 1992: 122).

However, the preferred location for an agricultural settlement does not necessarily indicate that the Rio Grande was regularly dry above the Río Conchos; the timing of the flood peaks may have simply made downriver locations preferred because they facilitated crop ripening and made multiple crops possible. The agriculture in the vicinity of La Junta was evidently almost entirely based on floodwater farming instead of ditch irrigation; Everitt (1998: 663) states that the first widespread ditch irrigation in the Presidio Valley developed after 1900. In the mid-nineteenth century, Parry described both the hazards of the overflow method and its potential for double-cropping in La Junta region: Those places which are supplied with the necessary moisture by the overflow of rivers have a still more precarious dependence than those where irrigation is practiced. In these the quantity of water cannot be regulated, and they are exposed to the two extremes of scarcity or superabundance. One of the best examples of this system of cultivation is seen at Presidio del Norte, where the Concho unites with the Rio Grande. As these two rivers have different periods of high water the inhabitants are enabled to frequently secure two crops from the same fields in one season. In order to accomplish this the first crop, depending on the overflow of the Rio Grande, must be sown and harvested in time to admit of the planting of the second crop, depending upon the later rise of the Concho. All this depends on so many contingent circumstances that it is oftener attended by disappointment than by success, and, between the extremes of flood and drought, the people frequently suffer for want of food. (Emory 1987, vol. II, pt. 1, 15) Double-cropping was practiced by La Junta farmers as early as 1747 (Ydoiaga 1992: 82, 83).

The late-summer rise of the Río Conchos may have also facilitated the ripening of corn crops. Corn requires two periods of moisture to produce a crop—one during the germination period and one during fruit set (Peterson 1994b: 37). Madrid (1996: 18) suggests that Espejo’s sixteenth-century report of being fed ears of green corn in August at La Junta indicates a late-summer harvest by farmers in the region.

Because of the significant agricultural development that has existed in the El Paso Valley throughout most of the historic period, it might be expected that the river’s flow was disrupted more often below El Paso. However, occasional disruptions also occurred above El Paso. In a paper presented at the 1998 New Mexico Water Resources Research Institute Conference on Water Challenges on the Lower Rio Grande, Ackerly (1998) uses a variety of narrative accounts to argue that even before extensive agricultural use of water in the San Luis Valley of Colorado began, the river’s flow was highly erratic and at times ceased entirely in southern and central New Mexico. However, a point made by one of Ackerly’s quotes is that such cessations were not a normal enough occurrence to be expected with any regularity. Ackerly quotes von Humboldt’s 1811 description of a drying up of the river: “The inhabitants of the Paso del Norte have preserved recollection of a very extraordinary event which took place in 1752. The whole bed of the river became dry all of a sudden for more than thirty leagues [78 miles] above, and twenty leagues [52 miles] below the Paso [for several weeks]” (emphasis added; von Humboldt quoted in Ackerly 1998: 27). The

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high-lighted phrase, “very extraordinary,” would seem to suggest that such disruptions were not frequent events to be expected on a regular basis.

In addition to illustrating how uncommon a dry Rio Grande was, Ackerly (1998) makes a point of describing how patchy such cessations probably were; for instance, he includes Follett’s report of the river going dry for a thirty mile stretch somewhere between Albuquerque and the Mesilla Valley in 1894, noting that there was water both above and below that stretch (Ackerly 1998: 28). Biologically, it would seem that patchy disruptions of surface flow would mean that aquatic organisms might be able to move to and persist in areas where surface flows did not cease.

Patchy surface flow disruptions also suggest that the water table under the river was high enough to allow surface flow to reappear downstream of a disruption. Additional support for the idea that high water tables were maintained in the vicinity of a dry river bed comes from observations of standing and sub-surface water recorded in Emory’s Boundary Survey: In his Geological Report, Parry describes the river in the El Paso Valley, writing “Occasionally, in very dry seasons, it ceases to run altogether, and stands in stagnant pools.” (Emory 1987, vol. I, pt. 2: 7). When describing the 1851 flow disruption, Emory (vol. I, pt. 1: 50) notes, “The bed was dry for nearly the whole distance, occasional pools of water standing in places where the river-bed was formed of rock or clay, impervious to water. It was always possible, however, to procure water in sufficient quantities for drinking or watering animals by digging in the river-bed a few feet below the surface.” Such high water tables would also allow for maintenance of the various still water habitats found in the flood plain, such as ponds and marshes. Such habitats must have been significant to aquatic organisms during droughts; as Ackerly (1998: 30) explains, “The floodplain of the Rio Grande contained oxbow lakes that simultaneously formed refuges for many animal species during periods of low flow….”

Still-Water Features and Water Table The floodplain of the Rio Grande historically contained numerous marshes, swamps, oxbows and pools. In addition to providing evidence of channel shifting and flooding, such aquatic features also suggest a high water table within the floodplain. An early report of such habitats comes to us from the Gallegos’ account of the Rodriguez expedition in 1581, which encountered, in the valley below modern El Paso, “a valley of swamps, which extends over eight leagues [about 21 miles]” (Gallegos 1927: 23).

More extensive descriptions of such swampy habitats come to us from Espejo’s party, which traveled along the desert Rio Grande in 1582-1583. In 1583, Luxan (1929) noted four significant pools or marshes encountered by the party in the El Paso and Mesilla valleys: January 8, they name a site “La Cienaga Grande.” It is a “swamp is formed by the Turbio river [Rio Grande] when it overflows its banks. It contains an abundance of game such as ducks, geese, and cranes” (p. 68). January 9, they “…stopped at some pools near the river which are formed by it. We named this site Los Charcos del Canutillo. It was named Canutillo [reed] because there were numerous reeds and large marshes and pools with quantities of fish close by the river” (p 69). [Metcalf (1967: 32) locates these first two sites between modern Guadalupe and El Paso and assumes they represent the same location as the preceding Gallegos’ description .] January 15, 5 leagues (about 13 miles) farther upriver, they “…stopped at some pools which we named Las Salinas” (Luxan 1929: 70). January 16, another 5 leagues upriver, they “…reached a pool which is formed by the river when it overflows its banks: (p. 70).

Additional significant marshes were noted upriver from Selden Canyon. Luxan (1929) identifies two— “La Cienega Helada” [named “the frozen marsh” because the water was ice-covered when they arrived on January 23; p. 70] and “El Mal Pais” [named “the bad land” because of its proximity to bad lands; p. 72]— occurring along the stretch of the river below modern San Marcial. Later travelers catalogued additional marshes and ponds above the Mesilla Valley. For instance:

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an advance party of Oñate’s 1598 expedition encountered “…a marsh below a plateau of black rock near present-day San Marcial” (Sanchez 1987: 56); Cooke, in 1846, reported an apparent contradiction, finding “standing water in a dry slough…a quarter mile from the [camp]” somewhere in the vicinity of present-day Caballo, New Mexico (Bieber 1938: 97); in 1846, Abert (1962: 120) reported camping next to a small “bayou” just upriver from Socorro; Ferguson, traveling down the river in 1847 and camped about 3 miles above Fra Cristobal, noted having passed “salt marshes for the several past days” (Bieber 1936: 334); on Aug 29, 1849 Powell (1981: 102) said of their journey through Las Palomas Valley, “Our road lay in an arc close under the bluffs; the intermediate space between it and the river being a swamp or pond of very brakish [sic] water.”; Fort Thorn, established in 1853, was built along the edge of a marsh about 3 miles northwest of present-day Hatch (Fugate and Fugate 1989: 48); Eccleston (1950: 167) described a campsite in this same area in 1849 as being “…situated on skirt of a beautiful wood, at edge of which was a lagoon of good water”; and calling it the new settlement of Santa Barbara, Bartlett camped near this general area in 1851, explaining: ““We pitched our tents in a thick grove of large cotton-woods, near which passed the acequia; while on the opposite side was a pond or laguna, extending a mile or more. As this body of water was not wider than the river, and presented many sinuosities, I think it must have been formerly the channel of the Rio Grande….The laguna is now supplied by overflows from the river. There were many wild fowl in it; but its banks were so open, we could not approach the game” (Bartlett 1965: 217-218). Ohmart et al. (1975: 243) interpreted a similar description of a slough along the lower Colorado River that lacked vegetation along its shores as a slough that had only recently formed.

In contrast to the valley reaches, the confined canyon stretches of the river had relatively few marshes because of their topography. In fact, the relative paucity of marshes near the mouth of Selden Canyon may be why Ft. Selden was established there; military planners wanted to escape the malaria-carrying mosquitoes they were encountering elsewhere (Ackerly 1998: 30). Below Selden Canyon, in the Mesilla and El Paso valleys, nineteenth-century travelers noted additional aquatic features along the river. In 1807, Zebulon Pike found a “salt lake” near Montoya, just south of present-day Canutillo, Texas (Metcalf 1967: 32). In the El Paso Valley, downstream of San Elizario, Whiting reported that “in a small pond hard by our trail, we saw a flock of twenty-five huge white pelicans” and later that day, they “…came suddenly upon an old cut-off of the river; at the point we struck it, it was so boggy as to be impassable.” (Bieber 1938: 300-301) Also below San Elizario, another emigrant travelling in 1849 reported passing a series of ponds from September 5-7 (Eccleston 1950: 130-131). When his party first entered the El Paso Valley to the south, he observed, “It was extremely boggy, and I met a man leading his horse and carrying a shovel. He had to dig his horse out” (p. 125). Of the partially developed agricultural areas farther upstream, closer to El Paso, Eccleston (1950: 140) wrote “The farms (if I may so speak) are nearly all watered by ditches, through which is let, on and off at pleasure, the waters of the Rio Grande. There are a number of small lakes or ponds scattered about, where will be found large quantities of duck & some geese….” Near Las Cruces, Eccleston’s party camped at a pond about a mile (1.6 km) east of the river (Eccleston 1950: 160). July 29, 1857 Beale mentions camping at a water hole 1 ½ miles (2.4 km) from the river and 1 ½ miles (2.4 km) from Fort Fillmore (Lesley 1949: 171). In 1854, Parry reported that in the El Paso Valley, “[The lower portions of the alluvial strip along the river] are marked by frequent sloughs and river beds…[When the river floods] the various sloughs and lagoons that line its course [often cut] off all approach by land to the main channel” (Emory 1857, vol. I, pt. 2: 7). Edwards, marching with Doniphan’s Army in 1846, describes camping in a “fine rush bottom, the first we have seen in Mexico worthy of notice” at the northern end of the Mesilla Valley (Bieber 1936: 222).

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Edwards later describes camping “at a small pond called Alamitos” (p. 237), south of the Brazito Battlefield.

This same campsite below Brazito seems to be mentioned repeatedly in nineteenth-century accounts: Gibson (1935: 309-310), who was also with Doniphan’s Army, calls it “the lagunita” and says the water was “very brackish…we could not even make coffee fit to drink.” Another member of Doniphan’s Army, Hughes, describes a camp “near a salt lake” (quoted in Metcalf 1967: 135). In 1847, Susan Shelby Magoffin (1926: 203-4), described a camp in this vicinity rather negatively, writing, “Our camp is not on the River, but five or six miles [8-9.6 km] from it, in real Indian country. The place is called La Laguna, simply a saltwater pond, half grown over with reeds; gloomy looking mountains rear their heads in our rear and sides; the grass has been all camped off, and all together it is a gloomy place. The musquite [sic] thicket [is] all around us….” The location of this campsite was probably just south of modern Anthony: a Butterfield Overland Mail Station called Cottonwoods Station was established on a site previously known as “Los Alamos” in this area (Fugate and Fugate 1989: 32), and surveyors noted that “[t]he well know camping ground called the cottonwoods is on the east bank of the river...” where the line between Townships 26 and 27S crossed the river in 1857 (Garrettson 1857: T26S R3E, Section 34).

Similar pond and marsh habitats existed in the floodplain of the Presidio Valley. Parry described the river in this area as “forming frequent sloughs along its main banks, subject to regular overflows” (Emory 1987, vol. I, pt. 2: 50). In a description of the archeology of this valley, Kelley (1992: 259) describes the junction of the Rio Grande and Río Conchos: Both rivers meander through alluvial flood plains averaging about a mile in width. Both streams change their courses from time to time in their winding through this sandy lowland. The Rio Grande especially meanders in broad, twisting loops which are often abandoned to form sloughs and marshes….The low-lying flood plain was thus naturally irrigated and ideal for farming by primitive methods.

The frequent mention of brackish water and salt marshes above are matched by additional descriptions of various sorts of salt deposits by numerous authors; these reports are of interest because they may be indicative of a high water table, which would result in poor drainage and high salinity, but could also create and recharge non-riverine aquatic habitats. In the El Paso and Mesilla Valleys, Espejo’s party encountered at least three such areas: January 7, they arrived to “…a spot we named Las Salinillas. In this locality [4 leagues, about 10 miles, below “La Cienaga Grande” described above] there is abundant salty soil, and as we were short of salt we boiled some and obtained very fine salt” (Luxan 1929: 68). January 8, La Cienega Grande has “…large salines around it” (p. 68). January 15, halfway between La Cienega Grande and Las Salinas, they “…found some salines of white rock salt, wonderful beyond comparison, and very plentiful” (p 70). In the Presidio Valley of 1747, a salty plain was noted less than 14 leagues above the mouth of the Río Conchos (Ydoiaga 1992: 67).

Later travelers reported similar evidence of high salinity. Emory (1976: 48), describing the area around La Joya, wrote in 1846 “Now and then we came to spots from which the waters were prevented from escaping by the sand, and had evaporated, leaving saline incrustations; about these we found growing abundantly atriplex and salicornia [now known as pickleweed, Allenrolfea, according to Calvin (1951: 199)].” From an 1846 camp at the Bosque del Apache, Abert (1962: 122) reported that “[t]he road for many miles, in the latter part of our march, was covered with a deposit of saline substances which lay like new fallen snow….” In addition to the salt marshes described above, Ferguson reported that “…in many places the salt (or saltpeter) form[s] a thin, curling crust looking like snow” (Bieber 1936: 334). 42 miles below Socorro, Cooke (in 1846) noted that in the river bottom “…a white efflorescence…[is found] which is said to contain much carbonate of potash and to render the soil unfit for agriculture” (Bieber 1938: 88).

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In 1857, surveyors noted bottom land “covered with a white incrustation of alkali” NW of modern Mesquite, New Mexico (Garrettson 1857: T24S R2E, corner of sections 34 & 35). Similarly, the soil was “covered with an incrustation of salt” just north of modern Sunland Park, New Mexico (Garrettson 1857: T28S R 3E, section 36).

Many different processes may have contributed to the formation of a variety of still water features of the desert Rio Grande. Shallow, underlying bedrock can create marshes. Graf (1994: 102-3) describes how the basalt flow at San Marcial, which creates the narrows there, also affects groundwater flow, bringing it closer to the surface. Thus, prior to construction of a railroad embankment, much of this area was a backswamp and lake (Graf 1994: 196). A marsh was also described in this same location in 1598 by members of Oñate’s expedition (Sanchez 1987: 56), suggesting that in this sort of situation, the general location of backwater features might be fairly long-lived.

As explained previously, the small-scale changes associated with a meandering channel allow for the creation of oxbows when meander cutoffs develop. In addition, sloughs can form in depressions occurring in meander scrolls, topographically varied areas left behind as a meander migrates downriver and laterally (Leopold et al. 1992: 317). Sloughs can also form along valley walls where they are created by the scouring effects of high flood waters: many of the sloughs noted during township and range line surveys of the Mesilla Valley in 1857 were close to the edge of the valley (see Map 4, Garrettson 1857).

Large-scale channel shifting can also create still water features if abandoned channels remain connected to the main channel through sub-surface flow, if high water tables exist, or if periodic flooding recharges them. For instance, following the shift of the main flow of the Rio Grande out of the “Rio Viejo” channels near San Elizario in 1829, portions of the old channels contained sloughs and marshes (Peterson 1994a: 9). Because of evaporation and the deposition of sediments and organic debris, these sorts of still water features may be relatively short-lived; Ohmart et al. (1975: 250) estimated that similar sorts of backwaters which formed along the lower Colorado River in the mid- to late-nineteenth century lasted only 50 to 70 years. Hendrickson and Minckley (1984: 168) describe the marshes of desert rivers as “transitory communities” and note that because they are relatively short-lived, less organic material collects in these backwaters, creating less anaerobic conditions than in some other types of marshes.

Floodplain Vegetation The hydrology of the desert Rio Grande—including high water tables, a meandering, shifting channel, and periodic flooding—influenced the vegetation greatly, creating a dynamic mosaic of habitat types across the river valley. Some of the earliest systematic descriptions of the different types of floodplain vegetation come from biological studies completed in the El Paso and Mesilla valleys near the end of the nineteenth century. [Note: Because the systematics of some of the plant taxa (particularly the cottonwoods and willows) have changed significantly since these accounts were written, many of the names provided by these authors do not agree with currently accepted taxonomy, but the old names are provided to accurately portray the vegetation as these authors understood it.]

Between 1892 and 1894, Mearns recorded vegetation characteristics at mammal survey stations in the El Paso Valley. Near Ft. Hancock, he noted “Lines of cottonwood and willow mark the shifting courses of the river….The river flats are occupied by dense patches of arrowwood, flanked by the tornillo or screwbean and mesquite” (Mearns 1907: 77). Of the area around the Belen Station of the Southern Pacific Railroad (northwest of Socorro, Texas), he wrote: It is largely irrigated and under cultivation….The Rio Grande and irrigation acequias are lined with the almondleaf willow, Fremont cottonwood, arrowwood, and Baccharis; the rich bottom land, where uncultivated, supports a luxuriant growth of mesquite and tornillo, or screw bean; and green orchards, gardens, and fields of grain and alfalfa are situated between the river and the canal. (p. 79) For El Paso he explained “As usual, the river is bordered by a line of cottonwoods and willows, with arrowwood, Baccharis, screw bean, and mesquite covering the adjacent land” (p. 80).

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An undergraduate thesis written at what is now New Mexico State University provides greater detail about turn-of-the-century vegetation in the Mesilla Valley. In it, Metcalfe (1903) identified 5 distinct plant zones arrayed across the river bottom: Baccharis zone occurred on impermanent sandbars in and along the river, often flooded by one to several feet of water in spring. The seepwillow (Baccharis glutinosa) shrubs were 5 to 12 feet tall, and sometimes grew so densely “as to make walking through it rather laborious” (Metcalfe 1903: 5). Nevertheless, some annuals grew in understory. Populus and Salix zone was next to the Baccharis zone and included the cottonwood Populus fremontii Wislizeni and the willow species Salix nigra and S. interior, according to Metcalfe (Metcalfe’s cottonwood and willow species probably correspond to P. deltoides ssp. wislizeni, S. gooddingii and S. exigua of current taxonomy; see Carter 1997: 322, 324, 405). In a few places the cottonwoods and willows were so dense that the cover excluded all other vegetation including salt grass (Distichlis spicta). The cottonwood-willow zone intergraded with zones on either side and was characterized by “[a]lmost constant surface moisture…” but not severe enough flooding to disrupt first-year trees and shrubs (Metcalfe 1903: 14). Metcalfe claims that tornillo (Prosopis pubescens) could grow in this zone, but that it was probably outcompeted by the cottonwoods and willows. Tornillo zone was “[c]onfined to old river beds or deserted flood plains…”(Metcalfe 1903: 7). It covered thousands of acres, and its typical growth was dominated almost entirely by tornillo (also known as screwbean) and salt grass. It grew on what was probably the best soil for agriculture, but most agriculture occurred in the Cachanillo zone. Tornillo soil was drier and less alkaline than that of the Populus-Salix zone Cachanilla zone occurred 5 to 8 feet above the tornillo zone and was dominated by arrowweed (Tessaria sericea, now known as Pluchea sericea), with Sporobolus wrightii. Scattered honey mesquite (Prosopis glandulosa), saltbush (Atriplex canescens) and cottonwoods also occurred in this zone. Dondia zone was characterized by a small, salt-tolerant plant (D. sufrutescens), now known as seepweed or sea-blight (Suaeda; see Powell 1988: 136-138). The zone was a narrow, broken strip of land where the floodplain met the mesa, “and where all of the salts leached out of these first hills or mesas seems to come to the surface” (Metcalfe 1903: 8). Again, scattered saltbush and honey mesquite occurred in this zone.

Cottonwood-Willow Stands. Mearns (1907) and Metcalfe (1903) were not the first people to describe the river-edge distribution of cottonwoods and willows: many early travelers noted the same thing. Upon reaching the Rio Grande in the El Paso Valley, a member of Oñate’s 1598 expedition described “the pleasant shade of the wide spreading trees which grew along the river banks” (Villagra 1933: 126-7). In the lower El Paso Valley, Beale reported that “we came in sight of a grove of cotton-woods, which mark the line of the river” (Lesley 1949:169). The cottonwoods lining the river near El Paso “extend[ed] a few hundred yards on each side of the banks” in 1846 (Ruxton 1973: 168). Where the river passes through the narrows between the Mesilla and El Paso valleys, Magoffin (1926: 204) observed, in 1847, that “cottonwood trees and willow bushes [are] scattered along [the river’s] banks.” In the Mesilla Valley, near Brazito, Gibson (1935: 300) noted, in 1846 “a little timber and mesquite along the banks of the river….” Hutton (1859: 86) in 1857 described the banks of the river through the Mesilla Valley as being “well timbered with cottonwood.” Farther north, near Valverde, in 1846 “The timber extends half a mile from the river, and the cotton-wood trees are of large size, without any undergrowth of bushes.” (Ruxton 1973: 174). Also in 1846, Wislizenus (1969: 37) described the area just downstream of Valverde, writing “Along the river spreads a broad seam of cotton timber….”

The distribution of these river-edge forests was largely determined by hydrologic processes and the geomorphology of the river bottom. The sexual reproduction of cottonwoods and willows is closely tied to seasonal flooding, as both produce seeds which germinate and grow best in open, moist areas (Howe and Knopf 1991: 218). Fremont cottonwood (Populus fremontii) growing along the Salt River in central Arizona release their small, windborne seeds from mid-April through mid-June, with a peak in mid-May; the timing of this peak corresponds with the end of the spring snow-melt flood on the Salt River (Fenner et al. 1985: 137). Because Fremont cottonwood seeds have a short period of viability (about 5 weeks under typical natural conditions) and require a moist soil surface for germination (Fenner et al. 1984: 57-58,

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Stromberg et al. 1991: 225), seedlings often appear as a spring flood diminishes. However, even in years without a large spring flood, germination can occur on deposits left by floods in previous seasons if sufficient rainfall occurs during the spring (Stromberg et al. 1991: 230).

Willows also release small, windborne seeds, although typically, they are thought to have shorter periods of viability than cottonwoods (Moss 1938: 532). In addition, willows generally occur on finer-textured soils, whereas cottonwoods are found more often in soils with coarser textures (McBride and Strahan 1984: 236, Graf 1994: 102). McBride and Strahan (1984: 243) argue that, at least in their study area in California, this distributional pattern occurs because cottonwoods have an earlier period of seed release than willows, which coincides with higher flows. Thus, when cottonwood seeds are released the only potential germination sites that are exposed are areas with larger substrates on the higher parts of gravel bars, whereas willow seeds are released during lower flows when sandier substrates on the lower portions of gravel bars are exposed and are the only ones wet enough to allow for seed germination (McBride and Strahan 1984: 243). Stromberg et al. (1991:231) noted that Goodding Willow (Salix gooddingii) seeds were dispersed and germinated later than Fremont Cottonwood seeds in central Arizona, resulting in willow stands at lower elevations, closer to the stream.

The germination requirements of cottonwood and willow seeds place them in a paradox. The best sites for seed germination also are often the sites most susceptible to scouring during subsequent floods, which can reduce the likelihood of establishment (Asplund and Gooch 1988: 20, Segelquist et al. 1993: 283). Two characteristics of willows may reduce some of the risks associated with later flooding: they are more tolerant of inundation than cottonwoods (McBride and Strahan 1984: 243, Stromberg et al. 1991: 231) and the stems of some species are more flexible than cottonwood saplings, which makes them less likely to break or be uprooted during flood events (McBride and Strahan 1984: 244). For cottonwoods, areas near the dry end of the moisture gradient of the riparian zone and microsites safe from scouring tend to be the most likely sites for long-term establishment (Asplund and Gooch 1988: 20, Segelquist et al. 1993: 283). Scouring is relatively rare at microsites such as alluvial fans created by tributaries (Scott et al. 1996: 337), in areas near stream constrictions, and in secondary channels or backwater areas (Asplund and Gooch 1988: 21).

Some modes of asexual reproduction may help to compensate for the germination vs. establishment paradox outlined above. Although the production of new shoots from root suckering can be difficult to document (Rood and Mahoney 1990: 456), it does appear to occur in many species, including cottonwoods. Irvine and West (1979: 342) found that root suckers from P. fremontii were the only way cottonwoods were becoming established along the lower flood terraces of the Escalante River in southern Utah because the suckers were more resistant to scouring than free-standing seedlings. Along the Middle Rio Grande, Howe and Knopf (1991: 221) documented reproduction by root suckers among Rio Grande cottonwoods; in this instance, old trees produced suckers during years of relatively low flows. In addition to producing suckers from roots, poplars can typically resprout from stem tissues that get buried by sediments; in North Dakota, such sprouting from flood-trained saplings can result in clumps containing more than a dozen trees (Everitt 1968: 424).

The germination vs. establishment paradox, coupled with a variety of geomorphic processes, probably resulted in several different types of cottonwood and willow stands along different reaches of the desert Rio Grande. Scott et al. (1996) identify three different geomorphic processes that can lead to cottonwood and willow establishment: meandering, channel narrowing, and flood deposition. Each of these processes results in a different relationship between flow regime and establishment, and each results in a different type of stand (Scott et al. 1996: 328). Because all three processes typically occur along a variable stretch of river alternating between canyon and valley reaches, and because each reacts to flow regimes differently, the relative importance of each will vary spatially and temporally (Scott et al. 1996: 336).

A meandering channel moves gradually across the floodplain, with most deposition occurring on point bars during moderate flows. Because of the gradual movement of the channel, resulting stands tend to occur in even-aged bands parallel to the direction of flow, and flood-trained stems (bent in a downstream direction by high flows occurring after establishment) are often evident because point bars may be inundated during floods following establishment (Scott et a. 1996: 330). Point-bar stands were probably most common in

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the unconstrained valley reaches of the desert Rio Grande. For instance, while establishing township and range lines in the Mesilla Valley, surveyors encountered the river where its direction of flow shifted from south to west, describing the vegetation as “a point of willows” with “a few cottonwoods” (Garrettson 1857: T 22S, R 1E, section 33). Another description that may refer to a point-bar stand comes from Emory (1976: 49), who described a camp near La Joya as “…one of the prettiest of the whole march, on the curve of the river, fringed with large cottonwoods growing at intervals.”

The second geomorphic process which can result in cottonwood and willow establishment is channel narrowing, which can occur both within a channel that has been abandoned after an avulsion event and along the edge of an active channel following major flood-induced widening or during several years of reduced flows (Scott et al. 1996: 328). The stands that result usually are not even-aged as establishment may occur over several years, and they tend to have an irregular shape that roughly parallels the direction of flow in the channel (Scott et al. 1996: 329). Trees rarely show evidence of flood-training since they establish in areas away from the currently active channel or during periods of low flow. Stands of this sort may have been noted during the 1857 surveys of the Mesilla Valley, when cottonwoods were noted along dry channels near modern Mesquite; some of these channels were so narrow they reminded the surveyors of irrigation canals (see Map 4, Garrettson 1857: T 24S, R1E, section 36; T 25S, R1E, sections 12 and 13).

The final geomorphic process that can lead to cottonwood and willow establishment is flood deposition, which follows periods of high flows and it is particularly important for cottonwood establishment along constrained channels where significant lateral movement of the channel cannot occur (Scott et al. 1996: 330). In narrow valley or canyon reaches, the only sites out of the reach of later scouring floods are sites well above the channel; thus in such locations, small, even-aged stands may occur in which the trees rarely exhibit flood-training (Scott et al. 1996: 330-331). Although he did not mention the vegetation growing on the site, Hill (1901: 163) did describe camping on such a flood deposit in a canyon just below the Presidio Valley: “…we were glad to camp in a narrow bank of sandy silt between the river and its walls.”

Because of the spatial and temporal variability built into the geomorphic processes and the plant reproduction dependent upon them, a continuous ribbon of cottonwood and willows did not occur along the river; specific mention of groves of trees or patchy distributions were common in the early accounts. In 1846, nine miles below the mouth of the Rio Puerco, Abert (1962: 120) camped “under a large grove of cotton wood trees.” Johnston (1848: 570) “[e]ncamped opposite La Jozin [La Joya], in a pleasant grove of cottonwoods” in 1846. Cooke (in 1846) camped in “an open grove of the river bottom” about 28 miles downstream from Socorro (Bieber 1938: 87). Near Fra Cristobal, an abandoned wagon was left “standing near a little woods” in 1847 (Magoffin 1847: 196). In 1851, Bartlett camped 8 miles upriver from the San Diego crossing, in “a beautiful grove of cottonwoods” (Bartlett 1965: 216). In the southern end of the El Paso Valley, Eccleston (1950: 131) described a day’s travel, “The country was handsome which we passed, part being a forest of large trees.” In 1582, Luxan (1929: 64) described the three-league wide floodplain near the mouth of the Conchos as a “plain….covered with numerous groves of poplars and willows…” The Presidio Valley of the mid-nineteenth century was still “…variously occupied by scattering growths of cotton-wood, willow, [etc.]” (Emory 1987, vol. I, pt. 2: 50).

Occasionally relatively untimbered stretches were noted. Abert’s party, while staying at Valverde for a few days in 1846, started in a fairly open area, but then shifted their camp “to a more sheltered position where we had plenty of cotton wood trees” (Abert 1962: 128). Also in 1846, Ruxton described the area near San Antonio, 10 or 12 miles north of Fra Cristobal, noting “The river is but thinly timbered here, the soil being arid and sterile…” (p 183). In 1849, in an unsettled part of the El Paso Valley (south of San Elizario), one party traveled through an area where trees were sparse enough that they “stopped [at noon] under a large cottonwood tree, whose grateful shade was pleasant indeed” (Eccleston 1950: 128). Describing an 1846 campsite across from La Joya, Turner (1966: 78) wrote: “…encamped immediately on the bank of the river….A few cotton wood trees stand about our present camp.”

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In addition to having a patchy distribution, cottonwood-willow stands were variable in terms of tree density and size, as well as the amount of undergrowth found in them. A few descriptions of dense stands exist. In 1747, a scouting party reported that the cottonwoods along the river near the lower end of the El Paso Valley (or perhaps in one of the small valleys downriver) were dense enough to make it “possible to hide a detachment of soldiers” (Ydoiaga 1992: 71). In the El Paso Valley below San Elizario, Whiting noted that “This trail lies through a fine tract, heavily timbered—the trees are very large” (Bieber 1938: 302). In 1854 Bartlett (1965: 186) wrote: “The Rio Grande Valley near El Paso, and generally in other places, is thickly timbered with cotton-wood. The trees sometimes grow to a large size.” Large trees were also noted near the mouth of the Río Conchos in 1849: “Nearly opposite the Mexican town we passed a fine part of the valley where the mesquite, the willow, and cottonwood abound in size” (Bieber 1938: 289).

In some areas, travelers noted the absence of any undergrowth under the cottonwoods. Camped south of Limitar with Doniphan’s force, Gibson (1935: 291) observed that “the river bottoms look more like an apple orchard in ‘the states’ than cottonwood groves, this being the only growth.” Later, Gibson described the cottonwood grove at Valverde as “a pretty grove like an old orchard, the trees about as close” (p. 293). Also camped at Valverde in 1846, Ruxton (1973: 178) noted that the large cottonwoods grew “without any undergrowth of bushes.” In the early 1850s the river bottom in vicinity of Las Cruces, had “but little shrubbery” (Bartlett 1965: 200). During his northbound, 1849 journey, Whiting’s description of the “heavily timbered” tract below San Elizario continued, “We saw nothing of the southern chapparal and undergrowth to impede us” (Bieber 1938: 302).

The open groves in the descriptions above were generally in or close to settled areas. In between these more populated areas, a few descriptions of more extensive undergrowth were noted in the mid-nineteenth century. Camped a few miles upstream from Fra Cristobal, Ferguson wrote “Our encampment tonight is at the edge of a large brake, or thicket, of cane grass intermixed with willow twigs and cottonwoods, so thick as to be almost impassable” (Bieber 1936: 334). Johnston (1848: 573) wrote of “a dense thicket of willows” near the base of Fra Cristobal mountain. Beale, near the southern end of the El Paso Valley in 1857, observed, “We found the river after groping some distance through a dense undergrowth of weeds, briars and willows...” (Lesley 1949: 169).

Mesquite and Screwbean. Some of the undergrowth of the river bottom was found in areas dominated by tornillo and honey mesquite. South of La Joya, a member of Doniphan’s force noted that “Mesquite bushes and chamiso [saltbush] have made their appearance…” (Gibson 1935: 291). In 1846, Ruxton (1973: 171) described the vegetation in the Mesilla Valley as “cotton-wood, dwarf oak, and mezquite, under which is a thick undergrowth of bushes.” In 1857, a chronicler of a military expedition exploring the feasibility of using camels in the desert southwest noted at a campsite near Ft. Fillmore: “Grass indifferent; mesquite wood abundant, especially a kind of which the camels are particularly fond, the fornia [tornillo] or screwbean” (Lesley 1949: 171). In anticipation of the Battle of Brazito, Edwards wanted to hide horses “…in the chapparal, or thick mesquite bushes (which somewhat resemble locust but stunted)…” (Bieber 1936: 228). During township and range line surveys near modern Berino in the lower Mesilla Valley, surveyors encountered an undergrowth of dense “mezquite, cottonwood, and other bushes in great abundance. They form quite an obstruction to our progress” (Garrettson 1857: T25S R3E, section 32). About 7 leagues (18 miles) above the mouth of the Conchos, Luxan (1929: 65) noted: [t]his river is lined mostly with trees resembling tornillo trees which produce a fruit like harquebus screws, yellowish in color, which has in between the twists some small seeds similar to those of a prickly pear. On this other bank of the river, on the hills, there is a quantity of small mesquite plants all along the river, so abundant that we no longer carried anything in our pack saddles but fodder. Describing the river bottom below Santa Elena Canyon in 1852, Chandler noted: “There is an abundance of cottonwood and mezquite timber” (Emory 1987, vol. I, pt. 1: 83). Michler, describing the Rio Grande near the mouth of the Pecos River in 1856, wrote “…a narrow strip of soil is then occasionally found at the base of the rocks, and gives growth to some fine live-oak and mezquite trees” (Emory 1987, vol. I, pt. 1: 78).

As in cottonwoods and willows, mesquite seeds may be dispersed to potential germination sites during floods (Horton 1977: 174), but mesquite seeds can remain viable for many years (sources in Siegel and

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Brock 1990: 7). In addition, mesquites may be less dependent upon moist conditions for germination and growth than cottonwoods and willows (Cleverly et al. 1997: 12, Siegel and Brock 1990: 6). Thus, mesquite bosques can form on terraces above the active river channel (Minckley and Clark 1984: 26). Such a mesquite stand was noted in the canyon country just below the Presidio Valley, in 1901: “In places, patches of fine white silt form bordering sand bars; about 25 feet above these there is a second bench, covered by a growth of dark-green mesquite. The whole is inclosed by vertically steep, jointed rock walls” (Hill 1901: 163).

Grasses and other plants. As the accounts compiled in the previous section illustrate, many of the plant descriptions recorded by early travelers and explorers related to plants potentially useful as sources for food, shelter, or firewood. This sort of notation of vegetative features important to travelers (and their domesticated animals) is prominent in Mendoza’s itinerary of an ecclesiastical journey from El Paso to the mouth of the Río Conchos made in 1683. For instance, he described “a thick-trunked cottonwood” as a landmark for reaching a watering hole at an early stopping point along the journey (Mendoza 1952: 321). In addition, at least 10 sites with good meadows and wood sources along the south side of the Rio Grande between El Paso and the Río Conchos were noted (pp. 321-324). Not all explorers agreed with Mendoza’s assessment of the pastures along the river: in December of 1747, Ydoiaga (1992: 66) complained about the poor quality, “hard grasses of a wide leaf that makes a straw if tightly twisted” found in the floodplain above the mouth of the Río Conchos.

Nineteenth-century travelers were also concerned with locating good forage for their horses and the stock travelling with them. In many places the grass was scarce in the river bottom; for instance, in the spring of 1849 Whiting observed that in the southern end of the El Paso Valley, “the grass is generally poor” and the bottom “[is] nearly destitute of grass” (Bieber 1938: 301). After camping in that same grass-poor area in the fall of 1849, Eccleston moved to a camp upstream of El Paso and enthusiastically described a camp where “The freshness and verdancy of the pasture make our worthy cattle laugh…” (Eccleston 1950: 157). A few years later, Bartlett (1965: 196) noted a similar increase in grass cover above El Paso: The bottom lands [near El Paso] are not grassy, as many suppose, but are entirely bare, save in isolated spots; hence it is necessary to drive mules and cattle to these hills and valleys to feed. There are, however, some portions of the higher valley about Frontera [8 miles above the diversion dam at El Paso] where grazing is to be found. Farther up the Mesilla Valley however, Bartlett noted that “a large portion of this rich bottom is destitute of grass” (p. 200). Along the river in the Las Palomas Valley, Bartlett observed “more grass than we had seen since leaving El Paso….There was excellent grass here, and in great abundance” (p. 216). In 1857, Hutton (1859: 86) contrasted the “coarse” grass of the floor of the Mesilla Valley with the “excellent” grama grass of the slopes above it; Leopold (1951: 308) suggests that the coarse grass reported in some river bottoms may have been “fine-topped sacaton [Sporobolus sp.] , which is harsh when dry.”

Other grasses and grass-like plants were noted by some other travelers. For instance, a grass with above- ground runners caught the attention of Ferguson, who in 1846 “noticed a singular kind of grass running along the ground from twenty to fifty feet like a vine, having joints about six inches apart, from nearly every one of which a straight shoot springs up a foot and takes root in the ground. I have heard no name for it” (Bieber 1936: 334). A member Doniphan’s 1846 expedition wrote as they neared El Paso from the north, “After an advance of 15 miles camp was selected near a salt lake, where there was a moderate supply of natural forage, such as grass and rushes” (Hughes quoted in Metcalf 1967: 19). Rushes were also described near an 1846 campsite 13 miles south of Doña Ana, where “a fine lot of rushes” grew between the river and “a thick piece of timber” (Bieber 1936: 224), and they were woven into the walls of temporary shelters built by Abert’s party at Valverde in 1846 (Abert 1962: 128). At Valverde, Abert (1962: 127) also mentioned “a reed, ‘arundo phragmites’.” Probably referring to the same species, Mendoza (1952: 325) noted one area with “dense canebrakes” near the mouth of the Río Conchos in 1683, and near the north end of the Mesilla Valley, surveyors described a swamp where the “[g]rass is very coarse, it is 8 feet high in this swamp” (Garrettson 1857: T21S R1W, section 25).

Aside from these occasional mentions of reeds and rushes, the early accounts record relatively few of the plants associated with various pond and marsh habitats of the river’s floodplain. The earliest extensive list of such plants comes from 1930, when Fosberg (1940: 584-593) listed 19 species of plants he collected in a

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variety of wet habitats of the Mesilla Valley, in addition to 24 species occurring on ditch and river banks (Table 2-1): these included aquatic plants such as duckweed (Lemna minor) and pondweed (Potamogeton sp.), as well as emergents like cattails (Typha angustifolia), rushes (Juncus balticus), a variety of sedges (Cyperus, Eleocharis, and Scirpus spp.), and horsetails (Equisetum hyemale).

Table 2-1. Plants collected in relatively mesic microsites of the Mesilla Valley in 1930 (from Fosberg 1940: 584-593).

Plants listed as occurring within wet areas, sloughs, Non-woody plants listed as occurring on canal, ditch, canals, or ditches and river banks Typha angustifolia Equisetum hyemale var. robustum Potamogeton interior Paspalum distichum Najas guadalupensis Setaria lutescens Lophotocarpus calycinus Sporobolus contractus Imperata brevifolia Sporobolus flexuosus Muhlenbergia asperifolia Anemopsis californica Distichlis spicata Atriplex argentea Cyperus speciosus Ranunculus cymbalaria Cyperus esculentus Potentilla anserina Eleocharis montana Glycyrrhiza lepidota Scirpus americanus Strophostyles helvola Scirpus aculus Gaura podocarpa Scirpus paludosus Centaurium calycosum Lemna minor Apocynum sibiricum var. salignum Juncus balticus Lycopus americanus Rumex mexicanus Grindelia squarrosa Sitilias multicaulis Haplopappus heterophyllus Aster spinosus Aster parvulus Helianthus ciliaris Aster exilis Aster tanacetifolius Psilactis asteroides Gnaphalium chilense Bidens vulgata Helenium microcephalum

A handful of nineteenth-century travelers made note of other types of vegetation in their journals. The most extensive plant list comes from Emory’s journal from 1846 (Emory 1976), in which he documented his initial observation of several different species during his southbound journey (Table 2-2). In addition, in 1846, between La Joya and Socorro, Abert (1962: 120) observed “…mistletoe that grows so abundantly on the cottonwood, and is called ‘bayote de alamo.’ The cockle burr and sand burr are very abundant, so much so, as to annoy us….” In the Presidio Valley, Parry observed that “…the flora partakes a character of that of Mexico, and more tropical forms prevail. We find here Kallstroemia grandflora, Martynia violacea, M. arenia, Talinopsis frutescens, Nicolettia Edwardsii, and several special of Boerhavia. Cereus Greggii is quite common, and the delicious fruited Cereus stramineus grows in its greatest perfection” (Emory 1987, vol. II, pt. 1: 14). Near the mouth of the Pecos River, Michler noted that “grape-vines flourish in abundance, yielding a very palatable fruit” (Emory 1987, vol. I, pt. 1: 78).

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Table 2-2. Plants recorded along the Rio Grande by Emory (1976) in 1846.

General Location Plant Descriptions Notes (p. 48) Calvin (1951: 199) La Joya “atriplex and salicornia” identifies the latter as Allenrolfea (p 199). “lycium in great abundance, senecis longilobus, La Joya martynia proboscidea, (cuckold’s horns), and a (p. 49) small shrub with a flower like convolvus.” “reed grass, and a short salty grass, uniola Socorro (p. 52) distichophylla” “One or two large white cedars were seen today, and in addition to the usual plants, was that (p. 53-4) Calvin (1951: 200) rare one cevallia sunuata, gauva parviflora, Valverde identifies white cedar as alligator oenothera sinuata, and a species of wild juniper. liquorice, but with a root not sweet, like the European kind.”

Qualitative Descriptions of Changes in Vegetation Along some stretches of the river, human impacts may have begun to have significant impacts on natural environments even before the coming of the Spanish in the sixteenth century. Using the riparian habitats in Chaco Canyon (in northwestern New Mexico) as an example, Sublette et al. (1998: 9) argue that pueblo- dwelling cultures along the Middle Rio Grande could have negatively impacted such habitats through activities such as wood gathering and irrigated agriculture. In the Presidio Valley, native farming settlements also impacted the environment through the practice of burning their agricultural fields to clear them for planting. In December of 1747, Ydoiaga (1992: 65) asked residents to be more careful in tending such fires because they were reducing the amount of forage available for horses and mules. Madrid (1996: 19) suggests that these fires may have affected the ecology of the Presidio Valley by suppressing the growth of some shrubs, while favoring fire-adapted grasses.

Conversion of river-bottom habitats to agricultural fields obviously reduced the acreage covered by natural vegetation and it may be that certain types of vegetation were more susceptible to conversion than others. In 1903, Metcalfe (1903: 3, 7) noted that in the Mesilla Valley, the Cachanilla zone, found on higher ground and dominated by arrowweed and grasses, was the habitat type most impacted by agriculture. Similarly, based on observations made in 1930, Fosberg (1940: 580) noted that agriculture had probably displaced the grass Sporobolus airoides as the dominant plant of the river valley. Such open, grassy areas may have been preferred for agriculture because they were relatively easy to cultivate. Early in the twentieth century, Nelson and Holms (1914: 28) explained that some of the fine sandy soils deposited by the river in the Mesilla Valley would have been good for agriculture, but relatively little was under cultivation because of “the difficulty frequently encountered in clearing the land of willow and other brush.” When some of these same soils were carried from the river’s edge by wind and deposited elsewhere, their use was made difficult by the need to level the soil before cultivating it (Nelson and Holms 1914: 34). Similar limits to agricultural development were noted elsewhere in the southwest: A 1904 soil survey along the Gila River in Arizona reported that “a small proportion of the Pecos sand is at present cultivated, mainly because of the difficulty and expense of clearing off the willow, cottonwood, and mesquite, and leveling the land for irrigation” (Lapham and Neill quoted in Burkham 1972: G12).

Regardless of whether the clearing was accomplished for agriculture or simply by wood-cutting for fuel and construction needs, by the mid-nineteenth century, it was evident that centuries of intensive settlement had impacted the riparian forest along the Middle Rio Grande. At a camp near the mouth of the Rio Puerco, Turner (1966: 77) noted, in 1846, that trees were a rare and valuable resource: The country along this part of the Rio Del Norte resembles very much that on the Platte and Arkansas rivers—the sand hills showing on either side of the river, and the valleys between the bluffs about the same in width. There is little or no timber on the Del Norte: perhaps less than on either of the above mentioned rivers. There is great difficulty in obtaining sufficient fuel for

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cooking purposes—in some the men have to go a distance of several miles to obtain a handful of wood. Occasionally see a grove of cotton wood which is preserved with great care, as it furnishes the only material with which carts for the whole country are made. These groves are always on private property.

Turner’s observation about the lack of trees on the Middle Rio Grande was echoed by other southbound travelers in the mid-nineteenth century. Like Turner, Abert (1962: 119) noted that trees became more abundant below La Joya: “From Joya we observed quite a change in the appearance of the country. The river banks are now heavily timbered with cotton wood; the high sand bluffs close in to the river, and the climate has become much milder….” Before reaching Socorro, Emory (1976: 51) linked the lack of settlement with an increase in trees: Yesterday and today we came across some unoccupied strips of ground. Their number yesterday was greater than to-day; for, since we passed Pulvidera, the sand-hills encroach on the river and leave the valley scarcely a mile wide. The cottonwood, however, is getting more plentiful, and we have not been obliged to use the ‘bors de vache’ in cooking for some days. [Calvin (1951: 200), in annotations of Emory’s journal, identifies ‘bors de vache’ as the French term for dried buffalo or cow dung used for fuel]. For Cooke, a noticeable increase in timber became evident along the river downstream of Socorro, “We rejoice once more in plenty of fuel and good fires; for the last twenty-five or thirty miles the timber on the fine wide bottoms of the river has been quite a striking feature in the landscape…” (Bieber 1938: 87).

Cottonwood stands were also impacted elsewhere along the desert Rio Grande. In the limited valley reaches of the Big Bend region, cottonwood trees “once [were] more abundant that [they are] today,” a decline that Wauer (1980: 24) blames on woodcutters working for mines and construction projects in the late-nineteenth century. In addition, some ranching and agriculture occurred along the river in this region; following the establishment of Big Bend National Park in 1944, the riparian vegetation responded to the cessation of grazing and farming by becoming more dense, including renewed growth of grasses, cane, and mesquite (Boeer and Schmidly 1977: 214).

Settlers were not the only ones impacting the plant communities along the river. Many of the grass-poor sites catalogued in the preceding section on grasses and other plants were in areas of heavy traffic where previous travelers’ stock probably had eaten all the grass. Because of the extensive traffic along the Rio Grande, finding good grass sometimes could come as a surprise; for instance, at La Joya in 1846, Emory (1976: 50) wrote “On either side [of the river] is excellent grass, apparently untouched, and shaded by large cottonwoods” and at a camp near the base of Fra Cristobal Emory wrote “Our present camp is in a valley 70 or 100 acres in extent, well grassed and wooded, and apparently untrodden by the foot of man” (p. 55). More often the grass along the well-traveled river was in poor condition. In 1847, Magoffin (1926: 203-4) noted that at the often-used campsite near Brazito, “the grass has been all camped off.” Eccleston’s party experienced a similar situation when they first entered the southern El Paso Valley in 1849, and they decided to move on, in part because “the grass also was pretty well used up” (Eccleston 1950: 127). A few days later, when camped near Socorro, Texas, Eccleston complained, “The Army ox train came up today and camped about ¼ mile below us. This is a bad business, as they will eat all the grass clear up” (p. 136). In 1846, Abert camped “directly in front of Socorro [New Mexico]” because “the prospect of obtaining wood and grass on the other side was not very favorable” (Abert 1962: 121). In fact, the search for forage became so desperate for Abert’s party, that at Valverde, “We cut down some huge cotton wood trees, and turned our animals loose to browse upon the tender bark and the twigs” (Abert 1962: 131).

Travelers and settlers both likely played a role in another significant change in the vegetation along the river—the introduction of exotic plants. In 1930, Fosberg (1940: 581) collected 23 species of introduced plants in the Mesilla Valley (Table 2-3), ranging from woody plants (Tamarix sp.) to tumbleweed (or Russian thistle, Salsola kali), thistles (Sonchus sp.) and an introduced reed (Arundo donax).

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Table 2-3. Non-native plants collected in the Mesilla Valley in 1930 (from Fosberg 1940: 581).

Monocots Dicots Sorghum vulgare Rumex crispus Caesalpinia gilliesii Cynodon dactylon Polygonum lapathifolium Tribulus terrestris Arundo donax Salsola kali var. tenuifolia Tamarix gallica Asparagus officinalis Chenopodium glaucum Conium maculatum Chenopodium leptophyllum Pastinaca sativa Chenopodium paganum Ipomoea purpurea Chenopodium album Convolvulus arvenis Melilotus alba Plantago major Medicago sativa Sonchus asper Helianthus annuus

One of the most important of these exotics was tamarisk, also referred to as salt cedar. Introduced from the Mediterranean, this exotic was used as an ornamental and a windbreak, as well as for erosion control, and like cottonwoods and willows it is a phreatophyte that produces seeds which germinate best on open, moist soil (Horton 1977: 124). In small numbers at least, it was present in the Albuquerque area by 1908, in Mesilla Park by 1910, in El Paso by 1926, and in the Presidio Valley by 1935 (Crawford et al. 1993: 30, Everitt 1998: 664). As dam-building, flow-regulation, and channelization occurred, tamarisk became more and more dominant; Everitt (1998:665) argues that tamarisk was not responsible for changes in river hydrology (such as channel width or flood stage), but that it simply responded to such changes that were already underway. In both the Middle Rio Grande and Presidio valleys, extensive spreading of tamarisk occurred after significant flood events, in 1929 and 1942, respectively (Crawford et al. 1993: 30, Everitt 1998:665). As Everitt (1998: 665) explains, such floods dispersed tamarisk seeds widely across the floodplain to areas previously not colonized and also opened new habitats via scouring and channel migration.

Everitt (1998: 658) concludes that “[t]here is no evidence that [tamarisk] actively displaced native species” along the Rio Grande in the El Paso and Presidio valleys. However, in some areas, its “prodigious production of airborne seeds, long germination period, and rapid growth allowed it to compete favorably with native trees in colonizing newly stabilized sandy or silty surfaces” (Graf 1994: 99). Regardless of whether tamarisk has played an active role in replacing native vegetation, it has come to dominate many areas along the Rio Grande. From Ft. Quitman through the Presidio Valley, “tamarisk occupies land once covered by cottonwood woodland and tornillo thickets” (Everitt 1998: 665). In the early 1960s tamarisk and screwbean each made up about 40% of the overstory cover in a bosque near Las Cruces, compared to less than 5 % of the cover occupied by cottonwood trees (Campbell and Dick-Peddie 1964: 496). Data from 1982 and 1989, for the area between Bernardo and San Marcial, document 6560 hectares of tamarisk, compared to just 1685 hectares of “cottonwood dominated timber and brush” (Crawford et al. 1993: 35).

The spread of tamarisk may have significant impacts on animal communities. Along the river above Presidio, Engel-Wilson and Ohmart (1978) found that the distributions of many different groups of vertebrates were affected by the presence of tamarisk. For instance, most bird species that showed habitat preferences were found most often in cottonwood-willow or screwbean-wolfberry habitats in summer and in cottonwood-willow habitats in winter; the only bird species showing a strong preference for tamarisk- dominated habitats was the white-winged dove, which nested in these areas (Engel-Wilson and Ohmart 1978: 24-30). Rodent densities were highest in honey mesquite-dominated areas and were relatively low in the salt-cedar community (Engel-Wilson and Ohmart 1978: 39-43). Skunks, raccoons, and bobcats were the only species of large mammals observed to make significant use of the salt-cedar community (Engel- Wilson and Ohmart 1978: 46-50). While reptiles were almost never observed in the salt-cedar community and were only observed in areas where its dense canopy was disrupted by fencelines or other habitat edges, Texas toads were observed relatively often in the salt-cedar, and the shading effects of its canopy may have extended their period of activity after rains (Engel-Wilson and Ohmart 1978: 51-54).

A second exotic tree, Russian olive (Elaeagnus ausutifolia) was introduced to the region early in the twentieth century (Crawford et al. 1993: 30). Though it has spread widely through the western U.S., its spread along the desert Rio Grande has been less dramatic than that of tamarisk. Campbell and Dick-

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Peddie (1964) found that it only occurred along the river in New Mexico north of Elephant Butte Reservoir, although scattered individuals do occur along the river in the Mesilla Valley (pers. obs.).

Quantifying Changes in Vegetation Areal Extent. Data describing the relative abundance of different plant communities along the desert Rio Grande prior to extensive agricultural development are scarce. In 1889, Follett (1901: 195) described the lower end of the Texas portion of the Mesilla Valley as about 6200 hectares of uncultivated “swampland.” He further detailed this acreage as including the following types of vegetation: 25% “moderately well timbered…with cottonwoods,” 50% “not overflowed” and “composed of tornillo thickets,” and 25% “overflowed land” including bare sand bars, willow thickets, and “flat lands, which overflow every time the river rises, and yearly produce a fair crop of cockleburs” (Follett 1901: 196).

Although they include cultivated lands, even earlier estimates of the proportions occupied by different types of floodplain vegetation can be derived from cadastral surveys of exterior township and range lines made following the New Mexico Principal Meridian Survey in the mid-1850s (see Appendix A for a description of these surveys and how summary data were extracted from them). In the Mesilla Valley about 61 kilometers of complete lines were run in 1857, and in the Las Palomas Valley, about 27 kilometers were run in 1857 and 10 in 1877 (Maps 4 and 5). Only 2.7 kilometers of survey lines were run in Selden Canyon, all in 1857. Of the 7 different habitat types compiled from the survey data, areas timbered by cottonwood and untimbered or open areas dominated, each accounting for about 1/3 of the distance traversed by the lines (Table 2-4). The “No timber” category includes areas dominated by mesquite (probably both honey mesquite and screwbean) or other shrubby growth, as well as areas with little or only low-growing vegetation.

Table 2-4. Proportion of Township and Range lines crossing 7 habitat types during Garrettson’s 1857 surveys, and McBroom and Shaw’s 1877 survey.

Las Palomas Habitat Type Mesilla Valley % Selden Canyon % Valley % Cottonwood timber 34.6 26.7 No timber 25.9 36.8 44.8 Cultivated land 23.8 0 River channel 9.1 21.1 14.6 Willow thicket 4.2 42.2 12.2 Pond/slough/marsh 1.9 1.4 Dry river channels 0.6 0.3

In the Mesilla Valley, the pond/slough/marsh category is likely a slight underestimation, because a few sloughs were noted by the surveyors without recording a distance for the line across the feature; however, these unrecorded widths were most likely fairly narrow (less than 20 meters, or 0.3 % of the total survey distance in the Mesilla Valley, each) since the location of other features often limited the potential size of these unrecorded widths. The river channel percentage is likely a slight overestimation, since difficulties crossing the river sometimes kept surveyors on one side of the river in areas where it paralleled or meandered along the line. For instance, between Las Cruces and Mesilla, where the river crossed a north- south line three times in less than a mile (in the shape of a Z-curve), the surveyors did not run the line through the curves, and so I categorized this entire length as “river channel.” This area likely contained some land falling into the willow and pond/slough/marsh categories (this problematic area represents 2.5% of the total distance of the Mesilla Valley surveys).

In contrast to the 1857 data, in 1999, cultivated land dominates the areas traversed by the surveyors, and the straightened, channelized river occupies much less area (Table 2-5). These modern summary data were derived by applying lines to modern 7.5 minute U.S.G.S. quads and ground-truthing vegetation types as needed. This method does not quantify phreatophytic vegetation lining agricultural drains in the valleys and because of the location of these lines, two of the largest areas with riverine forest in the Mesilla and Las Palomas valleys (the Old Refuge southwest of Mesilla and Percha Dam State Park below Caballo

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Reservoir) are not included in these proportions. Thus, the modern data probably underestimate the area covered by riparian woodlands and marsh plants that have become established in drains. However, none of the ponds, sloughs or marshes documented by the surveyors currently exist, and these sorts of natural wetland habitats have been virtually eliminated in the Mesilla and Las Palomas valleys.

Table 2-5. Proportion of survey lines crossing 7 zones in 1999.

Zone Mesilla Valley % Selden Canyon % Las Palomas Valley % Cultivated/Rural 87.4 48.9 Residential Reservoir (Caballo) 30.4 Municipal (Las Cruces) 8.2 Leveed floodplain* 2.6 12.3 River channel 1.4 17.8 1.8 Mesquite/saltbush 0.2 30.2 5.1 Tamarisk/River edge 0.2 52.1 1.6 forest (outside levees) * This area includes some land west of the Rio Grande where the river runs close to the western edge of the valley and only one levee, on the east side of the river, exists. These west-bank floodplains (0.6 % of the Mesilla Valley total and 9.9 % of the Las Palomas Valley total) often support tamarisk/river edge forest and mesquite/saltbush shrublands.

As part of the planning for the Middle Rio Grande Conservancy Project, somewhat comparable habitat coverage data for the Socorro District (excluding the areas around the Bosque del Apache, south of San Antonio) were presented by New Mexico’s Chief Engineer in 1928 (Burkholder 1928). From these data (Table 2-6) it appears that the area from San Acacia through San Antonio apparently contained a much higher proportion of wetland habitats in the early 1920s than the township and range surveys documented for the Mesilla and Las Palomas valleys 70 years earlier. There are at least two potential reasons for this difference. First, Burkholder’s data come from a period of high water tables and soil saturation due to irrigation. In fact, high water levels were rendering some farmland useless, and in the early to mid-1930s drainage canals were constructed, which reduced the extent of wetland communities extensively (Crawford et al. 1993: 31). In addition, the mid-nineteenth-century surveys followed a dry decade which may have reduced river flows enough to effect the creation and recharge of wetlands. Seven of the 11 years from 1845 through 1855 were drought years (severe enough to have been described as a causal factor behind Native American raids on Anglo settlements) and 1856 was one of the 10 driest years on record in Albuquerque for the period from 1850-1994 (Scurlock 1998: 40, 19).

Table 2-6. Classification Rio Grande Valley lands in the Socorro District (approximately San Acacia through San Antonio) in 1928. Data from Burkholder (1928: 200-201).

Burkholder’s Habitat Designations Acres Proportion of Total Bosque 7274 28.6 Salt grass + Sand dunes + Gravel 2230+44+110 9.4 Cultivated land 5057 19.9 River channel* 5888 23.1 Swamp and lake 873 3.4 Rural Homesites+ Cities and 26+160 0.7 Towns Area between ditches and hills 3775 14.8 (vegetation not classified)* *Total acreages for these two categories were presented for the entire Socorro Division (San Acacia through San Marcial) in Burkholder’s Table 24 (1928: 201). To limit the river channel area to the valley above San Antonio, Burkholder suggested multiplying the total acreage by 0.75; I applied the same correction factor to the unclassified lands above the ditches.

The apparent increase in floodplain area classified as river channel between the mid-nineteenth century and 1928 may be a reflection of the heavy sedimentation that followed the increase in logging and grazing in the second half of the eighteenth century. As the channel aggraded, it became shallower and wider (Crawford et al. 1993: 20), which may account for some of the increase in coverage. In addition,

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methodological differences may be responsible for some of the difference between the river channel proportions reported in Tables 2-4 and 2-6. When summarizing the eighteenth-century survey data, I classified islands between river channels as one of the other habitat types (typically “no timber” or “willow thicket”), but I do not know how Burkholder’s data were compiled. Given his primary interest in quantifying “irrigable lands” he may have included them in the river channel total, if he assumed that the likelihood of overflow and even complete destruction in floods made them poor candidates for irrigation projects.

A different classification scheme was applied to the Socorro Reach (Bernardo through San Marcial) in the Middle Rio Grande Ecosystem: Bosque Biological Management Plan for data collected in 1935 and 1989 (Crawford et al. 1993: Map 1). Some of the differences between the 1928 data in Table 2-6 and the 1935 data in Table 2-7 may result from slightly different reaches that are covered; the data in Table 2-6 exclude the area south of San Antonio (Bosque del Apache) which included a large portion of the non-river wetland habitats in 1935. As Table 2-7 shows, since 1935 the area devoted to river channel, forest, and wetlands has been reduced substantially, while agricultural, urban, and to a lesser extent, shrubby areas have increased.

Table 2-7. Classification of floodplain between Bernardo and San Marcial, 1935 and 1989. Data from Crawford et al. (1993: Map 1).

Proportion of Floodplain Cover type 1935 1989* River or man-made channel 18.2 8.2 Forest 17.3 6.6 Scrub-shrub 26.2 32.0 Lake, wet meadow, marsh or pond 8.6 5.0 Urban 1.1 4.0 Range 16.3 17.3 Agriculture 12.4 26.5 *The missing 0.4% represents areas not covered in aerial photos for this time period.

Plant Densities and Size-Class Distributions. The eighteenth-century township and range line surveys’ dependence upon witness trees to permanently fix corners also allows us to get some rough estimates of cottonwood densities (see Appendix A for a description of how summary data were extracted from these surveys). In general, the tree densities are quite low (Table 2-8), supporting earlier descriptions of open groves and scattered cottonwood trees. (Note: although the surveyors noted a few scattered cottonwoods in Selden Canyon, none grew close enough to their lines to be recorded as witness trees.) The relative density of cottonwoods at different locations in the valleys are illustrated in Maps 4 and 5; generally, the surveyors were more likely to locate a full set of witness trees at points close to the active river channel, dry channels, or sloughs.

Table 2-8. Cottonwood tree densities (trees per hectare) in the Mesilla and Las Palomas valleys, estimated from witness tree data from Garrettson (1857) and McBroom and Shaw (1877). Sample size (n) indicates the number of survey points contributing to density estimates; the difference between the sample sizes for maximum and minimum estimates corresponds to the number of points where no cottonwoods were recorded. Mesilla Valley Las Palomas Valley Maximum density Minimum density Maximum density Minimum density Habitat Type (n) (n) (n) (n) Cottonwood 1.38 (24) 0.39 (32) 3.51 (12) 1.97 (13) timber No timber 3.86 (4) 0.09 (23) 0.31 (2) 0.12 (21) areas Cultivated land 0.97 (10) 0.21 (17) n/a n/a River edge 5.14 (14) 0.31 (23) 7.94 (16) 0.47 (28) Willow thicket 2.86 (3) 0.50 (4) 13.35 (4) 0.50 (7)

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An undergraduate thesis written at what is now New Mexico State University also allows us to estimate a variety of woody plant densities in an area dominated by tornillo bushes. In 1898, Mead mapped the dominant woody vegetation in an approximately two-acre (0.8 hectare) plot, “a little N.W. of the depot at Mesilla Park.” Though calculated in a very different way, the cottonwood density calculated from Mead’s data (6.25 trees/hectare; see Table 2-9) falls within the range of densities estimated from the witness tree data (Table 2-8). The cottonwoods recorded by Mead may have been relicts from an earlier channel location. At the time of Mead’s study, the main channel of the river was west of Mesilla, perhaps as many as 5 kilometers west of his study site, assuming the river was close to its 1903 channel (Map 2); however, prior to the 1865 channel shift, the river probably passed within half a kilometer of the site (based on the location of the 1844 channel).

Table 2-9. Number of individual plants occurring on a 0.8-hectare plot mapped by Mead (1898: 28, Plate IV).

Plant Species No. Mapped Density (plants/hectare) Tornillo (Prosopis pubescens) 114 142.5 Mesquite (P. glandulosa) 14 17.5 Lycium torreyi 31 38.75 Atriplex canescens 6 7.5 Cottonwood trees (Populus fremontii) 5 6.25

The witness tree data in the 1857 surveys also provide some indication of the age-structure of the cottonwood population along the river. The surveyors recorded the diameter-at-breast-height (in inches, to the nearest whole inch) of all witness trees and any trees that straddled the lines they were surveying; the resulting frequency distributions are presented in Figure 2-3. The lower end of these distributions (dbh<6 inches or 12.5 cm) is probably not representative of the actual population; surveyors are instructed to use trees with a dbh of at least 6 inches for witness trees (T. Maestes, pers. comm.), but along the Rio Grande they were evidently occasionally forced into using smaller trees when no others were available. However, if a tree with a dbh>5 inches were accessible in a quadrant, even if a smaller tree were closer to the corner point, the surveyors should have preferentially marked and recorded the larger tree.

What is most striking about these distributions is that is appears there were two distinct cohorts of trees in both valleys (Fig. 2-3.). Very few trees with a dbh of 11-12 inches (28-30.5 cm) were recorded by the surveyors in either valley. Although the dynamic precipitation and flood cycles, as well as variable soil conditions across the floodplain, make dbh-to-age correlations problematic in cottonwoods unless applied within relatively short reaches (see Hinchman and Birkeland 1995), the prominence of this pattern in both the Mesilla and Las Palomas valleys suggests that conditions therein were consistent enough to document a recruitment bottleneck. Howe and Knopf (1991:220) present a dbh-to-age correlation for the cottonwoods in the Middle Rio Grande Valley (age=22.2 + 0.27*dbh in cm). If we apply this to the low point in the frequency distributions in Figure 2-3 and subtract the result from 1857, the recruitment bottleneck would have occurred around 1827, which matches well with climatological data. As Howe and Knopf (1991:406) explain, reductions in flood frequency and decreases in the peak flow of flood events can reduce recruitment in riparian species like cottonwood. According to Scurlock (1998: 40), the years 1824-5 were drought years, and no major floods were recorded along the Middle Rio Grande between 1823 and 1828 (Scurlock 1998: 34). In 1828 however, a “mega event” occurred, a flood with an estimated flow of 100,000 cfs (Scurlock 1998: 32), which may have scoured small saplings and seedlings from prior years. Thus it may be that the witness trees with dbh’s of greater than 30 cm represent survivors of this drought- flood cycle, whereas the trees with smaller dbh’s became established after the 1828 flood.

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Figure 2-3. Size-distribution of cottonwoods recorded during mid-eighteenth-century surveys of the Mesilla and Las Palomas Valleys. Data from Garrettson (1857).

30 Mesilla Valley Las Palomas Valley 25

15 Frequency 10

0 11.5 19.5 27.5 35.5 43.5 51.5 59.5 67.5 75.5 Central Value of Size Class (cm)

In addition to documenting an apparent recruitment bottleneck, the size-class distribution of the trees encountered in Garrettson’s 1857 surveys indicates that few large, old trees existed at the time. Of 165 trees measured, the maximum dbh recorded by the surveyors was 30 inches (76 cm), which would represent an individual about 43 years old using Howe and Knopf’s (1991: 220) age-to-dbh relationship. In contrast (Figure 2-4), Howe and Knopf found at least 42 individuals (of 607 measured) with a dbh>76 cm in their 1988 study of the Middle Rio Grande valley, with a maximum age of about 67 years (1991: 219). While the difference in maximum age may simply be an artifact of sample size, it also lends support to the argument that large, old cottonwood trees may have been rare under variable flow regimes because flooding and channel migration could destroy cottonwood stands (Crawford et al. 1993: 25, 28-9; Graf 1994: 99). The surveyors noted a few scattered cottonwoods, all dead, near the western edge of the lower Mesilla Valley at a time when the main river channel was about 2 miles to the east (Garrettson 1857: corner of T25, 26S; R2, 3E)

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Figure 2-4. Comparison of size-class distributions of cottonwood trees in the Middle Rio Grande Valley in 1988 and the Mesilla and Las Palomas Valleys in 1857. Data from Howe and Knopf (1991: 219) and Garrettson (1857).

120 1988 100 1857 80

Frequency 40

0 3.5 19.5 35.5 51.5 67.5 83.5 99.5 116 132 148 Central Value of Size Class (cm)

Fauna Given the significant changes that have occurred to the river’s hydrology and the plant populations along the river, it is not surprising that the animal populations have changed as well. The chapters following this one provide species lists and a discussion of past and present occurrence of individual vertebrate species along the Rio Grande. This section combines first-hand narrative accounts of the early explorers’ and travelers’ observations of the animal life along the desert Rio Grande with discussion of natural processes that impact such populations to provide a more general impression of the fauna and how it has been influenced by changes along the river.

Written in 1849, one traveler’s journal is particularly striking because it makes note of animals generally omitted from other accounts, including rodents, reptiles, and insects. While camped in Las Palomas Valley, Powell’s party …discovered we were in a perfect den of rattlesnakes. All set to work beating the bushes and killing the snakes. How many we killed I do not know. They were very large, had black and white rings round their tails just above the rattles….One I helped kill had 13 rattles and his fangs were nearly an inch long!…Besides snakes, we have rats, mice, black tailed rabbits, quails and a few centipedes around us. (Powell 1981: 102-103) A few days later, Powell reflected on the significance of such wildlife encounters: Our lives are in constant danger. Saw centipedes today, and a dirty yellow worm about an inch and a half long, which, those who have been in this country before say, is poisonous. The grasshoppers are singularly variegated here; some black and white; others red, yellow and black, and some I have seen that have a dress of many bright colours, putting me in mind of a clown at a circus more than anything else. (p. 105)

Fish. More typically, the animals mentioned in the explorers’ and travelers’ accounts were significant either as food or fur sources, or were larger animals that attracted the writers’ attention. Within the waters of the Rio Grande, fish and fresh-water turtles were common and of interest as food sources. While stopped at a large marshy area in the lower El Paso Valley in 1583, a member of Espejo’s party commented

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on the “quantities of fish close by in the river” (Luxan 1929: 69). Upon reaching the river near modern El Paso, the chronicler of Oñate’s 1598 journey explained that the river’s “bountiful waters teemed with many fish and we easily caught a number” (Villagra 1933: 127).

A more specific account of the fish in the El Paso area comes from a 1773 description of life in El Paso: “…the river abounds in fish, known as rock fish, although some call it bream. Other delicious kinds are the corazon and the enguila, all of more than medium size. The enguilas [eels] are found more often in the ponds formed by the overflow of the river than in its channel” (Hackett 1902: 508-509). In 1846, large fish and eels were still being reported as quite common in the river near El Paso (Ruxton 1973: 168).

Along the northernmost reaches of the desert Rio Grande, catfish and soft-shelled turtles were featured in some mid-nineteenth-century travelers’ accounts (e.g.: Johnston 1848: 570, Bieber 1936: 337, Emory 1976: 49). In 1847, Ferguson described catching “[s]everal white catfish with blue spots…” several miles below Socorro (Bieber 1936: 333). Two years later, opposite Fra Cristobal, Powell (1981: 100) reported catching some blue catfish weighing from 5 to 20 pounds. “Very large and heavy” catfish, as well as soft-shell turtles, were also reported from near the mouth of the Pecos River (Emory 1987, vol. I, pt. 1: 78).

Obligate aquatic organisms like fish obviously suffered when reduced flows and flow disruptions became more prevalent following the late-nineteenth and early twentieth centuries. In contrast to the earlier descriptions of a river full of fish, in the late 1890s, near El Paso, Mearns (1907: 80-81) observed that “[o]wing to the lowness of the water in this portion of the Rio Grande at certain seasons, the fish fauna is limited and variable….” Negative impacts have continued into more recent years, and flow reductions are not the only problem; for instance the fish fauna below the mouth of the Río Conchos declined noticably between 1977 and 1988, perhaps due to pollution from sewage (Bestgen and Platania 1988).

Changes in the river’s natural flow regime and flooding and sedimentation patterns, as well as a reduction in meandering could have affected fish populations in a number of ways. The loss of backwater habitats such as sloughs and ponds probably had a negative impact on species preferring pools and still water, such as eels and sunfish. Small, short-lived fish largely restricted to the mainstream flow of the Rio Grande— including the endangered Rio Grande silvery minnow (Hybognathus amarus), and 3 types of shiners (Notropis simus simus, N. orca, N. jemezanus) and one chub (Hybopsis aestivalis) that have disappeared from the river in New Mexico—were negatively impacted by reductions in flows which reduced and fragmented available habitat (Bestgen and Platania 1990: 7). Increasing levels of fine sediments could negatively impact species like the blue sucker (Cycleptus elongatus), which prefers hard-bottomed or gravelly substrates (Propst 1999: 52-53); because its eggs attach to bedrock and cobbles (Propst 1999: 52), its spawning habitat could also be affected by reductions in flow, which can allow fine sediments to clog the spaces between cobbles (Beschta and Jackson cited in Poff et al. 1997: 775).

Mammals. Another group of vertebrates that underwent a severe decline due to human activity was fur- bearing mammals. However, their decline preceded the severe flow reductions of the late-nineteenth century. As Weber (1982: 130) explains, after the opening of the Santa Fe trade in the early 1820s, American fur-trappers were quick to exploit the beaver populations in New Mexico, which previously had been largely ignored by the Mexicans because they did not have access to an established market for the furs. The Americans, however, effectively trapped out all the beaver in the areas closest to the New Mexico settlements of central and northern New Mexico by 1823 (Weber 1982: 130).

When the trapping of beavers moved into more remote areas, including both the mountains and desert, Mexican authorities began to take notice. In 1826, an official complained that “The taking of peltries of beaver is a branch of trade profitable only for the Anglo-Americans, who make up hunting parties and also establishments for them which last several months; as a result the specie will soon be destroyed.” (Madrid quoted in Marshall 1916: 259). To avoid such officials, in 1827, American trappers used rafts to float down the Rio Grande to El Paso; after trapping beavers along the river, they dismantled the rafts, sold the valuable wood, and snuck out of Mexican territory with their furs (Weber 1971: 157). In 1838, a similar raft expedition was planned to include the Rio Grande all the way to the mouth of the Pecos (Weber 1971: 224). By this time, official concern about the survival of beaver populations had reached El Paso, where

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authorities wrote to Chihuahuan officials about the imminent extinction of both beavers and otters along the Rio Grande (Weber 1971: 224).

In spite of such dire predictions, beaver populations evidently managed to survive or return to the Rio Grande; a number of 1846 journals report them. Ruxton (1973: 170) reported beaver sign along the river near the Alamitos campground in the southern Mesilla Valley. One days’ march above Socorro, Ferguson noted beaver sign (Bieber 1936: 331). Camped near Fra Cristobal, Emory (1976: 55) also saw beaver sign. Cooke’s party caught beavers at two separate locations (separated by 5 days of travel) between Socorro and modern Rincon (Bieber 1938: 92, 96). Though reported less frequently, otters may have survived as well: in Engle Valley, Johnston (1848: 575) noted otter tracks along the bank of the river. To this day, beavers maintain a tenuous hold along some reaches of the desert Rio Grande (see Chapter 5).

Many other types of large mammals were recorded in the early accounts. Deer were mentioned in numerous nineteenth-century accounts, especially in the relatively unsettled stretches of the river: between Socorro and the San Diego crossing, they were observed by Pike (Jackson 1966: 408) in 1807; and by Ruxton (1927: 178), Turner (1966: 80), Emory (1976: 54, 55), Johnston (1848: 575), Cooke (Bieber 1936: 93, 95); and Abert (1962: 131) in 1846; between modern Canutillo and the narrows above El Paso, they were observed by Ruxton (1927: 170) and Eccleston (1950: 156) in 1846 and 1849, respectively; near modern Ft Quitman they were observed by Whiting in 1849 (Bieber 1938: 300); and in the lower canyons above the Pecos River, Michler reported them (Emory 1987, vol. I, pt. 1: 78). Only a few of these observations were accompanied by details allowing us to identify the deer species: near Fra Cristobal, Emory reported that a member of his party “killed a common Virginia deer” (1976: 54), while near Ft. Quitman and above the mouth of the Pecos, the deer were described as having black tails (Bieber 1938: 300; Emory 1987, vol. I, pt. 1: 78).

Large predators—bears, mountain lions, and wolves—were mentioned in mid-nineteenth-century accounts, but only occasionally. Emory, Cooke, and Ferguson all reported seeing bears (or sign of bears) along the northernmost stretches of the desert Rio Grande upstream of the San Diego crossing (Emory 1976: 55; Bieber 1938: 93; Bieber 1936: 331). Ruxton (1927: 178) reported hunting a “panther” in an arroyo near Valverde. When camped on a bluff overlooking the river (probably near San Diego Mountain) Ferguson mentioned killing “wolves” in the vicinity of his camp (Bieber 1936: 337); as coyotes were often called “prairie wolves” at this time, he may have been referring to them instead of gray or Mexican wolves. Johnston (1848: 575) provides one of the most exhaustive lists of mammal and bird sign for a single stretch along the river, in the Engle Valley: “In passing along the river, I saw the tracks of the otter, the catamount, the wildcat, the bear, the raccoon, the polecat, the crane, the duck, the plover, the deer, and the California quail.”

For some southbound travelers, the animal life of the desert Rio Grande was strikingly more abundant than what they had encountered farther north in New Mexico. Near modern Truth or Consequences, Cooke observed that “We have got among wild animals—turkeys, deer, and bears.” (Bieber 1938: 93) Similarly, near Fra Cristobal, Emory (1976: 55) observed “here we saw for the first time in New Mexico, any considerable ‘signs’ of game in the tracks of bear, the deer, and the beaver.” Contrast that statement with one Emory made just 3 days earlier (and farther north), when he observed that “Game in New Mexico, is almost entirely extinct, if it ever existed to any extent” (p. 54). The relative lack of game upriver may have been the result of centuries of settlement along the upstream reaches of the Rio Grande (Calvin 1951: 201).

Birds. As with fish and mammals, much attention was given to birds as potential food. Game birds (including cranes, ducks, geese, turkeys, and quail) were prominent in many accounts from 1582-1902 (e.g.: Bartlett 1965: 218; Bieber 1938: 93; Bieber 1936: 337; Emory 1976: 49, 54, 55; Gibson 1935: 293; Granjon 1986: 34; Johnston 1848: 571, 573, 575; Luxan 1929: 68; Ruxton 1973: 178; Turner 1966: 77, 80; Villagra 1933: 127; Wislizenus 1969: 37). A series of entries Eccleston’s journal (1950), written as he traveled from south to north through the El Paso Valley in 1849, highlights such travelers’ interest in birds as food, and is particularly revealing given the fact he recorded no deer along this stretch of the river. September 3. “There are plenty of ducks about here….Our boys killed a mess of birds, some young ducks & quails, [etc.]…” (p. 128).

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September 5. Some other travelers came by “with about 40 birds of various kinds—ducks, quail, curlews, [etc.], of all sizes” (p. 129). September 8. Someone brings his party “a couple of ducks…he shot on the lagoon near the 1st settlement [San Elizario]” (p. 133-4). September 12. Two members of his party bring back 8 ducks to eat (p. 136). September 13. Eccleston mentions that his brother’s mess has “lived nearly entirely on ducks lately; they have killed so many” (p. 139). In his general description of the El Paso area written on this same date he notes “There are a number of small lakes or ponds scattered about, where will be found large quantities of duck & some geese…” (p. 140).

Relatively few travelers noted other types of birds. In 1849, Whiting described seeing “a flock of twenty- five huge white pelicans” in a pond near the southern end of the El Paso Valley (Bieber 1938: 300). Abert and Emory each noted a number of non-game birds along the northernmost reaches of the desert Rio Grande in 1846, along with the more commonly noted game species (Table 2-10).

Table 2-10. Birds listed in the accounts of Abert (1962) and Emory (1976) from their travels along the desert Rio Grande above San Diego crossing in 1846. When possible, likely modern names derived from alternative names listed in Terres (1980) and from abundance codes in the bird list for Bosque del Apache National Wildlife Refuge (US Fish & Wildlife Service 1999) are provided.

Abert’s List Emory’s List Likely Modern Name loon (colymbus glacialis) Common Loon blue crane Great Blue heron swan (cygnus americanus) Tundra Swan wild geese wild geese Snow Goose brant Canada Goose mallard Mallard teal blue-winged duck summer duck merganier (anas merganser) Common Merganser bald-headed eagle Bald Eagle sparrow-hawk (Falco sparverius) American Kestrel hawk (like sparrow-hawk, but lead Merlin colored) turkey Wild Turkey quail (with crests on their heads) quail (ortix squamosa?), blue Scaled Quail quail crane (grulla) sandcranes Sandhill Crane plovers Killdeer avocet American Avocet red-winged flickers (Picus Northern Flicker (red-shafted mexicanus) form) golden-winged woodpeckers Northern Flicker (yellow-shafted form) creeper (Picus querulus, or carpentero) butcher birds (lanins borealis) Loggerhead Shrike crow shore lark Horned Lark little sapsucker (sitta carolina) White-breasted Nuthatch Mexican blue birds (sialia Western Bluebird occidentalis) Mexican meadowlark (sturna meadowlarks Western Meadowlark neglecta)

Although relatively few bird species have been completely extirpated from the desert Rio Grande, many species have been impacted by human activities along the river (see Chapter 6). Finch et al. (1995: 149)

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identify 6 human-related factors that have influenced bird populations along the Middle Rio Grande, all of which also occurred along other reaches of the desert Rio Grande: 1. replacement of native vegetation with exotic woody plants like tamarisk, 2. reduction in marsh habitats, 3. reduced cottonwood regeneration, 4. loss of native habitats to agriculture and urbanization, 5. cowbird parasitism, and 6. nest disruption by humans or domesticated animals. As the third item in this list suggests, the impact of changes in the natural hydrologic regime of the river was not limited to aquatic birds. The structural diversity and heterogeneity of the riparian forests found along the river was influenced by flooding and channel changes, and thus the birds using those forests were impacted. Farley et al. (1994: 1106) suggest that at a regional scale, high species diversity would have been maintained by natural flow regimes because Rio Grande cottonwood forests of different ages each support a different bird community; they found, for instance, that even though a two-year-old stand supported relatively few bird species (compared to older stands), some of the species using such young stands did not occur in any of the older stands (Farley et al. 1994: 1105).

A similar result might be expected for any taxon of organisms living along the desert Rio Grande. Regional diversity would be supported not only by the different age-classes of riparian forest stands created by natural geomorphic processes, but also by the diversity of non-forest habitats spread across the floodplain and found within the river. The dynamic and patchy nature of the riparian landscape helped support the regional biodiversity catalogued in Chapters 3-6, and thus, even the terrestrial organisms of the desert Rio Grande should be viewed in light of the hydrologic and geomorphic processes that ultimately determine the riparian landscape.

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Hutton, N. H. 1859. Report on the El Paso and Fort Yuma Wagon Road. In Report on the Pacific wagon roads, ed. A.H. Campbell, 77-93. 35th Congress, 2nd Session, House Executive Document No. 108.

International Boundary Commission. 1903. Chamizal Case # 4. Proceedings of the International (Water) Boundary Commission, United States and Mexico, Treaties of 1884 and 1889, Volume 1. Washington, D.C.: Department of State.

International Boundary and Water Commission. 1956. Summary Water Bulletin, 1889-1955.

International Boundary and Water Commission. 1956-1997. Water Bulletin No. 24 through No. 67.

International Boundary and Water Commission. 1978. Final Environmental Statement: Rio Grande Boundary Preservation, Hudspeth and Presidio Counties, Texas.

Irvine, J.R. and N.E. West. 1979. Riparian tree species distribution and succession along the lower Escalante River, Utah. Southwestern Naturalist 24: 331-346.

Jackson, D., ed. 1966. The journals of Zebulon Montgomery Pike, with letters and related documents. Norman: University of Oklahoma Press.

Johnson, C.A., ed. 1977. A preliminary appraisal of cultural and historical resources found along the Rio Grande between Fort Quitman and Haciendita, TX, Publications in Anthropology, No. 5. El Paso Centennial Museum, University of Texas at El Paso.

Johnston, A. R. 1848. Journal of Captain A.R. Johnston, First Dragoons. In Report of Lieutenant J. W. Abert, of his examination of New Mexico in the years 1846-’47. 30th Congress, 1st Session, House Executive Document 41. Washington, D.C.: United States Engineering Department.

Kelley, P. 1986. River of lost dreams: Navigation on the Rio Grande. Lincoln: University of Nebraska Press.

Lagasse, P.F. 1981. Geomorphic response of the Rio Grande to dam construction. New Mexico Geological Society, Special Publication No. 10: 27-46.

Leopold, L.B. 1951. Vegetation of the southwestern watersheds in the nineteenth century. Geographical Review 41: 295-316.

Leopold, L.B., M.G. Wolman, and J.P. Miller. 1992. Fluvial processes in geomorphology. New York: Dover Publications. [Reprint of 1964 publication by W.H. Freeman and Co.]

Lesley, L.B. 1949. Uncle Sam’s camels, the journal of May Humphreys Stacey supplemented by the report of Edward Fitzgerald Beale, 1857-1858. Cambridge, MA: Harvard University Press.

Luxan, D. P. 1929. Expedition into New Mexico made by Antonio de Espejo, 1582-1583, as revealed in the journal of Diego Perez de Luxan, a member of the party, eds. G.P. Hammond and A. Rey. Los Angeles: The Quivira Society.

Madrid, E.R. 1996. Native American and mestizo farming at La Junta de los Rios. Journal of Big Bend Studies 8: 15-31.

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Magoffin, S.M. 1926. Down the Santa Fe Trail and into Mexico: The Diary of Susan Shelby Magoffin, 1846-1847, ed. S.M. Drum. New Haven, Yale University Press.

Malanson, G.P. 1993. Riparian landscapes. Cambridge: Cambridge University Press.

Marshall, T. M. 1916. St. Vrain’s expedition to the Gila in 1826. Southwestern Historical Quarterly 19: 251-260.

McBride, J.R. and J. Strahan. 1984. Establishment and survival of woody riparian species on gravel bars of an intermittent stream. American Midland Naturalist 112: 235-245.

McBroom, W. and J. Shaw. 1877. Government Land Office Survey field notes. Microfiche: available at Las Cruces District Office, Bureau of Land Management, Las Cruces, NM.

Mead, I.R. 1898. Study of the life of the tornillo zone. Undergraduate Thesis, New Mexico College of Agriculture and Mechanical Arts, Mesilla Park. Hobson-Huntsinger University Archives, New Mexico State University Library.

Mearns, A.E. 1907. Mammals of the Mexican Boundary of the United States: A Descriptive catalogue of the species of mammals occurring in that region; with a general summary of the natural history and a list of trees. Washington, D.C.: United States National Museum Bulletin 56/Smithsonian Institution.

Mendoza, J. 1952. Itinerary of Juan Dominguez de Mendoza,1684. In Spanish exploration in the southwest, 1542-1706, ed. H.E. Bolton, pp. 320-325. New York: Charles Scribner and Sons.

Metcalf, A.L. 1967. Late Quaternary mollusks of the Rio Grande Valley, Caballo Dam, New Mexico to El Paso, Texas. El Paso: University of Texas at El Paso Science Series, No. One/Texas Western Press.

Metcalfe, O.B. 1903. The flora of the Mesilla Valley. Undergraduate Thesis, New Mexico College of Agriculture and Mechanical Arts, Mesilla Park. Hobson-Huntsinger University Archives, New Mexico State University.

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Minckley, W.L. and T.O. Clark. 1984. Formation and destruction of a Gila River mesquite bosque community. Desert Plants 6 (1): 23-30.

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Nelson, J.W. and L.C. Holms. 1914. Soil survey of Mesilla Valley, New Mexico-Texas. Washington: USDA, Bureau of Soils.

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Peterson, J.A. 1994a. The Lower Valley environment. In El Valle Bajo: the culture history of the Lower Rio Grande Valley of El Paso, Volume 1: Culture and Environment in the Lower Valley, ed. J.A.

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Peterson and D.O. Brown, pp. 5-9. Prepared for the El Paso County Lower Valley Water District Authority. El Paso: Archaeological Research, Inc/ Austin: Hicks and Company.

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Segelquist, C.A., M.L. Scott, and G.T. Auble. 1993. Establishment of Populus deltoides under simulated alluvial groundwater declines. American Midland Naturalist 130: 274-285.

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Sublette, J.E., M.D. Hatch, and M. Sublette. 1990. The fishes of New Mexico. Albuquerque: University of New Mexico Press.

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White, P.S. 1979. Pattern, process, and natural disturbance in vegetation. Botanical Review 45 (3): 229- 299.

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Wozniak, F.E. 1987. Irrigation in the Rio Grande Valley, New Mexico: a study of the development of irrigation systems before 1945. Amarillo, TX: Southwest Regional Office, Bureau of Reclamation.

Ydoiaga, J. 1992. Expedition to La Junta de los Rios, 1747-1748, Captain Commander Joseph de Ydoiaga’s Report to the Viceroy of New Spain. trans E.R. Madrid. Office of the State Archeologist, Special Report 33. Austin: Texas Historical Commission.

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50—Historic Ecosystem Descriptions

Chapter 3: Fishes of the Desert Rio Grande

Between the Rio Puerco, NM and the Devils River, TX, the Rio Grande’s fish fauna includes (Table 3-1): 7 native fishes completely extirpated from the Rio Grande (including 3 extinct endemics), 8 native fishes extirpated from at least part of their historic range along the Rio Grande, 23 native fishes that still may occur throughout their historic range along the Rio Grande, 6 species that are native to part of the desert reach and introduced to other parts, 22 introduced species with established populations, and 2 non-native species whose introductions failed. In addition, there are 12 native fishes (two extinct) that occur (or occurred) in waters adjacent to the desert Rio Grande (including the Devils River), although their distributions appear to be limited to these tributaries. Fourteen of the desert Rio Grande’s fish species are listed as threatened or endangered in either Mexico, the United States, or both (see Appendix B).

Table 3-1 presents fish distributions across 6 reaches of the Rio Grande through the Chihuahuan Desert. Species were noted as occurring in a particular reach of the river only when a clear collection record or literature discussion of its range for that stretch was available; citations are provided in the species accounts following the table. Because most of the distributional records are from the twentieth century and therefore post-date much of the degredation of aquatic environments, the data do not necessarily reflect the virgin distribution of fishes prior to human modifications of the Rio Grande. This may be particularly important between El Paso and the mouth of the Pecos, as the first extensive sampling in this area was done in 1977 (Bestgen and Platania 1990).

Taxonomy follows Mayden et al. (1992); relatively recent name changes are traced in the species accounts following Table 3-1. In addition, the species accounts briefly describe species’ habitat preferences (including the breeding habitat of native species, if known) and distribution along the desert Rio Grande.

Fishes—51 Table 3-1. Fishes of the Rio Grande, for 6 reaches through the Chihuahuan Desert. E = Endemic to the drainage, N = Native, I = Introduced, T = distribution limited to tributaries, x = extirpated from reach. Sources for distributional data are presented in species accounts following table.

Above Caballo— El Paso— Quitman— Conchos— Boquillas— Family Species Common name Caballo El Paso Quitman Conchos Boquillas Devils River Acipenseridae Scaphirhynchus playtorynchus shovelnose sturgeon N-x N-x N-x N-x N-x N-x Lepisosteidae Atractosteus spatula alligator gar N Lepisosteus oculatus spotted gar N L. osseus longnose gar N-x N-x N N Anguillidae Anguilla rostrata American eel N-x, I N-x N-x N-x N-x N-x Clupeidae Dorosoma cepedianum gizzard shad N N N N N N D. petenense threadfin shad I I Cyprinidae Campostoma anomalum central stoneroller I-x T C. ornatum Mexican stoneroller N Ctenopharyngodon idella grass carp I Cyprinella lutrensis red shiner N N N N N N Cyprinella lutrensis blairi Maravillas red shiner T(E)-x Cyprinella proserpinus proserpine shiner T Cyprinella venusta blacktail shiner N Cyprinus carpio common carp I I I I I I Dionda argentosa manantial roundnose minnow T (E) Dionda diaboli Devils River minnow E-x D. episcopa roundnose minnow T T Gila pandora Rio Grande chub N-x N-x Hybognathus amarus Rio Grande silvery minnow N N-x N-x N-x N-x N-x Macrhybopsis aestivalis speckled chub N-x N-x N-x N N N

Above Caballo— El Paso— Quitman— Conchos— Boquillas— Family Species Common name Caballo El Paso Quitman Conchos Boquillas Devils River Notemigonus crysoleucas golden shiner I Notropis amabilis Texas shiner T N. braytoni Tamaulupis shiner N N N. buchanani ghost shiner N N. chihuahua Chihuahua shiner N N N. jemezanus Rio Grande shiner N-x N-x N N N. ludibundus sand shiner N N N. orca phantom shiner E-x E-x E-x E-x E-x E-x N. simus simus Rio Grande bluntnose shiner E-x E-x E-x Pimephales promelas fathead minnow N N N N P. vigilax bullhead minnow I I I I I Platygobio gracilis flathead chub N Rhinichthys cataractae longnose dace N N N N N Agosia chrysogaster longfin dace I Catostomidae Carpiodes carpio river carpsucker N N N N N N Cycleptus elongatus blue sucker N-x N-x N N Ictiobus bubalus smallmouth buffalo N N N N N N Scartomyzon austrinus west Mexican redhorse T S. congestus gray redhorse N-x N-x N-x N N Characidae Astyanax mexicanus Mexican tetra N-x N N Ictaluridae Ameiurus melas black bullhead I I A. natalis yellow bullhead I I I Ictalurus furcatus blue catfish N N N N I. lupus headwater catfish N N I. punctatus channel catfish I I N N N N Ictalurus sp. Chihuahua catfish N-x N-x Pylodictis olivaris flathead catfish N N-x N N N

Above Caballo— El Paso— Quitman— Conchos— Boquillas— Family Species Common name Caballo El Paso Quitman Conchos Boquillas Devils River Esocidae Esox lucius northern pike I Salmondiae Oncorhynchus mykiss rainbow trout I I Atherinidae Membras martinica rough silverside I Menidia beryllina inland silverside I I I Fundulidae Fundulus zebrinus plains killifish I I Lucania parva rainwater killifish I Poeciliidae Gambusia affinis mosquitofish I I N N N N G. amistadensis Amistad gambusia T(E)-x G. gaigei Big Bend gambusia T (E) G. senilis blotched gambusia T-x G. speciosa Mexican mosquitofish T Poecilia latipinnia sailfin molly I Cyprinodontidae Cyprinodon eximius Devils River pupfish N N Moronidae Morone chryops white bass I I I I I M. saxatalis striped bass I Centrarchidae Ambloplites rupestris rock bass I-x Lepomis auritus redbreast sunfish T (I) L. cyanellus green sunfish I I N N N N L. gulosus warmouth I I-x T (N) L. macrochirus bluegill N N N N L. megalotis longear sunfish I I N N N L. microlophus redear sunfish I-x

Above Caballo— El Paso— Quitman— Conchos— Boquillas— Family Species Common name Caballo El Paso Quitman Conchos Boquillas Devils River L. punctatus spotted sunfish N Micropterus dolomieui smallmouth bass I I M. salmoides largemouth bass I I N N N Pomoxis annularis white crappie I I P. nigromaculatus black crappie I Percidae Etheostoma grahami Rio Grande darter N Perca flavescens yellow perch I Percina macrolepida bigscale logperch T Stizostedion vitreum walleye I I Sciaenidae Aplodinotus grunniens freshwater drum N N Cichlidae Oreochromis aureus blue tilapia T (I) Cichlasoma cyanoguttatum Rio Grande cichlid N

Fish: Species Accounts ACIPENSERIDAE Scaphirhynchus platorynchus (shovelnose sturgeon). Habitat preferences: Large rivers with sandy bottoms and strong currents (Tomelleri and Eberle 1990). Spawning is thought to occur in over rocky substrates in river channel (Tomelleri and Eberle 1990). Rio Grande distribution: Though limited to a single voucher specimen from New Mexico, the general consensus is that sturgeon used to be found in the Rio Grande, probably throughout the Chihuahuan desert reach (Hubbs et al. 1977, Williams et al. 1985, Sublette et al. 1990, Hubbs et al. 1991).

LEPISOSTEIDAE Atractosteus spatula (alligator gar). Habitat preferences: Estuaries, swamps, and river overflows (Tomelleri and Eberle 1990). Eggs are probably laid in shallow, running water (Chilton 1997). Rio Grande distribution: Campbell (1962) reported this species in the river as far west as Presidio, though it was more common in the vicinity of the mouths of the Pecos and Devils rivers. A nineteenth century collection was also reported for the Devils River (Evermann and Kendall 1894: 96).

Lepisosteus oculatus (spotted gar). Habitat preferences: Clear, quiet, vegetated water of oxbows and lakes (Tomelleri and Eberle 1990). Spawning begins in spring, in flowing water (Chilton 1997). Rio Grande distribution: A voucher specimen exists for this species from the mouth of the Devils River (W. Minckley, pers. comm.), and a collection was reported (though no specimen was preserved) from the mouth of the Pecos River (Campbell 1962).

Lepisosteus osseus (longnose gar). Habitat preferences: Relatively deep, quiet waters (Sublette et al. 1990). Beginning in spring, adhesive eggs are spawned over shallow, gravelly riffles (Chilton 1997). Rio Grande distribution: Based on archaeological evidence and eye-witness accounts recorded in the late 17th century, Sublette et al. (1990) and the New Mexico Department of Game and Fish (NMG&F 1999) conclude that this species probably occurred in the Rio Grande at least between Albuquerque and Socorro, NM. Dave Propst (pers. comm.) also considers it likely to have occurred in the reach below Caballo Reservoir. It has also been collected in the Rio Grande between Boquillas and the Devils River (Trevino- Robinson 1959, Hubbs et al. 1977) and Hubbs et al. (1977) expect it to occur in the reach above Boquillas as well.

ANGUILLIDAE Anguilla rostrata (American eel). Habitat preferences: A 1773 account of life in El Paso reported that local eels were “found more often in the ponds formed by the overflow of the river than in its channel” (Hackett 1902: 509). In addition to the loss of habitat associated with changes in the flow regime and channel morphology of the river, eels were impacted by downstream dam construction, which effectively blocked their migration to the ocean, where they reproduce. Rio Grande distribution: This species has been extirpated from the Rio Grande throughout the Chihuahuan Desert (Sublette et al. 1990, Hubbs et al. 1991, NMG&F 1999); Sublette et al. (1990) explain that recent records of eels in and around Elephant Butte Reservoir most likely represent individuals that escaped from privately stocked populations in Colorado.

CLUPEIDAE Dorosoma cepedianum (gizzard shad). Habitat preferences: Quiet, open water of lakes and rivers (Sublette et al. 1990). This fish spawns in spring, laying adhesive eggs in shallow water over rocky or sandy substrates (Sublette et al. 1990). Rio Grande distribution: Sublette et al. (1990) describe gizzard shad populations throughout the Chihuahuan reach of the Rio Grande in New Mexico as stable. This native species has also been collected in all reaches of the Rio Grande between El Paso and the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

D. petenense (threadfin shad). Habitat preferences: Lakes or rivers with moderate currents (Sublette et al. 1990). Rio Grande distribution: This species has been introduced to the Rio Grande in New Mexico (Sublette et al. 1990).

Fishes—56

CYPRINIDAE Campostoma anomalum (central stoneroller). Habitat preferences: Moving water of small streams (Sublette et al. 1990). Rio Grande distribution: This species was unsuccessfully introduced into the Rio Grande near Caballo Reservoir (Sublette et al. 1990). It occurs in the Devils River (Garrett et al. 1992), which represents the western edge of its native range in Texas (Hubbs et al. 1991).

C. ornatum (Mexican stoneroller). Habitat preferences: Clear, spring-fed water (Hubbs 1958). Although more common in small tributaries, this species is sometimes found in the Rio Grande of the Big Bend region (Hubbs and Wauer 1973, Hubbs et al. 1977). Because it breeds in tributaries like Terlingua Creek, Hubbs and Wauer (1973) suggest that tributaries may be key to the species’ survival in Big Bend. Rio Grande distribution: This threatened species has been reported in the Rio Grande at the mouth of Alamito Creek and below (Hubbs et al. 1977, Bestgen and Platania 1988).

Ctenopharyngodon idella (grass carp). Habitat preferences: Large bodies of water like rivers and reservoirs (Sublette et al. 1990). Rio Grande distribution: This Asian species has been introduced into the Rio Grande in Doña Ana County, NM (NMG&F 1999), and although it does not occur in the river in the uppermost reach of the desert Rio Grande, it occurs in ponds in the floodplain there (D. Propst, pers. comm.). According to Sublette et al. (1990), the New Mexico stocking was limited to sterile, triploid individuals to preclude reproduction among stocked individuals.

Cyprinella lutrensis (red shiner). Habitat preferences: Wide variety of habitats, ranging from ephemeral waters and small streams to rivers and lakes (Sublette et al. 1990, Becker 1983). This species can tolerate relatively high turbidity and a wide range of other environmental parameters including temperature, salinity, pH, and dissolved oxygen (Matthews and Hill 1977, Becker 1983). Red shiner eggs are adhesive (Platania and Altenbach 1998), and spawning occurs in spring and summer, over many different substrates including sunfish nests, sand or gravel riffles, and aquatic plants (Sublette et al. 1990); small tributaries are used for breeding in the Big Bend region (Hubbs and Wauer 1973). Rio Grande distribution: This native is currently found in the Rio Grande in New Mexico (NMG&F 1999), and its populations are stable (Sublette et al. 1990). It has been collected in all reaches of the Rio Grande below El Paso as well (Trevino- Robinson, 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

Cyprinella lutrensis blairi (Maravillas red shiner). Habitat preferences: Limited to Garden Spring and Peña Colorado Creek, near Marathon, TX (Hubbs 1940). Rio Grande distribution: This subspecies, known only from two sites in the Maravillas Creek drainage in the Big Bend region, appears to be extinct (Matthews 1987, Miller et al. 1989, Hubbs et al. 1991).

Cyprinella proserpinus (proserpine shiner). Habitat preferences: Springfed streams, especially low current areas (Williams et al. 1985). This species may increase its reproductive output following floods (Harrell 1978), with reproduction occurring from late spring to early fall (Valdes Cantu and Winemiller 1997). According to Hubbs and Miller (1978), although this species occurs in the Pecos and Devils rivers and many smaller tributaries of the Rio Grande, it does not occur in the Rio Grande itself. Rio Grande distribution: This species is not known to occur in the Rio Grande in New Mexico (Sublette et al. 1990), and is currently threatened in Texas and Mexico (Hubbs et al. 1991, CONABIO 1999). Trevino-Robinson (1959) collected this species in San Felipe Creek, just below the confluence of the Rio Grande and Devils River, but failed to capture any in the Rio Grande nearby. According to Williams et al. (1985) this fish no longer occurs in the lower reaches of the Pecos and Devils rivers that have been innudated by Amistad Reservoir.

Cyprinella venusta (blacktail shiner). Habitat preferences: Clear streams with sandy or gravelly bottoms (Lee et al. 1980, Chilton 1997). In the Devils River, this species is most abundant in vegetated sites near the channel margin, and it appears to have at least two periods of reproduction annually, including one in winter (Valdes Cantu and Winemiller 1997). Rio Grande Distribution: Trevino-Robinson (1959) collected this fish from the Rio Grande between the Pecos and Devils rivers, and it has been introduced into the Pecos River near Pandale, TX (Hubbs et al. 1991). This fish is abundant in the Devils River (Hubbs and Echelle 1972, Valdes Cantu and Winemiller 1997).

Fishes—57

Cyprinus carpio (common carp). Habitat preferences: Warm, quiet water (Sublette et al. 1990). This Asian species is considered a pest because it feeds on eggs of more desirable fishes and increases the turbidity of the water (Sublette et al. 1990). Rio Grande distribution: This fish has been introduced into the Rio Grande in New Mexico (NMG&F 1999, Sublette et al. 1990); it has also been introduced and is widespread in Texas (Hubbs et al. 1991). Specimens are known from all reaches of the river between El Paso and the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

Dionda argentosa (manantial roundnose minnow). Habitat preferences: Spring runs and spring-influenced headwaters (Hubbs et al. 1991). Peak reproduction may occur in fall (Valdes Cantu and Winemiller 1997). Rio Grande distribution: This species is limited to spring-influenced reaches of the Devils River and San Felipe and Sycamore Creeks, TX (Hubbs et al. 1991).

D. diaboli (Devils River minnow). Habitat preferences: This endemic species inhabits springfed, flowing streams (Williams et al. 1985), preferring fast-flowing water and gravel bottoms (Garrett et al. 1992). It is thought that this species is probably a broadcast spawner, with nonadhesive, sinking eggs (USF&WS 1999). Rio Grande distribution: Recently listed as threatened by the U.S. Fish and Wildlife Service (USF&WS 1999), this fish is limited to a few streams near and including the Devils River and the Rio San Carlos in Coahuila (Williams et al. 1985). Although not expected as a part of the regular Rio Grande fauna (Hubbs and Brown 1956, Garrett et al. 1992), before the flooding of Amistad Reservoir, the Rio Grande may have represented “an avenue of dispersal and recolonization” for this fish in the Devils River region (Garrett et al. 1992: 261).

D. episcopa (roundnose minnow). Habitat preferences: Spring-influenced headwaters (Hubbs et al. 1991) and shallow, vegetated pools (Sublette et al. 1990). Spawning of non-adhesive eggs occurs in spring (Sublette et al. 1990). Rio Grande distribution: This species has been captured from tributaries of the Rio Grande below its confluence with the Río Conchos (Hubbs et al. 1977, Trevino-Robinson 1959). Matthews (1987) suggests that this fish is increasing in abundance in the Big Bend region, perhaps to the detriment of other spring-dwelling fish.

Gila pandora (Rio Grande chub). Habitat preferences: Still water of streams, spawns in spring and summer (Sublette et al. 1990). Rio Grande distribution: This fish previously occurred in Doña Ana County and Elephant Butte Reservoir (Sublette et al. 1990, NMG&F 1999); it appears to have been extirpated by the end of the 1960s (Sublette et al 1990,). According to Hubbs et al. (1991), it is absent from the Rio Grande in Texas.

Hybognathus amarus (Rio Grande silvery minnow). Habitat preferences: Mainstream habitats of moderate depth (Bestgen and Platania 1990, Propst 1999). This species spawns in the water column and produces semi-bouyant, non-adhesive eggs that drift in the current, although fully developed larvae probably move into backwaters typified by warmer, still water and relatively abundant food (Platania and Altenbach 1998). Because the drifting eggs and protolarvae could potentially travel dozens, even hundred of kilometers before moving into backwaters, this reproductive strategy may have allowed for dispersal and recolonization of temporarily de-watered reaches during periods of high flow, but it is severely impacted by diversion structures, reservoirs, and changes to natural flow regimes (Platania and Altenbach 1998). Rio Grande distribution: Once widely distributed in the Rio Grande throughout the Chihuahuan desert, this species is now limited to a single population ranging from Elephant Butte Reservoir to Cochiti Dam in New Mexico (Bestgen and Platania 1991). It was eliminated from the reach below Elephant Butte Reservoir in New Mexico by the 1950s (Propst 1999), and the last collections from the Big Bend area and the lower Pecos River were taken in 1960 and 1940, respectively (Bestgen and Platania 1991). Trevino-Robinson (1959) collected this species on the Rio Grande between the Pecos and Devils rivers, (reported as H. placitus, Cook et al. 1992). Reasons for its exptirpation are numerous and may vary regionally; in addition to flow reductions and decreased water quality, factors such as the establishment of non-native species and range fragmentation may have had an impact in some areas (Propst 1999).

Macrhybopsis aestivalis (speckled chub, previously placed in the genera Hybopsis and Extrarius). Habitat preferences: Shallow, flowing, sometimes turbid water (Sublette et al. 1990). This species spawns in the water column and produces semi-bouyant, non-adhesive eggs that drift in the current, although fully

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developed larvae probably move into backwaters typified by warmer, still water and relatively abundant food (Platania and Altenbach 1998). Because the drifting eggs and protolarvae could potentially travel dozens, even hundred of kilometers before moving into backwaters, this reproductive strategy may have allowed for dispersal and recolonization of temporarily de-watered reaches during periods of high flow, but it is severely impacted by diversion structures, reservoirs, and changes to natural flow regimes (Platania and Altenbach 1998). Rio Grande distribution: This species has been extirpated from the Rio Grande in New Mexico (Sublette et al. 1990, NMG&F 1999, Bestgen and Platania 1990); the last records from Doña Ana county were from the 1960’s (Sublette et al. 1990). Specimens have been collected from the Rio Grande from the upper Presidio Valley through the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

Notemigonus crysoleucas (golden shiner). Habitat preferences: Quiet water (Sublette et al. 1990). Rio Grande distribution: This common bait species has been introduced and is established around Elephant Butte Reservoir (Sublette et al. 1990, Hatch cited in NMG&F 1999).

Notropis amabilis (Texas shiner). Habitat preferences: This species prefers springs and headwaters, but may be flexible in its requirements (Garrett et al. 1992). Though this species’ spawning behavior has not been studied (Chilton 1997), year-round recruitment of small individuals appears to occur (Valdes Cantu and Winemiller 1997). Rio Grande distribution: Texas shiners never occurred in the Rio Grande in New Mexico (Sublette et al. 1990) and have been collected only from tributaries of the Rio Grande near the Devils River (Trevino-Robinson 1959, Garrett et al. 1992). This species may be increasing in abundance in the vicinity of the Devils River (Garrett et al. 1992). Hubbs (1958) suggested this species might have inhabited the river in the Big Bend region prior to extensive soil erosion caused by grazing.

N. braytoni (Tamaulipas shiner). Habitat preferences: Quieter water of river (Hubbs 1958). Although this fish occurs in the Rio Grande, Hubbs et al. (1977) note that it is rarely found far from the mouths of tributary streams in Texas. Rio Grande distribution: This species occurs in the Rio Grande and Río Conchos basins in Texas and Mexico, and its populations are declining (Hubbs et al. 1991). Collections are known from the Rio Grande below the confluence with the Río Conchos (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

Notropis buchanani (ghost shiner). Habitat preferences: Pools and backwaters of low gradient rivers and creeks (Lee et al. 1980). Rio Grande distribution: Trevino-Robinson (1959) collected this species from the Rio Grande between the Pecos and Devils rivers.

N. chihuahua (Chihuahua shiner). Habitat preferences: Although this species prefers streams with cool, clear water (Burr and Mayden 1981), it has been caught in the mainstem Rio Grande. Hubbs and Wauer (1973) suggest that small tributaries may be necessary for the species’ survival in the Big Bend region, because it breeds in them. Rio Grande distribution: This species has been reported from the Rio Grande between the mouths of the Río Conchos and Marvillas Creek (Hubbs et al. 1977, Bestgen and Platania 1988).

N. jemezanus (Rio Grande shiner). Habitat preferences: Large, open rivers and streams (Sublette et al. 1990). This species spawns in the water column and produces semi-bouyant, non-adhesive eggs that drift in the current, although fully developed larvae probably move into backwaters typified by warmer, still water and relatively abundant food (Platania and Altenbach 1998). Because the drifting eggs and protolarvae could potentially travel dozens, even hundred of kilometers before moving into backwaters, this reproductive strategy may have allowed for dispersal and recolonization of temporarily de-watered reaches during periods of high flow, but it is severely impacted by diversion structures, reservoirs, and changes to natural flow regimes (Platania and Altenbach 1998). Rio Grande distribution: This species was extirpated from the Rio Grande in New Mexico by 1949 (Bestgen and Platania 1990); desert Rio Grande records were limited to Doña Ana County (Sublette et al. 1990, NMG&F 1999). More recently, specimens have been collected between the Río Conchos and the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

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N. ludibundus (sand shiner, previously known as N. stramineus). Habitat preferences: Wide variety of habitats, though it generally favors deeper, quieter water (Sublette et al. 1990). This species typically spawns in the water column over gravel and rubble substrates, where adhesive eggs remain until hatching; spawning does not appear to be linked to flow spikes (Platania and Altenbach 1998). Rio Grande distribution: This species never occurred in the Rio Grande in New Mexico (Sublette et al. 1990), and in Texas, is currently limited to a few areas including the Big Bend region and the Edwards Plateau (Hubbs et al. 1991). It has been recorded from the Rio Grande below the mouth of the Pecos River (Tanyolaç 1973), and Hubbs and Echelle (1972) described it as “abundant” in the Devils River.

N. orca (phantom shiner, recently recognized as distinct from N. simus, Chernoff et al. 1982). Habitat preferences: Mainstream habitats (Bestgen and Platania 1990). This species probably spawned in the water column and produced semi-bouyant, non-adhesive eggs which could potentially travel dozens, even hundred of kilometers before hatching; this reproductive strategy may have allowed for dispersal and recolonization of temporarily de-watered reaches during periods of high flow, but it is severely impacted by diversion structures, reservoirs, and changes to natural flow regimes (Platania and Altenbach 1998). Rio Grande distrubution: Now presumed extinct, this species once occurred in the Rio Grande throughout the Chihuahuan Desert (Williams et al. 1985, Miller et al. 1989, Sublette et al. 1990, Hubbs et al. 1991, NMG&F 1999).

N. simus simus (Rio Grande bluntnose shiner). Habitat preferences: Deeper mainstream habitats (Bestgen and Platania 1990). This species probably spawned in the water column and produced semi-bouyant, non- adhesive eggs which could potentially travel dozens, even hundred of kilometers before hatching; this reproductive strategy may have allowed for dispersal and recolonization of temporarily de-watered reaches during periods of high flow, but it is severely impacted by diversion structures, reservoirs, and changes to natural flow regimes (Platania and Altenbach 1998). Rio Grande distribution: Now extinct throughout its range, this endemic subspecies was extirpated from below Caballo Reservoir by 1940 and was last collected along the Middle Rio Grande in 1964. Its original range spanned from the Rio Chama in northern New Mexico to near El Paso (Bestgen and Platania 1990). A distinct subspecies, the Pecos bluntnose shiner (N. simus pecoensis) is restricted to portions of the Pecos River in eastern New Mexico and is listed as threatened by both the state of New Mexico and the U.S. federal government (Propst 1999).

Pimephales promelas (fathead minnow). Habitat preferences: Vegetated waters, can withstand high turbidities, temperatures, and salinities (Sublette et al. 1990). Although this fish occurs in the Rio Grande, it is rarely found far from the mouths of tributary streams in Texas (Hubbs et al. 1977). Adhesive eggs are laid in nests under objects; males maintain nest sites to keep them well oxygenated and to reduce sedimentation (Sublette et al. 1990). Rio Grande distribution: In New Mexico, records for this common bait minnow are limited to the Rio Grande above Caballo Dam (Sublette et al. 1990, NMG&F 1999), but David Propst (pers. comm.) considers it likely this species occurred in the reach below Caballo. It has also been collected from the upper Presidio Valley through the western edge of Val Verde County (Hubbs et al. 1977, Bestgen and Platania 1988).

P. vigilax (bullhead minnow). Habitat preferences: Pools and backwaters of perennial streams and rivers (Sublette et al. 1990). Rio Grande distribution: This species has been widely introduced into the Rio Grande throughout the Chihuahuan Desert (Sublette et al. 1990, Hubbs et al. 1991, NMG&F 1999). Collections have been made in all reaches of the Rio Grande between Ft. Quitman and the Devils River except in the canyon reach below the mouth of the Río Conchos (Hubbs et al. 1977, Bestgen and Platania 1988, Garrett et al. 1992); Hubbs et al. (1977) consider this distribution gap to be real instead of a sampling artifact. Between 1977 and 1988, this species became more widespread and common between El Paso and the mouth of the Río Conchos (Bestgen and Platania 1988).

Platygobio gracilis (flathead chub). Habitat preferences: Currents of rivers and streams, commonly found in turbid water and over shifting sand substrates (Sublette et al. 1990, Olund and Cross 1961). This chub spawns in late summer (Olund and Cross 1961), though its preferred spawning habitat is unknown (Tibbs 1998). Rio Grande distribution: This species is limited to reaches of the desert Rio Grande upstream of Elephant Butte Reservoir (Sublette et al. 1990, Tibbs 1998, NMG&F 1999).

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Rhinichthys cataractae (longnose dace). Habitat preferences: Spaces between cobbles and rocks in riffles or deeper water (Sublette et al. 1990); also in relatively warm-water canyons (Hubbs et al. 1977). Adhesive eggs are laid in early spring and summer, over riffles or rocky, wave-swept shorelines (Sublette et al. 1990). Rio Grande distribution: Smith and Miller (1986) and Hubbs et al. (1991) consider this species native to both the upper and lower Rio Grande, although Sublette et al. (1990) consider it introduced to the lower elevations of the Rio Grande in New Mexico, where tailwaters created by impoundments mimic its preferred habitat. It has been collected from the El Paso Valley (Bestgen and Platania 1988) and from Big Bend National Park through the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Allan et al. 1998).

Agosia chrysogaster (longfin dace, though listed in the genus Rhinichthys by Mayden et al. 1992, most authors, including Simons and Mayden 1999, still consider this fish a species of Agosia). Habitat preferences: A wide variety of stream habitats (Sublette et al. 1990). Rio Grande distribution: Native to other watersheds of New Mexico and the southwest, this fish has been introduced and established in the river between Elephant Butte and Caballo reservoirs (Propst et al. 1987, Sublette et al. 1990, NMG&F 1999).

CATOSTOMIDAE Carpiodes carpio (river carpsucker). Habitat preferences: Quiet water of lakes, rivers, and large creeks (Sublette et al. 1990). This species inhabits creeks when young, moving into the river as adults (Hubbs et al. 1977). Adhesive eggs are spawned in spring and summer over silt and sand substrates (Sublette et al. 1990). Rio Grande distribution: This native has been collected in all reaches of the desert Rio Grande (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988, Sublette et al. 1990, NMG&F 1999).

Cycleptus elongatus (blue sucker). Habitat preferences: Young occur in shallower riffles, adults prefer deeper, fast-moving water of medium to large rivers (Burr and Mayden 1999). In the Big Bend region, young live in tributaries, but as adults many move into the river (Hubbs et al. 1977). Adults spawn in spring, laying adhesive eggs over riffles, cobbles, or bedrock (Burr and Mayden 1999, Propst 1999). Rio Grande distribution: Though no voucher specimens exist from the upper reaches of the desert Rio Grande, Gehlbach and Miller’s (1961) analysis of thirteenth-century archeological remains led them to conclude that this fish once had a continuous distribution from the Big Bend region to northern New Mexico. Sublette et al. (1990) and NMG&F (1999) consider this species extirpated from the Rio Grande in New Mexico. According to Hubbs (1958), a blue sucker was captured at Castolon in Big Bend National Park, and in 1977, Hubbs et al. reported it between Maravillas Canyon and western edge of Val Verde County, TX. It also has been reported from the mouths of the Pecos and Devils rivers, and it is fairly abundant in the Rio Grande through Big Bend National Park (Burr and Mayden 1999). The Rio Grande population may represent a distinct taxon compared to blue suckers found elsewhere in North America (Burr and Mayden 1999).

Ictiobus bubalus (smallmouth buffalo). Habitat preferences: Deep, quiet water (Hubbs et al. 1977). Adhesive eggs are spawned during spring and summer, over shoals and recently inundated terrestrial vegetation (Becker 1983). Rio Grande distribution: Though considered widespread and fairly common (Sublette et al. 1990, Hubbs et al. 1991, NMG&F 1999), this species is largely restricted to the reservoirs of the Rio Grande in New Mexico instead of occurring in the river (D. Propst, pers. comm.). This species has also been reported from the river near Castolon (in Big Bend National Park) and between Maravillas Canyon and western edge of Val Verde County, TX (Hubbs 1958, Hubbs et al. 1977). The similar black buffalo (I. niger) has been reported from a few scattered sites in the Rio Grande drainage, though Sublette et al. (1990) and Hubbs et al. (1991) suggest that those reports may represent misidentifications or introductions.

Scartomyzon austrinus (west Mexican redhorse, recently known as Moxostoma austrinum). Habitat preferences: Small to large streams (Lee et al. 1980). Rio Grande distribution: Native to the Río Conchos watershed, this species has been collected in Alamito Creek (Lee et al. 1980, Hubbs et al. 1991).

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S. congestus (gray redhorse, recently known as Moxostoma congestum). Habitat preferences: Deep, slow- moving water (Propst 1999). In the Big Bend region, young live in tributary streams, but as adults, they may spend most of their time in the mainstem of the river (Hubbs et al. 1977). Spawing occurs in spring, over pebbles near the tail of pools (Martin 1986). Rio Grande distribution: This species once occurred in the Rio Grande in New Mexico below Socorro, but it has been extirpated (Propst 1999). It also previously occurred at El Paso (Miller 1976). In early 1970s this species was found in the Big Bend region (Hubbs et al. 1977) and in 1989, Garrett et al. (1992) collected it in the Rio Grande just above Del Rio, TX.

CHARACIDAE Astyanax mexicanus (Mexican tetra). Habitat preferences: Along the Pecos River in New Mexico, mostly near springs, but elsewhere uses various habitats including flowing water and pools (Sublette et al. 1990). Although more common in tributaries, this species is sometimes found in the Rio Grande (Hubbs et al. 1977). Adhesive eggs are spawned in late spring and early summer (Sublette et al. 1990). Because it breeds in small creeks, Hubbs and Wauer (1973) suggest that such tributaries may be necessary for the species’ survival in the Big Bend region. Rio Grande distribution: Sometime after the early 1950s, this species was extirpated from in Doña Ana County, NM, where it was limited to the reach below Radium Springs (NMG&F 1999, Sublette et al. 1990). Specimens have been collected from reaches between the Río Conchos and the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

ICTALURIDAE Ameiurus melas (black bullhead, previously known as Ictalurus melas). Habitat preferences: Ponds, lakes, and pools of streams (Sublette et al. 1990). Shallow nests are constructed under logs or mats of aquatic vegetation (Sublette et al. 1990). Rio Grande distribution: This species has been introduced into Elephant Butte Reservoir and has been reported from near El Paso (Sublette et al. 1990). It has also been reported from the Devils River (Valdes Cantu and Winemiller 1997).

A. natalis (yellow bullhead, previously known as Ictalurus natilis). Habitat preferences: Clear, still, vegetated pools (Lee et al. 1980). In late spring and early summer, adhesive eggs are laid in shallow nests built under banks or other protective cover (Sublette et al. 1990). Rio Grande distribution: This species has been introduced into the Chihuahuan Desert reach of the Rio Grande in New Mexico (Sublette et al. 1990, NMG&F 1999), and in 1988 it was collected from standing water in an irrigation drain in the lower El Paso Valley (Bestgen and Platania 1988).

Ictalurus furcatus (blue catfish). Habitat preferences: Large, swift rivers (Sublette et al. 1990). Spawning occurs in late spring and early summer, in nest cavities typically located in pools or backwaters (Sublette et al. 1990). Rio Grande distribution: Sublette et al. (1990) reported that this native species is present but declining in New Mexico reservoirs, and according to Chris Hoagstrom (pers. comm.) it is declining throughout most of its native range. It has been collected from all reaches between Ft. Quitman and the Devils River (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

I. lupus (headwater catfish). Habitat preferences: Clear water, moderate gradients (Sublette et al. 1990). Rio Grande distribution: Collections of this species have been made near the mouths of the Pecos and Devils rivers, in the Lower Canyons, and in the Rio Grande and its tributaries between the Río Conchos and Boquillas (Kelsch and Hendricks 1990, Garrett 1997).

I. punctatus (channel catfish). Habitat preferences: Wide range of relatively still-water habitats (Sublette et al. 1990). In summer, adhesive eggs are laid in nests constructed in protected sites such as under banks, logs, and boulders (Sublette et al. 1990). Rio Grande distribution: This species occurs in the Rio Grande throughout the Chihuahuan Desert (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988, Sublette et al. 1990, Hubbs et al. 1991, NMG&F 1999). The species is introduced to the Rio Grande in New Mexico, but is native to the lower reaches of the desert Rio Grande, the Río Conchos, and the Pecos River (Hubbs et al. 1977, Smith and Miller 1986, Bestgen and Platania 1988, Sublette et al. 1990).

Ictalurus sp. (Chihuahua catfish). This undescribed species has probably been extirpated from the Rio Grande in Doña Ana County, NM; it also occurred near El Paso (NMG&F 1999).

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Pylodictis olivaris (flathead catfish). Habitat preferences: Deep quiet pools in rivers, turbid water (Sublette et al. 1990). Rio Grande distribution: Archeological evidence suggests that this fish is native to the Rio Grande in New Mexico (Sublette et al. 1990), and Smith and Miller (1986) consider it native to the lower reaches of the river. It has been functionally extirpated from Doña Ana County, NM (NMG&F 1999, C. Hoagstrom, pers. comm.), but still occurs in Elephant Butte Reservoir (Sublette et al. 1990). Specimens are also known from the Rio Grande between the upper Presidio Valley and the Devils River (Trevino- Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988).

ESOCIDAE Esox lucius (northern pike). Habitat preferences: Cool-water lakes, ponds, and rivers. Rio Grande distribution: This non-native gamefish has been introduced to Elephant Butte and Caballo reservoirs (Sublette et al. 1990, NMG&F 1999).

SALMONIDAE Oncorhynchus mykiss (rainbow trout). Habitat preferences: Cool, clear lakes and streams (Sublette et al. 1990). Rio Grande distribution: This species was introduced into Elephant Butte and Caballo reservoirs (Sublette et al. 1990) and has been seasonally stocked below Elephant Butte Reservoir (D. Propst, pers.comm., Hatch cited in NMG&F 1999).

ATHERINIDAE Membras martinica (rough silverside). Habitat preferences: Coastal waters (Hubbs et al. 1991). Rio Grande distribution: This species has been introduced into Amistad Reservoir (Hubbs et al. 1991).

Menidia beryllina (inland silverside). Habitat preferences: Brackish water (Sublette et al. 1990). Rio Grande distribution: This species has probably never occurred in the Rio Grande in New Mexico (Sublette et al. 1990). It has been reported in the Rio Grande from just upstream of the Río Conchos to the western edge of Val Verde County, TX (Hubbs et al. 1977, Bestgen and Platania 1988). Though Hubbs et al. (1977) considered such specimens descendents from baitfish released in Amistad Reservoir (completed in 1969), Minckley (1965) found introduced silversides in the upper reaches of the Río Conchos in 1964.

FUNDULIDAE Fundulus zebrinus (plains killifish, previously known as F. kansae). Habitat preferences: Shallow, turbid water (Sublette et al. 1990). Although more common in small tributaries, this species is sometimes found in the Rio Grande (Hubbs et al. 1977). Rio Grande distribution: It has been collected between Elephant Butte and Caballo reservoirs (Propst et al. 1987) and between Maravillas Canyon and the western edge of Val Verde County, TX (Hubbs et al. 1977). In the Big Bend region, Hubbs et al. (1977: 95-96) considered this species “recently introduced” and described its potential spread as a “primary concern” because of potential impacts on Cyprinodon eximius, Campostoma ornatum, and Notropis chihuahua; by 1988, the species had reached Alamito Creek, west of Big Bend National Park (Bestgen and Platania 1988). Poss and Miller (1983) also consider populations of this species to be introduced into the Big Bend region, though it is native to the Pecos River. A congener, F. grandis, which typically inhabits estuaries, has also been collected in the lower reaches of the Pecos and Devils rivers in Texas (Hillis et al. 1980, Garrett et al. 1992).

Lucania parva (rainwater killifish). Habitat preferences: This species inhabits “river edges, backwaters; springs, [and] marshes” (Minckley et al. 1991: 254). Rio Grande distribution: It was introduced and has become established below Elephant Butte Reservoir in New Mexico (Propst et al. 1987, Sublette et al. 1990, NMG&F 1999) and it also has been reported from La Joya Refuge since 1977 (Sublette et al. 1990). The native range of this species includes the lower Pecos River in Texas (Hubbs et al. 1991, Minckley et al. 1991).

POECILIDAE Gambusia affinis (mosquitofish). Habitat preferences: A wide range of habitats, including river channels, margins, and backwaters; as well as springs, marshes and man-made habitats (Minckley et al. 1991). Although common in tributaries, this species is also found in the Rio Grande (Hubbs et al. 1977). Like other members of this family, mosquitofish reproduce via internal fertilization, and young typically appear

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in spring and summer (Sublette et al. 1990); however, year-round reproduction appears to occur in the Devils River (Valdes Cantu and Winemiller 1997). Rio Grande distribution: This species is found throughout the desert Rio Grande (Trevino-Robinson 1959, Hubbs et al. 1977, Bestgen and Platania 1988, Sublette et al. 1990, Garrett et al. 1992). Although Sublette et al. (1990) consider this fish native to lower elevation sections of the Rio Grande in New Mexico, Platania (1991) presents stocking records that document its introduction to the Rio Grande in central New Mexico, supporting Smith and Miller’s (1986) classification of this species as introduced to the upper reaches of the river.

G. amistadensis (Amistad gambusia). Habitat preferences: Spring and outflow (Minckley et al. 1991), limited to Goodenough Spring, 1.3 km from the channel of the undammed Rio Grande, near the Devils River. Rio Grande distribution: This species went extinct after its habitat was inundated by the creation of Amistad Reservoir (Minckley et al. 1991). Though eventually destroyed by the river’s waters, before the reservoir was built this population withstood periodic flooding of its habitat by river water (Peden 1973).

G. gaigei (Big Bend gambusia). Habitat preferences: Clear, warm-water springs, outflows, and marshes (Minckley et al. 1991). Limited to a few thermal springs near the Rio Grande in Big Bend National Park, this endangered species may not be part of the river fauna, since unlike G. amistadensis, this warm-water endemic probably would not survive having its springs flooded by river water (Hubbs and Springer 1957, Williams et al. 1985, Hubbs 1986). Rio Grande distribution: Extirpated from Boquillas Spring, remaining populations of this fish are being managed in other springs in the Rio Grande Village area (U.S. Dept. of Interior 1984). Potential threats include competition with G. affinis, water development, flooding, and predation (U.S. Dept. of Interior 1984).

G. senilis (blotched gambusia). Habitat preferences: This species tolerates a wide range of thermal conditions, inhabiting a variety of stream habitats, as well as springs and marshes (Hubbs and Springer 1957, Minckley et al. 1991). Rio Grande distribution: It formerly occurred along the Devils River in Texas, but has been extirpated from Texas, and is now limited to the Río Conchos watershed in Mexico (Hubbs et al. 1991, Garrett et al. 1992).

G. speciosa (Mexican mosquitofish, treated as a subspecies of G. affinis by many authors, Rauchenberger 1989). Habitat preferences: Springs, marshes, and streams (Minckley et al. 1991). Rio Grande distribution: Its native range is “undefined” because this species was only recently recognized as a full species (Minckley et al. 1991: 258). This fish is found in the Devils River in Texas (Hubbs et al. 1991).

Poecilia latipinna (sailfin molly). Habitat preferences: Warm, brackish water (Sublette et al. 1990). Rio Grande distribution: This popular aquarium fish has been introduced along the Rio Grande in New Mexico (Sublette et al. 1990); Propst et al. (1987) considered their 1987 collections of this fish between Elephant Butte and Caballo reservoirs to be the first records from the Rio Grande in New Mexico.

CYPRINODONTIDAE Cyprinodon eximius (Devils River pupfish). Habitat preferences: Shallow water at the edges of rivers and at the mouths of creeks, as well as marshes and springs (Williams et al. 1985, Minckley et al. 1991). Although more common in tributaries, this species is sometimes found in the Rio Grande itself (Hubbs et al. 1977). Rio Grande distribution: Before construction of Amistad Reservoir, this species occurred in the Rio Grande at its confluence with the Devils River (Davis 1980, W. Minckley pers. comm.). It is now limited to the Río Conchos in Mexico, to a few locations farther up the Devils River, and to tributaries of the Rio Grande in the Big Bend region and near Presidio, TX (Davis 1980, Williams et al. 1985, Hubbs and Garrett 1990). This species has been collected in Alamito Creek and in the Rio Grande nearby (Hubbs et al. 1977, Bestgen and Platania 1988).

MORONIDAE Morone chryops (white bass). Habitat preferences: Open, quiet water (Hubbs et al. 1977, Sublette et al. 1990). Rio Grande distribution: It has been introduced into the Rio Grande in New Mexico (Sublette et al. 1990). Hubbs et al. (1977) reported white bass between Ft. Quitman and the Río Conchos which they assumed had come from stocking in Amistad Reservoir, although Campbell (1962) recorded it from the

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mouth of the Pecos River prior to the dam’s construction. Bestgen and Platania (1988) documented this species’ occurrence in the El Paso Valley in 1988.

Morone saxatalis (striped bass). Habitat preferences: Estuaries and coastal waters (Sublette et al. 1990). Rio Grande distribtion: This gamefish was introduced into Elephant Butte Reservoir, and spread to Caballo Reservoir (Sublette et al. 1990).

CENTRARCHIDAE Ambloplites rupestris (rock bass). Habitat preferences: Shallow pools, lakes (Sublette et al. 1990). Rio Grande distribution: This species was introduced unsuccessfully to Elephant Butte and Caballo reservoirs (Sublette et al. 1990).

Lepomis auritus (redbreast sunfish). Habitat preferences: Warm, sluggish water (Tomelleri and Eberle 1990). Rio Grande distribution: This species, native to the eastern United States, has been introduced into much of Texas, including the Devils River (Tomelleri and Eberle 1990, Garrett et al. 1992), and was described as “abundant” in the Devils River by Hubbs and Echelle (1972).

L. cyanellus (green sunfish). Habitat preferences: Warm, shallow water of ponds, lakes, and quiet waters of rivers (Sublette et al. 1990). Although more common in tributaries in the Big Bend region, this species is sometimes found in the Rio Grande itself (Hubbs et al. 1977). Adhesive eggs are laid in nests built in shallow water with gravel, silt or sand substrates (Sublette et al. 1990, Chilton 1997). Rio Grande distribution: This species was introduced to the Rio Grande in New Mexico (NMG&F 1999), where populations are established and stable (Sublette et al. 1990). It has been also reported it in all reaches of the river between El Paso and the western edge of Val Verde County, TX, where it is native (Hubbs et al. 1977, Smith and Miller 1986, Bestgen and Platania 1988).

L. gulosus (warmouth). Habitat preferences: Weedy, turbid rivers and backwaters (Sublette et al. 1990). Adhesive eggs are laid in scoop nests built in shallow water (Sublette et al. 1990). Rio Grande distribution: This species occurs in Elephant Butte Reservoir, where it was probably introduced (Sublette et al. 1990, NMG&F 1999). In the 1950s, it was also reported from Tornillo Creek in the Big Bend region; these fish were also presumed introduced (Hubbs 1958). A 1950s collection from the Devils River also exists, though it was considered native to that river (Garrett et al. 1992).

L. macrochirus (bluegill). Habitat preferences: Relatively slow-moving water or pools (Garrett et al. 1992). Sublette et al. (1990: 308) describe this species as “the most ubiquitous species in smaller, perennial warm-water streams of New Mexico.” Although more common in tributaries in the Big Bend region, this species is sometimes found in the Rio Grande itself (Hubbs et al. 1977). Nests, typically built in gravel substrates of shallow water, sometimes occur in colonies containing 50 or more nests (Chilton 1997). Rio Grande distribution: Smith and Miller (1986) consider this fish native to the lower reaches of the desert Rio Grande only, but nineteenth century records from the El Paso area support Sublette et al.’s (1990) contention that this species may be native to the lower elevation reaches of the river in New Mexico. Stable populations exist in the Rio Grande in New Mexico (Sublette et al. 1990, NMG&F 1999). This species has also been reported from the Rio Grande between the mouth of the Río Conchos and the western edge of Val Verde County, TX (Hubbs et al. 1977, Bestgen and Platania 1988).

L. megalotis (longear sunfish). Habitat preferences: Small streams and creeks (Chilton 1997), habitats with dense brush cover over the water (Hubbs et al. 1977). Although most common in tributaries in the Big Bend region, this species is sometimes found in the Rio Grande itself (Hubbs et al. 1977). Males build and guard nests dug into gravel substrates in shallow water (Sublette et al. 1990). Rio Grande distribution: This species was introduced into the Rio Grande in New Mexico, but it is considered native to the lower river (Smith and Miller 1986, Sublette et al. 1990, NMG&F 1999). Hubbs et al. (1977) reported this species between Ft. Quitman and the Río Conchos; adding the El Paso and Presidio valleys to its distribution, Bestgen and Platania (1988) noted that it had become more widespread and common between 1977 and 1988. This species has also been reported from the Devils River (Garrett et al. 1992, Valdes Cantu and Winemiller 1997).

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L. microlophus (redear sunfish). Habitat preferences: Warm, still, vegetated water (Chilton 1997). Nests are clustered in areas with gravel or silt substrates, in somewhat deeper water than that used by other sunfish (Chilton 1997). Rio Grande distribution: Hubbs (1958) reported this species from lower Tornillo Creek and considered it introduced.

L. punctatus (spotted sunfish). Habitat preferences: Clear, vegetated streams and lakes (Tomelleri and Eberle 1990). Rio Grande distribution: This species was described as “abundant” in the Devils River by Hubbs and Echelle (1972).

Micropterus dolomieui (smallmouth bass). Habitat preferences: Cool, clear streams and lakes (Sublette et al. 1990). Rio Grande distribution: This introduced species has established populations in Elephant Butte and Caballo reservoirs (Sublette et al. 1990, NMG&F 1999). It has also been introduced into Amistad Reservoir, and now is abundant in the Devils River (Valdes Cantu and Winemiller 1997).

Micropterus salmoides (largemouth bass). Habitat preferences: Deep, quiet water (Hubbs et al. 1977), or relatively slow-moving water and pools (Garrett et al. 1992). Males build and defend nests dug into sand or gravel substrates in relatively shallow water; reservoir drawdown and wave action can destroy nests in water that is too shallow (Sublette et al. 1990). Rio Grande distribution: Native to the lower Rio Grande, this sportfish was introduced into the Rio Grande in New Mexico (Smith and Miller 1986, Sublette et al. 1990, NMG&F 1999). Hubbs et al. (1977) reported it between Maravillas Canyon and the western edge of Val Verde County, TX and they expect it to occur upstream of there, at least as far as the Río Conchos. Bestgen and Platania (1988) added the lower El Paso Valley to its distribution in 1988.

Pomoxis annularis (white crappie). Habitat preferences: Rivers and lakes, especially in warm, still, and even turbid water (Sublette et al. 1990). Rio Grande distribution: This species was introduced to the Rio Grande in New Mexico (NMG&F 1999), but it “occurs only sporadically” in the state (Sublette et al. 1990: 321); similarly, in spite of widespread introductions, it has not become established in the upper portions of the Rio Grande in Texas (Hubbs et al. 1991), though Campbell (1962) did report it from the El Paso area in the early 1960s.

P. nigromaculatus (black crappie). Habitat preferences: Clear, quiet water. Rio Grande distribution: Introduced to Elephant Butte and Caballo Reservoirs (Sublette et al. 1990, NMG&F 1999). In the early 1960s, this species was collected in two small lakes, one in an El Paso park and one near the mouth of the Devils River (Campbell 1962).

PERCIDAE Etheostoma grahami (Rio Grande darter). Habitat preferences: Clear, spring-fed streams and channels with moving water (Williams et al. 1985, Garrett et al. 1992). Although it seems unlikely it was ever a significant part of the Rio Grande fauna, Garrett et al. (1992) did collect this species in the Rio Grande just above Del Rio, TX. This species lays eggs onto rocks or vegetation when water temperatures are 20-25° C (Carlander 1997). Rio Grande distribution: This species is limited to areas around the Pecos and Devils rivers in Texas and a few tributaries of the Rio Grande in Coahuila and Nuevo Leon (Williams et al. 1985). Trevino-Robinson (1959) collected it in San Felipe Creek, which enters the Rio Grande just below Devils River and Garrett et al. (1992) collected it in the Rio Grande near Del Rio.

Perca flavescens (yellow perch). Habitat preferences: Shorelines of lakes, ponds, and river backwaters (Sublette et al. 1990). Rio Grande distribution: Introduced to the Rio Grande in southern New Mexico (Sublette et al. 1990, NMG&F 1999) this species has been collected between Caballo and Elephant Butte reservoirs (Propst et al. 1987).

Percina macrolepida (bigscale logperch). Habitat preferences: Deep, flowing water, with large gravel or cobbles (Propst 1999). Spawning occurs in spring, in flowing water over cobbles (Propst 1999). Rio Grande distribution: Along the Rio Grande, this species is limited to the Devils River, and before Amistad Reservoir was built, it occurred in Devils Lake, near the Rio Grande (Stevenson 1971).

Fishes—66

Stizostedion vitreum (walleye). Habitat preferences: Large rivers and reservoirs (Sublette et al. 1990). Rio Grande distribution: Introduced into the Rio Grande in New Mexico (Sublette et al. 1990, NMG&F 1999).

SCIAENIDAE Aplodinotus grunniens (freshwater drum). Habitat preferences: Rivers, lakes, and reservoirs, typically found along the bottom (Tomelleri and Eberle 1990). Spawning occurs in spring, probably in open water, where eggs float until hatching (Chilton 1997). Rio Grande distribution: Though Smith and Miller (1986) do not consider this fish native to the upper Rio Grande, Sublette et al. (1990) consider it extirpated from the river near present-day Albuquerque and Cochiti, based on archaeological evidence. It currently has a statewide distribution in Texas (Hubbs et al. 1991) and has been collected from the Rio Grande between the Río Conchos and the Devils River (Hubbs 1958, Trevino-Robinson 1959, Campbell 1962, Allan et al. 1998).

CICHLIDAE Cichlasoma cyanoguttatum (Rio Grande cichlid). Habitat preferences: Clear, warm water with dense vegetation (Hubbs 1958, Chilton 1997). After spawning over rocky substrates in shallow water, territorial pairs exhibit parental care of eggs and young (Itzkowitz and Nyby 1982). Rio Grande distribution: Within Texas, this species’ range is limited to Pecos and Devils rivers, and the Rio Grande below the Pecos (Lee et al. 1980). Trevino-Robinson (1959) collected it from the Rio Grande between the Pecos and Devils rivers.

Oreochromis aureus (blue tilapia, previously known as Tilapia aurea). Habitat preferences: Fresh and brackish water greater than 55° F (Chilton 1997). Rio Grande distribution: This African species has been introduced to parts of the Rio Grande drainage, and has recently been reported from the Devils River (Chilton 1997, Valdes Cantu and Winemiller 1997).

Fishes—67

Literature Cited

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Bestgen, K.R. and S.P. Platania. 1991. Status and conservation of the Rio Grande silvery minnow, Hybognathus amarus. Southwestern Naturalist 36 (2): 225-232.

Burr, B.M. and R.L. Mayden. 1981. Systematics, distribution and life-history notes on Notropis chihuahua (Pisces: Cyprinidae). Copeia 1981: 255-265.

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Chernoff, B., R.R. Miller, and C.R. Gilbert. 1982. Notropis orca and Notropis simus, cyprinid fishes from the American southwest, with description of a new subspecies. Occasional Papers of the Museum of Zoology, University of Michigan 698: 1-49.

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Cook, J. A., K.R. Bestgen, D.L. Propst, and T.L. Yates. 1992. Allozymic divergence and systematics of the Rio Grande silvery minnow, Hybognathus amarus (Teleostei: Cyprinidae). Copeia 1992 (1):36-44.

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Garrett, G.P., R.J. Edwards, and A.H. Price. 1992. Distribution and status of the Devils River minnow, Dionda diaboli. Southwestern Naturalist 37 (3): 259-267.

Gehlbach, F.R. and R.R. Miller. 1961. Fishes from archaeological sites in northern New Mexico. Southwestern Naturalist 6 (1): 2-8.

Harrell, H.L. 1978. Response of the Devil’s River (Texas) fish community to flooding. Copeia 1978: 60- 68.

Hillis, D.M., E. Milstead, and S.L. Campbell. 1980. Inland records of Fundulus grandis (Cyprinodontidae) in Texas. Southwestern Naturalist 25 (2): 271-272.

Hubbs, C.L. 1940. Fishes from the Big Bend region of Texas. Transactions of the Texas Academy of Science 3: 3-12.

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Hubbs, C. 1986. An enigmatic population of Gambusia gaigei. Southwestern Naturalist 31 (1): 121-123.

Hubbs, C. and W.H. Brown. 1956. Dionda diaboli (Cyprinidae), a new minnow from Texas. Southwestern Naturalist 1 (2): 69-77.

Hubbs, C. and A.A. Echelle. 1972. Endangered non-game fishes of the upper Rio Grande basin. In Symposium on rare and endangered wildlife of the southwestern United States, pp. 147-167. Santa Fe: New Mexico Department of Game and Fish.

Hubbs, C., R.J. Edwards, and G.P. Garrett. 1991. An annotated checklist of the freshwater fishes of Texas, with keys to identification of the species. Texas Journal of Science 43 (4/Supplement): 1-56.

Hubbs, C. and G.P. Garrett. 1990. Reestablishment of Cyprinodon eximius (Cyprinodontidae) and the status of Dionda diaboli (Cyprinidae) in the vicinity of Dolan Creek, Val Verde Co., Texas. Southwestern Naturalist 35 (4): 446-448.

Hubbs, C.L. and R.R. Miller. 1978. Notropis panarcys, Notropis sp., and N. proserpinus, cyprinid fishes of the subgenus Cyprinella, each inhabiting a discrete section of the Rio Grande complex. Copeia 1978: 582-592.

Hubbs, C., R.R. Miller, R.J. Edwards, K.W. Thompson, E. Marsh, G.P. Garrett, G.L. Powell, D.J. Morris, and R.W. Zerr. 1977. Fishes inhabiting the Rio Grande, Texas and Mexico, between El Paso and the Pecos confluence. In Importance, preservation and management of riparian habitat: a symposium, coord. R.R. Johnson and D.A. Jones, pp. 91-97. USDA, Forest Service, General Technical Report RM-43. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station.

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Hubbs. C. and V.G. Springer. 1957. A revision of the Gambusia nobilis species group, with descriptions of three new species, and notes on their variation, ecology, and evolution. Texas Journal of Science 9: 279-327.

Hubbs, C. and R. Wauer. 1973. Seasonal changes in the fish fauna of Tornillo Creek, Brewster County, Texas. Southwestern Naturalist 17 (4): 375-379.

Itzkowitz, M. and J. Nyby. 1982. Field observations of parental behavior of the Texas cichlid Cichlasoma cyanoguttatum. American Midland Naturalist 108 (2): 364-368.

Kelsch, S.W. and F.S. Hendricks. 1990. Distribution of the headwater catfish Ictalurus lupus (Osteichthyes: Ictaluridae). Southwestern Naturalist 35 (3): 292-297.

Lee, D.S, C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, eds. 1980. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History/U.S. Fish and Wildlife Service.

Martin, R.F. 1986. Spawning behavior of the gray redhorse, Moxostoma congestum (Pisces: Catostomidae) in central Texas. Southwestern Naturalist 31: 399-400.

Matthews, W. J. 1987. Geographic variation in Cyprinella lutrensis (Pisces: Cyprinidae) in the United States, with notes on Cyprinella lepida. Copeia 1987 (3): 616-637.

Matthews, W.J. and Hill, L.G. 1977. Tolerance of the red shiner, Notropis lutrensis (Cyprinidae) to environmental parameters. Southwestern Naturalist 22 (1): 89-98.

Mayden, R.L., B.M. Burr, L.M. Paige, and R.R. Miller. 1992. The Native Freshwater Fishes of North America. In Systematics, Historical Ecology, and North American Freshwater Fishes, ed. R.L. Mayden, pp. 827-863. Stanford, CA: Stanford University Press.

Miller, R.R. 1976. An evaluation of Seth E. Meek’s contributions to Mexican ichthyology. Fieldiana: Zoology 69 (1): 1-31.

Miller, R.R., J.D. Williams, and J.E. Williams. 1989. Extinctions of North American fishes during the past century. Fisheries 14 (6): 22-38.

Minckley, W.L. 1965. Records of atherinid fishes at inland localities in Texas and northern Mexico. Great Basin Naturalist 25(3/4): 73-76.

Minckley, W.L. , G.K. Meffe, and D.L. Stoltz. 1991. Conservation and management of short-lived fishes: the Cyprinodontoids. In Battle against Extinction: Native fish management in the American West, eds. W.L. Minckley and J.E. Deacon, pp. 247-282. Tucson: University of Arizona Press.

New Mexico Dept. of Game and Fish. 1999. New Mexico Species List: Fish. Available at http://www.fw.vt.edu/fishex/nmex_main/fish.htm. [29 July 1999]

Olund, L.J. and F.B. Cross. 1961. Geographic variation in the North American cyprinid fish, Hybopsis gracilis. University of Kansas Publications, Museum of Natural History 13 (7): 323-348.

Peden, A.E. 1973. Virtual extinction of Gambusia amistadensis n. sp., a poeciliid fish from Texas. Copeia 1973: 210-221.

Platania, S.P. 1991. Fishes of the Rio Chama and upper Rio Grande, New Mexico, with preliminary comments on their longitudinal distribution. Southwestern Naturalist 36 (2): 186-193.

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Platania, S.P. and C.S. Altenbach. 1998. Reproductive strategies and egg types of seven Rio Grande Basin cyprinids. Copeia 1998 (3): 559-569.

Poss, S.G. and R.R. Miller. 1983. Taxonomic status of the plains killifish, Fundulus zebrinus. Copeia 1983 (1): 55-67.

Propst, D.L. 1999. Threatened and endangered fishes of New Mexico. Santa Fe: New Mexico Department of Game and Fish, Technical Report No. 1.

Propst, D.L., G.L. Burton, and B.H. Pridgeon. 1987. Fishes of the Rio Grande between Elephant Butte and Caballo reservoirs, New Mexico. Southwestern Naturalist 32 (3): 408-411.

Rauchenberger, M. 1989. Appendix 1: Annotated list of species of the subfamily Poeciliinae. In Ecology and Evolution of Livebearing Fishes (Poeciliidae), eds. G.K. Meffe and F.F. Snelson, pp. 359- 367. Englewood Cliffs, NJ: Prentice-Hall.

Simons, A.M. and R.L. Mayden. 1999. Phylogenetic relationships of North American cyprinids and assessment of homology of the open posterior myodome. Copeia 1999 (1): 13-21.

Smith, M. L. and R.R. Miller. 1986. The evolution of the Rio Grande basin as inferred from its fish fauna. In The Zoogeography of North American Freshwater Fishes, eds. C.H. Hocutt and E. O. Wiley, pp. 457-485. New York: John Wiley & Sons.

Stevenson, M.M. 1971. Percina macrolepida (Pisces, Percidae, Etheostomatinae), a new percid fish of the subgenus Percina from Texas. Southwestern Naturalist 16 (1): 65-83.

Sublette, J.E., M.D. Hatch, and M. Sublette. 1990. The fishes of New Mexico. Albuquerque: University of New Mexico Press.

Tanyolaç, J. 1973. Morphometric variation and life history of the cyprinid fish Notropis stramineus. Occasional Papers of the Museum of Natural History, University of Kansas 12: 1-28.

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Tomelleri, J.R. and M.E. Eberle. 1990. Fishes of the central United States. Lawrence, KS: University Press of Kansas.

Trevino-Robinson, D. 1959. The ichthyofauna of the lower Rio Grande, Texas and Mexico. Copeia 1959 (3): 253-256.

United States Department of the Interior. 1984. Big Bend Gambusia Recovery Plan. Albuquerque: U.S. Fish and Wildlife Service.

United State Fish and Wildlife Service. 1999. Final rule to list the Devils River minnow as threatened. Federal Register 64 (202): 56596-56609.

Valdes Cantu, N.E. and K.O. Winemiller. 1997. Structure and habitat associations of Devils River fish assemblages. Southwestern Naturalist 42 (3): 265-278.

Williams, J.E., D. B. Bowman, J.E. Brooks, A.A. Echelle, R.J. Edwards, D.A. Hendrickson, and J.J. Landyne. 1985. Endangered aquatic ecosystems in North American deserts with a list of vanishing fishes of the region. Journal of the Arizona-Nevada Academy of Sciences 20 (1): 1-61.

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Fishes—72

Chapter 4: Herpetofauna of the Desert Rio Grande

Along the Rio Grande through the Chihuahuan Desert, as many as 100 species of amphibians and reptiles may occur (Table 4-1). Of these, 7 are obligate river residents, 31 are facultative floodplain residents, and 62 are incidental floodplain users. These three categories of river use were determined by examining the habitat requirements of each species. “Obligate” residents include river-dwelling turtles and water snakes that require aquatic habitats. “Facultative” residents, such as the tiger salamander, are generally associated with mesic or forested habitats, but they are not restricted to the river’s floodplain because they can also be found in other areas where appropriate conditions can be found. “Incidental” users are species that are generally either desert- adapted species or widespread species whose occurrence along the river does not seem to be related to the presence of the river itself; these species, such as the four rattlesnakes which occur along the river, are equally, if not more, likely to be found in areas away from the river. Brief habitat descriptions, which help justify these categorizations, are provided in the species accounts following Table 4-1.

Relatively few extirpations of amphibians and reptiles along the river seem to have been documented, perhaps because of both the lack of research and the fact that unlike fish, many of them are not obligate river residents. The few local extirpations which have occurred involve obligate and facultative river residents: the New Mexico garter snake and western painted turtle appear to have been lost in the El Paso area because of habitat degredation (Garrett and Barker 1994, Tennant 1986), and Woodhouse’s Toad may have been lost from the river’s floodplain in Big Bend National Park because of flow regulation upstream (Sam Droege, pers. comm.). None of the species along the desert Rio Grande is currently listed as threatened or endangered in the United States, but 13 are listed as threatened in Mexico (see Appendix B).

Table 4-1 and the species accounts which follow were compiled from a variety of sources. Two comprehensive references exist for the state of New Mexico (Degenhardt et al. 1996, Williamson et al. 1994) with detailed enough maps to determine specific locations where each species has been collected or is known to occur. The most comprehensive reference for Texas (Dixon 1987) maps verified records for each species on a county-by-county basis. Because of the large size of the counties in west Texas, such maps do not indicate whether a species occurs along the river specifically, so Dixon’s maps were supplemented with other sources cited in the species accounts. Thus, for the Texas stretches of the Rio Grande, a species is listed as native (or introduced) only when I could locate a specific literature discussion of its occurrence for a particular stretch of the river. Species are described as “possible” when I located only county records for a particular stretch, but the species has been documented to occur along the river elsewhere in the Chihuahuan Desert. Occurrence is described as “unknown” when all I have is a county record, with no specific mention of the species’ occurrence along the river.

Taxonomy for the species that occur in New Mexico largely follows Degenhardt et al. (1996); for species limited to Texas, it follows Conant and Collins (1991). Because subspecies may be of interest to those interested in herpetofauna diversity, the species accounts identify which subspecies may occur along the Rio Grande.

Herpetofauna—73 Table 4-1. Amphibians and Reptiles of the Rio Grande, for 6 reaches through the Chihuahuan Desert.

Stretch Occurrence Codes: N=Native, I=Introduced, N/I=native status unclear, P=Possible (collected in county bordering the river and has been reported from the Rio Grande elsewhere), ?=Unknown (collected in county but has not been reported from Rio Grande elsewhere); x=extirpated from at least a portion of particular stretch.

Riparian Use Codes: O=Obligate river resident, F=Facultative floodplain resident (generally found only in mesic or forested habitats, but not restricted to the river or floodplain), I=Incidental (equally or more likely to occur in habitats away from river).

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo Ambystomatidae Ambystoma tigrinum tiger salamander N/I N/I P P P P F Pelobatidae Scaphiopus couchii Couch’s spadefoot N N P N N P I Spea bombifrons plains spadefoot N N P P P P I New Mexico S. multiplicata N N P N P P I spadefoot Leptodactylidae Eleutherodactylus eastern barking ? I augusti frog spotted chirping Syrrhopus guttilatus N I frog S. marnockii cliff chirping frog ? I Bufonidae Bufo cognatus Great Plains toad N N P N P I B. punctatus red-spotted toad N N P P N P I B. speciosus Texas toad P P N N P I B. valliceps Gulf Coast toad P N F B. woodhousii Woodhouse’s toad N N N P N-x N F Hylidae Blanchard’s cricket Acris crepitans N F frog Pseudacris triseriata western chorus frog N F

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo Microhylidae Gastrophryne Great Plains N N P F olivacea narrowmouth toad Ranidae Rio Grande leopard Rana berlandieri P P N P F frog Rana blairi plains leopard frog N F R. catesbeiana bullfrog N/I N/I P N/I P F northern leopard R. pipiens N N N F frog Chelydridae Chelyedra common snapping I F serpentina turtle Emydidae western painted Chrysemys picta N N N-x O turtle Pseudemys gorzugi Rio Grande cooter N O ornate (or desert) Terrapene ornata N N P P P P I box turtle Trachemys gaigeae Big Bend slider N N P N N N O T. scripta red-eared slider I P O Kinosternidae Kinosternon yellow mud turtle N P P N P F flavescens Big Bend K. hirtipes N F mud turtle Trionychidae Trionyx spiniferus spiny softshell N N N N N N O Testudinae Gopherus Texas tortoise I ? I berlandieri Polychridae Anolis carolinensis green anole I F Crotaphytidae Crotaphytus collaris collared lizard N N P P P P I

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo longnose leopard Gambelia wislizenii N N P P N I lizard Phrynosomatidae Cophosaurus southwestern N N P N N P I texanus earless lizard Holbrookia maculata earless lizard N N P P P P I Phrynosoma Texas horned lizard N N P N P P I cornatum roundtail horned P. modestum N N P N N P I lizard twin-spotted spiny Sceloporus magister N N P P N P F lizard S. merriami canyon lizard P N P I S. olivaceus Texas spiny lizard P P I S. poinsettii crevice spiny lizard N N P P N P I southern prairie S. undulatus N N P N N P I lizard Urosaurus ornatus tree lizard N N P N P P I Uta stansburiana side-blotched lizard N N P N N P I Gekkonidae Texas banded Coleonyx brevis P N N P I gecko C. reticulatus reticulated gecko N P I Hemidactylus Mediterranean I I I turcicus gecko Teiidae Cnemidophorus Chihuahuan N N P N P P I exsanguis spotted whiptail C. grahamii/ checkered whiptail N N P N N P I tesselatus Texas spotted C. gularis ? ? ? I whiptail C. inornatus little striped whiptail N N P N P P I C. marmoratus/tigris marbled whiptail N N P N N P I New Mexico C. neomexicanus N N N N F whiptail

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo plateau spotted C. septemvittatus ? ? ? ? I whiptail desert grassland C. uniparens N N P N I whiptail Scincidae Eumeces obsoletus Great Plains skink N N P P N P F E. tetragrammus short-lined skink P N P F Scincella lateralis ground skink ? F Leptotyphlopidae New Mexico blind Leptotyphlops dulcis N N P N P I snake Trans-Pecos blind L. humilis N P N N P I snake Colubridae Arizona elegans glossy snake N N N P N P I Bogertophis Trans-Pecos rat N N P P N P I subocularis snake Coluber constrictor yellowbelly racer N P F Diadophis punctatus ringneck snakes N P P N P F Drymarchon corais Texas indigo snake ? F Elaphe bairdi Baird’s rat snake ? ? I Elaphe guttata rat snake N P N N P F western hooknose Gyalopion canum P N P P N P I snake Heterodon nasicus hognose snake N N P P P P I Hypsiglena torquata night snake N N P P N P I gray-banded Lampropeltis alterna P P P P I kingsnake Lampropeltis getula desert kingsnake N N P N N P I New Mexico milk L. triangulum N N P P P P I snake Masticophis coachwhip N N P N N P I flagellum desert striped M. taeniatus N N P P N P I whipsnake

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo Nerodia blotched water P N N O erythrogaster snake diamondback water N. rhombifera P N O snake Opheodrys aestivus rough green snake ? F Pituophis gopher (or bull) N N N N N P I melanoleucus snake Rhinocheilus longnose snake N N P P N P I lecontei Salvadora Big Bend N N P P N P I deserticola patchnose snake Texas patchnose S. grahamiae ? I snake Sonora ground snake N N P N N P I semiannulata Tantilla gracilis flathead snake ? I southwestern Tantilla hobartsmithi N P P P P I blackhead snake plains blackhead T. nigriceps N N P P P P I snake Devils River T. rubra diabola ? F blackhead snake Thamnophis blackneck garter N P N N P F cyrtopsis snake checkered garter T. marcianus N N P N N P F snake western ribbon T. proximus P N F snake New Mexico garter T. sirtalis N N N-x F snake Trimorphodon lyre snake N N P P N P I biscutatus Tropidoclonion lined snake I-x F lineatum Elapidae Micrurus fulvius Texas coral snake ? I

Rio Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Family Species common name Puerco— El Paso Ft. Quitman Conchos Boquillas Devils River Use Caballo Viperidae Agkistrodon Trans-Pecos P N P F contortix Copperhead western Crotalus atrox diamondback N N P N N P I rattlesnake C. lepidus rock rattlesnake N P P N P I C. molossus blacktail rattlesnake N N P N N P I C. scutulatus Mojave rattlesnake P N N P I Arizona black C. viridis N N P P P P I rattlesnake Sistrurus catenatus desert massasauga N N P I

SPECIES ACCOUNTS

SALAMANDERS

Ambystomatidae Ambystoma tigrinum (tiger salamander). This species is widespread throughout much of North America and it can utilize a wide variety of habitats as long as there is non-flowing water nearby for breeding (Degenhardt et al. 1996). It has been reported from all along the Rio Grande in New Mexico (Degenhardt et al. 1996), and has been reported from all the counties bordering the river through the Chihuahuan Desert in Texas (Dixon 1987). However, Minton (1958) suggested that this species was limited to the higher elevation grasslands in the Big Bend region and the tiger salamander is listed as a hypothetical species for Big Bend National Park, where is has not been reported from anywhere along the river in the park (Amphibians 1996). The subspecific taxonomy of the species is under debate (Degenhardt et al. 1996) and the native ranges of western subspecies may be difficult to determine due to widespread introduction of salamanders as fish bait (Dixon 1987, Conant and Collins 1991). Tiger salamander populations do not seem to be negatively impacted by urbanization or agriculture unless pollution becomes too high (Degenhardt et al. 1996).

TOADS AND FROGS

Pelobatidae Scaphiopus couchii (Couch’s spadefoot). Widely distributed across the southwestern United States and much of Mexico, this species breeds in ephemeral water after thunderstorms. In New Mexico, it tends to prefer arid environments with sandy, well-drained soils, although they do show up in irrigated agricultural lands along rivers too (Degenhardt et al. 1996). This species occurs along the Rio Grande throughout the Chihuahuan Desert reach in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and it has been reported from all counties bordering the Chihuahuan stretch of the river in Texas (Dixon 1987). In Big Bend National Park, Couch’s spadefoot is common and its range of occurrence includes the river’s floodplain (Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

Spea bombifrons (plains spadefoot). This Great Plains species most often occurs in grasslands (Degenhardt et al. 1996). Nevertheless it has been reported from along the Rio Grande throughout New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and from all the counties bordering the river in Texas except for Brewster County (Dixon 1987). This apparent Big Bend gap in its distribution is further supported by this species’ exclusion from national park’s list of amphibians and reptiles (Amphibians 1996).

S. multiplicata (New Mexico or southern spadefoot). Previously known as Scaphiopus hammondii, this spadefoot ranges from the southwestern United States to southern Mexico and uses various habitats including river valleys and agricultural lands (Degenhardt et al. 1996). It has been reported along the Rio Grande’s Chihuahuan reach in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) as well as from all counties bordering the river in Texas (Dixon 1987). Jameson and Flury (1949) found this toad using the tamarisk-mesquite habitats along the river between Ft. Quitman and Presidio. This species may not occur in Big Bend National Park, and may utilize higher elevation habitats (especially grasslands) than Couch’s spadefoot (Minton 1958, Amphibians 1996).

Leptodactylidae Eleutherodactylus augusti latrans (eastern barking frog). This frog was recently moved from the genus Hylactophryne. In New Mexico, this rock-crevice inhabitant is limited to a few areas near the Pecos River (Degenhardt et al. 1996). In Texas, the only counties along the Chihuahuan Rio Grande it has been reported from are Terrell and Val Verde counties (Dixon 1987); because of its tight association with rocky outcrops and escarpments, if it does occur along the river, it would be in such areas.

Herpetofauna —80 Syrrhopus guttilatus (spotted chirping frog). This is another rock-crevice dweller, and it is limited to the Big Bend region in the United States (reported only from Presidio and Brewster counties; Dixon 1987), with disjunct populations occurring further south in Mexico (Conant and Collins 1991). This species is rare in Big Bend National Park, where it has been reported from the entrance to Santa Elena Canyon as well as the Chisos Mountains (Amphibians 1996). In 1999, amphibian surveys by USGS biologists have also found this frog in other canyons along the Rio Grande in Big Bend (Sam Droege, pers. comm.).

S. marnockii (cliff chirping frog). This species is limited to central and eastern Texas, where it lives in caves and crevices of limestone hills (Garrett and Barker 1994). It has been reported from Terrell and Val Verde Counties (Dixon 1987); if it occurs (or occurred) along the river, it would be in rocky areas.

Bufonidae Bufo cognatus (Great Plains toad). Widespread through the Great Plains, the desert southwest and much of Mexico, this species lives in arid and semi-arid environments, where it survives via burrowing; river bottoms are among its preferred habitats (Degenhardt et al. 1996). It has been reported from all along the Rio Grande in New Mexico, and all of the counties bordering the river from El Paso through Brewster County (Dixon 1987). Jameson and Flury (1949) found this species in tamarisk-mesquite habitats along the river between Ft. Quitman and Presidio, but it is not included in Big Bend National Park’s list of amphibians (Amphibians 1996).

B. punctatus (red-spotted toad). Found throughout much of the southwestern United States and Mexico, this species prefers dry rocky areas like arroyos (Degenhardt et al. 1996). It occurs all along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is widespread throughout river bottom and lowland desert habitats of Big Bend region (Minton 1958, Amphibians 1996).

B. speciosus (Texas toad). As its common name implies, the range of this species is largely limited to Texas and neighboring parts of northern Mexico. In New Mexico, its distribution is limited to the Pecos River drainage, although it may also occur in southernmost Dona Ana County (Conant and Collins 1991, Williamson et al. 1994). It has been reported from all the counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987) and prefers sandy soils where short grasses or mesquite dominate (Degenhardt et al. 1996). This species is common in Big Bend National Park, where it occurs in the river’s floodplain and other desert habitats (Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

B. valliceps valliceps (Gulf Coast toad). The edge of this species’ range occurs in Terrell and Val Verde counties (Dixon 1987) and a disjunct population has been reported from the Big Bend region (Conant and Collins 1991), but it is not included in the national park’s list of amphibians (Amphibians 1996). Conant (1977) presents a collection record for this species from the mouth of the Devils River.

B. woodhousii (Woodhouse’s toad). This widely distributed species generally occurs in mesic habitats near perennial streams and rivers and has been reported from all along Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It has also been reported from all Texas counties along the river from El Paso through Brewster County (Dixon 1987). Conant (1977) documents this species’ occurrence along the river in El Paso County and at the mouth of Maravillas Creek east of Boquillas. Woodhouse’s toad is rare in Big Bend National Park, where its distribution is limited to the Rio Grande’s floodplain (Minton 1958, Amphibians 1996). However, recent surveys by USGS biologists at the park have failed to discover any specimens of this toad, suggesting it may have been extirpated in recent years (Sam Droege, pers. comm.). Park records indicate that the last report of this species in the park was in the late 1970s (Robin Jung, pers. comm.). According to Sam Droege (pers. comm.), changing river flows, which have effectively eliminated the backwater habitats this species breeds in, are probably responsible for its extirpation; interactions with bullfrogs are a less likely cause because the two species utilize different habitats within the floodplain.

Herpetofauna —81 Hylidae Acris crepitans blanchardi (Blanchard’s cricket frog). This mesic-adapted species of the eastern United States prefers marshy edges of streams, rivers and springs and does not occur along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It has been reported from Brewster, Terrell and Val Verde counties in Texas (Dixon 1987) and Conant (1977) presents a record of its collection from the mouth of the Devils River, before the flooding of Amistad Reservoir. Axtell (1959) says this species requires permanent running water, and suggests it may be restricted to higher elevation habitats at the western edge of its range, e.g.: Brewster County.

Pseudacris triseriata (western chorus frog). This more northern species may just sneak into the Chihuahuan Desert along the Rio Grande in Socorro County, NM (Williamson et al. 1994, Degenhardt et al. 1996); it has been found just north of Socorro, and may occur at the Bosque del Apache National Wildlife Refuge (New Mexico Department of Game and Fish 1999).

Microhylidae Gastrophryne olivacea (Great Plains narrowmouth toad). This species uses a variety of habitats including grasslands, sparse woodlands, marshy areas, and flooded irrigation ditches (Conant and Collins 1991, Degenhardt et al. 1996). It does not occur along the Rio Grande in New Mexico (Degenhardt et al. 1996), but has been reported from Presidio, Brewster, Terrell and Val Verde counties, TX (Dixon 1987). This species is uncommon in Big Bend National Park, where it is found in the river’s floodplain and other mesic microhabitats in the desert (Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

Ranidae Rana berlandieri (Rio Grande leopard frog). Preferring clear flowing streams or perennial pools, this species does not occur along Rio in New Mexico (Degenhardt et al. 1996, Williamson et al. 1994). This species is widely distributed in most of Texas and the Mexican states bordering the Rio Grande (Conant and Collins 1991), and has been collected in all the Texas counties bordering the Rio Grande through the Chihuahuan Desert (Dixon 1987). Occurring in the river’s floodplain and other aquatic habitats up into the foothills, this frog is common in Big Bend National Park (Minton 1958, Amphibians 1996); USGS surveys in 1999 confirm its continued presence there (Sam Droege, pers. comm.).

Rana blairi (plains leopard frog). The only Rio Grande population of this species is found in an area near Truth or Consequences, NM, where it hybridizes with R. pipiens (Degenhardt et al. 1996). Throughout its distribution in the central U.S., it occurs in a wide variety of ephemeral and perennial waters (Degenhardt et al. 1996).

R. catesbeiana (bullfrog). Bullfrogs are found most often in large bodies of permanent water, though they move to ephemeral waters in the rainy season (Degenhardt et al. 1996). They have been widely introduced, making determination of their original native distribution difficult in both Texas and New Mexico (Dixon 1987, Degenhardt et al. 1996). It has been reported from all along the Chihuahuan stretch of the Rio Grande in New Mexico (Degenhardt et al. 1996), where its population has been increasing as R. pipiens’ population has decreased (New Mexico Dept. of Game and Fish 1999). While Dixon’s (1987) map for Texas shows this species occurring in all the counties along the Rio Grande except for Brewster County, the Big Bend National Park amphibians list describes an established, introduced population in Rio Grande Village and says that the frog has been collected near Lajitas and heard calling elsewhere along the river (Amphibians 1996). USGS surveys in 1999 confirm its continued presence in the park (Sam Droege, pers. comm.).

R. pipiens (northern leopard frog). Generally occurring in streams and rivers, this species occurs along Rio Grande in New Mexico except around Elephant Butte and Caballo reservoirs (Williamson et al. 1994, Degenhardt et al. 1996). Dixon (1987) presents Texas records of this species from El Paso County only, though he says its range probably extends to southern Hudspeth County. Engel-Wilson and Ohmart (1978) report this species from the river valley below Ft. Quitman. At the Bosque del Apache National Wildlife Refuge, this species is declining, perhaps because of increases in bullfrogs or other factors (New Mexico Department of Game and Fish 1999).

Herpetofauna —82

TURTLES

Chelydridae Chelydra serpentina serpentina (common snapping turtle). This species may have been introduced into the Rio Grande in Socorro County, NM (Williamson et al. 1994, Degenhardt et al. 1996).

Emydidae Chrysemys picta bellii (western painted turtle). This turtle prefers slow-moving, permanent water and is found all along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). Milstead (1960) and Dixon (1987) show this species occurring along the river in El Paso County, but according to Garrett and Barker (1994), this population may have been extirpated due to habitat degredation.

Pseudemys gorzugi (Rio Grande cooter or western river cooter). This species prefers rivers, especially deeper pools, and is not found along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It occurs mostly along the lower Rio Grande in Texas, including Terrell and Val Verde counties (Dixon 1987). Conant (1977) presents a collection record for Chrysemys concinna from the mouth of the Devils River, and from Degenhardt et al.’s discussion of the recent taxonomy of this species, it seems that this record would now be called P. gorzugi.

Terrapene ornata (ornate or desert box turtle). This arid adapted turtle is not dependent upon free water and prefers grasslands where they often use kangaroo rat burrows for shelter (Degenhardt et al. 1996). It occurs all along the river in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river through the Chihuahuan Desert of Texas. However, it may not occur along the river in all those counties: it has never been reported from along the river in Big Bend National Park and is largely restricted to grassland habitats north of the park (Amphibians 1996, Minton 1958). Two subspecies of this turtle could occur along the river, T. ornata luteola from Big Bend up into New Mexico, and T. ornata ornata (or intergrades between the two) downstream of Big Bend (Conant and Collins 1991).

Trachemys gaigeae (Big Bend slider). This species prefers deep river, lake, and reservoir habitats and has been collected in the Rio Grande in Sierra and Socorro counties, NM (Degenhardt et al. 1996), and Paul Hyder (pers. comm.) has photographed this species along the Rio Grande south of Las Cruces. This species has been collected in Hudspeth, Presidio, and Brewster counties (Dixon 1987) and in the Big Bend area at least, it is restricted to the river’s floodplain (Minton 1958, Axtell 1959, Amphibians 1996). Conant (1977) maps collection locations for this slider (though he calls it Chrysemys scripta, the pond slider, writing before recent taxonomic revisions) from the mouths of the Río Conchos, and the Pecos and Devils rivers, as well as the Big Bend region, and Engel-Wilson and Ohmart (1978) reported Pseudemys scripta from the stretch of the river below Ft. Quitman.

T. scripta elegans (red-eared slider). Native to central North America east of the Pecos River (Collins and Conant 1991), this turtle of permanent wetlands has been introduced to the Rio Grande in Socorro and Sierra Counties, NM (Degenhardt et al. 1996). Native turtles have been reported from both Terrell and Val Verde counties, TX (Dixon 1987).

Kinosternidae Kinosternon flavescens flavescens (yellow mud turtle). This species occurs in arid and semi-arid grasslands and woodlands, and prefers quiet shallow water for the aquatic part of its life cycle (Degenhardt et al. 1996). It occurs along the Rio Grande in New Mexico below Caballo Reservoir (Williamson et al. 1994, Degenhardt et al. 1996) and it has been reported from all the counties bordering the river in the Texas Chihuahuan Desert (Dixon 1987). This species is uncommon in Big Bend National Park, where it occurs in the floodplain and other desert environments, often in muddy, temporary pools (Amphibians 1996).

K. hirtipes murrayi (Big Bend mud turtle). The United States distribution of this species is restricted to the Alamito Creek drainage in Presidio County, TX (Conant and Collins 1991). It lives in permanent water

Herpetofauna —83 habitats in mesquite grasslands (Ernst et al. 1994). In the Rio Grande at Lajitas, spiny softshells and Big Bend sliders are much more common (Ernst et al. 1994).

Trionychidae Trionyx spiniferus emoryi (Texas spiny softshell). Some authors place this species in the genus Apalone; see Degenhardt et al. (1996:120) for an overview of recent taxonomy. Occurring mostly in permanent water, especially rivers or ponds in their floodplains, this species occurs all along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). This species has been reported from all the counties bordering the Chihuahuan Rio Grande in Texas too (Dixon 1987) and in the Big Bend area at least, it is restricted to the river’s floodplain (Minton 1958, Amphibians 1996). Conant (1977) presents collection records along the river for the stretch below El Paso, the mouth of the Río Conchos, the Big Bend region, and the mouth of the Devils River, and Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

Testudinidae Gopherus berlandieri (Texas tortoise). This species may sneak into the eastern edge of the Chihuahuan desert. The western edge of this species’ range is near the Pecos River in Texas (Dixon 1987). Tortoises have been found in at Rio Grande Village in Big Bend National Park, but those are likely introduced individuals (Amphibians 1996).

LIZARDS

Polychridae Anolis carolinensis (green anole). This species of the eastern United States has been introduced to and established in Rio Grande Village of Big Bend National Park (Amphibians 1996).

Crotaphytidae Crotaphytus collaris (collared lizard). This wide-ranging species can utilize a variety of habitats, including riparian gallery forests and riparian grasslands (Degenhardt et al. 1996), and it has been reported from all along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It has also been reported from all the counties along the Rio Grande in Texas (Dixon 1987), although in the Big Bend Region it prefers open desert habitats and has not been reported along the river (Minton 1958, Amphibians 1996). Two subspecies occur along the Rio Grande: C collaris collaris from about Hudspeth County on down, and C. collaris fuscus upstream of Hudspeth County (Dixon 1987, Conant and Collins 1991).

Gambelia wislizenii wislizenii (longnose leopard lizard). This lizard generally prefers rocky areas or fairly open habitats with sandy soils (Degenhardt et al. 1996) It has been reported from all stretches of the Rio Grande in the Chihuahuan Desert of New Mexico (Degenhardt et al. 1996) and from El Paso, Hudspeth and Brewster counties in Texas (Dixon 1987). Though extremely rare in Big Bend National Park, this species has been reported from a few different sites along the river (Amphibians 1996).

Phrynosomatidae Cophosaurus texanus (Southwestern and Texas earless lizards). This Chihuahuan Desert endemic (Morafka 1977) prefers gravelly and rocky habitats, including arroyos and floodplains (Degenhardt et al. 1996). It has been collected all along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has also been reported from all the counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987). Common and fairly widely distributed in Big Bend National Park, it has been reported from sites along the river there (Minton 1958, Amphibians 1996). Engel-Wilson and Ohmart (1978) reported Holbrookia texana along the river below Ft. Quitman. Two subspecies occur along the Chihuahuan Rio Grande: C. texanus scitulus (Southwestern earless) through most of the range, switching to C. texanus texanus (Texas earless) in Val Verde County, TX (Dixon 1987, Conant and Collins 1991).

Holbrookia maculata approximans (speckled earless lizard). This species prefers level terrain, loose soils, and relatively sparse vegetation and has been reported all along the Chihuahuan Rio Grande of New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It has also been reported from all the Texas

Herpetofauna —84 counties along the Chihuahuan Rio Grande except for Val Verde (Dixon 1987), but it may not occur along the river throughout this range. It does not appear on the Big Bend National Park list of reptiles (Amphibians 1996), and Minton (1958) suggested this species might be restricted to higher elevation grasslands in the Big Bend region.

Phrynosoma cornatum (Texas horned lizard). This species prefers open deserts and grasslands and has been reported from all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). It has also been reported from all the counties along the Chihuahuan Rio Grande in Texas (Dixon 1987), but it may not occur along the river throughout this range. Minton (1958) says its restricted to short grass prairie in the Big Bend region and it is extremely rare in Big Bend National Park, where it has been reported only from areas in the northern part of the park, away from the river (Amphibians 1996). However, Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman. In Texas and Oklahoma this species is declining because of habitat loss, fire ant spread, and illegal collecting (Degenhardt et al. 1996), but Donaldson et al. (1994) conclude that Texas horned lizard populations are doing fairly well in western Texas, with the significant declines mostly limited to eastern and central Texas.

P. modestum (roundtail horned lizard). This species is largely restricted to the Chihuahuan Desert (Morafka 1977, Conant and Collins 1991) and it occurs in a wide variety of desert habitats, especially those with gravelly soils (Degenhardt et al. 1996). It occurs all along the Chihuahuan reach of the river in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all Texas counties bordering the river (Dixon 1987). Although this species prefers the more arid parts of the Big Bend region (Minton 1958), the Big Bend National Park reptile list suggests that it can be found in desert flats near the river (Amphibians 1996). In addition, Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

Sceloporus magister bimaculosus (twin-spotted spiny lizard). Typically arboreal, and therefore often found in riparian areas in deserts, this species occurs all along Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). In Texas, it has been reported from El Paso, Hudspeth and Brewster counties (Dixon 1987). This species is fairly common in Big Bend National Park, where it ranges from the river’s floodplain to foothill habitats in areas with fairly dense vegetation (Amphibians 1996).

S. merriami (canyon lizard). This Chihuahuan Desert endemic (Morafka 1977) likes rocky, sparsely vegetated areas such as limestone hills, canyons and steep-walled gorges (Olson 1973). It ranges from Presidio through Val Verde County in Texas (Dixon 1987) and can be found along the river in Big Bend National Park (Amphibians 1996). Two subspecies may occur along the river: S. merriami longipunctatus (Presidio canyon lizard) in Presidio County, and S. merriami merriami (Merriam’s canyon lizard) from Brewster County and on to the east (Dixon 1987). A third subspecies (S. merriami annulatus) is restricted to higher elevation areas of the Chisos Mountains (Minton 1958, Axtell 1959).

S. olivaceus (Texas spiny lizard). Mostly arboreal, this species is generally found in trees including mesquites and cottonwoods and ranges through most of Texas and into eastern Mexico (Conant and Collins 1991). It has been reported from Brewster, Terrell and Val Verde counties in Texas (Dixon 1987), although it does not appear on the reptile list for Big Bend National Park (Amphibians 1996).

S. poinsetii poinsetii (crevice spiny lizard). This species prefers rocky areas, and in New Mexico, its distribution is generally bisected by the Chihuahuan portion of the Rio Grande valley; as such, Degenhardt et al. (1996:173) describe the few scattered specimens that have been collected along the river as “curious,” though perhaps indicative of a previously wider distribution. For Texas, the species has been reported from all the counties bordering the river through the Chihuahuan Desert (Dixon 1987); populations that occur along the edge of the Edwards Plateau are limited to major river canyons (Degenhardt et al. 1996). In Big Bend National Park this species is common in rocky, higher elevation sites, but it has also been reported occasionally from the river’s canyons (Amphibians 1996).

Herpetofauna —85 S. undulatus consobrinus (southern prairie lizard). This species utilizes a wide variety of habitats, including riparian zones, and is sometimes arboreal (Degenhardt et al. 1996). It has been reported from all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and from all the counties bordering the river in Texas (Dixon 1987). Jameson and Flury (1949) found this species in the cottonwood-dominated areas of the river’s floodplain between Ft. Quitman and Presidio, and in Big Bend National Park, where it is fairly common, it uses a wide variety of habitats, including areas along the river (Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

Urosaurus ornatus (tree lizard). This wide-ranging species is most often found on rocks or trees (Conant and Collins 1996); it occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Jameson and Flury (1949) found this species in the salt-cedar/mesquite habitats of the river’s floodplain between Ft. Quitman and Presidio and expect it to occur in other floodplain habitats. Minton (1958) reported this lizard from higher elevation regions of Big Bend only, not along river; similarly, the Big Bend National Park reptile list described this species as fairly common, but limited to the foothills and mountains (Amphibians 1996). Several subspecies may occur along the river: through most of Texas, U. ornatus schmidti (Big Bend tree lizard) should occur, while U. ornatus ornatus (eastern tree lizard) may sneak into the Chihuahuan Desert in Val Verde County (Dixon 1987, Conant and Collins 1991). In New Mexico, the subspecies U. ornatus linearus occurs along the desert Rio Grande, with a small zone of overlap with U. ornatus schmidti in southernmost New Mexico (Smith 1946).

Uta stansburiana stejnegeri (desert side-blotched lizard). This wide-ranging lizard prefers areas of sparse cover, and tends to avoid woodlands and grasslands (Degenhardt et al. 1996). It has been found all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and reported from all the counties bordering the river in Texas (Dixon 1987). Smith and Sanders (1952) collected this species 3.9 miles northwest of Fort Hancock and Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman. Side-blotched lizards are common in Big Bend National Park, where they use a variety of lower elevation habitats, including those along the river (Amphibians 1996, Minton 1958).

Gekkonidae Coleonyx brevis (Texas banded gecko). This native gecko prefers rocky habitats such as canyons (Conant and Collins 1991) and limestone hills (Degenhardt et al. 1996) and is not found along the Rio Grande in New Mexico (Degenhardt et al. 1996). It has been reported from all the counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987) including some sites along the river in the Big Bend area (Minton 1958). Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

C. reticulatus (Reticulated gecko). Another native gecko that prefers rugged, rocky habitats, this species is restricted to the Big Bend area of Texas and two small areas in north-central Mexico (Conant and Collins 1991) and it is considered an endemic of the Chihuahuan Desert (Morafka 1977). It has been reported from Presidio and Brewster counties in Texas (Dixon 1987). This species is extremely rare in Big Bend National Park, where it occurs in rocky outcrops and desert lowlands (Amphibians 1996), and it has been reported from sites along the river west of Lajitas, especially in rocky roadcuts at the edge of the river’s floodplain (Easterla and Reynolds 1975).

Hemidactylus turcicus (Mediterranean gecko). This introduced species is most often found in and around human habitations (Degenhardt et al. 1996). The first New Mexico report of this species was in 1992, from Las Cruces, where the population is spreading quickly (Degenhardt et al. 1996). First introduced to Texas in 1955, by 1987 this gecko had been reported from 41 counties (Dixon 1987). This species was established in Cuidad Acuña, Coahuila by 1966 (Scudday 1977) and had arrived at Boquillas, Coahuila by 1972 (Wauer and Burdick 1974). It established itself at Rio Grande Village in Big Bend National Park by 1973 (Easterla 1978); in 1996 this species was still described as “very rare” in Big Bend National Park, and still limited to Rio Grande Village (Amphibians 1996). A Mediterranean gecko was

Herpetofauna —86 reported from El Paso in 1980, but it was unknown if it was evidence of a self-sustaining, breeding population (Price 1980).

Teiidae NOTE: The taxonomy of whiptails is a subject of much debate. Because names are applied inconsistently, and some full-species vs. subspecies distinctions are not terribly clear, the list below includes more subspecies and alternate names than the lists for most other families.

C. exsanguis (Chihuahuan spotted whiptail). This parthenogenic species occurs in relatively mesic habitats, especially juniper woodlands, and has been found in degraded riparian habitat near Las Cruces (Degenhardt et al. 1996). It is found all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from El Paso, Hudspeth and Brewster counties in Texas (Dixon 1987). However, it may not occur along the river in all of these Texas counties. Minton (1958) describes a Cnemidophorus sacki ssp. which he suspects is an intergrade between C. sacki exanguis and C. sacki gularis (both of which have subsequently been elevated to full species status) from grassland habitats near Alpine in the Big Bend region; none of his records come from along the river, and this whiptail does not appear on the reptile list for Big Bend National Park (Amphibians 1996). However, Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman.

C. grahamii/tesselatus (checkered whiptail). According to Degenhardt et al. (1996) most of the lizards previously referred to as C. tesselatus should probably be called C. grahamii; however, C. tesselatus is still widely used. This parthenogenic whiptail occurs in a variety of habitats, including cottonwood-willow- tamarisk areas, and occurs all along Chihuahuan Rio Grande in New Mexico (Degenhardt et al. 1996). Jameson and Flury (1949) found C. grahamii and a whiptail they call C. tessellatus in the salt-cedar mesquite habitats of the river’s floodplain between Ft. Quitman and Presidio. [Degenhardt et al.’s discussion of C. grahamii’s checkered past suggests that perhaps Jameson and Flury’s C. tessellatus could have been C. tigris, since the name tessellatus was inappropriately applied to many tigris whiptails in the past.] C. tesselatus is common in Big Bend National Park, especially in the river’s canyons (Amphibians 1996) and Engel-Wilson and Ohmart (1978) reported both C. tesselatus and C. tigris along the river below Ft. Quitman.

C. gularis gularis (Texas spotted whiptail). This subspecies uses a wide variety of habitats, including sites dominated by tamarisk and Sporobolus airoides (alkali sacaton) in southeastern New Mexico, but it has not been reported from the Rio Grande in New Mexico (Degenhardt et al. 1996). It has been reported from the following counties along the Chihuahuan Rio Grande in Texas: Presidio, Brewster, Terrell and Val Verde (Dixon 1987); however, it may not occur along the river throughout this area. Minton (1958) describes a Cnemidophorus sacki ssp. which he suspects is an intergrade between C. sacki exanguis and C. sacki gularis from grassland habitats near Alpine in the Big Bend region; none of his records come from along the river and this whiptail does not appear on the reptile list for Big Bend National Park (Amphibians 1996).

C. inornatus (Trans-Pecos or little striped whiptail). Endemic to the Chihuahuan Desert (Morafka 1977), this whiptail prefers grasslands or areas with low-growing shrubs and it has been reported as common in the Rio Grande floodplain of Doña Ana County, NM where Disticholis (salt grass) and Salsola (Russian thistle) dominate (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico, and has been reported from all the counties bordering the river in Texas (Dixon 1987) although it may not occur along the river throughout that area. C. inornatus is uncommon in Big Bend National Park where it is restricted to intermediate elevations (Amphibians 1996), and therefore evidently does not occur along the river. However, Engel-Wilson and Ohmart (1978) reported this species’ occurrence along the river below Ft. Quitman. The subspecies C. inornatus heptagrammus occurs throughout the Texas range; both heptagrammus and C. inornatus llanuras are reported from the Bosque del Apache National Wildlife Refuge (New Mexico Department of Game and Fish 1999).

C. marmoratus/tigris (marbled whiptails). Degenhardt et al. (1996) call this whiptail C. tigris marmoratus, but because the taxonomy is so confused, they do not seem too committed to this name; some other authors grant marmoratus full species status. This whiptail occurs in open desert shrublands, on

Herpetofauna —87 many soil types (Degenhardt et al. 1996). C. tigris marmoratus is reported to occur all along the Chihuahuan Rio Grande in New Mexico (Degenhardt et al. 1996). Dixon (1987) lists collections of C. marmoratus for all the counties bordering the Chihuahuan Rio Grande in Texas. C. marmoratus is common in Big Bend National Park, using a variety of barren desert habitats including the river’s floodplain (Minton 1958, Amphibians 1996). Engel-Wilson and Ohmart (1978) reported both C. tesselatus and C. tigris along the river below Ft. Quitman.

C. neomexicanus (New Mexico whiptail). Most of this whiptail’s New Mexico distribution is limited to the Rio Grande valley, where periodic flooding helped to maintain the highly disturbed habitats it prefers; now it occurs commonly in vacant lots and xeriscapes around Las Cruces (Degenhardt et al. 1996). This parthenogenic species occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and its range in Texas probably extends to about Candelaria (Degenhardt et al. 1996). Axtell (1977) maps collection records for this whiptail near El Paso and downstream of Ft. Quitman and Engel-Wilson and Ohmart (1978) also reported this species occurring along the river below Ft. Quitman.

C. septemvittatus (plateau spotted whiptail/rusty-rumped whiptail). This whiptail is limited to the Big Bend area in Texas and parts of northern and central Mexico and it generally occurs in rocky habitats including mountains, foothills and canyons (Conant and Collins 1991). It has been reported from Hudspeth, Presidio, Brewster and Terrell counties only (Dixon 1987), but it may not occur along the river throughout this area. C. septemvittatus is common in Big Bend National Park, where it occurs in the mountains and foothills (Amphibians 1996).

C. uniparens (desert grassland whiptail). This parthenogenic species prefers desert grasslands and shrublands, and has been reported from all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). According to Dixon (1987) its Texas distribution is restricted to the El Paso area (Dixon 1987), although Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

Scincidae Eumeces obsoletus (Great Plains skink). This species occurs in a wide variety of habitats, including riparian corridors; its main requirement is a mesic microhabitat (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). It is uncommon in Big Bend National Park (Amphibians 1996) and is largely restricted to areas along the river or mesic environments in the mountains (Minton 1958).

E. tetragrammus brevilineatus (short-lined skink). This skink can be found in a wide variety of habitats including grasslands and riparian woodlands (Conant and Collins 1991). It has been reported from all the counties bordering the Chihuahuan Rio Grande from Presidio County through Val Verde County, Texas. Although uncommon in Big Bend National Park, this species can be found almost anywhere in the park, including along the river, as long as it can find a moist area (Amphibians 1996).

Scincella lateralis (ground skink). This species of the eastern United States may just sneak into the Chihuahuan Desert near the Pecos River; it has been reported from Val Verde County (Dixon 1987). It prefers woodland habitats and will enter shallow water to escape predators (Conant and Collins 1991).

SNAKES

Leptotyphlopidae Leptotyphlops dulcis dissectus (New Mexico blind snake). This is a burrowing species that requires light soil (Degenhardt et al. 1996). It occurs along the Chihuahuan Rio Grande of New Mexico in Doña Ana and Socorro counties (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from El Paso, Brewster and Terrell counties in Texas (Dixon 1987). Although Minton (1958) reported a specimen of this species from near the river in the Big Bend region, the Big Bend National Park list describes this species as uncommon and restricted to sites in the Chisos Mountains (Amphibians 1996).

Herpetofauna —88

L. humilis segregus (Trans-Pecos blind snake). This species also requires soil appropriate for burrows and generally prefers deserts and grasslands (Degenhardt et al. 1996). It occurs along the Rio Grande in New Mexico below Caballo Reservoir (Williamson et al. 1994) and has been reported from all the counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987). This species is fairly rare in Big Bend National Park, where it utilizes the river’s floodplain and other desert habitats (Amphibians 1996). Engel- Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

Colubridae Arizona elegans (glossy snake). Found through much of the southwestern United States and northern and central Mexico (Conant and Collins 1991), this species is most commonly found in sandy grasslands and shrublands (Degenhardt et al. 1996) It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Glossy snakes are uncommon in Big Bend National Park, where they are known to utilize the river’s floodplain as well as other habitats (Amphibians 1996). Axtell (1977) maps collection locations for this species in the river valley below El Paso. The subspecies A. elegans phillipi, the Painted Desert glossy snake, occurs through the New Mexico portion of this range and into El Paso County, Texas; the rest of the Texas range is inhabited by A. elegans elegans, the Kansas glossy snake (Conant and Collins 1991, Dixon 1987). Along the river in parts of northern Mexico, other subspecies may occur (Conant and Collins 1991).

Bogertophis subocularis subocularis (Trans-Pecos rat snake). Recently known as Elaphe subocularis, this snake requires rocky terrain, and does not require a permanent water source (Degenhardt et al. 1996). This Chihuahuan Desert endemic (Morafka 1977) occurs along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Uncommon in Big Bend National Park, this snake uses the river’s floodplain along with many other habitats (Amphibians 1996).

Coluber constrictor (racer). This widespread species occurs in a variety of habitats, including abandoned agricultural fields and rocky ledges along watercourses (Tennant 1984), but when in an arid environment, it appears to be limited to areas near water (Degenhardt et al. 1996). This species can be found along the Chihuahuan Rio Grande in New Mexico in Socorro County only (Williamson et al. 1994, Degenhardt et al. 1996) and in Texas, a few specimens have been found in Val Verde County (Dixon 1987, Conant and Collins 1991).

Diadophis punctatus regalis (regal ringneck snake). Though this species occurs in various habitats ranging from woodlands to desert grasslands, it seems to prefer damp soil (Degenhardt et al. 1996) and in arid areas is limited to riparian or high elevation areas (Williamson et al. 1994). It occurs along the Chihuahuan Rio Grande in New Mexico above Caballo Reservoir (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas except Hudspeth County (Dixon 1987). This species is uncommon in Big Bend National Park, where it most commonly occurs in the Chisos Mountains, but it is occasionally found in canyons along the river (Amphibians 1996).

Drymarchon corais erebennus (Texas indigo snake). This eastern species may just sneak into the Chihuahuan Desert near the mouths of the Pecos and Devils River and perhaps used to occur along the Rio Grande in this region. Tennant (1984) reports that an isolated population of these snakes exists near Juno, Texas, and he suggests that habitat degredation, including the flooding of Amistad Reservoir, may have destroyed a riparian corridor that used to allow this snake (and perhaps other sub-tropical species) to get into Trans-Pecos Texas.

Elaphe bairdi (Baird’s rat snake). This snake is limited to forested canyons and uplands (Conant and Collins 1991). Although it has been reported from Brewster, Terrell and Val Verde counties (Dixon 1987), its habitat requirements make it seem unlikely that it would occur along the Rio Grande throughout this range. In Big Bend National Park, it is limited to sites above 4000 feet in elevation (Amphibians 1996). However, farther east, at the edge of the Edwards Plateau, it does occur in riparian habitats, especially limestone canyons (Tennant 1984).

Herpetofauna —89

E. guttata (rat snake). This widespread species requires permanent water and good cover (Degenhardt et al. 1996). Along the Chihuahuan Rio Grande in New Mexico, its distribution is limited to central Doña Ana County (Williamson et al. 1994, Degenhardt et al. 1996) and it has been reported from all the counties bordering the river in Texas (Dixon 1987). Jameson and Flury (1949) found this species in the salt- cedar/mesquite habitats of the river’s floodplain between Ft. Quitman and Presidio. This snake is rare in Big Bend National Park, where it is restricted to the river’s floodplain (Amphibians 1996). Two subspecies of this snake occur along the river: emoryi and meahllmorum (Smith et al. 1994). According to Smith et al. 1994, E. guttata emoryi is found along the Rio Grande from New Mexico into Texas, switching to E. guttata meahllmorum near the eastern edge of Hudspeth County. The subspecies meahllmorum also occurs in a small patch along the river near El Paso and southern Doña Ana county, NM.

Gyalopion canum (western hooknose snake). Generally a desert-dwelling species, this snake occurs most often in grasslands and low foothills (Degenhardt et al. 1996) and is considered to be endemic to the Chihuahuan Desert (Morafka 1977). Although Degenhardt et al. (1996) document specimens of this snake from Doña Ana County only, Williamson et al. (1994) show it occurring throughout the Chihuahuan reach of the Rio Grande in New Mexico. It has been reported from all counties along the river in Texas (Dixon 1987). This species is rare in Big Bend National Park, where it prefers rocky outcrops and ranges from the river up into the Chisos Mountains (Amphibians 1996).

Heterodon nasicus (Mexican hognose snake). This snake prefers grasslands with sandy soils (Degenhardt et al. 1996). It occurs along the Chihuahuan Rio Grande of New Mexico in Socorro and Doña Ana counties (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987), although it may not occur along the river throughout that stretch. In the Big Bend area, this species is limited to prairie habitats north of park (Minton 1958, Amphibians 1996). Three subspecies may occur along the desert Rio Grande: nasicus in New Mexico, kennerlyi through most of the reaches along the international border, and gloydi perhaps just reaching the river below its confluence with the Pecos (Conant and Collins 1991).

Hypsiglena torquata jani (Texas or spotted night snake). Although this wide-ranging species can be found in many different habitats, in New Mexico it occurs mostly in desert and semi-desert habitats, especially grasslands (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Smith and Sanders (1952) reported collecting a nightsnake at El Paso. This species is common in Big Bend National Park and uses the river’s floodplain as well as other habitats (Amphibians 1996); this species is commonly seen along the river road between Lajitas and Presidio (Tennant 1984).

Lampropeltis alterna (gray-banded kingsnake). This species prefers rocky habitats and does not occur along the Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996). This snake has been reported from all the counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987), although it may not occur along the river throughout that stretch. Minton (1958) explains that this snake is probably restricted to rock crevices high in Chisos Mountains in the Big Bend area. Extremely rare in Big Bend National Park, this snake is restricted to the Chisos Mountains in the park, though it has been reported from “rock lowlands outside the park” (Amphibians 1996). Tennant (1984) mentions some specimens of this kingsnake that were collected along the river west of Lajitas and suggests this species may be more common near watercourses along the lower Pecos and Devils rivers.

L. getula splendida (desert kingsnake). This widespread species uses many different habitats, including riparian zones (Degenhardt et al. 1996) and in New Mexico and western Texas is often found near water and in river valleys (Tenant 1984, Williamson et al. 1994). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is rare in Big Bend National Park, but it uses the river’s floodplain as well as many other habitats in the park (Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

Herpetofauna —90 L. triangulum (milk snake). Found through much of the eastern United States, this species can be found in a wide variety of habitats, including riparian zones (Degenhardt et al. 1996). Along the Chihuahuan Rio Grande of New Mexico, it is limited to Doña Ana County (Degenhardt et al. 1996, Williamson et al. 1994), and it has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is very rare in Big Bend National Park, where it occurs only in the Chisos Mountains (Amphibians 1996). However, Tennant (1984) reports that this species can be found crossing the river road west of the park. Two subspecies occur along the Chihuahuan Rio Grande— celaenops and annulata. The latter occurs in Val Verde County, Texas, whereas the former occurs in the rest of the Chihuahuan range (Dixon 1987, Conant and Collins 1991).

Masticophis flagellum testaceus (western coachwhip). Ranging from deserts to pinyon-juniper woodlands, coachwhips can be found in a wide variety of habitats (Degenhardt et al. 1996). They occur along the Chihuahuan Rio Grande in New Mexico, except in the vicinity of Caballo and Elephant Butte Reservoirs (Williamson et al. 1994, Degenhardt et al. 1996) and have been reported from all the Texas counties bordering the river (Dixon 1987). This snake is very common in Big Bend National Park, where it uses many habitats, including the river’s floodplain (Amphibians 1996); Minton (1958) reported collecting a specimen from shallow water at the edge of the river in the Big Bend area. Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

M. taeniatus (whipsnake). This snake occurs mostly in brushy, rocky foothill habitats, although it can be found in lowland ones crossed by many arroyos (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is uncommon in Big Bend National Park, though it can be found throughout the park (Amphibians 1996). Two subspecies occur along the river: M. taeniatus taeniatus (desert striped whipsnake) in New Mexico and El Paso County, and M. taeniatus girardi (central Texas whipsnake) from Hudspeth County on down (Dixon 1987).

Nerodia erythrogaster transversa (blotched water snake). This species requires relatively warm, permanent water, and is not found along the Rio Grande in New Mexico (Degenhardt et al. 1996). Along the river in Texas, it has been reported from Brewster, Terrell, and Val Verde counties (Dixon 1987). Conant (1969) collected this species on both the Mexican and United States’ sides of the river where Brewster County meets it, and in the Devils River very close to the Rio Grande. Rare in Big Bend National Park, this snake is restricted to river between Hot Springs and Boquillas (Amphibians 1996). Small, hand- dug irrigation canals can provide good habitat for water snakes, but large concrete ones do not (Conant 1969).

N. rhombifera rhombifera (diamondback water snake). This water snake can use a wide variety of habitats near water, feeding in dense vegetation along the water’s edge (Tennant 1984). In Texas, this water snake has been collected in Brewster, Terrell and Val Verde counties (Dixon 1987). Conant (1969) collected this species at Del Rio and in the Devils River, and reported that they were common in the Rio Grande’s backwaters in that area. Small, hand-dug irrigation canals can provide good habitat for water snakes, but large concrete ones do not (Conant 1969).

Opheodrys aestivus majalis (western rough green snake). This species is widely distributed through the eastern United States where it is often found foraging in trees or vegetation overhanging water; it can also be found in the water sometimes (Conant and Collins 1991). The western edge of its range occurs near the Pecos, so the only places it might occur along the river are in Terrell and Val Verde counties (Dixon 1987).

Pituophis melanoleucus (gopher or bullsnake). This widespread species uses many different habitats, including cultivated fields and marshes (Degenhardt et al. 1996). Although it can survive in more arid habitats, this snake seems to do best in the riparian zones of the southwest (Tennant 1984). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Tennant (1984) reported this species from irrigated fields south of Fabens, Texas and Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman. Although it can be found parkwide, this species is uncommon in Big Bend National Park (Amphibians 1996). Two subspecies occur along the Chihuahuan

Herpetofauna —91 Rio Grande: Pituophis melanoleucus affinis (Sonoran gopher snake) in New Mexico and west Texas, and P. melanoleucus sayi (bullsnake) from Presidio County on downstream.

Rhinocheilus lecontei tesselatus (Texas longnose snake). This species prefers valleys and plains with sandy soil (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico, except perhaps the area around Elephant Butte and Caballo Reservoirs (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is uncommon in Big Bend National Park, but the river’s floodplain is listed as one of the many habitats it can be found in (Amphibians 1996).

Salvadora deserticola (Big Bend patchnose snake). Though it is not finicky about soil types, this species is generally found in desert habitats and is sometimes referred to as S. hexalepis (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). This species is uncommon in Big Bend National Park, but occurs in many different habitats including the river’s floodplain (Amphibians 1996).

S. grahamiae lineata (Texas patchnose snake). This species has been reported from Val Verde County (Dixon 1987), and according to Conant and Collins (1991) it can be found in a wide variety of habitats, ranging from cultivated bottomlands to rugged grasslands and brushy areas. A second subspecies of patchnose snake (S. grahamiae grahamiae, mountain patchnose snake) occurs in the Chihuahuan Desert, but it seems to be restricted to higher elevation sites and does not appear to occur along the river.

Sonora semiannulata semiannulata (ground snake). Found in plains, valleys and foothills, this snake prefers well-drained, light soils (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Although uncommon in Big Bend National Park, this species uses many different habitats including the river’s floodplain (Amphibians 1996, Minton 1958). Engel- Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

Tantilla gracilis (flathead snake). This secretive snake is often found under rocks or in other moist hiding places (Conant and Collins 1991) and it prefers the loose light soils of mesic woodlands and grasslands (Tennant 1984). If it sneaks into the Chihuahuan Desert it would be in Val Verde County, Texas, where it has been reported (Dixon 1987).

T. hobartsmithi (southwestern blackhead snake). Although it occurs in a variety of habitats, this species is found most often in shrubby or brushy areas (Degenhardt et al. 1996). It is considered to be an endemic of the Chihuahuan Desert (Morafka 1977). Along the Chihuahuan Rio Grande of New Mexico, this snake is limited to southern Doña Ana County (Williamson et al. 1994, Degenhardt et al. 1996) but it has been reported from all the counties bordering the river in Texas (Dixon 1987). However, it may not occur along the river throughout this Texas range. Minton (1958) reported this snake only from higher elevation sites in the Chisos Mountains and although this species is common in Big Bend National Park, it is not found along the river (Amphibians 1996).

T. nigriceps (plains blackhead snake). This species generally occurs in grasslands and desert foothills (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987), although it may not occur along the river throughout Texas. In the Big Bend region, this snake is limited to grasslands north of the national park (Amphibians 1996).

T. rubra diabola (Devils River blackhead snake). Largely limited to Val Verde County, Texas (Dixon 1987), this snake has been collected along the Devils River and in canyons nearby (Fouquette and Floyd 1961, Treadwell and Hibbitts 1969). According to Tennant (1984) it frequents broken country where the Chihuahuan Desert meets the Edward’s Plateau and also the canyons of the Pecos and Devils rivers’ drainages. Since this species was first described in 1961, we may never know if it ever occurred along the Rio Grande near the mouth of the Devils River before Amistad Reservoir was created.

Herpetofauna —92

Thamnophis cyrtopsis (blackneck garter snake). Almost always occurring near water, this species feeds on tadpoles (Degenhardt et al. 1996). The consensus of many sources is that this garter snake prefers higher elevation locations to lowland sites (Minton 1958, Tennant 1984, Degenhardt et al. 1996). Nevertheless, it has been reported from several reaches of the desert Rio Grande. Along the desert Rio Grande of New Mexico, this species occurs in Sierra and Socorro counties (Williamson et al. 1994, Degenhardt et al. 1996) and it has been collected in all the counties bordering the river in Texas (Dixon 1987). Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman. This garter snake ranges throughout Big Bend National Park, and although it is most common in the mountains and foothills it has been reported from sites along the river (Amphibians 1996, Minton 1958). Two subspecies occur along the river: Thamnophis cyrtopsis cyrtopsis (western blackneck garter snake) and T. cyrtopsis ocellatus (eastern blackneck garter snake). The former subspecies occurs alone in New Mexico and westernmost Texas, while the two subspecies’ ranges overlap from Big Bend on into eastern Texas (Conant and Collins 1991).

T. marcianus marcianus (checkered garter snake). This species prefers wet, lowland habitats (Degenhardt et al. 1996) and may be more common in lower elevation sites than T. cyrtopsis (Minton 1958). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Jameson and Flury (1949) found this species in a cleared field in the river’s floodplain between Ft. Quitman and Presidio. It is listed as uncommon in Big Bend National Park, where it is restricted to the river’s floodplain and major tributaries (Amphibians 1996).

T. proximus diabolicus (arid land ribbon snake). According to Tennant (1984), this snake can often be found in brush at the edge of water, and it occurs at the heads of narrow creeks and almost any small water source in desert grasslands, as well as along river courses through the Chihuahuan Desert. This species does not occur along the Rio Grande in New Mexico, being limited to parts of the Pecos and Canadian drainages in the state (Degenhardt et al. 1996). In Texas, it has been reported from three counties that border the Chihuahuan Rio Grande: Brewster, Terrell and Val Verde counties (Dixon 1987). Conant (1977) presents a collection record for this species from the mouth of the Pecos River.

T. sirtalis dorsalis (New Mexico garter snake). Although this wide-ranging species can be found in a wide variety of habitats, the New Mexico subspecies is limited to sites along the Rio Grande, including ponds, marshes and canals (Degenhardt et al. 1996). It has also been reported from El Paso County, Texas (Dixon 1987). However, according to Tennant (1984) this snake has effectively been extirpated from areas along the river in El Paso because of habitat degredation; it is now restricted to residential neighborhoods and creeks in the Franklin Mountains.

Trimorphodon biscutatus vilkinsoni (Texas lyre snake). This snake prefers rugged, rocky habitats and is found commonly in rock crevices (Degenhardt et al. 1996, Williamson et al. 1994). It occurs along the Chihuahuan Rio Grande in Doña Ana and Sierra counties, New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from El Paso, Hudspeth and Brewster counties in Texas (Dixon 1987). It is extremely rare in Big Bend National Park, where it uses a variety of rocky habitats including the river’s canyons (Amphibians 1996).

Tropidoclonion lineatum (lined snake). This species prefers relatively mesic environments including prairies and woodlands; the lone Doña Ana County record along the Rio Grande in New Mexico probably was an introduced individual (Degenhardt et al. 1996).

Elapidae Micrurus fulvius tenere (Texas coral snake). This species has been reported from Terrell and Val Verde counties in Texas (Dixon 1987). According to Milstead (1960), the only Chihuahuan Desert record in Texas is from along Independence Creek (a tributary of the Pecos River) in Terrell County.

Herpetofauna —93 Viperidae Agkistrodon contortix pictigaster (Trans-Pecos copperhead). This species requires a source of permanent water (Conant and Collins 1991) and is found in a variety of canyon, spring and riverside habitats in Trans-Pecos Texas (Minton 1958, Axtell 1959, Milstead 1960, Tennant 1984). It has been reported from Presidio, Brewster, Terrell and Val Verde counties (Dixon 1987). Though rare in Big Bend National Park, this snake can potentially be found anywhere there is a dependable water source (Amphibians 1996).

Crotalus atrox (western diamondback rattlesnake). This common rattlesnake uses a wide variety of arid and semi-arid habitats, especially brushy areas (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the counties bordering the river in Texas (Dixon 1987). Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman. Common in Big Bend National Park, this snake occurs in almost all areas, including the river’s floodplain (Amphibians 1996, Minton 1958).

C. lepidus (rock rattlesnake). As the common name suggests, this rattlesnake prefers steep rocky terrain such as canyons, talus slopes, or rocky stream beds (Degenhardt et al. 1996). In New Mexico the only sites along the Chihuahuan Rio Grande that it frequents are in northern Doña Ana County (Williamson et al. 1994, Degenhardt et al. 1996); it has been reported from all the counties bordering the river in Texas (Dixon 1987). This rattlesnake can be found in most any rocky habitat in Big Bend National Park, such as the river’s canyons, though it is more common in the mountains (Amphibians 1996). Two subspecies occur along the river: C. lepidus klauberi (banded rock rattlesnake) from Hudspeth County, Texas into New Mexico, and C. lepidus lepidus (mottled rock rattlesnake) from Presidio County on down (Dixon 1987, Conant and Collins 1991).

C. molossus molossus (blacktail rattlesnake). Though it generally prefers montane areas, this species occurs in a variety of habitats, including rocky stream beds (Degenhardt et al. 1996). Its distribution along the Chihuahuan Rio Grande of New Mexico is patchy, although it occurs on both sides of Caballo Reservoir (Williamson et al. 1994, Degenhardt et al. 1996). It has also been reported from all counties bordering the Chihuahuan Rio Grande in Texas (Dixon 1987). Although it is found throughout the Big Bend region, including along the river, this species is most common in the Chisos Mountains (Amphibians 1996, Minton 1958). Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

C. scutulatus scutulatus (Mojave rattlesnake). Occurring most often in grasslands, this species does not occur along the Rio Grande in New Mexico (Degenhardt et al. 1996). However, it has been reported from all the counties bordering the river from El Paso to Big Bend (Dixon 1987). This species is uncommon in the Big Bend region, where it uses a variety of habitats including the floodplain of the river (Minton 1958, Amphibians 1996). Engel-Wilson and Ohmart (1978) reported this species occurring along the river below Ft. Quitman.

C. viridis viridis (prairie or western rattlesnake). Preferring sandy and alkali soils, this species is often found in remnant grasslands (Degenhardt et al. 1996). It occurs all along the Chihuahuan Rio Grande in New Mexico (Williamson et al. 1994, Degenhardt et al. 1996) and has been reported from all the Texas counties bordering the river between El Paso and Big Bend (Dixon 1987), although it may not occur along the river throughout that area of Texas. Minton (1958) suggests this species is uncommon and limited mostly to grassland habitats in the Big Bend region and the reptile list for Big Bend National Park agrees, saying that if it occurs in the park, it would be restricted to grasslands in north (Amphibians 1996).

Sistrurus catenatus edwardsi (desert massasauga). This rattlesnake prefers sandy soils in grasslands and short grass prairies (Degenhardt et al. 1996). Along the Chihuahuan Rio Grande in New Mexico, it has been reported from Doña Ana and Socorro counties (Williamson et al. 1994, Degenhardt et al. 1996) and it has also been reported from El Paso County, Texas (Dixon 1987).

Herpetofauna —94 Literature Cited

Amphibians and Reptiles Checklist: Big Bend National Park, Rio Grande Wild and Scenic River. 1996. Published by the Big Bend Natural History Association in cooperation with the National Park Service.

Anderson, . 1960. Storeria storeiodes in western Mexico. Herpetologica 16: 63-70.

Axtell, R. W. 1959. Amphibians and reptiles of the Black Gap Wildlife Management Area, Brewster County, TX. Southwestern Naturalist 4 (2): 88-109.

Axtell, R.W. 1977. Ancient playas and their influence on the recent herpetofauna of the northern Chihuahuan Desert. In Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Region, United States and Mexico, eds. R.H. Wauer and D.H. Riskind, pp. 493-512. US Department of the Interior, National Park Service Transactions and Proceedings Series, Number 3.

Conant, R. 1969. A review of the water snakes of the genus Natrix in Mexico. Bulletin of the American Museum of Natural History 142 (1): 1-140.

Conant, R. 1977. Semiaquatic reptiles and amphibians of the Chihuahuan Desert and their relationships to drainage patterns of the region. In Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Region, United States and Mexico, eds. R.H. Wauer and D.H. Riskind, pp. 455-491. US Department of the Interior, National Park Service Transactions and Proceedings Series, Number 3.

Conant, R. and J.T. Collins. 1991. A field guide to reptiles and amphibians: eastern and central North America, 3rd Edition. Boston: Peterson Field Guide Series/Houghton Mifflin Co.

Degenhardt, W.G., C.W. Painter, and A.H. Price. 1996. Amphibians and reptiles of New Mexico. Albuquerque: University of New Mexico Press.

Dixon, J. R. 1987. Amphibians and reptiles of Texas: with keys, taxonomic synopses, bibliography, and distribution maps. College Station: Texas A&M University Press.

Donaldson, W., A.H. Price, and J. Morse. 1994. The current status and future prospects of the Texas horned lizard (Phrynosoma cornutum) in Texas. Texas Journal of Science 46 (2): 97-113.

Easterla, D.A. 1978. The Mediterranean gecko, Hemidactylus turcicus, at Big Bend National Park, Texas. Southwestern Naturalist 30 (2): 199.

Easterla, D.A. and R.C. Reynolds. 1975. Additional records and ecological notes on the reticulated gecko, Coleonyx reticulatus (Davis and Dixon), from the southern Trans-Pecos of southwestern Texas. Journal of Herpetology 9 (2): 233-236.

Ernst, C.H., R.W. Barbour, and J.E. Lovich. 1994. Turtles of the United States and Canada. Washington, D.C.: Smithsonian Institution Press.

Fouquette, M.J. and F.E. Floyd. 1961. A new black-headed snake (Tantilla) from southwestern Texas. Copeia 1961 (2): 144-148.

Herpetofauna —95 Garrett, J.M. and D.G. Barker. 1994. A field guide to reptiles and amphibians of Texas. Houston: Texas Monthly Fieldguide Series/Gulf Publishing House.

Jameson, D.L. and A. G. Flury. 1949. The reptiles and amphibians of the Sierra Vieja range of southwestern Texas. Texas Journal of Science 1 (2): 54-79.

Milstead, W. W. 1960. Relict species of the Chihuahuan Desert. Southwestern Naturalist 5 (2): 75-88.

Minton, S. A. 1958. Observations on amphibians and reptiles of the Big Bend Region of Texas. Southwestern Naturalist 3: 28-54.

Morafka, D.J. 1977. Is there a Chihuahuan Desert? A quantitative evaluation through a herpetofaunal perspective. In Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Region, United States and Mexico, eds. R.H. Wauer and D.H. Riskind, pp 437-454. US Department of the Interior, National Park Service Transactions and Proceedings Series, Number 3.

New Mexico Department of Game and Fish. 1999. New Mexico Species List: Reptiles and Amphibians. Available at: http://www.fw.vt.edu/fishex/nmex_main/reptiles.htm [4 August 1999]

Olson, R. E. 1973. Variation in the canyon lizard, Sceloperus merriami Stejneger. Herpetologica 29: 116- 127.

Price, A.H. 1980. Hemidactylus turcicus (Mediterraneaen gecko). Herpetological Review 11 (2): 39.

Scudday, J.F. 1977. Some recent changes in the herpetofauna of the northern Chihuahuan Desert. In Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Region, United States and Mexico, eds. R.H. Wauer and D.H. Riskind, pp. 513-522. US Department of the Interior, National Park Service Transactions and Proceedings Series, Number 3.

Smith, H.M. 1946. Handbook of lizards: lizards of the United States and of Canada. Ithaca, NY: Comstock Publishing.

Smith, H.M. and O. Sanders. 1952. Distribution data on Texan amphibians and reptiles. Texas Journal of Science 4 (2): 204-219.

Smith, H.M, D. Chizar, J. R. Staley and K. Tepedelen. 1994. Population relationships in the corn snake Elaphe guttata (Reptilia: Serpentes). Texas Journal of Science 46 (3): 259-292.

Tennant, A. 1984. The snakes of Texas. Austin: Texas Monthly Press.

Treadwell, R.W. and T. Hibbitts. 1969. Tantilla diaboli from Val Verde County, Texas. Texas Journal of Science 20 (3): 281-2.

Wauer, R.H. and G.T. Burdick. 1974. Range extension of Meditteraneaen gecko in Coahuila, Mexico. Southwestern Naturalist 19: 446.

Williamson, M.A., P.W. Hyder, and J.S. Applegarth. 1994. Snakes, lizards, turtles, frogs, toads and salamanders of New Mexico. Santa Fe: Sunstone Press.

Herpetofauna—96

Chapter 5: Mammals of the Desert Rio Grande

As many as 102 species of mammals may occur (or have occurred) along the desert Rio Grande (Table 5- 1). Of these: 6 are species introduced from other continents, 2 are species whose populations along the Rio Grande may have been introduced from elsewhere in North America, 12 appear to have been extirpated from all or part of their range along the river, and 14 are federally listed as threatened or endangered in the United States or Mexico (see Appendix B). The factors leading to these extirpations, as well as population trends and habitat preferences for the other species, are provided in the species accounts following Table 5-1.

For some species, the river, particularly the canyon-dominated stretch through and below Big Bend, has functioned as a dispersal barrier, limiting the distribution of entire species or subspecies. According to Schmidly (1977a) and Baker (1956) that stretch of the river has determined the edge of the following species’ ranges: Black-tailed Prairie Dog, Southern Plains Woodrat, Mexican Ground Squirrel and Nelson’s Kangaroo Rat. They also note that for several species—Botta’s Pocket Gopher, Yellow-faced Pocket Gopher, Ord’s Kangaroo Rat, and the Eastern Cottontail—the river provides enough of a barrier to create distinct subspecies on each side.

In a single volume (Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Region), three sets of authors have compiled different lists of the native mammals of the Chihuahuan Desert (Findley and Caire 1977, Packard 1977, Schmidly 1977a). Schmidly’s list is the longest, containing 119 species, and 84 of those species appear in Table 5-1. Thus, approximately 70% of the desert’s native mammalian fauna can be found along the Rio Grande. Of the 10 native species listed here, but not on Schmidly’s list: 4 appear on one of the other lists in the volume (Hairy-legged Vampire, Nine-banded Armadillo, White-tailed Ground Squirrel, and New Mexican Jumping Mouse), 1 has been more recently confirmed along the river below Big Bend (Eastern Pipistrelle), and 5 have relatively few records attesting to their occurrence along the river (Least Shrew, Mink, River Otter, Jaguarundi, and Jaguar).

Table 5-1 and the species accounts which follow were compiled from a variety of sources. For the state of New Mexico, the maps and specimen lists of Findley et al. (1975), supplemented by the New Mexico Department of Game and Fish’s BISON-M database (NMG&F 1999), were used to determine specific locations where each species has been collected or is known to occur. The most recent and comprehensive reference for Texas (Davis and Schmidly 1994) maps verified records for each species on a county-by- county basis. Because of the large size and varied topography of the counties in west Texas, such maps do not indicate whether a species occurs along the river specifically, so Davis and Schmidly’s maps were supplemented with other sources cited in the species accounts. Thus, for the Texas stretches of the Rio Grande, a species is listed as native (or introduced) only when I could locate a specific literature discussion of its occurrence for a particular stretch of the river. Species are described as “possible” when I located only county records for a particular stretch, but the species has been documented to occur along the river elsewhere in the Chihuahuan Desert. Occurrence is described as “unknown” when all I have is a county record, with no specific mention of the species’ occurrence along the river.

Mammals—97 Table 5-1. Mammals occurring along the Rio Grande for 6 stretches through the Chihuahuan Desert. See species accounts for habitat descriptions and discussion of distributional records.

Riparian Use: O=Obligate resident of aquatic or riparian habitats, F=Facultative floodplain resident (associated with mesic or forested habitats, but not restricted to the river or floodplain), I=Incidental (equally or more likely to occur in habitats away from river).

Rio Puerco— Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Common Name Species Caballo El Paso Quitman Conchos Boquillas Devils River Use Virginia Opossum Didelphis virginiana N/I N/I N N N O Least Shrew Cryptotis parva ?-x F Desert Shrew Notiosorex crawfordi P N P I Eastern Mole Scalopus aquaticus ? F Mormoops Ghost-faced Bat P N P F megalophylla Mexican Long-nosed Leptonycteris nivalis N I Bat Hairy-legged Diphylla ecaudata ? I Vampire California Myotis Myotis californicus N P N F Western Small- Myotis ciliolabrum N P P N I footed Myotis Little Brown Myotis Myotis lucifugus N N N F Fringed Myotis Myotis thysanodes N N P P N I Cave Myotis Myotis velifer N N N N F Yuma Myotis Myotis yumanensis N N N P N N F Lasionycteris Silver-haired Bat N N P P F noctivagans Western Pipistrelle Pipistrellus hesperus N N P N N F Pipistrellus Eastern Pipistrelle P N F subflavus Big Brown Bat Eptesicus fuscus N N P N F Western Red Bat Lasiurus blossevillii N P F Eastern Red Bat Lasiurus borealis N N N P P P F

Rio Puerco— Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Common Name Species Caballo El Paso Quitman Conchos Boquillas Devils River Use Hoary Bat Lasiurus cinereus N N N P N P F Western Yellow Bat Lasiurus xanthinus ? F Spotted Bat Euderma maculatum N N I Townsend’s Big- Corynorhinus N P P N N I eared Bat townsendii Pallid Bat Antrozous pallidus N N N N N N I Brazilian Free-tailed Tadarida brasiliensis N N N N N N I Bat Pocketed Free-tailed Nyctinomops N I Bat femorosacca Nyctinomops Big-Free-tailed Bat N P N I macrotis Western Mastiff Bat Eumops perotis P N N I Nine-banded Dasypus ? ? F Armadillo novemcinctus Desert Cottontail Sylvilagus audubonii N N N N N N I Eastern Cottontail Sylvilagus floridanus ? I Black-tailed Lepus californicus N N N N N N I Jackrabbit Texas Antelope Ammospermophilus N N N N I Squirrel interpres White-tailed Ammospermophilus N I Antelope Squirrel leucurus Mexican Ground Spermophilus N N I Squirrel mexicanus Spotted Ground Spermophilus N N N P I Squirrel spilosoma Spermophilus Rock Squirrel N N N N N N I variegatus Black-tailed Prairie Cynomys N-x N-x I Dog ludovicianus Eastern Fox Squirrel Sciurus niger ? F Botta’s Pocket Thomomys bottae N N N P N P I Gopher Desert Pocket Geomys bursarius/ N N F Gopher arenarius Yellow-faced Pocket Cratogeomys N N N N F Gopher castanops

Rio Puerco— Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Common Name Species Caballo El Paso Quitman Conchos Boquillas Devils River Use Silky Pocket Mouse Perognathus flavus N N P P N I Merriam’s Pocket Perognathus N N I Mouse merriami Perognathus Plains Pocket Mouse N N I flavescens Chaetodipus Hispid Pocket Mouse N P P I hispidus Chaetodipus Rock Pocket Mouse N N N I intermedius Nelson’s Pocket Chaetodipus nelsoni N N I Mouse Desert Pocket Chaetodipus N N N N P I Mouse penicillatus Merriam’s Kangaroo Dipodomys merriami N N N N N P I Rat Nelson’s Kangaroo Dipodomys nelsoni N I Rat Ord’s Kangaroo Rat Dipodomys ordii N N N N N I Banner-tailed Dipodomys N N P I Kangaroo Rat spectabilis American Beaver Castor canadensis N N N N N N O Fulvous Harvest Reithrodontomys ? ? F Mouse fulvescens Western Harvest Reithrodontomys N N N N N F Mouse megalotis Plains Harvest Reithrodontomys N N P I Mouse montanus Peromyscus Cactus Mouse N N N N N N I eremicus Peromyscus White-footed Mouse N N N N N N F leucopus Peromyscus Deer Mouse N N N N N I maniculatus Peromyscus White-ankled Mouse N P N I pectoralis Northern Pygmy Baiomys taylori ? I Mouse

Rio Puerco— Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Common Name Species Caballo El Paso Quitman Conchos Boquillas Devils River Use Mearn’s Onychomys N N N N P I Grasshopper Mouse arenicola Northern Onychomys N N N P I Grasshopper Mouse leucogaster Tawny-bellied Cotton Sigmodon N-x F Rat fulviventer Hispid Cotton Rat Sigmodon hispidus N N N N N N F White-throated Neotoma albigula N N N P P P I Woodrat Southern Plains Neotoma micropus N N N N P I Woodrat Common Muskrat Ondatra zibethicus N N N N-x? P O Black or Roof Rat Rattus rattus I I P (I) P (I) I I Norway Rat Rattus norvegicus P (I) P (I) P (I) P (I) P (I) P (I) I House Mouse Mus musculus I I I I I P (I) I New Mexican Zapus hudsonius N F Jumping Mouse Porcupine Erethizon dorsatum P N N P F Nutria Myocastor coypus I I O Coyote Canis latrans N N N N N N I Gray Wolf Canis lupus N-x P-x I Kit Fox Vulpes macrotis N N N N N I Urocyon Common Gray Fox N N N N N I cinereoargenteus Black Bear Ursus americanus N-x P P F Ringtail Bassariscus astutus P N N N F Common Raccoon Procyon lotor N N N N N N F White-nosed Coati Nasua narica ? ? F Long-tailed Weasel Mustela frenata N N N N I Mink Mustela vison N/I O American Badger Taxidea taxus N N N N N I Western Spotted Spilogale gracilis N N N N I Skunk Hooded Skunk Mephitis macroura ? F Striped Skunk Mephitis mephitis N N N N N F Common Hog-nosed Conepatus N P N N N F Skunk mesoleucus

Rio Puerco— Caballo— El Paso— Quitman— Conchos— Boquillas— Riparian Common Name Species Caballo El Paso Quitman Conchos Boquillas Devils River Use River Otter Lutra canadensis N-x O Mountain Lion Felis concolor N N N N N I Ocelot Felis pardalis ?-x I Jaguarundi Felis yagouaroundi ? ?-x F Jaguar Panthera onca N-x I Bobcat Lynx rufus N N N N N N I Feral Pig Sus scrofa ? (I) I Collared Peccary Tayassu tajacu N N P I Odocoileus Mule Deer N N N N N N I hemionus Odocoileus White-tailed Deer N-x N N I virginianus Mountain Sheep Ovis canadensis N-x I Barbary Sheep Ammotragus lervia I I I

Species Accounts

Virginia Opossum (Didelphis virginiana). In arid areas, this mesic-adapted species is restricted to riparian woodlands (Davis and Schmidly 1994). Only recently reported from the Socorro and Mesilla Valleys, this species has either been introduced to southern New Mexico or has undergone a natural range expansion (NMG&F 1999). It has been reported from the El Paso area (Schmidly 1977b), as well as from Boquillas and Villa Acuña (now Cuidad Acuña), Coahuila (Baker 1956) and the mouth of the Pecos River (Hall 1991). This species is listed as “hypothethical” for Big Bend National Park, on the basis of a few sightings in the Chisos Basin (Mammal Checklist 1997).

Least Shrew (Cryptotis parva). This species prefers grassy areas, where it often travels in the runways made by rodents like cotton rats (Davis and Schmidly 1994). It has been reported along the river in Val Verde County, Texas (Davis and Schmidly 1994) and was collected at Del Rio (Choate 1970). If this shrew did occur along the river above the mouth of the Devils River, it was likely extirpated from this reach with the flooding of Amistad Reservoir.

Desert Shrew (Notiosorex crawfordi). Though generally found in arid environments, this species is not restricted to any particular habitat and has been captured in marshes as well as other habitats (Davis and Schmidly 1994). Along the desert Rio Grande of New Mexico, a specimen was captured in a talus slope of the Caballo Mountains (Findley et al. 1975), and in Texas they have been collected in El Paso and Brewster counties (Davis and Schmidly 1994). The type specimen for this species was captured at Fort Bliss, near El Paso (Baker 1956). It is restricted to higher elevation parts of Big Bend National Park (Mammal Checklist 1997).

Eastern Mole (Scalopus aquaticus). This eastern species is known from the desert Rio Grande from a single specimen collected in 1887, from somewhere in what are now Brewster, Jeff Davis, and Presidio counties (Schmidly 1977b); Schmidly (1977b) speculates that because of this species’ preference for moist loamy or sandy soils, it most likely came from a site along the river.

Ghost-faced Bat (Mormoops megalophylla). Inhabiting lowlands, including desert scrub and riparian habitats (Schmidly 1991), this colonial bat roosts in caves, mine shafts, and crevices, and it has been collected in Brewster, Presidio, and Val Verde counties of Texas (Davis and Schmidly 1994). It occurs along river in Big Bend National Park (Mammal Checklist 1997), and Schmidly (1977b) lists a specimen from near Lajitas. The subspecies along the river is M. m. megalophylla (Schmidly 1991).

Mexican Long-nosed Bat (Leptonycteris nivalis). The only known U.S. colony is on Emory Peak in Big Bend National Park, although it has also been collected in the Chinati Mountains of Presidio County, Texas (Schmidly 1991). Though generally considered a grassland and montane species, this bat has been collected at a pool in Rio Grande Village (Schmidly 1977b).

Hairy-legged Vampire (Diphylla ecaudata). The only Texas record of this tropical bat comes from a railroad tunnel west of Comstock, but Davis and Schmidly (1994) suggest that both this species and the common vampire bat (Desmodus rotundus) could occur in caves along the Rio Grande in this area.

California Myotis (Myotis californicus). Active even in winter (Mammal Checklist 1997), this species uses a wide variety of habitats and typically roosts in crevices, shallow caves, or houses (Davis and Schmidly 1994). According to Baker (1956), this species is typically captured within 1 mile (1.6 km) of a cliff. Although it has not been recorded along the desert Rio Grande in New Mexico (Findley et al. 1975), it has been collected in El Paso (Schmidly 1977b) and in the mountains of Presidio County (Schmidly 1991), and it occurs along the river in Big Bend National Park (Mammal Checklist 1997).

Western Small-footed Myotis (Myotis ciliolabrum). Inhabiting arid areas and desert mountains, this species used to be lumped with Myotis leibii (Davis and Schmidly 1994). There are relatively few records along the desert Rio Grande. In New Mexico, it has been collected near Socorro (Findley et al. 1975), and in Texas there are records from El Paso, Presidio, and Brewster counties (Schmidly 1991, Davis and Schmidly 1994). There is only one record in Big Bend National Park (Mammal Checklist 1997); while the

Mammals—103 park checklist doesn’t list where that individual came from, Anderson (1972) lists a Myotis leibii melanorhinus from Santa Elena Canyon.

Little Brown Myotis (Myotis lucifugus). Like the Yuma Myotis, this species is strongly associated with water sources (Findley et al. 1975). It has been recorded in both the Socorro and Mesilla valleys of New Mexico (Findley et al. 1975), but the only Texas record of this species is from Ft. Hancock (Schmidly 1991, Davis and Schmidly 1994). Because this species occurs in higher elevation conifer forests, Schmidly (1977b) argues that this specimen must have been a migrant and that resident populations probably do not exist in Trans-Pecos Texas. The Texas specimen represents the subspecies M. l. occultus, which some authors consider a separate species (see Schmidly 1991 for discussion).

Fringed Myotis (Myotis thysanodes). This species is found in mountainous areas of Trans-Pecos Texas, often associated with grassland habitats (Schmidly 1977b). It occurs along the river in Big Bend National Park, where nursery colonies occur in caves near the river (Mammal Checklist 1997). Along the desert Rio Grande in New Mexico, specimens have been collected from the south side of San Diego Mountain (Findley et al. 1975) and at the Bosque del Apache National Wildlife Refuge (Valdez et al. 1999). Anderson (1972) mapped a specimen collected along the river below the mouth of the Río Conchos, and specimens have been collected from several counties bordering the desert Rio Grande in Texas: El Paso, Hudspeth, Presidio and Brewster counties (Schmidly 1991, Davis and Schmidly 1994).

Cave Myotis (Myotis velifer). This species occurs mostly in deserts and grasslands, frequently along watercourses (Schmidly 1977b). Specimens have been collected along the river from Ft. Hancock through Langtry, Texas (Baker 1956, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Manning et al. 1987, Yancey and Jones 1996). It occurs along the river in Big Bend National Park (Mammal Checklist 1997) and county records exist from Hudspeth through Val Verde counties (Davis and Schmidly 1994). The subspecies occurring along the river is probably M. velifer incautus (Davis and Schmidly 1994).

Yuma Myotis (Myotis yumanensis). Closely associated with water (Mammal Checklist 1997), this species occurs all along the desert Rio Grande. In New Mexico, it occurs along the desert river both above and below Caballo Dam, including large maternity colonies in riparian areas near Socorro (Findley et al. 1975). In Texas, the species has been collected near the river in El Paso, in Big Bend Ranch State Park, in Big Bend National Park, near Langtry, and at the mouth of the Pecos River (Baker 1956; Schmidly 1977b, 1991; Manning et al. 1987; Yancey 1997). In addition, it has been collected in the Sierra Vieja and Chinati Mountains of Presidio County (Schmidly 1911). The Texas specimens represent the subspecies M. y. yumanensis (Schmidly 1991).

Silver-haired Bat (Lasionycteris noctivagans). In general, this species is a forest-dweller and tree-rooster (Davis and Schmidly 1994). The only record of its occurrence along the desert Rio Grande in New Mexico comes from the Bosque del Apache National Wildlife Refuge (Findley et al. 1975, Valdez et al. 1999); this record may represent a migrant individual (Valdez et al. 1999). Along the river in Texas, specimens have been collected in El Paso (Schmidly 1977b) and from the confluence of Pecos River and Independence Creek, about 75 straight-line kilometers from the Rio Grande (Dowler et al. 1992). In addition, it is known from the Sierra Vieja in Presidio County, Texas (Schmidly 1991).

Western Pipistrelle (Pipistrellus hesperus). Found in all the counties along the desert river in Texas, this bat often occurs along watercourses with cliffs or canyons (Schmidly 1991, Davis and Schmidly 1994). In New Mexico, it has been collected near Socorro and Elephant Butte Dam (Findley et al. 1975) and in Texas, it has been collected in El Paso, near Lajitas, along the river through the Big Bend area, near the mouth of the Pecos, and in a steep-walled canyon near Langtry (Schmidly 1977b, Manning et al. 1987, Mammal Checklist 1997, Yancey 1997). The Texas specimens represent the subspecies P. h. maximus.

Eastern Pipistrelle (Pipistrellus subflavus). Frequenting wooded areas along streams (Schmidly 1977b), this species has been collected along the river near Del Rio, at the mouth of the Pecos, and at Langtry (Manning et al. 1987). In addition, this species has also been collected at Big Bend Ranch State Park, in riparian vegetation along a stream (Yancey, Jones, and Manning 1995). According to Baker (1956), the

Mammals—104 Rio Grande Valley may have provided a westward migration route into Coahuila for this eastern, mesic species. The subspecies collected in the Del Rio area is P. s. clarus (Schmidly 1991).

Big Brown Bat (Eptesicus fuscus). Typically living in forests, where it roosts under bark and in tree cavities (Davis and Schmidly 1994), this species will also use rock crevices and caves as it does in Big Bend National Park (Mammal Checklist 1997). It has been collected in the Mesilla Valley of New Mexico, though Findley et al. (1975) suspect those records represent migrants, not residents. In 1977, these bats were known to roost in a warehouse on Ft. Bliss in the El Paso (Schmidly 1977b) and specimens were collected from along the river in Big Bend Ranch State Park and at Boquillas (Baker 1956, Yancey 1997). This bat has also been recorded from Hudspeth and Presidio counties (Davis and Schmidly 1994). Along the desert Rio Grande, the subspecies represented is E. fuscus pallidus (Davis and Schmidly 1994).

Western Red Bat (Lasiurus blossevillii). According to Schmidly (1991: 119), this species seems “to prefer riparian areas where they roost in tree foliage.” Though originally reported as the eastern red bat (L. borealis), a specimen of this species was collected near Las Cruces, New Mexico (Valdez et al. 1999). In addition, it has been collected in the Sierra Vieja Mountains of Presidio County, Texas (Schmidly 1991).

Eastern Red Bat (Lasiurus borealis). Often using open roosts in foliage of trees, this species has been reported from El Paso, Presidio, Brewster and Val Verde counties in Texas (Schmidly 1991, Davis and Schmidly 1994). The El Paso specimen was collected in large elm trees near the river (Schmidly 1977b). In addition, a specimen, possibly a migrant, was captured over a pool at the Bosque del Apache National Wildlife Refuge in New Mexico (Valdez et al. 1999). The only Big Bend National Park record is from the Chisos Mountains (Mammal Checklist 1997).

Hoary Bat (Lasiurus cinereus). Like the preceding species, this bat also uses open roosts in tree foliage, and has been reported from El Paso, Presidio, Brewster and Terrell counties, Texas (Davis and Schmidly 1994). Along the desert Rio Grande, it has been documented in the Socorro, Mesilla and lower El Paso valleys, near the mouth of the Río Conchos, and along the river in Big Bend National Park (Anderson 1972, Findley et al. 1975, Schmidly 1977b, Mammal Checklist 1997). Along the desert Rio Grande, the subspecies L. c. cinereus occurs (Schmidly 1991).

Western Yellow Bat (Lasiurus xanthinus). Described as a “tree bat,” this species has only recently been collected from a spring along an intermittent stream in the desert lowlands of Big Bend National Park (Higginbottom et al. 1999: 346). These recent records may represent migrant individuals, or perhaps an expansion of this species’ range, made possible by recovery of cottonwood stands following establishment of the national park (Higginbottom et al. 1999: 346-7).

Spotted Bat (Euderma maculatum). In Big Bend National Park, this species generally inhabits lower elevations, occurring along the river (Mammal Checklist 1997). The park is the only place in Texas where it occurs, and it evidently breeds there during the summer (Davis and Schmidly 1994). A lone specimen captured in Mesilla Park, New Mexico was likely a migrant individual (Findley et al. 1975).

Townsend’s Big-eared Bat (Corynorhinus townsendii). Previously placed in the genus Plecotus, this species is associated with rocky areas, roosting in caves and old mines, but not crevices (Davis and Schmidly 1994, Valdez et al. 1999). In Texas, it has been documented in El Paso, Hudspeth, Presidio, Brewster, and Val Verde counties (Davis and Schmidly 1994). It is known to occur along the river in the Socorro Valley (Findley et al. 1975, Valdez et al. 1999), in Big Bend National Park (Mammal Checklist 1997), and in Val Verde County (Schmidly 1977b). The subspecies along the desert Rio Grande is P. townsendii pallescens (Schmidly 1991, NMG&F 1999).

Pallid Bat (Antrozous pallidus). This species is often found near rocky areas where it roosts in crevices and caves, though it will also roost in human structures (Davis and Schmidly 1994); for instance, it occurs along river in Big Bend National Park, especially in Rio Grande Village, where it often hangs from buildings (Mammal Checklist 1997). Specimens have been documented for all reaches of the desert Rio Grande (Findley et al. 1975; Schmidly 1977b, 1991; Engel-Wilson and Ohmart 1978; Yancey 1997). The subspecies A. pallidus pallidus occurs in this region (Davis and Schmidly 1994).

Mammals—105

Brazilian Free-tailed Bat (Tadarida brasiliensis). Nursery colonies of this migratory bat, located in guano caves, sometimes contain millions of individuals, though few colonies of this size are found along the desert Rio Grande. Although it has been documented all along the desert river (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Manning et al. 1987), one of the largest colony reported, roosting in a building near Canutillo, Texas, contained only several hundred individuals (Schmidly 1977b). The subspecies along the desert Rio Grande is T .b. mexicana (Schmidly 1991).

Pocketed Free-tailed Bat (Nyctinomops femorosacca). Previously included in the genus Tadarida, this bat prefers semi-arid habitats, often near cliffs or rocky outcrops (Schmidly 1977b, Davis and Schmidly 1994). It does not occur along the river in New Mexico (Findley et al. 1975) and the only records along the desert Rio Grande come from the Big Bend region (Easterla 1970, Schmidly 1977b).

Big-Free-tailed Bat (Nyctimnomops macrotis). This bat has also been shifted out of the genus Tadarida, and occurs in rugged, rocky areas in El Paso, Presidio, and Brewster counties (Schmidly 1991, Davis and Schmidly 1994). It has been documented along the river in Big Bend National Park and the El Paso Valley (Schmidly 1977b, Mammal Checklist 1997). No specimens have been collected along the river in New Mexico, where it is much less common than the Brazilian Free-tailed Bat (Findley et al. 1975).

Western Mastiff Bat (Eumops perotis). This species generally roosts in the crevices of cliffs (Davis and Schmidly 1994), and it has not been reported from along the upper reaches of the desert Rio Grande. However, it is known to occur along the river in the Big Bend area, ranging from the upper Presidio Valley to at least Langtry, Texas (Schmidly 1977b, 1991; Mammal Checklist 1997). The subspecies all along the desert river is E. perotis californicus (Schmidly 1991, NMG&F 1999).

Nine-banded Armadillo (Dasypus novemcinctus). It is not clear whether this species occurs naturally along the desert Rio Grande. It requires relatively loose, soft soils and avoids marshes, but stays near streams and pools in arid environments (Davis and Schmidly 1994); in fact, the northward and eastward expansion of its range from southern Texas during the early to mid-1900s occurred along riparian corridors (Davis and Schmidly 1994). Although there is no evidence it occurs along the river in New Mexico (Findley et al. 1975), a specimen has been collected in Rio Grande Village at Big Bend National Park, representing either an escaped individual or one that crossed river from Mexico (Mammal Checklist 1997). In 1956, Baker (1956) speculated that this species did not occur upriver from Villa Acuña (now Cuidad Acuña) on the Mexican side of the Rio Grande, but he cited reports that it ranged along the north side of the river as far as the mouth of the Pecos. Now, documented specimens exist for both Terrell and Val Verde counties, as well as other counties farther up the Pecos River (Davis and Schmidly 1994).

Desert Cottontail (Sylvilagus audubonii). Most often found in dense vegetation (Mammal Checklist 1997), this species uses a wide variety of habitats including grasslands and desert shrublands (Davis and Schmidly 1994). It has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Mammal Checklist 1997, Yancey 1997).

Eastern Cottontail (Sylvilagus floridanus). This species also prefers brushy areas, and is sometimes found along streams and in river bottoms; records exist for from Hudspeth through Val Verde counties, Texas (Davis and Schmidly 1994). In the western portion of its range, this species is limited to the mountains (Schmidly 1977b); for instance, it is limited to higher elevation portions of Big Bend National Park and New Mexico (Findley et al. 1975, Mammal Checklist 1997). The westernmost records from Texas have recently been placed into a separate species, S. robustus; this species is limited to montane habitats, where populations appear to be declining (Ruedas 1998). However, eastern cottontails also occur in Terrell and Val Verde counties (Davis and Schmidly 1994), where they prefer brushy lowland areas (Schmidly 1977b). On the Mexican side of the river, Baker (1956) doubted that this species ranged any farther upstream than Villa Acuña (now Cuidad Acuña), Coahuila.

Black-tailed Jackrabbit (Lepus californicus). Found in more open shrubby and grassy habitats than the cottontail rabbits (Mammal Checklist 1997), this species is generally associated with arid scrublands (Davis

Mammals—106 and Schmidly 1994). It has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

Texas Antelope Squirrel (Ammospermophilus interpres). This secretive species occurs in desert environments, especially gravel washes and rocky slopes and foothills (Findley et al. 1975, Davis and Schmidly 1994, Mammal Checklist 1997), and it seems to avoid level terrain (Schmidly 1977b). Although it has not been reported along the river in New Mexico (Findley et al. 1975), it has been recorded from all reaches along the international border from El Paso through at least the mouth of the Pecos River (Schmidly 1977b, Engel-Wilson and Ohmart 1978).

White-tailed Antelope Squirrel (Ammospermophilus leucurus). Most common in grasslands and piñon- juniper woodlands, this species has been collected at a few sites near the river above Caballo Dam (Findley et al. 1975). Its distribution appears to be limited to the west side of the river (Findley 1987).

Mexican Ground Squirrel (Spermophilus mexicanus). Preferring brushy and grassy areas (Davis and Schmidly 1994) with sandy or gravelly soils (Schmidly 1977b), this species occurs along the desert Rio Grande in the Big Bend area and below. Outside of Big Bend National Park, this species has been documented at Langtry and the mouth of the Pecos River (Schmidly 1977b). Within Big Bend National Park, it has been reported only from Rio Grande Village, although it has not been reported as often recently (Mammal Checklist 1997).

Spotted Ground Squirrel (Spermophilus spilosoma). This ground squirrel is most often found in dry, sandy habitats, but also occurs in grassy, brushy or forested habitats (Davis and Schmidly 1994). It has been documented to occur along all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978). The Rio Grande serves as a filter-barrier for this species, such that along the northern border of Coahuila, west of the Sierra Carmen, this species occurs on the north side of the river, but not the south (Baker 1956).

Rock Squirrel (Spermophilus variegatus). Closely associated with rocky habitats, including canyons along rivers, this species has been documented to occur in rocky areas along all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Yancey 1997).

Black-tailed Prairie Dog (Cynomys ludovicianus). Preferring short-grass prairies, this species often establishes colonies on alluvial fans at mouths of arroyos and near the edge of valleys (Davis and Schmidly 1994). Though extirpated now, specimens of this species were collected in El Paso and at the mouth of Pecos (Schmidly 1977b). The Black-footed Ferret (Mustela nigripes) used to occur in prairie dog towns, and was extirpated from Texas by the 1960s (Davis and Schmidly 1994). Because there are no specimens of ferrets from anywhere along the desert Rio Grande, the ferret does not appear on this species list. There are no records from southwestern New Mexico or Chihuahua, leading Findley et al. (1975) to suggest that they were more commonly associated with Gunnison’s Prairie Dog (Cynomys gunnisoni) than Black-tailed Prairie Dogs in New Mexico.

Eastern Fox Squirrel (Sciurus niger). Reported from Terrell and Val Verde counties in Texas, this species occurs in a wide variety of forest types, although populations in more arid areas generally restricted to river valleys where food trees such as pecans and oaks occur (Davis and Schmidly 1994). According to Baker (1956) this species occurs along the Rio Grande in Coahuila at least as far west as Villa Acuña (now Cuidad Acuña).

Botta’s Pocket Gopher (Thomomys bottae). Although it generally occurs in a wide variety of environments and soil types (Davis and Schmidly 1994), in Big Bend National Park this species is most common in areas where lechugilla, a preferred food plant, grows (Mammal Checklist 1997). Specimens have been collected from all reaches of the desert Rio Grande from its northern end through Boquillas, except the section between Ft. Quitman and the Río Conchos (Findley et al. 1975, Schmidly 1977b, Yancey 1997). In addition, collections have been made in Hudspeth, Presidio, Terrell and Val Verde counties (Davis and Schmidly 1994). The Rio Grande serves as a filter-barrier for this fossorial species, such that there are distinct subspecies of this species on either side of the river bordering western Coahuila: limitaris

Mammals—107 north of the river and villai south of the river (Baker 1956). Since specimens from near Comstock, Texas look like those from northeastern Coahuila, Baker (1956) suggests that perhaps the lower river does not act as a barrier to this species as it does through the Big Bend area. Along the desert Rio Grande in New Mexico, T. bottae opulentus is the subspecies that occurs (NMG&F 1999).

Desert Pocket Gopher (Geomys bursarius arenarius). The taxonomy of this species is unclear. The New Mexico Department of Game and Fish (1999) considers the pocket gopher along the desert Rio Grande to be G. bursarius arenarius, whereas Davis and Schmidly (1994) label it the full species G. arenarius, while warning that G. arenarius may not be separate from G. knoxjonesi (which was split out from G. bursarius recently). Regardless of its taxonomic status, this pocket gopher has a limited distribution along the desert Rio Grande, having been documented only in the Mesilla and El Paso valleys (Findley et al. 1975, Davis and Schmidly 1994). It is generally restricted to cottonwood-willow habitats and is known to occur along irrigation ditches (Davis and Schmidly 1994).

Yellow-faced Pocket Gopher (Cratogeomys castanops). Recently moved from the genus Pappogeomys (Davis and Schmidly 1994), this species is restricted to sandy soils along the river and its tributaries in Big Bend National Park (Mammal Checklist 1997). During dry periods, this pocket gopher may do better than others like Thomomys (Davis and Schmidly 1994); however, it appears to be outcompeted by Geomys and thus limited to shallower, hard soils (Davis and Schmidly 1994). This pocket gopher does not occur along the desert Rio Grande in New Mexico (Findley et al. 1975), but it has been reported from all reaches of the river along the international border (Anderson 1972, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Yancey 1997). The Rio Grande serves as a filter-barrier for this fossorial species, such that there are distinct subspecies of this species on either side of the river bordering northeastern Coahuila: angusticeps on the north side of the river and convexus on the south (Baker 1956).

Silky Pocket Mouse (Perognathus flavus). Frequenting areas with soils ranging from rocky to sandy substrates, this species is often found in the sandy soils of river bottoms (Davis and Schmidly 1994). Because Merriam’s Pocket Mouse was only recently split from this species (see Davis and Schmidly 1994), interpreting some of the older site-specific records is problematic. However, this species appears to occur along the desert Rio Grande in New Mexico (Findley et al. 1975) and has been reported from all Texas counties bordering the river as far downstream as Brewster County (Davis and Schmidly 1994). In Big Bend National Park this species is typically restricted to foothills, but its elevational range includes the river above Boquillas (Mammal Checklist 1997). In Big Bend Ranch State Park, the species occurs mostly in desert scrub and grassland habitats (Yancey 1997).

Merriam’s Pocket Mouse (Perognathus merriami). This species was recently split from P. flavus (see Davis and Schmidly 1994). It prefers areas with sparse vegetation, and has been reported from Hudspeth through Val Verde counties (Davis and Schmidly 1994). Baker (1956) reports a specimen of this pocket mouse along the river east of Langtry and Anderson (1972) lists one near mouth of Río Conchos.

Plains Pocket Mouse (Perognathus flavescens). Now including the Apache Pocket Mouse, this species utilizes sandy deserts, grasslands, and sand dune habitats (Findley et al. 1975, Schmidly 1977b). Along the desert Rio Grande it has been reported from the Socorro and El Paso valleys (Findley et al. 1975, Schmidly 1977b). In New Mexico, this species is less common than P. flavus (Findley et al. 1975).

Hispid Pocket Mouse (Chaetodipus hispidus). Previously placed in the genus Perognathus, this Great Plains species likes sandy soils and relatively open stands of herbaceous vegetation (Findley et al. 1975, Davis and Schmidly 1994). Along the desert Rio Grande, a specimen has been collected in Mesilla, New Mexico (Findley et al. 1975). The species is also known to occur in Presidio, Brewster and Val Verde counties (Davis and Schmidly 1994, Yancey 1997).

Rock Pocket Mouse (Chaetodipus intermedius). Also recently switched from the genus Perognathus, this species prefers rocky habitats, especially cliffs and canyons (Schmidly 1977b, Davis and Schmidly 1994). It has been reported from the western side of the Big Bend region and the reach of the river above the Río Conchos (Anderson 1972, Engel-Wilson and Ohmart 1978, Wilkins and Schmidly 1979).

Mammals—108 Nelson’s Pocket Mouse (Chaetodipus nelsoni). Another ex-Perognathus, this is a rock-dwelling species is reported from Presidio through Val Verde counties in Texas (Davis and Schmidly 1994). Although the park checklist says this species is limited to foothill habitats in Big Bend National Park (Mammal Checklist 1997), it was described as “rare,” but occurring, in the riparian zone along river by Boeer and Schmidly (1977). Preferring large rocks and boulders, steep slopes, and dense vegetation, this pocket mouse has been collected along the river at Lajitas, Boquillas, and Langtry (Schmidly 1977b).

Desert Pocket Mouse (Chaetodipus penicillatus). This species also has been moved from Perognathus and is generally restricted to soft or sandy alluvial soils (Davis and Schmidly 1994). In New Mexico, it has not been reported north of Caballo Dam (Findley et al. 1975) and it has been reported along the Texas- Mexico border from El Paso through the Rio Grande Village/Boquillas area (Schmidly 1977b, Engel- Wilson and Ohmart 1978). In addition, it occurs in Val Verde County, Texas (Davis and Schmidly 1994). In Big Bend National Park, this species is the most common mouse in the river bottom where mesquite (Prosopis sp.) and false willow (Bacharris sp.) grow (Schmidly 1977b). According to Lee et al. (1996), C. penicillatus eremicus should be elevated to a full species.

Merriam’s Kangaroo Rat (Dipodomys merriami). More of a habitat generalist than many other kangaroo rats, when this one co-occurs with Ord’s Kangaroo Rat, Merriam’s tends to end up in areas with harder, rocky soils while Ord’s occurs in areas with sandier soils (Davis and Schmidly 1994). However, within Big Bend National Park, it prefers loose soils and occurs along river (Mammal Checklist 1997). Specimens have also been collected from all reaches of the desert Rio Grande above Boquillas (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978). In addition, the species in known to occur in Terrell and Val Verde counties (Davis and Schmidly 1994).

Nelson’s Kangaroo Rat (Dipodomys nelsoni). Rio Grande serves as a filter-barrier for this species, such that this species lives near the Rio Grande in northern Coahuila, but not on the north side of the river (Baker 1956).

Ord’s Kangaroo Rat (Dipodomys ordii). In contrast to Merriam’s Kangaroo Rat, this species is largely restricted to sandy soils (Mammal Checklist 1997) and prefers open or sparsely vegetated areas (Boeer and Schmidly 1977). It has been reported from all reaches of the desert Rio Grande from the northern end through the Big Bend region (Findley et al. 1975, Schmidly 1977b). The Rio Grande serves as a filter- barrier for this species, such that there are distinct subspecies of this species on either side of the river bordering Coahuila (Baker 1956). In the late 1970s this kangaroo rat was described as “extirpated” from riparian areas along river in Big Bend National Park by Boeer and Schmidly (1977). They attribute this change to large increases in vegetative cover which followed the cessation of grazing along this corridor (Boeer and Schmidly 1977).

Banner-tailed Kangaroo Rat (Dipodomys spectabilis). Requiring heavier soils than Ord’s Kangaroo Rat (Findley et al. 1975), this species generally occurs on harder soils, and on brushy slopes or low hills (Davis and Schmidly 1994). It has been collected along the desert Rio Grande near El Paso (Schmidly 1977b) and along the river in New Mexico (Findley et al. 1975).

American Beaver (Castor canadensis). As an aquatic organism, this species is limited to riparian areas. Although famous for their dam-building, according to Schmidly (1977b) and Findley et al. (1975) beavers along the Rio Grande most often utilize burrows in the bank instead of building a dam and lodge. Beavers have been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel- Wilson and Ohmart 1978, Yancey 1997). In the early nineteenth century, many beaver populations along the Rio Grande were reduced by fur-trapping, especially in the El Paso Valley and above (see Chapter 2 and Weber 1971). Beavers were restocked into much of their former range in New Mexico between 1947 and 1958 (Findley et al. 1975). More recently, beaver populations have faced a new set of threats. Although the beaver population between Santa Elena Canyon and Boquillas Canyon in Big Bend National Park was estimated at 134 individuals in 1978 (Mammal Checklist 1997), at about that same time, Boeer and Schmidly (1977) warned that the general replacement of cottonwoods and willows with salt cedar could have adverse effects upon the beavers in the park because they do not eat salt cedar. In addition, channelization and changes to the river’s flow have evidently extirpated this species from El Paso County

Mammals—109 (Schmidly 1977b). According to Schmidly (1977b), the beavers found in the Rio Grande of Texas are a distinct subspecies, Castor canadensis mexicanus.

Fulvous Harvest Mouse (Reithrodontomys fulvescens). Often found in grassy or weedy areas, or creek bottoms, this species has been reported from Presidio, Brewster, and Val Verde counties, Texas (Davis and Schmidly 1994). It has not been documented along the desert Rio Grande of New Mexico (Findley et al. 1975), and in Big Bend National Park it is restricted to a few grassland areas (Mammal Checklist 1997). Recently, specimens were captured at Big Bend Ranch State Park, within riparian habitat (Yancey, Jones, and Goetze 1995).

Western Harvest Mouse (Reithrodontomys megalotis). Generally avoiding forests, this harvest mouse frequents grassy or weedy areas and is often found near water (Davis and Schmidly 1994). It has been collected along the desert Rio Grande in all reaches above the Río Conchos (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978) and it has been recently collected in Big Bend Ranch State Park (Yancey, Jones, and Goetze 1995). In Big Bend National Park it is restricted to dense grasslands above 2500 feet in elevation (Mammal Checklist 1997).

Plains Harvest Mouse (Reithrodontomys montanus). A species that prefers climax grasslands, this harvest mouse has been reported from El Paso, Presidio, and Brewster counties, Texas (Davis and Schmidly 1994). However, the only Big Bend National Park record comes from the north end of park (Mammal Checklist 1997). Specimens have been collected along the desert Rio Grande in the Socorro and El Paso valleys (Findley et al. 1975, Schmidly 1977b).

Cactus Mouse (Peromyscus eremicus). Occurring in many habitats (Mammal Checklist 1997), this species in generally found in desert environments, often associated with the base of cliffs or rocky slopes (Davis and Schmidly 1994). It has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Yancey 1997).

White-footed Mouse (Peromyscus leucopus). Because of its affinity for forested habitats, this species is generally restricted to riparian areas in arid environments (Davis and Schmidly 1994); it is also known to occur along irrigation ditches in the El Paso Valley (Schmidly 1977b) and frequents brushy areas where there are no trees in Big Bend National Park (Mammal Checklist 1997). It has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Yancey 1997). Boeer and Schmidly (1977) describe a large increase in the population of this species in the riparian corridor of Big Bend National Park between 1942 and 1977, which they attribute to significant increases in vegetative cover which followed the cessation of grazing along this corridor.

Deer Mouse (Peromyscus maniculatus). This species uses a wide variety of habitats including forests, grasslands, and open desert areas (Davis and Schmidly 1994). It has been reported from all reaches of the desert Rio Grande above Boquillas (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

White-ankled Mouse (Peromyscus pectoralis). This species occurs in rocky areas, including those along rivers (Davis and Schmidly 1994); for instance, Baker (1956) reported this species living in rocky ledges along the Rio Grande west of Langtry, Texas. Although the park’s mammal list describes this species as restricted to rocky areas above 4000 feet in Big Bend National Park (Mammal Checklist 1997), Schmidly (1977b) lists specimens collected at Castolon, Hot Springs, and Boquillas. In addition, a specimen was collected from along the river in Big Bend Ranch State Park (Yancey 1997) and they have also been recorded along the river above Presidio, Texas (Engel-Wilson and Ohmart 1978).

Northern Pygmy Mouse (Baiomys taylori). A tropical species which has been expanding its range northward and westward in Texas, this mouse has been reported from Val Verde county in Texas (Davis and Schmidly 1994).

Mearns’ Grasshopper Mouse (Onychomys arenicola). Previously lumped with O. torridus, this predatory mouse frequents low, sparsely vegetated desert areas (Davis and Schmidly 1994). Along the desert Rio Grande, it has been reported from the Belen, Socorro, and Las Palomas valleys (Findley et al.

Mammals—110 1975), as well as the reach of the river above the mouth of the Río Conchos (Engel-Wilson and Ohmart 1978). It has also been reported from El Paso, Presidio, and Brewster counties (Davis and Schmidly 1994, Yancey 1997) although the only record in Big Bend National Park came from a site away from the river, near Burro Mesa (Mammal Checklist 1997).

Northern Grasshopper Mouse (Onychomys leucogaster). This predatory mouse is commonly associated with Dipodomys ordii (Findley et al. 1975), with which it shares a preference for open brushy areas or grasslands with soft soils (Davis and Schmidly 1994). Along the desert Rio Grande, it has been reported from the Belen, Socorro, Mesilla and El Paso valleys (Findley et al. 1975, Schmidly 1977b). It also occurs in Terrell and Val Verde counties, Texas (Davis and Schmidly 1994).

Tawny-bellied Cotton Rat (Sigmodon fulviventer minimus). Findley et al. (1975) report that this species appears to have been replaced by the hispid cotton rat along the Rio Grande in New Mexico (previous records from Las Palomas and Bernardo).

Hispid Cotton Rat (Sigmodon hispidus). Preferring areas with tall grass cover, this species has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978). Boeer and Schmidly (1977) describe a large increase in population of this species in the riparian corridor of Big Bend National Park between 1942 and 1977, which they attribute to the significant increase in vegetative cover which followed the cessation of grazing along this corridor.

White-throated Woodrat (Neotoma albigula). Most often occurring in desert shrub habitats (Davis and Schmidly 1994), this woodrat frequents rocky areas (Schmidly 1977b) and is restricted to higher elevation sites in Big Bend National Park (Mammal Checklist 1997). Because of its habitat preferences, it generally occurs at higher elevations than the Southern Plains Woodrat (Schmidly 1977b); however, in southern New Mexico, it is much more common than the Southern Plains Woodrat (Findley et al. 1975). The White- throated Woodrat has been reported from sites along the river, both above and below Caballo Dam, in New Mexico (Findley et al. 1975) and from both sides of the river in the El Paso Valley (Anderson 1972, Schmidly 1977b). In addition, it is known to occur in Hudspeth, Presidio, Brewster, and Val Verde counties, Texas (Davis and Schmidly 1994).

Southern Plains Woodrat (Neotoma micropus). This woodrat prefers the brushlands of semi-desert areas and has been reported from all the counties bordering the desert Rio Grande in Texas (Davis and Schmidly 1994). In New Mexico, it is known to occur along the river only above Caballo Dam, and it is evidently replaced by N. albigula in southern New Mexico (Findley et al. 1975). It has also been documented along the river in the El Paso Valley, above the Río Conchos, and through the Big Bend region (Schmidly 1977b, Engel-Wilson and Ohmart 1978, Mammal Checklist 1997). In addition, this species occurs in Terrell and Val Verde counties, Texas (Davis and Schmidly 1994). The Rio Grande serves as a filter-barrier for this species in Coahuila, such that it does not occur on the south side of the river west of the Sierra Carmen (Baker 1956).

Common Muskrat (Ondatra zibethicus). This aquatic species is restricted to riparian habitats. In the El Paso area at least, the muskrat lives in man-made irrigation ditches, and does not build lodges, but instead lives in burrows (Schmidly 1977b). It has been reported from the Socorro, Mesilla and El Paso valleys (Findley et al. 1975, Schmidly 1977b). Also, it may have previously occurred in Big Bend National Park (Mammal Checklist 1997) and occurs at least along the Pecos River in Val Verde County (Davis and Schmidly 1994). Schmidly (1977b) reports that water pollutants in the El Paso area may be reducing this species’ reproductive rate in that area and presents fur-trapping data suggesting the population is declining; water diversions previously caused declines throughout the rest of Trans-Pecos Texas. The species may also be declining along the lower Pecos River, where competition from the introduced nutria (Myocastor coypus) may be affecting it (J. Karges, pers. comm.). The subspecies along much of the desert Rio Grande is probably the endemic O. zibethicus ripensis, the Pecos River Muskrat.

Black or Roof Rat (Rattus rattus). This European species was introduced to North America and has become widely established. It has occurred in Las Cruces since at least 1914, but Findley et al. (1975) do not expect it to occur farther north than Truth or Consequences. The species is found throughout Texas,

Mammals—111 especially in towns, as this species almost always lives as a commensal in close association with humans (Davis and Schmidly 1994). Specimens from along the desert Rio Grande have been reported from the El Paso Valley (Schmidly 1977b). In 1956, it was described as being well established in the larger communities of Coahuila, especially those along the Rio Grande (Baker 1956). This species does not occur in Big Bend National Park (Mammal Checklist 1997).

Norway Rat (Rattus norvegicus). Another introduced species, found in all major towns of New Mexico by the mid-1800s (Findley et al. 1975). It is also widely distributed in Texas, living both in close association with humans and in some areas with dense, tall vegetation (Davis and Schmidly 1994). By 1956, it occurred throughout Coahuila, near communities and dwellings (Baker 1956). This species does not occur in Big Bend National Park (Mammal Checklist 1997).

House Mouse (Mus musculus). Like the Norway Rat, this species was introduced and widely distributed in New Mexico by the mid-1800s (Findley et al. 1975). It is also widespread in Texas, and is often found in buildings, though it is not entirely dependent on human-created habitats and can become established in areas with dense vegetation (Davis and Schmidly 1994). Along the desert Rio Grande, specimens have been collected in the Socorro, Mesilla, El Paso, and Presidio valleys (Anderson 1972, Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978), as well as at Boquillas (Baker 1956).

New Mexico Jumping Mouse (Zapus hudsonius luteus). Previously lumped with Z. princeps, this species is generally a mouse of moist meadows at higher elevations. However, specimens of this species were reported from the Socorro Valley in the early 1900s (Findley et al. 1975), and in 1974, Findley and Caire (1974) speculated that this species had been extirpated from the desert Rio Grande. However, it evidently persists at the Bosque del Apache and perhaps in other areas near Socorro (NMG&F 1999).

Porcupine (Erethizon dorsatum). Though often an inhabitant of forested areas, this species occurs in a wide variety of habitats, often associated with rocky areas or slopes (Davis and Schmidly 1994). In New Mexico, it has not been reported along the desert Rio Grande and is most common in the mountains (Findley et al. 1975). However, it has been reported along the river below Ft. Quitman (Engel-Wilson and Ohmart 1978) and in Big Bend National Park (Mammal Checklist 1997). It is known to occur in all counties bordering the desert river in Texas (Davis and Schmidly 1994) and is found along the Devils and lower Pecos rivers (J. Karges, pers. comm.). The porcupine has been described as “rare” in the riparian zone along the river in Big Bend National Park (Boeer and Schmidly 1977) and List et al. (1999) identify habitat destruction (including diminished regeneration of riparian trees) and hunting as factors helping to make this species endangered in Mexico. Alternatively, Weniger (1984, Vol. 2: 166) argues that the porcupine is only a recent arrival to Texas, and may not have occurred in the region prior to 1940.

Nutria (Myocastor coypus). This introduced species, restricted to aquatic habitats like the native beaver and muskrat, was first reported in western Texas in 1985 in the Lower Canyons of Rio Grande, and has recently been reported from Boquillas Canyon and Rio Grande Village in Big Bend National Park (Mammal Checklist 1997). It was introduced to control aquatic vegetation, but populations grow quickly and often outstrip their food supply, so they disperse (Davis and Schmidly 1994). Their destruction of vegetation can impact other species including waterfowl and muskrats (Davis and Schmidly 1994). It has not been introduced to or established along the river in New Mexico (Findley et al. 1975).

Coyote (Canis latrans). This adaptable species uses a wide variety of habitats and has expanded its range with the extermination of other predators like wolves (Davis and Schmidly 1994). It occurs all along the desert Rio Grande (Findley et al. 1975, Engel-Wilson and Ohmart 1978, Davis and Schmidly 1994, Mammal Checklist 1997).

Gray Wolf (Canis lupus). The Mexican subspecies of this large predator, C. lupus baileyi, previously ranged widely through the desert southwest, but wolves were quickly exterminated by ranchers, settlers, and federal predator-control programs during the late nineteenth and early twentieth centuries. The New Mexico population was down to about 45 in 1918, and was eliminated by the 1930s or 1940s (Findley et al. 1975). The last two Texas records come from the 1970s, when individuals were shot in Brewster County (Davis and Schmidly 1994). According to Gehlbach (1981), only about 50 were left in Mexico in the late

Mammals—112 1970s, with occasional stragglers still showing up in the New Mexico panhandle and the Big Bend area of Texas. Specimens exist for the desert Rio Grande in Doña Ana County, New Mexico, from both the Las Palomas and Mesilla Valleys (Findley et al. 1975). Wolves frequent rugged, somewhat open country (Davis and Schmidly 1994) and may have occurred along much of the desert Rio Grande in spite of the relative lack of specimens.

Kit Fox (Vulpus macrotis neomexicana). The taxonomy of this fox is under debate; for instance, Davis and Schmidly (1994) lump the Kit and Swift Foxes into V. velox; however, because all the desert river occurrences (Schmidly 1977b, NMG&F 1999) seem to refer to the Kit Fox, this list follows the New Mexico Department of Game and Fish (1999) in considering the two species separate. These foxes are often found in open deserts or grasslands, but can adapt to pastures and agricultural areas (Davis and Schmidly 1994). Along the desert Rio Grande, they have been documented above Caballo Dam and for all reaches of the river along the international border (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Mammal Checklist 1997).

Common Gray Fox (Urocyon cinereoargenteus). This fox prefers wooded areas and is known to climb trees on occasion (Davis and Schmidly 1994, Mammal Checklist 1997). Along the desert Rio Grande, it has been documented above Caballo Dam and for all reaches of the river along the international border (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Mammal Checklist 1997). Some evidence suggests that this species is outcompeted by coyotes where they co-occur; removal of coyotes sometimes allows gray fox populations to increase (Davis and Schmidly 1994).

Black Bear (Ursus americanus). Bears have been extirpated from the northernmost reaches of the desert Rio Grande; numerous mid-nineteenth century travelers reported seeing bears or signs of bears along the river above Las Palomas Valley (Bieber 1936: 331; Bieber 1938: 93; Emory 1976: 55). Because these accounts make no mention of anything notable about these bears’ size, color, or temperament, I have assumed that they refer to black bears, which no longer occur along the river in this reach (Findley et al. 1975). There are also some reports of black bears along the river in the Big Bend region and below. A black bear photographed near the river in Big Bend National Park (Schmidly 1977b) may have been a bear dispersing from Mexico. They appear to be recolonizing the Chisos Mountains from mountains of northern Mexico; this population was estimated at about 20 individuals in 1994 (Davis and Schmidly 1994). Black bears may also be resident along some of the lower reaches of the desert river. Schmidly (1977b) examined a specimen collected somewhere in Terrell County and he cites Bailey’s 1905 report of seeing them in Pecos River Canyon in Val Verde County. In addition, Baker (1956) lists a specimen from along the river near the western edge of Terrell County. According to John Karges (pers. comm.), there are several recent, unpublished reports of black bears for this area along the lower reaches of the desert Rio Grande. There are no verified records of the black bear’s larger cousin, the grizzly (Ursus arctos) from along the desert Rio Grande; all New Mexico and Texas specimens come from mountain areas and the only observations along the desert river mentioned in Bailey’s Mammals of New Mexico (1931) come from James Ohio Pattie’s journal, a source of questionable credibility (see Goetzmann 1984). Thus the grizzly bear does not appear on this list. However, the grizzly’s previous wide distribution and occurrence in relatively open habitats and prairies suggest that it could have occurred more widely before human pressure forced it into more remote, rugged areas (Davis and Schmidly 1994). Nevertheless, Gehlbach (1981) argues that any grizzlies that occurred east of the Rio Grande in southern New Mexico or in lowland desert habitats were vagrant individuals, not residents.

Ringtail (Bassariscus astutus). This species is found in rocky areas, and less often, woodlands (Davis and Schmidly 1994). While it has not been reported from anywhere along the desert river in New Mexico (Findley et al. 1975), it has been documented in all reaches along the river below Ft. Quitman (Schmidly 1977b, Engel-Wilson and Ohmart 1978) and is known to occur in the Franklin Mountains near El Paso (Schmidly 1977b). Although Baker (1956: 301) described this species as “common along the Rio Grande” bordering Coahuila, it was later described as “uncommon” in the riparian zone along river in Big Bend National Park (Boeer and Schmidly 1977).

Mammals—113 Common Raccoon (Procyon lotor). Generally restricted to riparian areas in arid environments, this species has been reported from all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Mammal Checklist 1997, Yancey 1997).

White-nosed Coati (Nasua narica). Previously lumped with Nasua nasua, this Mexican species is often found in forests and rocky canyons (Davis and Schmidly 1994). In the mid-1950s, Baker (1956: 304) reported receiving “no definite records of the coati along the Rio Grande in Coahuila.” However, there were a handful of reports from Big Bend National Park in the 1980s (Mammal Checklist 1997), and scattered, though unverified, sightings have also been reported recently from river cane thickets and riparian woodlands along the river below Big Bend (J. Karges, pers. comm.).

Long-tailed Weasel (Mustela frenata). This secretive species occurs in a wide variety of habitats, especially areas where prey species like pocket gophers and ground squirrels are found (Davis and Schmidly 1994). Along the desert Rio Grande it has been documented in the Mesilla and El Paso valleys, as well as in Big Bend National Park and near Langtry, Texas (Findley et al. 1975, Schmidly 1977b, Engel- Wilson and Ohmart 1978, Mammal Checklist 1997). Because it is secretive, it is often overlooked (Mammal Checklist 1997), and thus may be more widely distributed than the records indicate (Yancey 1997).

Mink (Mustela vison energumenos). A single record exists for this species along the desert Rio Grande: a recent record from San Antonio, New Mexico, which could represent either a range expansion for this species or an individual that escaped from a fur farm (NMG&F 1999).

American Badger (Taxidea taxus). This predator of ground squirrels and prairie dogs can be found in a variety of open habitats such as grasslands and deserts (Davis and Schmidly 1994). Along the desert Rio Grande, it has been documented for all reaches of the river along the international border (Baker 1956, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

Western Spotted Skunk (Spilogale gracilis). Sometimes frequenting residential areas, this skunk uses a variety of habitats including rocky and brushy areas (Davis and Schmidly 1994). It used to be lumped with Spilogale putorius (Davis and Schmidly 1994) and has been reported from all reaches of the desert Rio Grande along the international border (Anderson 1972, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

Hooded Skunk (Mephitis macroura). A resident of dense, streamside vegetation, this skunk has been reported from Brewster and Presidio counties, Texas (Davis and Schmidly 1994). The only Big Bend National Park record for this species comes from a site away from the river, McKinney Spring (Mammal Checklist 1997).

Striped Skunk (Mephitis mephitis). Often found in wooded, brushy areas and farmlands (Davis and Schmidly 1994), this species has been documented for all reaches of the river below Caballo Dam (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978, Yancey 1997).

Common Hog-nosed Skunk (Conepatus mesoleucus). This skunk also likes brushy or lightly wooded areas (Davis and Schmidly 1994) and often inhabits areas near permanent water sources (Mammal Checklist 1997). Along the desert Rio Grande it has been documented in the Socorro Valley, and in all the reaches of the river below Ft. Quitman (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

River Otter (Lutra canadensis). Mostly aquatic, this species occurs most often in lakes and larger streams, and there in no indication it ever occurred along the desert Rio Grande in Texas (Davis and Schmidly 1994). However, it may have occurred along the northernmost reaches of the river in New Mexico. In 1846, Johnston (1848: 575) noted otter tracks along the bank of the river in the Engle Valley, and in the late 1830s, El Paso officials wrote to government officials in Chihuahua about their concerns that over-harvesting might lead to the extinction of both otters and beavers along the Rio Grande (Weber 1971: 224). The species was thought to be extinct in New Mexico by the 1970s (Findley et al. 1975).

Mammals—114 Mountain Lion (Felis concolor). This large predator used to occur throughout Texas and most of New Mexico, but it is now restricted to isolated mountains and parts of southern Texas (Findley et al. 1975, Davis and Schmidly 1994). Along the desert Rio Grande, it in known to occur in the Socorro Valley, and from all reaches of the river below Ft. Quitman (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978)

Ocelot (Felis pardalis). This species has been collected in Brewster County, Texas (Davis and Schmidly 1994), on the Alamo de Casarea Ranch (Schmidly 1977b).

Jaguarundi (Felis yagouaroundi). Although Davis and Schmidly (1994) say this species is restricted to extreme southern Texas (Cameron, Hidalgo, Starr and Willacy counties), Gehlbach (1981: 65) suggests that this species may have previously (before the flooding of Amistad and Falcon Reservoirs) ranged as far up the Rio Grande as the Devils River, originally connected to its subtropical haunts in southern Texas by the riparian strip of the Rio Grande. He suspects that the less continuous and more narrow riparian strip above this area kept this and other sub-tropical species from making it any farther west (Gehlbach 1981). Nevertheless, there have been many unconfirmed (by photo or specimen) sightings in Big Bend National Park (Mammal Checklist 1997).

Jaguar (Panthera onca). The previous range of this neotropical cat has been a subject of some debate. Gehlbach (1981) suspects that any recorded in the U.S. were “mere wanderers” as opposed to evidence of a sustained breeding population; he cites their rarity, age, and the male-biased sex ratio of the few caught as evidence. Findley et al. (1975) disagree, arguing that Bailey’s reports of jaguars in New Mexico prior to 1931 suggest a resident race of jaguars, adapted to temperate climates. The reports in Bailey’s Mammals of New Mexico (1931) all appear to describe jaguars found in mountain ranges, though two come from mountains relatively close to the desert Rio Grande (the Sierra de los Caballos and the San Andres Mountains); this species’ continued occurrence in remote mountain ranges was confirmed in 1996, when a jaguar was photographed in the Peloncillo Mountains along the southern Arizona/New Mexico border (Warner 1996). As for their historic distribution in Mexico, Anderson (1972) did not list jaguars as ever occurring in Chihuahua, while Baker (1956) argued that the watershed of the Rio Grande represented a dispersal route for jaguars coming into northern Coahuila from the east during colonial times and earlier periods; however, by the mid-1950s the only stragglers that reached Coahuila came in from the southeastern corner of the state. The only record from anywhere along the desert Rio Grande comes from Taylor (1947), who lists a jaguar record near the mouth of the Pecos River.

Bobcat (Lynx rufus). This species can be found in rocky outcrops (Davis and Schmidly 1994), although it generally prefers brushy areas close to water (Mammal Checklist 1997); according to Schmidly (1977b), the salt-cedar thickets along river between El Paso and Presidio are frequented by numerous bobcats. This species has been documented along all reaches of the desert Rio Grande (Findley et al. 1975, Schmidly 1977b, Engel-Wilson and Ohmart 1978).

Feral Pig (Sus scrofa). This introduced species is increasing in numbers throughout Trans-Pecos, Texas, and although the park’s mammal checklist says that it has not yet been recorded in Big Bend National Park (Mammal Checklist 1997), according to John Karges (pers. comm.), it does occur in the park’s Rosillos Mountains. Feral pigs were introduced into Big Bend Ranch State Park in the 1970s and though they were not observed within the park boundaries during recent surveys, they were seen near the northwest corner of the park (Yancey 1997).

Collared Peccary, Javelina (Tayassu tajacu). This native, pig-like ungulate occurs in brushy areas, often in association with prickly pears (Davis and Schmidly 1994). Along the desert Rio Grande, it has been documented in the Big Bend area and the reach below Ft. Quitman (Boeer and Schmidly 1977, Engel- Wilson and Ohmart 1978). It has also been recorded in Terrell and Val Verde counties (Davis and Schmidly 1994). Schmidly (1977b) suspects that heavy livestock grazing has reduced this species’ abundance in Trans-Pecos Texas.

Mule Deer (Odocoileus hemionus). This western deer uses a wide variety of habitat types, though they generally prefer relatively open, arid areas (Davis and Schmidly 1994). It occurs almost state-wide in New

Mammals—115 Mexico, including all of desert Rio Grande (Findley et al. 1975), and it is native throughout western Texas (Davis and Schmidly 1994). Mule deer are described as “uncommon” in the riparian zone along the river in Big Bend National Park (Boeer and Schmidly 1977). Although a specimen documents this species previous occurrence near Langtry, Texas (Schmidly 1977b), this species may have been extirpated from the area around the mouth of the Pecos (Davis and Schmidly 1994); interbreeding may be allowing White- tailed Deer to displace Mule Deer in some parts of Texas (Davis and Schmidly 1994). In the 1950s, Baker (1956: 319) described hunting of this species near Boquillas, and suggested that “[t]he mule deer is in danger of being exterminated [in Coahuila] because the population is so reduced in numbers. Most individuals that remain are found only in the most remote areas in Coahuila.”

White-tailed Deer (Odocoileus virginianus). This species is often associated with hardwoods, and in some areas occurs in lower elevation habitats than Mule Deer (Davis and Schmidly 1994). However, in Big Bend National Park, an endemic montane subspecies, O. virginianus carmini occurs, restricted to higher elevation areas (Mammal Checklist 1997). Findley et al. (1975) do not report any specimens from along the desert Rio Grande in New Mexico, but in 1846, Emory (1976: 54) reported that a member of his party “killed a common Virginia deer” along the river near Fra Cristobal Mountain. Anderson (1972) reports this species’ occurrence at the mouth of the Río Conchos, and transient individuals have been sighted along the river in Big Bend Ranch State Park (Yancey 1997).

Mountain Sheep (Ovis canadensis). Generally limited to remote mountain ranges, this species was extirpated from Texas by the 1960s (Davis and Schmidly 1994). Mountain sheep were never fully extirpated from New Mexico, though re-stocking programs in southern New Mexico may have replaced the native subspecies (O. canadensis mexicanus) with the Rocky Mountain subspecies (O. canadensis canadensis) in some areas (Findley et al. 1975). The only records of this species along the desert Rio Grande come from the Big Bend region. In 1899, the members of a USGS expedition reported seeing a mountain sheep in San Vicente Canyon (Hill 1901: 169). By the early 1920s, one of the last known herds of bighorns in the Chihuahuan Desert of Mexico frequented the Mexican side of Santa Elena Canyon; it disappeared around 1925 (Hailey 1977). Mountain sheep have been reintroduced to the Black Gap Wildlife Management Area, east of Big Bend National Park (J. Karges, pers. comm.).

Barbary Sheep (Ammotragus lervia). Introduced, this species is being reported more often in Big Bend National Park, throughout the park (Mammal Checklist 1997). It is also quite common in Val Verde County (J. Karges, pers. comm.). Though they have also been introduced to New Mexico, populations have only become established in the northern and eastern parts of the state (Findley et al. 1975). Due to similar habitat and food preferences, these sheep may compete with Bighorn Sheep and Mule Deer (Davis and Schmidly 1994).

Mammals—116 Literature Cited

Anderson, S. 1972. Mammals of Chihuahua: taxonomy and distribution. Bulletin of the American Museum of Natural History 148:149-410.

Bailey, V. 1931. The mammals of New Mexico. Washington: USDA, Bureau of the Biological Survey, North American Fauna No. 53.

Baker, R.H. 1956. Mammals of Coahuila, Mexico. University of Kansas Publications Museum of Natural History 9 (7): 125-335.

Bieber, R. P., ed. 1936. Marching with the Army of the West, 1846-1848. Glendale, CA: Arthur H. Clark Co.

Bieber, R.P., ed. 1938. Exploring southwestern trails, 1846-1854. Glendale, CA: Arthur H. Clark Co.

Choate, J.R. 1970. Systematics and zoogeography of Middle American shrews of the genus Cryptotis. University of Kansas Publications of the Museum of Natural History 19 (3): 195-317.

Davis, W.B. and D.J. Schmidly. 1994. The Mammals of Texas. Austin: Texas Parks and Wildlife Department.

Dowler, R.C., T.C. Maxwell, and D.S. Marsh. 1992. Noteworthy records of bats from Texas. Texas Journal of Science 44 (1): 121-123.

Easterla, D.A. 1970. First record of the pocketed free-tailed bat for Coahuila, Mexico and additional Texas records. Texas Journal of Science 22 (1): 92-93.

Findley, J.S. 1987. The natural history of New Mexico mammals. New Mexico Natural History Series, University of New Mexico Press.

Findley, J.S. and W. Caire. 1977. The status of mammals in the northern region of the Chihuahuan Desert. In Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico, ed. R.H. Wauer and D.H. Riskind, pp. 217-220. U.S. Department of the Interior, National Park Service Transactions and Proceedings Series, No. 3.

Findley, J.S., A.H. Harris, D.E. Wilson, and C. Jones. 1975. Mammals of New Mexico. Albuquerque: University of New Mexico Press.

Gehlbach, F.R. 1981. Mountain islands and desert seas: a natural history of the U.S.-Mexico borderlands. College Station: Texas A&M University Press.

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Goetzmann, W.H. 1984. Introduction. In The personal narrative of James O. Pattie, pp. v-xi. Lincoln: University of Nebraska Press.

Hailey, T.L. 1977. Past, present, and future status of the desert bighorn in the Chihuahuan Desert region. In Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico, ed. R.H. Wauer and D.H. Riskind, pp. 217-220. U.S. Department of the Interior, National Park Service Transactions and Proceedings Series, No. 3.

Hall, E.R. 1981. The mammals of North America, 2nd edition. New York: John Wiley and Sons.

Higginbottom, J.L., L.K. Ammerman, and M.T. Dixon. 1999. First record of Lasiurus xanthinus (Chiroptera: Vespertilionidae) in Texas. Southwestern Naturalist 44 (3): 343-347.

Lee, T.E, B.R. Riddle, P.L. Lee. 1996. Speciation in the desert pocket mouse (Chaetodipus penicillatus Woodhouse). Journal of Mammalogy 77: 58-68.

List, R., G. Ceballos, and J. Pacheco. 1999. Status of the North American Porcupine (Erethizon dorsatum) in Mexico. Southwestern Naturalist 44 (3): 400-404.

Mammal Checklist: Big Bend National Park, Rio Grande Wild and Scenic River. 1997. Big Bend Natural History Association, in cooperation with the National Park Service.

Manning, R.W., J.K. Jones, R.R. Hollander, and C. Jones. 1987. Notes on distribution and natural history of some bats on the Edwards Plateau and in adjacent areas of Texas. Texas Journal of Science 39 (3): 279-285.

New Mexico Dept. of Game and Fish. 1999. New Mexico Species List/Species Accounts. Available at http:/www.fw.vt.edu/fishex/states/nm.htm [10 December 1999]

Packard, R.L. 1977. Mammals of the southern Chihuahuan Desert: an inventory. In Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico, ed. R.H. Wauer and D.H. Riskind, pp. 141-153. U.S. Department of the Interior, National Park Service Transactions and Proceedings Series, No. 3.

Ruedas, L.A. 1998. Systematics of Sylvilagus Gray, 1867 (Lagomorpha: Leporidae) from southwestern North America. Journal of Mammalogy 79 (4): 1355-1378.

Schmidly, D. J. 1977a. Factors governing the distribution of mammals in the Chihuahuan Desert region. In Transactions of the symposium on the biological resources of the Chihuahuan Desert region, United States and Mexico, ed. R.H. Wauer and D.H. Riskind, pp. 163-192. U.S. Department of the Interior, National Park Service Transactions and Proceedings Series, No. 3.

Schmidly, D. J. 1977b. The mammals of Trans-Pecos Texas, including Big Bend National Park and Guadalupe Mountains National Park. College Station: Texas A&M University Press.

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Mammals—118 Taylor, W.P. 1947. Recent record of the jaguar in Texas. Journal of Mammalogy 28 (1): 66.

Valdez, E.W., J.N. Stuart, and M.A. Bogan. 1999. Additional records of bats from the Middle Rio Grande Valley New Mexico. Southwestern Naturalist 44 (3): 398-400.

Warner, G. 1996. Eyes of fire: encounter with a borderland jaguar. El Paso: Printing Corner Press.

Weber, D.J. 1971. The Taos trappers: the fur trade in the far southwest, 1540-1846. Norman: University of Oklahoma Press.

Weniger, D. 1984. The Explorers’ Texas. Austin: Eakin Press.

Wilkins, K.T. and D.J. Schmidly. 1979. Identification and distribution of three species of pocket mice (Genus Perognathus) in Trans-Pecos Texas. Southwestern Naturalist 24 (1): 17-32.

Yancey, F.D. 1997. The mammals of Big Bend Ranch State Park, Texas. Special Publications, Museum of Texas Tech University 39: 1- 210.

Yancey, F.D. and C. Jones. 1996. Notes on three species of small mammals from the Big Bend region of Texas. Texas Journal of Science 48: 247-250.

Yancey, F.D., C. Jones, and J.R. Goetze. 1995. Notes on harvest mice (Reithrodontomys) of the Big Bend region of Texas. Texas Journal of Science 47 (4): 263-268.

Yancey, F.D., C. Jones, and R.W. Manning. 1995. The eastern pipistrelle, Pipistrellus subflavus (Chiroptera: Vespertilionidae), from the Big Bend region of Texas. Texas Journal of Science 47 (3): 229-231.

Mammals—119

Mammals—120

Chapter 6: Birds of the Desert Rio Grande

As many as 351 species of birds regularly occur along the Rio Grande through the Chihuahuan Desert, and of these, 155 species (44%) breed in areas near the river (in either riparian, desert, or cliff habitats), while the remainder (196 species, 56%) use such areas during migration or during the non-breeding season (Table 6-1). Twenty-three of these regular species are federally listed as threatened or endangered in Mexico or the United States (see Appendix B).

In addition, 111 vagrant species (also referred to as “casual”, “accidental” or “irregular” species) have been recorded along 4 sections of the desert Rio Grande (Table 6-2); these are birds whose normal range would not include the river, though they may have wandered into these areas or been blown in on a few occasions by a storm. The 111 should be considered a minimum for the total number of vagrants seen along the river, as this compilation does not account for birds recorded at sites other than the four tallied in the table. Table 6-2 includes 3 additional breeding species, raising the total for species breeding along the river to 158 species. Ten of the vagrant species are listed as endangered or threatened by Mexico or the United States (see Appendix B).

As shown in the Habitat Use column of Table 6-1, the 351 regular species includes 134 obligate species (38% of the total) that are restricted to aquatic or riparian habitats: these habitats include open water, shorelines, and marshes; as well as cottonwoods, willows and other phreatophytic vegetation; and urban/agricultural areas within the floodplain. Another 165 species (47% of the total) are facultative users of valley habitats; these species are generally more abundant in relatively mesic or wooded habitats (for some of these birds, habitat preferences change with the seasons), such that their occurrence in the lowlands of the Chihuahuan Desert is largely dependent upon habitats found in the river valley. Fifty-one species (15% of the total) are incidental users of river valley habitats, more commonly found in desert, grassland, or rocky habitats; thus, these species are probably most likely to be found along the desert Rio Grande where it lacks a broad floodplain.

If we consider only breeding birds, the percentages remain similar: 37% restricted to riparian habitats, 41% facultative users of riparian habitats, and 21% incidental users. These habitat use percentages are somewhat different from those reported by Johnson et al. (1977), who concluded that 47% of species nesting in the lowlands of the southwest are completely dependent upon water-related habitats, 30% are somewhat dependent upon them, and 23% do not use them. There are at least two reasons that our percentages may differ. First, their geographic area ranged from southern California to the southern tip of Texas, and evidently excluded the Bosque del Apache (as their list of breeding birds excluded a number of birds listed as breeding at the Bosque), so they were considering a somewhat different set of birds.

Secondly, Johnson et al.’s (1977) habitat use designations differ from mine in a number of cases, perhaps because they were focusing on breeding habitats only (though they never explain if this is how they made their habitat-use determinations); for instance, they include Zone-tailed Hawk, Northern Flicker, Western Wood-Pewee, Bell’s Vireo, Blue Grosbeak, and Painted Bunting in their “Obligate Riparian” group, whereas the information used to develop Table 6-1 (see below) suggests that these species also use other habitats during the annual cycle. In addition, Johnson et al. (1977) include birds such as the Red-tailed Hawk, Harris Hawk, Elf Owl, Long-eared Owl, and Varied Bunting in their list of non-riparian species, whereas these species do appear to occur in riparian habitats along the desert Rio Grande. Though such habitat-use designations may be somewhat seasonal and site-specific, the bottom line is still clear: riparian habitats are used by the majority of bird species in arid regions.

Relatively few complete extirpations appear to have occurred among the avifauna, although a number of species have undergone significant population declines or increases (described more fully in the Species Accounts following Table 6-2). Wild Turkeys were extirpated from the northernmost reaches of the desert Rio Grande and have been reintroduced to the Bosque del Apache. In addition, habitat destruction associated with human activities has negatively impacted a variety of riparian obligates. For instance, birds that feed or nest in backwaters or marshes have likely been affected by changes in flow regimes and channelization; Chris Rustay (pers. comm.) also notes that obligate cottonwood bosque nesters, such as the Summer Tanager and Yellow-billed Cuckoo, have necessarily declined anywhere that the bosque has been destroyed. In contrast, a number of other species (including many of the doves, grackles, and cowbirds) have evidently benefited from human modifications to the environment and expanded their ranges. These factors also interact with one another: the combination of habitat destruction and expanding populations of the Brown-headed Cowbird, and to a lesser extent, the Bronzed Cowbird, may have made some passerine species more susceptible to nest-parasitism and local breeding declines.

The lists in Tables 6-1and 6-2 were compiled mostly from bird lists available at three federal sites along the river—Bosque del Apache National Wildlife Refuge (U.S. Fish and Wildlife Service 1999), Big Bend National Park (Selleck 1994), and Amistad National Recreation Area (Sorola, n.d.)—and an El Paso area checklist (including all of El Paso County, the southern third of Doña Ana County and the western half of Hudspeth County) published by the El-Paso/Trans-Pecos Audubon Society (Donaldson et al. 1987, Zimmer 1999). All but the Amistad list indicate breeding birds. Information from supplemental sources was used to clarify breeding status, habitat use, and population changes. Information from the original lists was modified as follows (all modifications are presented in [square brackets] in the tables). 1. Reports of breeding birds were switched to non-breeding occurrence if information indicated that breeding is limited to higher elevation sites away from the river. 2. One bird was omitted from the Bosque del Apache (BDA) list—Montezuma Quail—because it is limited to higher elevation sites away from the river (C. Rustay, pers. comm.). Six other species from the BDA list—Band-tailed Pigeon, Acorn Woodpecker, Pinyon Jay, Juniper Titmouse, Painted Redstart, and Hepatic Tanager— were placed into the table of vagrants (Table 6-2) instead of the regular occurrence table (Table 6-1) even though they were reported to be at least “rare” at BDA because any use they make of habitats along the river is quite irregular and fleeting (C. Rustay, pers. comm., Hammond 1978). 3. Two birds (Bald Eagle and Eastern Bluebird) known to breed along the river between BDA and El Paso, but not listed as breeding on the lists from either site, were designated as breeding birds in the Greater El Paso area column (GEP) of Table 6-1, with a description of where they breed in the accompanying species account. 4. Because the Amistad list does not designate breeding birds, I checked the literature to see if any species listed as occurring there, but not breeding at the other three sites, might breed near the eastern edge of the Chihuahuan Desert. The list of breeding birds in this column is thus incomplete; I only looked into breeding records for species not reported as breeding elsewhere along the desert Rio Grande. 5. Because the Amistad list is for all of Val Verde County, the birds listed on it were checked against a list of birds banded at Amistad (Natural Resources 1999) and Peterson and Zimmer’s (1998) Birds of Trans-Pecos Texas; the latter authors are more conservative in accepting sightings, and a handful a species they doubt really occur at Amistad or in riverine/desert habitats were omitted. Similarly, Peterson and Zimmer’s book and Christmas Bird Count results for Las Cruces and El Paso (BirdSource 1999) were used to confirm verified sightings along the river or within Las Cruces or El Paso for non-aquatic species listed by Zimmer (1999) but not listed as occurring along the river at one of the other sites. Species Accounts

Common Loon. Though this species is often associated with the deep water of reservoirs, its current presence along the Rio Grande is not merely an artifact of dams in the river. In 1846, Abert (1962: 125) collected a loon near an encampment at Valverde.

American White Pelican. Like the preceding species, pelicans is also typically associated with reservoirs, but their presence along the Rio Grande is not merely an artifact of dams in the river. In 1849, Whiting described seeing a flock of 25 “huge white pelicans” in a floodplain pond near the southern end of the El Paso Valley (Bieber 1938: 300).

Double-crested Cormorant, Neotropic Cormorant. The construction of Amistad Reservoir may be responsible for an apparent increase in these species’ abundance at Big Bend National Park (Wauer 1996). The Neotropic Cormorant has also been increasing in abundance along the river in New Mexico; the first nesting and regular occurrence around Elephant Butte Reservoir was reported in the early 1970s and a new breeding area at the Bosque del Apache was established in 1994 (NMG&F 1999).

Cattle Egret. Originally, this species was limited to the Old World. In the late 19th century, it flew across the Atlantic Ocean and became established in South America. It then expanded its range northward, reaching the Gulf Coast of Texas by 1955 (Oberholser 1974). Between 1958 and 1965 the number of breeding pairs in Texas increased from 11 to over 20,000 (Oberholser 1974). The first Big Bend National Park record was in 1967 (Wauer 1996), and Peterson and Zimmer (1998:39) say cattle egret numbers “have steadily increased [in Trans-Pecos Texas] since the 1970s.” The species was not reported in either Bailey’s (1928) Birds of New Mexico or Ligon’s (1961) New Mexico Birds, though the species is now established as a breeder at Bosque del Apache (US Fish and Wildlife Service 1999).

Black-bellied Whistling-Duck. According to a Del Rio area birdlist published by the Texas Parks and Wildlife Department, the Rio Grande and the creation Amistad Reservoir have allowed this tropical species to expand its range westward (Sorola n.d.).

Wood Duck. According to Peterson and Zimmer (1998), this species has increased in abundance in the El Paso area in recent years, though they give no reason for this change.

Mallard. The Mexican Duck used to be considered a full species but is now considered a subspecies of the Mallard because the two interbreed freely; the most obvious difference between Mexican Ducks and standard mallards is that Mexican males lack the green head of the standard Mallard. Along the desert Rio Grande in New Mexico, the Mexican Duck has historically occurred. Gehlbach (1981) notes that the Mallards north of El Paso are becoming more and more like the green-headed form, and less like Mexican Ducks; he attributes this shift away from the Mexican form to habitat changes generally more favorable to the green-headed Mallard form: a reduction in the marshes and riparian woodlands preferred by the more secretive Mexican form and an increase in reservoirs and steep-sided bodies of water used by green-headed Mallards.

Mississippi Kite. According to Peterson and Zimmer (1998), since the 1960s, this species has been reported more commonly in Trans-Pecos Texas.

Bald Eagle. In 1988, a single nest of Bald Eagles was discovered about 5 miles west of Caballo Reservoir; twelve young fledged from this nest between 1988 and 1997, but the nest does not appear to have been used since 1997 (S. Williams, pers. comm.).

Gray Hawk. Because of a growing number of sightings of this species in Trans-Pecos Texas, Peterson and Zimmer (1998) speculate that this species may be increasing in abundance or modifying its habitat requirements.

Birds—1 Common Black-Hawk. Peterson and Zimmer (1998) report a breeding record for this tree-nesting raptor from along the Devils River. Wauer (1996) also seems fairly confident this species breeds along the river in Big Bend National Park.

Zone-tailed Hawk. Although it breeds more commonly at higher elevations (Peterson and Zimmer 1998), there are records of this hawk breeding along the river in Big Bend National Park (Wauer 1996).

Peregrine Falcon. In the summer of 1999, this previously threatened species was removed from the United States’ federal list of threatened and endangered species. In the Chihuahuan Desert, breeding populations are restricted to areas where cliffs are available for nest sites, e.g.: in mountains and along the river canyons of Big Bend. Though non-migratory, breeding populations along the river in Big Bend region suffered a higher rate of reproductive failures than mountain nesting birds in the early 1970s, perhaps because they fed primarily upon migratory or insectivorous prey such as bats, swallows, waterfowl and shorebirds (Hunt 1976). However, in subsequent years, falcons nesting along the river were equally successful with mountain nesters and prey species throughout the Trans-Pecos area were found to have higher levels of pesticide residues than elsewhere in North America (Hunt et al. 1988). Though this species does not occur on the Del Rio area birdlist (Sorola n.d.), it has been reported from Seminole Canyon State Historical Park (Wiedenfeld 1989).

Ring-necked Pheasant. This Asian native has been widely introduced as a game bird. According to Bailey (1928) early introductions into the Rio Grande Valley of New Mexico happened around 1916, but these were evidently unsuccessful. Ligon (1961) suggests that the only successful introductions up to the time of his writing had been in “irrigated valleys,” though he does not provide any specific locations. An introduction by the Texas Parks and Wildlife Department near El Paso has evidently failed (Peterson and Zimmer 1998).

Wild Turkey. The Rio Grande race of the wild turkey (Meleagris gallopavo intermedia) historically occupied much of eastern Texas, with the western limit of its range occurring near the Pecos River (Gore 1973). In 1856, Micheler recorded “wild turkey in large number” in the Rio Grande’s river bottom near the mouth of the Pecos (quoted in Emory 1987, Vol. 1, Pt. 1: 78). The first Big Bend National Park records of wild turkeys began appearing in the mid-1970s, and according to Wauer (1996), this species was not actively introduced, but was expanding its range into the park. In New Mexico, the turkey’s history is less clear. The Rio Grande turkey (M. gallopavo intermedia) is reported to have only occurred along the river bottoms of the Canadian River drainage in the extreme northeast corner of the state (Bailey 1928, Ligon 1961). Merriam’s wild turkey (Meleagris gallopavo merriami), sometimes called the “mountain turkey” is generally restricted to montane habitats of southwestern North America, especially oak and conifer forests above 6000 feet in elevation (Ligon 1961). Two maps of this subspecies’ historic range show it restricted entirely to higher elevation mountains (Bailey 1928, Ligon 1946) while Aldrich’s map (1967) shows it occurring along the Rio Grande only above Socorro. However, a number of journals from the mid-1800s include specific mention of turkeys in the river bottoms of the Rio Grande between Socorro and what is now northern Doña Ana County: In 1846, Ruxton (1973:178) described wild turkey as “very abundant in the river bottom” near the Valverde encampment. Abert (1962) said his hunting party, sent out from Valverde in 1846, saw many turkeys, though they failed to kill one. Wislizenus (1969:37) said “wild turkey [were] found” in the river bottom just downstream of Valverde in 1846. In 1846, Johnston described seeing a flock of wild turkeys in a dense stand of willows near Fra Cristobal Mountain (1848: 573). In 1846, Cooke (Bieber and Bender 1938: 93) described the country along the river, about 71 miles below Socorro as being inhabited by many kinds of “wild animals”, including turkeys; his party killed a turkey along the river about 95 miles below Socorro. Ferguson (Bieber 1936), writing in 1847, described eating a turkey that was killed in the vicinity of their camp at San Diego (on a bluff overlooking the river); it seems most likely that this turkey would have been killed along the river instead of in the desert areas along the Jornada del Muerto.

Birds—2 As Ligon (1946, 1961) reports Merriam’s turkeys occurring in the Black Range (west of modern Truth or Consequences), perhaps this population at one time extended all the way to the river’s floodplain. Similar to what happened throughout the southwest, excessive hunting could have led to this population’s extirpation. Wild Turkeys (of the Rio Grande race) were re-introduced to the Bosque del Apache in 1974; by 1992, their population had grown to about 300 birds (Wunz 1992).

Whooping Crane. An introduced population of these endangered cranes winters at the Bosque del Apache; the population is considered “experimental” by the U.S. Fish and Wildlife Service. Although no verified (by specimen or photograph) records exist for this species anywhere along the desert Rio Grande, they may have occasionally migrated through New Mexico (U.S. F&W 1998). Images of whooping cranes have been found decorating some pottery found at an Anasazi site near Los Lunas (Scurlock 1998: 207). Also, there are sight records for Doña Ana county, in the mid-1800s. At this time, whooping cranes were sometimes considered “adult” cranes while sandhill cranes were thought to be juveniles (Bent 1963: 226), and in a describing Grus Americanus, Henry (1855: 315) wrote that during migration along the river in southern and central New Mexico, the young were “quite common” whereas “adults in full plumage [were] only occasionally seen and never in large flocks.” Four years later this same observer updated his New Mexico bird observations and included both Grus canadensis and G. Americanus on his species list (Henry 1859: 108). A 1940-41 sight record for a wintering Whooping Crane at a large wetland in west-central Chihuahua also exists (Drewien et al. 1996).

Black-necked Stilt. According to Peterson and Zimmer (1998: 57), this species is becoming “an increasingly regular wintering bird in El Paso County.”

Laughing Gull. This species began to nest at Amistad Reservoir in 1995, and it is being reported more often from Trans-Pecos Texas than it used to be (Peterson and Zimmer 1998).

Ring-billed Gull. This species has been seen more frequently in Big Bend National Park since the completion of Amistad Reservoir (Wauer 1996).

Least Tern. This species has also been reported recently, nesting near Amistad Reservoir (Peterson and Zimmer 1998).

Rock Dove. This dove is native to Europe and Asia, and has been widely introduced worldwide (Terres 1986); the earliest New Mexico populations were thought to be escaped “homing pigeons” (Ligon 1961). Bailey (1928) makes no mention of this species in New Mexico, and in 1961, Ligon suggests that only a few wild populations had become established in the state. Largely restricted to urban areas like El Paso (Peterson and Zimmer 1998), this species is rarely reported in Big Bend National Park, where the reports are limited to Panther Junction and Rio Grande Village (Wauer 1996). Though this species is not reported as breeding at the Bosque del Apache or Big Bend National Park, it does breed in urban environments along the Rio Grande.

White-winged Dove. This dove has undergone an extensive range expansion in the southwestern United States, reaching most of its current Arizona range by 1885 (Phillips 1968). According to Bailey (1928), although white-winged doves were known to breed in Arizona, one of the first New Mexico breeding records was from Mesilla in 1912 (though this pair was not observed to return in subsequent years). By 1926, they were “breeding commonly” in the southwestern corner of the state (Bailey 1928: 304). In 1961, Ligon reported that this species was rare in Las Cruces, and not known to winter anywhere in the state. The Mesilla Valley Audubon Society now engages in an annual battle with the Tran-Pecos Audubon Society to see which group will have the most White-winged Doves on their Christmas Count: in 1997, Las Cruces won, with 6468 doves sighted (Ortego 1997).

Inca Dove. Like the White-winged Dove, this species has undergone an extensive range expansion from its original range in Mexico: according to Phillips (1968), the first U.S. record was in 1866, in Laredo Texas. Van Tyne and Sutton reported Inca Doves from Johnson’s Ranch along the river in what is now Big Bend National Park in 1937. The first New Mexico record was from Silver City in 1924 (Bailey 1928). Valentine (1945) reported the first Inca Doves near the Rio Grande in New Mexico, on the now New

Birds—3 Mexico State University campus, in 1943. A 1956 record of Inca Doves from the Bosque del Apache represented the northernmost report of the species as of 1961 (Ligon 1961); by 1955 they were known to be breeding in Las Cruces (Ligon 1961).

Common Ground Dove. Though never common, this species was probably once more abundant along the Rio Grande for much of its length. For instance, Bailey (1928) presents a report of several pairs breeding in the Mesilla Valley near the turn of the century, whereas this species is currently listed as “hypothetical” for the Bosque del Apache, and accidental for most of Trans-Pecos Texas (Peterson and Zimmer 1998).

Monk Parakeet. This introduced species has become established in the El Paso area within the past 10 years and is increasing in abundance (Peterson and Zimmer 1998).

Yellow-billed Cuckoo. Peterson and Zimmer (1998) speculate that this species is declining in the El Paso area because of habitat loss; similarly, Craig Rustay (pers. comm.) feels that destruction of cottonwood bosque habitats in southern New Mexico has led to a decrease in this cuckoo.

Lucifer Hummingbird. This species breeds in the foothills and mountains of the Big Bend region, shifting into riparian areas along the river after breeding (Wauer 1996).

Ringed Kingfisher. According to a Del Rio area birdlist published by the Texas Parks and Wildlife Department, the Rio Grande and the creation Amistad Reservoir have allowed this tropical species to expand its range westward (Sorola n.d.). As Gehlbach (1981) explains, Ringed Kingfishers have increased in abundance along the lower Rio Grande since the 1960s, perhaps because the relatively clear, deep water below dams is their preferred habitat. This kingfisher breeds along streams and rivers near Del Rio (Peterson and Zimmer 1998).

Golden-fronted Woodpecker. According to Wauer (1996), since the 1970s this species has increased in abundance and has begun to breed in Big Bend National Park.

Northern Flicker. Although this species breeds in Big Bend National Park, breeding is limited to the higher elevations of the Chisos Mountains, where the only United States population of the Mexican race (nanus) of this species breeds (Wauer 1996: 97). Other types of red-shafted flickers occur as migrants and winter residents in the park.

Acadian Flycatcher. This eastern species ranges into Val Verde County, and is known to breed in riparian woodlands, including some along the Devils River (Peterson and Zimmer 1998).

Willow Flycatcher. The last confirmed breeding for this species in Trans-Pecos Texas was in 1890 (Peterson and Zimmer 1998).

Brown-crested Flycatcher. This species may be increasing in abundance in the Big Bend region (Peterson and Zimmer 1998).

Great Kiskadee. According to a Del Rio area birdlist published by the Texas Parks and Wildlife Department, the Rio Grande and the creation Amistad Reservoir have allowed this tropical species to expand its range westward (Sorola n.d.).

Bell’s Vireo. In parts of the southwest, this species has been negatively impacted by habitat destruction and cowbird parasitism (Phillips 1968, Peterson and Zimmer 1998). It is an abundant breeder at Big Bend National Park (Wauer 1996).

Black-capped Vireo. Although restricted to higher elevation areas of Big Bend, there are historic breeding records for this species in canyons near the Rio Grande (at the mouth of the Pecos River and along the Devils River). According to Graber (1961) the historic nesting area in the gorge at the mouth of the Pecos was abandoned in 1955-6, after a flood scoured out vegetation in the canyon bottom and a lengthy drought killed shrubs growing on the upper slopes.

Birds—4

Gray Vireo. This species can be seen along the Devils River (Peterson and Zimmer 1998) and also has been reported from Pecos River Canyon near its mouth (Barlow 1977).

Solitary (Blue-headed) Vireo, Cassin’s Vireo, Plumbeous Vireo. Because the Solitary Vireo was only recently split into the Blue-headed, Cassin’s and Plumbeous Vireos, the Solitary Vireos appearing on the Big Bend and Del Rio lists are difficult to interpret. However, Peterson and Zimmer (1998) describe the Blue-headed Vireo as a rare migrant in Trans-Pecos Texas, Cassin’s Vireo as an uncommon migrant, and Plumbeous Vireo as a fairly common migrant. Wauer (1996) lists both cassini and plumbeous forms as migrants in Big Bend National Park.

Western Scrub Jay. Although this species most commonly occurs in pine-oak habitats, in some winters, scrub jays can be found in good numbers in lower elevation habitats (Peterson and Zimmer 1998, C. Rustay, pers. comm.). For instance, the winter following extensive forest fires in the Organ Mountains, which burned much of the oak and ponderosa pine areas in the mountains, scrub jays were fairly common in the Mesilla Valley (N. Stotz, pers. observ.).

Green Jay. This tropical species has begun to appear occasionally in winter near Del Rio (Peterson and Zimmer 1998).

Pinyon Jay. Typically a resident of pine-oak woodlands, in years of pine seed crop failures, this species may roam widely, though its use of riparian zones is highly incidental (C. Rustay, pers. comm.)

Bank Swallow. In Trans-Pecos Texas, the only known breeding colony of this species is near Del Rio, but in the 1940s a breeding colony was also located in El Paso (Peterson and Zimmer 1998).

Cliff Swallow. Because of the expanding range of the Cave Swallow, which arrives to breeding sites before the Cliff Swallow each spring, nesting habitat for Cliff Swallows is being reduced; Cave Swallows are now more common than Cliff Swallows in El Paso and Hudspeth Counties (Peterson and Zimmer 1998).

Cave Swallow. In the last 15-20 years this species has expanded its range greatly, by starting to breed on manmade structures like bridges and overpasses (Peterson and Zimmer 1998). Natural breeding sites are not necessarily static: a breeding colony was known to have nested in a limestone sink 15 miles south of Comstock, TX until natural breakdown enlarged the edge of the entrance hole (Selander and Baker 1957).

Eastern Bluebird. This species has been documented breeding in pecan groves in the Las Cruces area (Meyer 1995).

Long-billed Thrasher. Wauer (1996) reports that this species is increasing in abundance at Big Bend National Park; he speculates that this is due to either increasing habitat degredation along the lower Rio Grande or a natural range extension.

European Starling. This European native was introduced to the United States in New York City’s Central Park in 1890 and 1891, and spread across the country rapidly (Terres 1980). Monson (1946) reported seeing wintering flocks of about 50 birds near the Bosque del Apache in the mid-1940s. In 1952, a winter flock of 10,000 was reported from that vicinity (Ligon 1961). The first New Mexico records for breeding starlings were reported in 1955 (Ligon 1961).

Lucy’s Warbler. This species has undergone a breeding range expansion eastward along the Rio Grande, reaching Big Bend National Park by the mid-1980s (Wauer 1996).

Yellow Warbler. This species used to be a common breeder in willows along the river in Big Bend National Park, but it does not breed there any more (Wauer 1996); in fact this species no longer breeds anywhere in the state of Texas (Peterson and Zimmer 1998). Wauer (1996) ascribes this change to

Birds—5 increasing parasitism by Brown-headed Cowbirds, although habitat degredation probably also was important (C. Rustay, pers. comm., Peterson and Zimmer 1998).

Black-chinned Sparrow. Though this species is typically found in foothills, Chris Rustay (pers. comm.) speculates it could be found anywhere along the river where a hillside abuts the river, such as near Radium Springs in northern Doña Ana County.

Common Grackle. This species may be increasing in abundance in the Mesilla Valley. Ray Meyer (pers. comm.) describes it as a “regular winterer” in the Las Cruces area, where he has seen at least one flock in each of the last four winters; it has also been seen on Christmas Bird Counts in Las Cruces since 1996 (BirdSource 1999).

Great-tailed Grackle. This species has undergone an extensive range expansion in the southwest. In the 1850s this species was abundant and breeding only along the lower Rio Grande near the Gulf of Mexico, and was a rare visitor to the El Paso area (Gehlbach 1981). The first New Mexico record was in 1913, from near Las Cruces, and at that time a pair was known to be nesting at La Mesa, 15 miles south of Mesilla (Bailey 1928). Ligon, writing in 1961, observed that grackles had become common in the Las Cruces area, where they were a significant egg predator, although they were rare in the area twenty-five years previously (1936). Ligon (1961) credits agricultural development in the Rio Grande and Pecos valleys for facilitating this species’ range expansion. In addition, Gehlbach (1981:117) suggests that increasingly urban environments, “suburbia,” have subsequently had an impact.

Bronzed Cowbird. In the nineteenth century, this species occurred no farther north than southern Texas and Mexico but since then it has undergone a significant range expansion (Robbins and Easterla 1981). Bailey does not include this species in her 1928 Birds of New Mexico and in 1961, Ligon reported that this species’ New Mexico range was limited to extreme southwestern New Mexico. Although still listed as hypothetical for the Bosque del Apache, this species is now established in the Mesilla Valley; for instance, I have seen this bird every summer for the past three years on the eastern edge of Las Cruces, and Zimmer (1999) describes this species as a “suspected breeder” in the El Paso area. The first Big Bend National Park record for this species was reported in 1969, and it has been seen regularly since then (Wauer 1996). Wauer (1996) links this nest parasite’s increase with a decrease in the Orchard and Hooded Oriole populations at the park. Summer Tanagers are another host species at Big Bend (Easterla and Wauer 1972).

Brown-headed Cowbird. This species has also undergone a natural, though human-habitat-related range expansion during the nineteenth and twentieth centuries. This species was breeding statewide in New Mexico by 1928, although the first state record was recorded in 1820 (Bailey 1928). However, in 1928, it was only a summer resident of New Mexico (Bailey 1928), whereas in 1961, Ligon (1961) lists it as also wintering around Las Cruces and Carlsbad. By the late 1990s its winter range had expanded: the Bosque del Apache bird list includes it as “occasional: seen a few times through the season” in winter (US Fish and Wildlife Service, 1999). Gehlbach (1981) cites Phillips, and Phillips and Thornton to say that this species was “scarce” in west Texas grasslands before the 1890s and credits both range cattle and man-made oases with their spread.

Orchard Oriole. This oriole has historically bred along the Rio Grande in Big Bend National Park (Van Tyne and Sutton 1937, Wauer 1996), but it is no longer listed as a breeding bird on the park’s list (Selleck 1994). Wauer (1996) suggests that the increasing abundance of the Bronzed Cowbird may have led to this breeder’s demise.

House Sparrow. This Eurasian native was introduced to North America in the middle of the nineteenth century, in Brooklyn, New York (Terres 1980). According to Bailey (1928), this species was well established in the “inhabited parts” of New Mexico by 1911. The first record for Big Bend National Park was in 1928, though the species disappeared from the park until 1936, when an established population was described for Boquillas.

Birds—6 Literature Cited

Aldrich, J.W. 1967. Taxonomy, distribution and present status. In The Wild Turkey and its Management, ed. O.H. Hewitt, pp. 17-44. Washington D.C. :The Wildlife Society.

Bailey, F.M. 1928. Birds of New Mexico. Washington D.C.: New Mexico Department of Game and Fish, in cooperation with the State Game Protective Association and the Bureau of Biological Survey.

Barlow, J.C. 1977. Effects of habitat attrition on vireo distribution and population density in the northern Chihuahuan Desert. In Transactions of the symposium on the biological resources of the Chihuahuan Desert Region, United States and Mexico, eds. R.H. Wauer and D. H. Riskind, pp 591-596. U.S. Dept. of Interior, National Park Service Transactions and Proceedings Series, Number 3.

Bent, A.C. 1965. Life histories of North American marsh birds. New York: Dover Publications. [Reprint of Smithsonian Institution, U.S. National Museum Bulletin No. 135, originally published in 1926.]

Bieber, R.P, ed. 1936. Marching with the Army of the West, 1846-1848. Glendale, CA: Arthur H. Clark Company.

Bieber, R.P. and A.B. Bender, eds. 1938. Exploring Southwestern Trails, 1846-1854. Glendale, CA: Arthur H. Clark Company.

BirdSource. 1999. National Audubon Society’s Christmas Bird Count. Searchable database available at http://www.birdsource.org/cbc/index.html [14 December 1999].

Donaldson, J., J.A. Sproul, B. Roberts, and B.R. Zimmer. 1987. Birds of El Paso County, Texas and adjacent areas, 7th edition. El Paso: El Paso/Trans-Pecos Audubon Society

Drewien, R.C., W.M. Brown, and D.S. Benning. 1996. Distribution and abundance of sandhill cranes in Mexico. Journal of Wildlife Management 60 (2): 270-285.

Easterla, D.A. and R.H. Wauer. 1972. Bronzed cowbird in West Texas and two bill abnormalities. Southwestern Naturalist 17 (3): 293-312.

Emory, W. H. 1987. Report on the United States and Mexican Boundary Survey, made under the direction of the Secretary of the Interior, 2 volumes.. Austin: Texas State Historical Association, Austin. [Reprints of 34th Congress, 1st Session, House Executive Document 135 (1857) and 34th Congress, 1st Session, House Executive Document 108 (1859).]

Gehlbach, F.R. 1981. Mountain islands and desert seas: a natural history of the U.S.-Mexican borderlands. College Station: Texas A&M University Press.

Graber, J.W. 1961. Distribution, habitat requirements, and life history of the black-capped vireo (Vireo atricapilla). Ecological Monographs 31: 313-336.

Birds—7 Gore, H.G. 1973. Land-use practices and Rio Grande Turkeys in Texas. In Wild Turkey Management: Current Problems and Programs, eds. G.C. Sanderson and H.C. Schultz, pp. 253-262. Columbia, MO: University of Missouri Press.

Henry T. C. 1855. Notes derived from observations made on the birds of New Mexico during the years 1853 and 1854. Proceedings of the Academy of Natural Sciences, Philadelphia 7: 306-317.

Henry. T.C. 1859. Catalogue of the birds of New Mexico as compiled from notes and observations made while in that territory, during a residence of six years. Proceedings of the Academy of Natural Sciences, Philadelphia 11: 104-109.

Hubbard, J.P. 1978. Revised check-list of the birds of New Mexico. New Mexico Ornithological Society Publication #6.

Hunt, W. G. 1976. Western Texas and northeastern Mexico. In The 1975 North American Peregrine Falcon Survey, eds. R.W. Fyfe, S.A. Temple, T.J. Cade. Canadian Field Naturalist 90: 228-273.

Hunt, W.G., J.H. Enderson, D. Lanning, M.A. Hitchock, and B.S. Johnson. 1988. Nesting peregrines in Texas and northern Mexico. In Peregrine Falcon Populations: Their Management and Recovery, eds. T.J. Cade, J.H. Enderson, C.G. Thelander, and C. M. White, pp 115-121. Boise, ID: The Peregrine Fund.

Johnson, R.R., L.T. Haight, and J.M. Simpson. 1977. Endangered species vs. endangered habitats: a concept. In Importance, preservation and management of riparian habitat: a symposium, coord. R.R. Johnson and D.A. Jones, pp. 68-80. USDA, Forest Service, General Technical Report RM- 43. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station.

Johnston, A.R. 1848. Journal of Captain A.R. Johnston, First Dragoons. In Report of Lieutenant J.W. Abert, of his examination of New Mexico in the years 1846-’47. 30th Congress, 1st Session, House Executive Document 41. Washington D.C.: United States Engineering Department.

Ligon, J.S. 1946. History and management of Merriam’s Wild Turkey. Albuquerque: New Mexico Game and Fish Commision/University of New Mexico Press.

Ligon, J.S. 1961. New Mexico birds and where to find them. Albuquerque: University of New Mexico Press.

Meyer, R.A. 1995. The avian community of an agricultural environment in the Rio Grande Valley of southern New Mexico. M.S. Thesis. New Mexico State University, Las Cruces.

Natural Resource Management. 1999. web-page at the National Park Service: Amistad National Recreation Area site. Available at http://www.nps.gov/amis/resources.htm [25 August 1999]

New Mexico Dept. of Game and Fish. 1999. New Mexico Species List: Birds. Available at http:/www.fw.vt.edu/fishex/states/nm.htm [29 November 1999]

Oberholser, H.C. 1974. The bird life of Texas, 2 volumes. Austin: University of Texas Press.

Ortego, B. 1997. Summary of the highest counts of individuals for Canada and the U.S. National Audubon Society Field Notes 51 (2): 699-710.

Peterson, J. and B.R. Zimmer. (1998). Birds of the Trans-Pecos. Austin: University of Texas Press.

Birds—8 Phillips, A. R. 1968. The instability of the distribution of land birds in the southwest. In Collected Papers in Honor of Lyndon Lane Hargrave, ed. A. H. Schroeder, pp. 129-162. Papers of the Archaeological Society of New Mexico: 1. Santa Fe: Museum of New Mexico Press.

Robbins, M.B. and D.A. Easterla. 1981. Range expansion of the Bronzed Cowbird with the first Missouri record. Condor 83: 270-272.

Ruxton, G.F. 1973. Adventures in Mexico and the Rocky Mountains. Glorieta, NM: Rio Grande Press. [Reprint of 1847 publication.]

Selander, R.K. and J.K. Baker. 1957. The Cave Swallow in Texas. Condor 59 (6): 345-363.

Selleck, J.M. 1994. Bird Checklist: Big Bend National Park, Texas, 5th revision. Published by the Big Bend Natural History Association in cooperation with the National Park Service.

Sorola, S.H, compiler. no date. Birds of Del Rio and vicinity. Austin: Texas Parks and Wildlife Department.

Terres, J.K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.

U.S. Fish and Wildlife Service. 1998. Threatened and endangered species of New Mexico. Albuquerque: Ecological Services Field Office, U.S. Fish and Wildlife Service.

U.S. Fish and Wildlife Service. 1999. Bosque del Apache National Wildlife Refuge: Birds. U.S. Department of the Interior.

Valentine, K.A. 1945. The Inca Dove at State College, New Mexico. Condor 47:80-81.

Wauer, R.H. 1977. Significance of Rio Grande riparian systems upon the avifauna. In Importance, preservation and management of riparian habitat: a symposium, coord. R.R. Johnson and D.A. Jones, pp. 165-174. USDA, Forest Service, General Technical Report RM-43. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station.

Wauer, R. 1996. A field guide to birds of the Big Bend, 2nd edition. Houston: Texas Field Guide Series/Gulf Publishing Co.

Wiedenfeld, S. 1989. Birds of Seminole Canyon State Historical Park: A field checklist. Texas Parks and Wildlife Department, Austin.

Birds—9 Wunz. G.A. 1992. Wild Turkeys outside their historic range. In The Wild Turkey: Biology and Management, ed. J.D. Dickson, pp. 361-384. Hornburg, PA: A National Wild Turkey Federation and USDA Forest Service Book/Stackpole Books.

Zimmer, B.R. 1999. Birds of El Paso County, Texas and adjacent areas, draft of bar graphs for 8th edition [7th edition compiled by J. Donaldson, J. A. Sproul, B. Roberts, and B.R. Zimmer.] El Paso: El Paso/Trans-Pecos Audubon Society.

Birds—10

Birds—11

Appendix A: Extracting Data from Township and Range Line Surveys

Soon after becoming a territory of the United States, the lands of New Mexico were surveyed by contract- surveyors hired by the Engineer’s Office. Microfiche copies of the surveyors’ notes are on file in the Las Cruces District BLM Office and other depositories for Government Land Office records. The initial surveys generally only involved the exterior township and range lines, and for the areas along the desert Rio Grande, Garrettson (1857) surveyed most of these lines in 1857, with a few areas being completed by a different team of surveyors in 1877 (McBroom and Shaw 1877).

Information in Surveyors’ Notes As they moved along these lines, the surveying teams recorded topographic features and significant vegetation zones they encountered. When they moved off of the surrounding uplands and into the river’s floodplain, they typically noted the point at which they “entered river bottom”; sometimes this was noted with a description like “descended [some number of feet] into river bottom.” A similar notation was used to document the point at which they left or ascended out of the river bottom. Within the floodplain the main topographic features they mentioned were ponds, sloughs, marshes, swamps, the edge of the river channel, and islands encountered in the river; typically the width of these features along the line was recorded. The extent of some vegetation zones—in particular, dense stands of timber, willow thickets, and cultivated land—was similarly noted with phrases like “entered [or left] willow thicket” at a particular point on the line.

As they surveyed these lines, the surveyors also established witness corners at the corner of each section, at ¼ section corners (halfway along the side of a section), and at points where the line reached the edge of the river. At full section-corners they always recorded a set of standard observations which evidently documented the economic potential of the area along the line just run: “Land” (followed by phrases describing soil type and topography), “No Timber” or “Timber” (followed by species, which was always cottonwood in these river bottom surveys, and some estimate of extent or density of the timber), and “Undergrowth” (followed by species and extent or density). Similar observations were sometimes recorded at corners where the line hit the river, but never at ¼ section corners.

In order to establish their permanent locations, the three types of corners were typically marked with a post or large rock, a set of trenches or a mound, and witness trees. Ideally, full section-corners were marked with 4 witness trees—one in each quadrant—but in the relatively open stands along the desert Rio Grande, more often only 2, 1, or no witness trees could be located. The surveyors recorded the dbh (in inches, to the nearest whole inch), compass bearing, and distance to all witness trees, and the trees were marked with a blaze for future reference. Because exact bearings and distances to these trees needed to be measured, cottonwoods were used instead of multi-trunked, shrubby forms such as mesquite, screwbeans, or willows; the surveyors also avoided young trees and generally used trees with a diameter-at-breast-height (dbh) of at least 5 inches.

Compiling Summary Statistics In order to summarize the data in the surveyors’ notes, I compiled transcripts of their notes for each line that crossed the river bottom. From these, the distance along each line comprised of the following categories was totaled: total floodplain width cottonwood timber no timber willow thickets cultivated land river channel

149—Appendix A

dry river channel pond/slough/marsh In the few cases where they did not record the exact edge of the river bottom, modern topographic maps and field checking were used to locate the edge. The distance covered by the final 5 categories (willow thickets, cultivated land, and the aquatic features) were relatively easy to total because the surveyors consistently identified them with “entered” and “left” phrases or provided specific width measurements. Distinguishing between “no timber” and “cottonwood timber” was more problematic because dense stands of timber where the surveyors noted where they “entered” and “left timber” were fairly uncommon. Therefore, these two categories relied more on the descriptive notes written at full-section corners and river edges. If they were not in cultivated land or willow thickets, I categorized corners (and therefore the lines on either side of them) as “no timber” when the corner description stated “No timber.” I categorized corners that were not in cultivated land or willow thickets as “cottonwood timber” if the Timber description mentioned “cottonwood,” “a few cottonwoods,” “scattered cottonwoods,” or “scattering cottonwoods.” A few corners where the surveyors specifically noted that the “scattered” or “few” cottonwoods were growing only “on” or “along the river” were categorized as “no timber” since survey lines were mostly traversing land away from the river and I had no way of knowing how wide the timber bordering the river was. The “Undergrowth” description for both cottonwood and no timber areas typically included one or more of the following shrub types: mesquite, “torneo” (screwbean), “chemisal”, “bushes,” willows, and cottonwood saplings.

Because these habitat data were not collected for an ecological study, but were incidentally collected as a part of the cadastral surveys, the data have some limitations. The primary limitation is that we have to assume that the surveyors consistently recorded all of the features and habitat changes they encountered. While we have no way of knowing whether they did this or not, Thom Maestes, a BLM surveyor who has resurveyed many historic surveys in New Mexico, told me that the Garrettson surveys, at least, seem to be fairly accurate and complete (pers. comm.).

Difficult river crossings, severe topography (such as the steep inclines of Caballo Mountain) and political boundaries sometimes kept the surveyors from completing survey lines all the way across the floodplain. For instance, 3 lines in the southern end of the Mesilla Valley did not cross to the east side of the river because the river was the boundary of New Mexico; therefore, these lines did not include a distance along the line for the “river channel” category. Because such incomplete lines could skew the proportions totaled into the 7 floodplain categories above, I did not include incomplete lines in the compilations presented in Table 2-4. In order to get a complete line between Ranges 5 and 4W in Las Palomas Valley, I had to include 6 miles of line run by McBroom and Shaw in 1877; for some reason Garrettson’s team did not run the line along the east side of T 17S R5W in 1857. However, McBroom and Shaw (1877) relocated Garrettson’s corners along the river on either side of this gap and thus, I feel confident that the two surveys match well spatially.

Data Extracted from Witness Tree Descriptions The witness tree data from all three corner types provided me an opportunity to estimate cottonwood tree densities. These calculations were done separately for the Mesilla and Las Palomas valleys, and corners were categorized as either river-edge or non-river-edge. The non-river-edge corners were further subdivided into the cottonwood, no timber, cultivated, and willow habitat categories as described above. I used the witness tree data from all corners in the density estimates, from both complete and incomplete lines.

Since few corners had 4 trees recorded, I was unable to use the point-quarter method for density calculations, and instead used the closest individual method (Cottam and Curtis 1956: 453), excluding the more distant witness trees for the corners with more than one tree. The equation used was 1 density = 4 * (mean distance)2 .

Because the surveyors did not record any witness trees for many of the corners, I followed the methods of Lunt (1998:630) to create maximum and minimum density estimates. The maximum estimates include only the corners where witness trees were recorded. This measure obviously overestimates densities

150—Appendix A

greatly for habitats such as “open areas” by excluding the numerous points where no witness trees were found.

The minimum estimates include the points where no witness trees were recorded by the surveyors. Since the density calculations require a nearest-tree-to-point distance for all points, I had to insert a distance for the points where no distance was recorded. In order to do this, Lunt (1998: 630) added 5 meters to the longest distance recorded for any tree in his sample; it appears that his decision to add 5 meters instead of some other length was arbitrary. Instead of choosing an arbitrary distance for the minimum density estimates, I tried to calculate a “likely maximum distance” for each valley based on the distribution of all distances measured. I did this by generating a histogram for all the distances recorded in the valley, and then fitting an asymptotic regression line to the distribution using SYSTAT’s NONLIN procedure (SYSTAT 1997). In both valleys the best-fitting line reached a frequency of zero at a value less than the maximum measured distance. For this reason, I decided to use that maximum measured distance as the likely maximum distance to use in the minimum density estimates.

The witness tree data were also used to examine the size-class distribution of trees recorded by the Garrettson survey in 1857. The frequency distributions of dbh measurements include all witness trees at all corners in each valley, along with all cottonwoods straddling the surveyed lines which the surveyors noted.

Literature Cited

Cottam, G. and J.T. Curtis. 1956. The use of distance measures in phytosociological sampling. Ecology 37(3): 451-460.

Garrettson, J.W. 1857. Government Land Office Survey field notes. Microfiche, available at Las Cruces District Office, Bureau of Land Management, Las Cruces, NM.

Lunt, I.D. 1998. Two hundred years of land use and vegetation change in a remnant coastal woodland in southern Australia. Australian Journal of Botany 46: 629-647. McBroom, W. and J. Shaw. 1877. Government Land Office Survey field notes. Microfiche: available at Las Cruces District Office, Bureau of Land Management, Las Cruces, NM.

SYSTAT. 1997. SYSTAT 7.0 for Windows. Chicago: SPSS, Inc.

151—Appendix A

152—Appendix A

Appendix B: Threatened and Endangered Vertebrates of the Desert Rio Grande

A total of 75 native vertebrates that occur along the desert Rio Grande are listed as endangered or threatened by the federal government of Mexico (72 species) or the United States (16 species; see Table B- 1). Eleven of these species are birds that have only been recorded occassionally, as vagrants, along the river (indicated with an asterisk in Table B-1; see also Chapter 6, Table 6-2). In the United States, an additional 50 species (including 9 birds recorded only as vagrants) have been listed as threatened or endangered by the states of New Mexico or Texas, although they are not listed by the U.S. federal government.

When comparing the list in Table B-1 to species lists in the preceeding chapters, a few of the scientific names will differ slightly; this is because these species may have been listed prior to a recent taxonomic revision and the governmental listings have not yet changed. In addition, some of the species listed by the two states and Mexico do not occur along the desert Rio Grande within their boundaries, but populations are at risk elsewhere within their borders (indicated with parentheses in Table B-1). These species have been included in Table B-1 for two reasons: first, they may be indicative of the importance of populations elsewhere along the desert Rio Grande, and secondly, some of these species, such as the hummingbirds, could be recorded in the future along the river in the state or country in question.

Appendix B—153 Table B-1. State and Federally listed vertebrates native to the desert Rio Grande. Bird species indicated with an asterisk have only been recorded as vagrants along the river. Sources: New Mexico Department of Game and Fish 1998, CONABIO 1999, Texas Parks and Wildlife 2000, U.S. Fish and Wildlife Service 2000.

E=Endangered, T=Threatened. Codes in (parentheses) indicate a species that is not known to occur along the river within that state or country.

U.S. Federal New Mexico Mexico Federal Species Scientific Name Texas Status Status Status Status

FISH Scaphirhynchus Shovelnose Sturgeon T E platorynchus Mexican Stoneroller Campostoma ornatum T E Red Shiner Cyprinella lutrensis T Proserpine Shiner Cyprinella proserpina T T Devil’s River Minnow Diondia diaboli T T E Roundnose Minnow Diondia episcopa E Rio Grande Chub Gila pandora (T) Rio Grande Silvery Minnow Hybognathus amarus E E E E Chihuahua Shiner Notropis chihuahua T Phantom Shiner Notropis orca E Bluntnose Shiner Notropis simus T E Blue Sucker Cycleptus elongatus E T Gray Redhorse Moxostoma congestum T Mexican Tetra Astyanax mexicanus T Mosquitofish Gambusia affinis E Big Bend Gambusia Gambusia gaigei E E Blotched Gambusia Gambusia senilis T T Conchos Pupfish Cyprinodon eximius T T Longear Sunfish Lepomis megalotis T Rio Grande Darter Etheostoma grahami T Bigscale Logperch Percina macrolepida (T)

AMPHIBIANS & REPTILES Great Plains Narrowmouth Gastrophryne olivacea (E) Toad Western River Cooter Pseudemys gorzugi (T)

New Mexico Mexico Federal Species Scientific Name US Federal Status Texas Status Status Status Chihuahuan Mud Turtle Kinosternon hirtipes T Texas Tortoise Gopherus berlandieri T T Collared Lizard Crotaphytus collaris T Southwestern Earless Lizard Cophosaurus texanus T Texas Horned Lizard Phrynosoma cornutum T T Reticulated Gecko Coleonyx reticulatus T Racer Coluber constricta T Indigo Snake Drymarchon corais T Gray-banded Kingsnake Lampropeltis alterna T Desert Kingsnake Lampropeltis getula T New Mexico Milk Snake Lampropeltis triangulum T Coachwhip Masticophis flagellum T Nerodia erythrogaster T Blotched Water Snake (E) transversa (full species) Blackneck Garter Snake Thamnophis cyrtopsis T Checkered Garter Snake Thamnophis marcianus T Thamnophis proximus T Western Ribbon Snake (T) diabolicus (full species) Trimorphodon discutatus Texas Lyre Snake T vilkinsoni Mottled Rock Rattlesnake Crotalus lepidus lepidus (T)

MAMMALS Notiosorex crawfordi Desert Shrew T crawfordi Least Shrew Cryptotis parva (T) Eastern Mole Scalopus aquaticus E Mexican Long-nosed Bat Leptonycterius nivalis E (E) E T Spotted Bat Euderma maculata T T Black-tailed Prairie Dog Cynomys ludovicianus T American Beaver Castor canadensis E Common Muskrat Ondatra zibethicus T New Mexican Jumping Mouse Zapus hudsonius luteus T Porcupine Erethizon dorsatum E Black Bear Ursus americanus T E

New Mexico Mexico Federal Species Scientific Name US Federal Status Texas Status Status Status E E (E) Mexican Gray Wolf Canis lupus baileyi E (full species) (full species) (full species) Kit Fox Vulpes macrotis T White-nosed Coati Nasua narica T American Badger Taxidea taxus T Jaguar Panthera onca E (restricted) E E Ocelot Felis pardalis E E E E Jaguarundi Felis yaguarondi E T (2 subspecies)

BIRDS Brown Pelican * Pelecanus occidentalis E (E) E T Least Bittern Ixobrychus exilis T Reddish Egret * Egretta rufescens T T Wood Stork * Mycteria americana E T White-faced Ibis Plegadis chihi T Swallow-tailed Kite * Elanoides forfucatus T T Mississippi Kite Ictinia mississipiensis T Haliaeetus Bald Eagle T T T E leucocephalus Northern Harrier Circus cyaneus T Sharp-shinned Hawk Accipiter striatus T Cooper’s Hawk Accipiter copperi T Northern Goshawk Accipiter gentilis (T) White-tailed Hawk * Buteo albicaudatus T Zone-tailed Hawk Buteo albondiatus T Gray Hawk Asturina nitida T Common Black Hawk Buteo anthracinus T T T Harris Hawk Parabuteo unicinctus T Golden Eagle Aquila chrysaetos T Merlin Falco columbarius T Prairie Falcon Falco mexicanus T T American Peregrine Falcon Falco peregrinus anatum de-listed T E (full species) Arctic Peregrine Falcon Falco peregrinus tundrius de-listed T T Coturnicops Yellow Rail * E noveboracensis

New Mexico Mexico Federal Species Scientific Name US Federal Status Texas Status Status Status E (experimental in Whooping Crane Grus americana E (E) (E) NM) Piping Plover * Charadrius melodus T E T T Mountain Plover * Charadrius montanus T Heerman’s Gull * Larus heermanni T Sterna antillarum E T Interior Least Tern T E athalassos (full species) (full species) Columbina passerina Common Ground Dove E pallescens Eastern Screech Owl Otus asio T Great-horned Owl Bubo virginianus T Short-eared Owl Asio flammeus T Barred Owl * Strix varia T Cyanthus latiorostris Broad-billed Hummingbird * T magicus Hylocharis leucotis White-eared Hummingbird * (T) borealis Violet-crowned Hummingbird * Amazilia violiceps ellioti (T) Lucifer Hummingbird Clothorax lucifer (T) Costa’s Hummingbird * Calypte costae (T) Southwestern Willow Empidonax traillii extimus E E Flycatcher Thick-billed Kingbird * Tyrannus crassirostris (E) Rose-throated Becard * Pachyramphus aglaiae T Bell’s Vireo Vireo bellii T Gray Vireo Vireo vicinor (T) Black-capped Vireo * Vireo atricappilus E E E Lucy’s Warbler Vermivora luciae T Tropical Parula * Parula pitiayumi T Hooded Warbler Wilsonia citrina T Baird’s Sparrow Ammodramus bairdii (T) Varied Bunting Passerina versicolor (T) Hooded Oriole Icterus cucullatus T Black-vented Oriole * Icterus wagleri T American Goldfinch Carduelis tristis T

Literature Cited

New Mexico Department of Game and Fish. 1998. New Mexican Wildlife of Concern: Status and Distribution. [document available in PDF format from http://www.fw.vt.edu/fishex/states/nm.htm]

Texas Parks and Wildlife. 2000. Texas Threatened and Endangered Species. Available at http://www.tpwd.state.tx.us/nature/endang/endang.htm [19 May 2000].

U.S. Fish and Wildlife Service. 2000. Threatened and Endangered Wildlife and Plants. Available at http://endangered.fws.gov/wildlife.html [19 May 2000].

Appendix B—158