Herpetology of the Sulphur Springs Valley, Cochise County, Arizona 1 Philip C
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This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Herpetology of the Sulphur Springs Valley, Cochise County, Arizona 1 Philip C. Rosen\ Shawn S. Sartorius , 2 2 Cecil R. Schwalbe , Peter A. Holm\ and Charles H. Lowe ABSTRACT The valleys of southeastem Arizona exemplify the biological diversity of the desert grassland. Among them, the Sulphur Springs Valley has especially significant amphibian and turtle populations, at least two of which (plains leopard frog and yellow mud turtle) are presently in danger of extirpation. It has one remaining key Chiricahua leopard frog population, but has already lost other populations of this threatened species. Based on our work 1993-6 and earlier, and on museum records, we present an annotated checklist of the 61 species (11 frogs and toads, 1 salamander, 3 turtles, 211izards, and 25 snakes) confirmed from the valley. Based on habitat use and geographic distribution, this fauna has a core of (Chihuahuan) Desert Grassland taxa (many of which also occupy plains grassland and Chihuahuan desertscrub), and a smaller number of widespread North American Desert species. Sonoran Desert species are either rare or restricted to low arid slopes, and Madrean Woodland species enter the valley only peripherally. Long utilized for farming and ranching, the Sulphur Springs Valley now faces suburbanization and increasing traffic. This could rapidly close its open spaces and eliminate the potential for native ecosystem restoration. This is so even though the herpetofauna is still robust--except for aquatic species and the massasauga. We recommend a conservation program that includes land acquisition, cooperative work with landholders, state protection, and additional survey and research as needed. INTRODUCTION The Sulphur Springs Valley (SSV) presents the herpetofauna of the desert grassland, including many characteristic species and subspecies, ranging widely over a large valley area. We focus on this valley for two reasons. First, it has heavy and increasing human impact, and second, it supports a diversity of wetland reptiles and has extensive amphibian populations, including declining species. We summarize our field observations, a national search of museum records, and discuss eco- and 1 Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ. 2 Biological Resources Division, U.S. Geological Survey, Cooperative Park Studies Unit, School of Renewable Natural Resources, University of Arizona, Tucson, AZ. ·65 biogeography of the herpetofauna. We conclude with a summary of key aspects of herpetological conservation biology. It has been suggested that the desert grassland in SE Arizona and nearby areas may have a characteristic herpetofauna (Parmenter and Van Devender, 1995), or that it is a filter barrier between biomes (Morafka, 1977). The desert grassland may also be envisioned as co-extensive with the Chihuahuan Desert (Schmutz eta/., 1992), although Morafka (1977) treats it as an ecotone with strongest ties to Chihuahuan (desert) and Kansan (plains grassland) biogeographic provinces. Parmenter and Van Devender (1995) noted taxonomic differentiation to only the subspecific level (except for the recently derived parthenogenetic species, the desert grassland whiptail), as expected for a recently derived biome (Van Devender, 1995). Perhaps there is a more unique component of this system, one involving arid-adapted species of the southern and western plains and of grassy aspects of the Chihuahuan Desert. If so, and after our limited geographic study we think so, then the desert grassland herpetofauna is indeed unique and diverse, and moreover, this area is an important evolutionary arena for herpetofauna. The grassland biome, compared to woodland or forest, is relatively recent in origin (although older than desert), perhaps of mid-Cenozoic vintage (Van Devender, 1995). In SE Arizona, desert grassland has been continuously present for perhaps 8,000 or 9,000 years, since the last pluvial (Martin, 1963), at which time woodland and forest flora descended at least to Willcox Playa. Over glacial-interglacial cycles in the Pleistocene, these biotas have presumably waxed and waned repeatedly at any given locale. Environment of the Chiricahua region desert grasslands. The grasslands in Cochise County are a mosaic of desert grassland proper (with dominance of arid-adapted grasses in their ecological metropolis), scrub-invaded grasslands with much mesquite and burroweed (lsocoma tenuisectus), Chihuahuan desertscrub, and sites with mixed thornscrub and perennial grass. Many of the grasslands, especially the scrub-invaded ones, are co-dominated by the introduced Lehmann•s love grass (Eragrostis lehmanniana). The SSV is the area from Douglas to Fort Grant, and encircled by the Galiuro, Santa Teresa, Pinalerio, Chiricahua, Dos Cabezas, Dragoon, Mule, Pedregosa, and Perilla Mountains (Fig. 1). It continues slightly farther south in Mexico, to the Sierras Anibacichi and Ceniza and Cerro Cabullona, but we did not work there. It is a large valley, about 190 long x 25-40 km wide. Elevations range from 4,000-4,300 ft (1,219-1,311 m) in the flats to 4,500-5,200 ft (1,372-1,585 m) at the base of the rock slopes. The SSV has a well developed slope gradient. There are rock slopes supporting juniper or mesquite savannah, grassland, grassland-shrub, thornscrub, or desertscrub. Immediately below the rock slopes, uppermost bajadas (less rocky and steep) may support similar vegetation, before giving way to middle bajadas that support either Chihuahuan desertscrub, plains grassland, or mesquite burroweed scrub. Lower bajadas are still slightly sloping but have finer and denser soils, and typically have more mesquite and burroweed, and often much grass and soaptree yucca (Yucca elata). We include all of these environments in this treatment of the SSV. Most characteristic of the SSV is the broad level floor extending at a distance from Whitewater Draw in the south and from Willcox Playa in the north. The southern area supports a distinctive tobosa (Hilaria mutica)-dominated desert grassland flora, extending from McNeal to about 3 mi north of Douglas. East of this is a classic swath of Chihuahuan desertscrub on the bajada, grading eastward into thornscrub-grassland around the Leslie Canyon riparian gallery forest. The valley floor near Douglas, below the tobosa patch, supports a diverse, medium-tall scrub of mesquite and other 66 dry tropic shrub-trees, yucca, agave, and mixed cactus, with Chihuahuan desertscrub in places. To the north, the saline flats around Willcox Playa support a grassland, dominated by alkali sacaton (S. wrightii) and saltgrass (Distich/is stricta), which is thoroughly invaded by mesquite dominated scrub except in the NE quadrant. Mesquite scrub extends up the Dragoon bajada to the west, while a bajada grassland extends east from the playa to mixed thornscrub, or to Madrean woodland, at the Dos Cabezas or Chiricahua Mountain bases respectively. The va~y north of Willcox is primarily agricultural, and was little surveyed by us. The Sulphur and Squaretop Hills dominate the center of the SSV, which is occupied by scrub and introduced grasses in most areas. South of this central area, the valley floor is extensively agricultural to Elfrida and even southwest of McNeal near Whitewater Draw. Martin (1963) presents an excellent description of vegetation and landform in the southern part of the valley. ETlDESERT ~GRASSLAND D Mts. 1 50km pSOO km, ARIZONA 50NORA Figure 1 Map of the study area, Sulphur Springs Valley (left) with surrounding mountains shown, and of the desert grassland (right, following Schmutz et al., 1992), showing the location of the study area. Additional descriptions are given in the text. 67 Natural perennial waters in SE Arizona grasslands are primarily valley bottom springs; mountain streams submerge before entering the valleys, except during floods. The San Bernardino, San Pedro, Santa Cruz, and Babacomari Rivers, and Cienega and Arivaca Creeks (and formerly the San Simon River) rise on grassland floors. Whitewater Draw rose in grassland as a partly permanent stream (Hendrickson and Minckley, 1985), perhaps largely drying during less rainy eras. The Sulphur Springs probably had the least perennial water of any SE Arizona valley, save the Avra-Aitar on the Sonoran Desert edge. Today, major valley spring systems are modified by impoundment and by down-cutting of streams into formerly marshy cienegas. Man-made stock ponds dot the landscape, and many sites are supplied with wind-powered wells, maintaining unnaturally constant water levels. Water is more widespread on the landscape than originally, but there is far less natural wetland habitat. Checklist of the Amphibians and Reptiles of the Sulphur Springs Valley, Cochise County, Arizona The primary focus of this checklist is to (1) present an overview of a desert grassland fauna, (2) outline community structure and biogeography in relationship to habitat, and (3) identify key issues for conservation or management. We worked extensively in the valley for three years, 1993-1996. In addition, we include data from previous work in the valley, principally during the 198Q•s and mid- 197o•s. The 199o•s field work produced 701 observations (195 for anurans, 8 for salamanders, 45 for turtles, 114 for lizards, 338 for snakes), with each observation being an independent locality record, sometimes of numerous individuals per species. Finally,