Tuesday, December 14, 2010

Part V

Department of the Interior Fish and Wildlife Service

50 CFR Part 17 Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Sonoran Population of the Desert as Endangered or Threatened; Proposed Rule

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DEPARTMENT OF THE INTERIOR Ecological Services Office (see Watersheds Project, dated November 26, ADDRESSES); by telephone at (602) 242– 2008. In that letter we also stated that Fish and Wildlife Service 0210; or by facsimile at (602) 242–2513. we had reviewed the information If you use a telecommunications device presented in the petition and 50 CFR Part 17 for the deaf (TDD), please call the determined that issuing an emergency [Docket No. FWS–R2–ES–2009–0032; MO Federal Information Relay Service regulation temporarily listing the 92210–0–008] (FIRS) at 800–877–8339. as per section 4(b)(7) of the Act SUPPLEMENTARY INFORMATION: was not warranted. We also stated that Endangered and Threatened Wildlife we intended to make our finding on Background and Plants; 12-Month Finding on a whether the petition presented Petition To List the Sonoran Section 4(b)(3)(B) of the Endangered substantial information that the Population of the as Species Act of 1973, as amended (Act) requested action may be warranted, to Endangered or Threatened (16 U.S.C. 1531 et seq.), requires that, the maximum extent practicable within for any petition to revise the Federal 90 days of receipt of the petition, AGENCY: Fish and Wildlife Service, Lists of Endangered and Threatened according to the provisions of section Interior. Wildlife and Plants that contains 4(b)(3) of the Act. ACTION: Notice of 12-month petition substantial scientific or commercial On August 28, 2009, we made our 90- finding. information that listing the species may day finding that the petition presented be warranted, we make a finding within substantial scientific information SUMMARY: We, the U.S. Fish and 12 months of the date of receipt of the indicating that listing the Sonoran Wildlife Service, announce a 12-month petition. In this finding, we determine population of the desert tortoise finding on a petition to list the Sonoran that the petitioned action is: (a) Not ( agassizii) may be warranted. population of the desert tortoise warranted, (b) warranted, or (c) The finding and notice of our initiation (Gopherus agassizii) as endangered or warranted, but the immediate proposal of a status review was published in the threatened and to designate critical of a regulation implementing the Federal Register on August 28, 2009 (74 habitat under the Endangered Species petitioned action is precluded by other FR 44335). Act of 1973, as amended (Act). After pending proposals to determine whether On April 10, 2010, a stipulated review of all available scientific and species are threatened or endangered, settlement agreement (WildEarth commercial information, we find that and expeditious progress is being made Guardians and Western Watersheds listing the Sonoran population of the to add or remove qualified species from Project v. Salazar, 10–cv–86–ACT–RHS desert tortoise is warranted. Currently, the Federal Lists of Endangered and (D. NM)) was filed. In this agreement, however, listing the Sonoran population Threatened Wildlife and Plants. Section we agreed to submit a 12-month finding of the desert tortoise is precluded by 4(b)(3)(C) of the Act requires that we to the Federal Register on or before higher priority actions to amend the treat a petition for which the requested December 5, 2010. The stipulated Lists of Endangered and Threatened action is found to be warranted but settlement agreement was signed and Wildlife and Plants. Upon publication precluded as though resubmitted on the adopted by the District Court of New of this 12-month petition finding, we date of such finding, that is, requiring a Mexico on April 15, 2010. will add the Sonoran population of the subsequent finding to be made within This notice constitutes our 12-month desert tortoise to our candidate species 12 months. We must publish these 12- finding for the petition to list the list. We will develop a proposed rule to month findings in the Federal Register. Sonoran population of the desert list the Sonoran population of the desert tortoise as threatened or endangered. tortoise as our priorities allow. We will Previous Federal Actions Other Federal Actions make any determination on critical On October 15, 2008, we received a habitat during development of the petition dated October 9, 2008, from Throughout this finding, we use proposed listing rule. In any interim WildEarth Guardians and Western ‘‘Mojave’’ to describe desert tortoise period we will address the status of the Watersheds Project (petitioners) populations north and west of the candidate taxon through our annual requesting that the Sonoran population Colorado River, as well as any reference Candidate Notice of Review (CNOR). of the desert tortoise be listed under the to the biotic community known as the ‘‘ ’’ ‘‘ DATES: The finding announced in this Act as a distinct population segment Mojave Desert or Mojave document was made on December 14, (DPS), as threatened or endangered desertscrub.’’ These uses are consistent 2010. rangewide (in the United States and with the previous and current spelling Mexico), and critical habitat be of the common name in Federal actions ADDRESSES: This finding is available on designated. The petition contained that have addressed this population. We the Internet at http:// detailed information on the natural use ‘‘Mohave’’ in the geographic context www.regulations.gov at Docket Number history, biology, current status, and to remain consistent with its reference FWS–R2–ES–2009–0032. Supporting distribution of the Sonoran population by the U.S. Board of Geographic Names documentation we used in preparing of the desert tortoise. It also contained (e.g., Mohave County). In addition, this finding is available for public information on what the petitioners while the Sonoran population of the inspection, by appointment, during reported as potential threats to the desert tortoise is not currently formally normal business hours at the U.S. Fish Sonoran population of the desert recognized as a unique taxonomic and Wildlife Service, Arizona Ecological tortoise, such as livestock grazing, entity, for ease of reference, we refer to Services Office, 2321 West Royal Palm urbanization and development, mining, the Sonoran population of the desert Road, Suite 103, Phoenix, Arizona international border patrol activities, tortoise as the ‘‘Sonoran desert tortoise’’ 85021. Please submit any new illegal collection, inadequacy of existing in this finding. information, materials, comments, or regulations, altered fire regimes, off- On December 30, 1982, we published questions concerning this finding to the highway vehicle use, drought, and a notice of review which determined the above address. climate change. We acknowledged the desert tortoise throughout its range in FOR FURTHER INFORMATION CONTACT: receipt of the petition in a letter to the the United States and Mexico to be a Steven L. Spangle, Field Supervisor WildEarth Guardians and Western Category 2 Candidate species (47 FR

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58454); this was reaffirmed on Pending Petitions and Description of centimeters (cm)), with a relatively high September 18, 1985 (50 FR 37958). Progress of Listing Actions’’ (53 FR domed shell (AGFD 2001, p. 1; Brennan Category-2 status was granted to species 52746, December 29, 1988); ‘‘Emergency and Holycross 2006, p. 54). The record for which information in our possession Determination of Endangered Status for length for a Sonoran desert tortoise is indicated that a proposed listing as the Mojave Population of the Desert 19.4 in (49 cm) total carapace length threatened or endangered was possibly Tortoise’’ (54 FR 32326, August 4, 1989); (Jackson and Wilkinson-Trotter 1980, p. appropriate, but for which sufficient ‘‘Desert Tortoise’’ (54 FR 42270, October 430). The carapace is usually brownish data were not available to make a 13, 1989); ‘‘Determination of Threatened with a definite pattern and prominent determination of listing status under the Status for the Mojave Population of the growth lines (AGFD 2001, p. 1). The Act. Desert Tortoise’’ (55 FR 12178, April 2, plastron (bottom shell) is yellowish and On April 2, 1990, we issued a final 1990); ‘‘Finding on a Petition to List the is not hinged (AGFD 2001, p. 1; Brennan rule designating the Mojave population Sonoran Desert Tortoise as Threatened and Holycross 2006, p. 54). The hind of the desert tortoise (occurring north or Endangered’’ (56 FR 29453, June 27, limbs are very stocky and elephantine; and west of the Colorado River) as a 1991); ‘‘Proposed Determination of forelimbs are flattened for digging and threatened species under the Act (55 FR Critical Habitat for the Mojave covered with large conical scales (AGFD 12178; see final rule for a summary of Population of the Desert Tortoise’’ (58 2001, p. 1; Brennan and Holycross 2006, previous actions regarding the Mojave FR 45748, August 30, 1993); p. 54). Male Sonoran desert are population of the desert tortoise). ‘‘Determination of Critical Habitat for differentiated from females by having Currently, the Mojave population of the the Mojave Population of the Desert elongated gular (throat) shields, chin desert tortoise is recognized as a distinct Tortoise’’ (59 FR 5820, February 8, glands visible on each side of the lower population segment under the Act. As 1994); ‘‘Determination of Critical Habitat jaw (most evident during the breeding part of that rulemaking, we designated for the Mojave Population of the Desert season), a concave plastron, and larger any desert tortoise from the Sonoran Tortoise’’ (59 FR 9032, February 24, overall size (AGFD 2001, p. 1). population as threatened when observed 1994); ‘‘Notice of Final Decision on Distribution outside of its known range, due to Identification of Candidates for Listing similarity of appearance under section as Endangered or Threatened’’ (61 FR The desert tortoise includes portions 4(a) of the Act. 64481, December 5, 1996); and ‘‘90–Day of southern California, southern Nevada, On December 5, 1996, we published Finding on a Petition To List the southwestern Utah, and the western, northwestern, and southern portions of a rule that discontinued the practice of Sonoran Population of the Desert Arizona in the United States, and also keeping a list of Category 2 Candidate Tortoise (Gopherus agassizii) as a includes the Mexican State of Sonora species (61 FR 64481). Since that time, Distinct Population Segment (DPS) with into the northern portion of Sinaloa. the Sonoran desert tortoise observed Critical Habitat’’ (74 FR 44335, August inside its known range has had no One-third of the geographic range of the 28, 2009). Federal Endangered Species Act status. desert tortoise occurs in northwestern For a detailed account of previous Species Information Mexico (Bury et al. 2002, p. 86). The Federal actions that pertained to the specific distribution of desert tortoise is desert tortoise in the United States, influenced by habitat and climatic please review the following Federal The desert tortoise is in the characteristics (vegetation community Register documents: ‘‘Proposed Gopherus (Rafinesque 1832), or gopher for food), soil and substrate Endangered Status and Critical Habitat tortoises, and is a member of the characteristics (for shelter), and for the Beaver Dam Slope Population of Testudinidae family, or terrestrial precipitation pattern (for water the Desert Tortoise’’ (43 FR 37662, tortoises. The North American tortoises availability) within the appropriate August 23, 1978); ‘‘Requirement to formerly comprised two genera, elevation range. withdraw or supplement proposals to Gopherus and Xerobates, with the latter The distribution of the Sonoran desert determine various U.S. taxa of plants including X. agassizii, the desert tortoise in the United States is and wildlife as Endangered or tortoise (Crumly 1994, pp. 7–8). considered to be entirely within Arizona Threatened or to determine Critical Scientific nomenclature assigned to the and comprises approximately 26.8 Habitat for such species’’ (44 FR 12382, desert tortoise has undergone a series of million acres (ac) (10.8 million hectares March 6, 1979); ‘‘Reproposal of Critical changes since its initial description by (ha)); east and south of the Colorado Habitat for the Illinois mud and Cooper (1863) as X. agassizii (Barrett River (Barrett and Johnson 1990, pp. 4– Beaver Dam Slope population of the and Johnson 1990, p. 5); the currently 5; Lamb et al. 1989, p. 84). Sonoran desert tortoise’’ (44 FR 70680, December recognized scientific name for the desert desert tortoise distribution in Arizona is 7, 1979); ‘‘Listing as Threatened With tortoise is Gopherus agassizii. Further limited to the northeast by the limits of Critical Habitat for the Beaver Dam information is available in Barrett and the Sonoran Desert. The Arizona portion Slope Population of the Desert Tortoise Johnson (1990, p. 5) or in the detailed of their range constitutes approximately in Utah’’ (45 FR 55654, August 20, account of desert tortoise phylogeny 52 percent of their total distribution. In 1980); ‘‘Review of Vertebrate Wildlife for (evolutionary development) and Arizona, the Sonoran desert tortoise Listing as Endangered or Threatened systematics (taxonomic classification) occurs primarily on Federal land but Species’’ (47 FR 58454, December 30, by Crumly (1994, pp. 7–32). The desert also occurs on a variety of non-federal 1982); ‘‘Notice of Findings on Four tortoise is known in Mexico with the lands as well as on ten Native American Petitions, and Review of One Species’’ common names of ‘‘tortuga del monte,’’ reservations: (1) Fort Mojave Indian (50 FR 13054, April 2, 1985); ‘‘Review of ‘‘Gala´pago de desierto,’’ or the Tribe; (2) Colorado River Indian Tribe; Vertebrate Wildlife’’ (50 FR 37958, ‘‘xtamo´osni’’ (Rorabaugh 2008, p. 35). (3) Hualapai Tribe; (4) Fort McDowell September 15, 1985); ‘‘Finding on Desert Yavapai Nation; (5) Salt River Pima- Tortoise Petition’’ (50 FR 49868, Physical Description of Sonoran Desert Maricopa Indian Community; (6) Gila December 5, 1985); ‘‘Findings on Tortoises River Indian Community; (7) Ak Chin; Pending Petitions and Description of Adult Sonoran desert tortoises range (8) Tohono O’odham Nation; (9) Pasqua Progress of Listing Actions’’ (53 FR in total carapace (straight-line top shell) Yaqui Tribe; and, (10) San Carlos 25511, July 7, 1988); ‘‘Findings on length from 8 to 15 inches (in) (20 to 38 Apache Tribe (AIDTT 2000, p. 40).

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In Mexico, where 48 percent of their the origin of this population. However, that habitat selection by Sonoran desert range occurs, the distribution of the because Sonoran desert tortoises are tortoises was most closely associated Sonoran desert tortoise extends from the infrequently documented from this area with topographic (degree of steepness of international border of Sonora and and recent genetic testing indicated that slope) and geomorphologic (rock type Arizona, south to the vicinity of observations represent released and structure) influences rather than by Guaymas, and north of the Rı´o Yaqui captives, we conclude that desert vegetation type. Specifically, Zylstra (the southern and southeastern-most tortoises from this area do not represent and Steidl (2008, p. 747) found that the border of their distribution), in southern a naturally-occurring, disjunct likelihood of observing Sonoran desert Sonora (Germano et al. 1994, p. 77; population. Consequently, we will not tortoises increased with increasing Fritts and Jennings 1994, p. 51; Bury et evaluate potential threats to the tortoises slope, with a strong association to al. 2002, p. 88; Van Devender 2002a, p. in this area of Cochise County in this aspect (the direction to which a slope 5; Edwards et al. 2009, pp. 7–8). This finding. faces), with east-facing slopes preferred includes approximately the western half Habitat over north-facing slopes. However, the of the State of Sonora from the Gulf of season of use may affect which slope- California coast east roughly to the Sonoran desert tortoises are most aspects (the direction a particular slope transition to unsuitable woodland and closely associated with the Arizona faces) Sonoran desert tortoises are likely conifer forest areas in the higher Upland and Lower Colorado River to use based on their needs at that time elevations of the Sierra Madre subdivisions of Sonoran desertscrub and (Zylstra and Steidl 2008, p. 752). Occidental. In 30 timed searches Mojave desertscrub vegetation types. Specifically, Sonoran desert tortoises conducted August to September 1983, They occur most commonly on rocky have different thermoregulatory and and beyond the known distribution of (predominantly granitic rock), steep physiological needs based upon their Sonoran desert tortoises in Sonora, slopes and bajadas (lower mountain seasonal behaviors, such as hibernation Mexico, Fritts and Jennings (1994, p. 52) slopes often formed by the coalescing of or seeking temporary shelter during the found several patterns in Sonoran desert several alluvial fans (fan-shaped tortoise’s surface-active seasons. deposits at the ends of canyons formed tortoise distribution. First, most In addition to steep, rocky slopes and Sonoran desert tortoises in the eastern when fast flowing streams slow and widen)) and in paloverde-mixed cacti bajadas, Sonoran desert tortoises also and northern extent of their distribution use inter-mountain valleys as part of in Mexico occur below the 2,600 foot (ft) associations (Ortenburger and Ortenburger 1927, p. 120; Burge 1979, p. their home ranges and for dispersal at (790 meters (m)) elevation contour 49; 1980, p. 48). Sonoran desert tortoise all age classes (Averill-Murray and (Fritts and Jennings 1994, p. 52). density has been observed to be higher Averill-Murray 2002, p. 16). In the Second, populations may be the densest in the Arizona Upland subdivision of Ironwood National Forest, Averill- and the least patchy between elevations the Sonoran desertscrub than in the Murray and Averill-Murray (2005, p. 65) of 900 and 1,600 ft (270 and 490 m) Lower Colorado subdivision of the found tortoises or their signs (such as (Fritts and Jennings 1994, p. 52). They Sonoran desertscrub or in Mojave scat (droppings) and burrows) on 92 were also not found in habitat in Mexico desertscrub (Berry 1984, p. 434; AIDTT percent of transects in boulder habitat, that received an average of 3.9 in (10 2000, p. 4; Boarman and Kristan 2008, on 71 percent of transects that included cm) or less of rain annually (Fritts and p. 19). In addition to the use of incised washes (dry stream beds that Jennings 1994, p. 53). vegetation to meet energy and flow in response to precipitation), and One question about the distribution of nutritional needs, the Sonoran desert on 25 percent of transects that had the Sonoran desert tortoise concerns the tortoise uses vegetation for predator neither boulder habitat nor incised origin of a small number of tortoises that avoidance, thermal protection, and in washes. Sonoran desert tortoises were have been found in far southeastern social behaviors (Avery and Neibergs found up to one mile (mi) (1.6 Cochise County, Arizona, an area 1997, p. 13; Grandmaison et al. in press, kilometers (km)) away from the nearest generally considered well east of the p. 3). An important attribute of Sonoran slope, indicating that they occur in low known distribution. There is some desert tortoise habitat is the presence of densities in inter-mountain valleys. evidence that these tortoises may cryptogamic crusts (soil crusts with Averill-Murray and Averill-Murray represent a naturally occurring unique, microscopic association of flora (2005, p. 65) stated that maintaining population based on the presence of and fauna) (Bowker et al. 2008, p. 2309). these areas ‘‘may be important for long- suitable habitat (Rorabaugh 2009, pers. These occur on the surface of Sonoran term population viability.’’ Washes comm.), similar communities Desert soils and assist with nitrogen- might also be selectively chosen by (Rosen 2009, pers. comm.), and historic fixing to enhance soil fertility, improve reproductive female Sonoran desert and current observations of tortoises in water infiltration into soils, and prevent tortoises as all eggs and hatchling desert the area (Hulse and Middendorf 1979, p. or lessen effects from wind and water tortoises observed by Barrett (1990, p. 546; Radke 2009, pers. comm.; Van erosion, all of which help to sustain 205) occurred there. Sonoran desert Devender et al. 1976, pp. 300–303). vegetation vital to the Sonoran desert tortoises on the 40-square-mile (sq mi) However, these observations have tortoise (DeFalco 1995, p. 22; DeFalco et (64-square-kilometer (sq km)) Florence traditionally been discounted as al. 2001, pp. 1, 9). Military Reservation in Pinal County, released pets rather than a natural Sonoran desert tortoises rarely occur Arizona, primarily use xeroriparian population (AIDTT 2000, p. 3; Germano in oak woodland habitat. However, one habitat (a habitat association with plant et al. 1994, p. 81). Also, recent genetic such population occurs at species tolerant to hyper-arid analysis of a Sonoran desert tortoise approximately 5,000-ft (1,500-m) conditions) along washes, with caliche collected from this area in 2009 elevation in Chiminea Canyon in the caves (caves formed along steep banks indicated it was most closely related to of Pima County, of washes within cemented, tortoises in the Phoenix, Arizona, area Arizona (Van Devender 2002a, p. 23), sedimentary rock formations of calcium and is likely, therefore, a ‘‘released or and they are also known from similar carbonate) within washes being an escaped captive’’ tortoise (Edwards elevation in the Atascosa and Pajarito important component to occupied 2010, pers. comm.). We recognize there Mountains in south-central Arizona. habitat (Lutz et al. 2005, p. 22; Riedle is a fair amount of uncertainty regarding Zylstra and Steidl (2008, p. 747) found et al. 2008, p. 418). Another frequently

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used habitat type on the Florence Colorado subdivision of the Sonoran months of inactivity), female Sonoran Military Reservation included gently Desert in Mexico (Bury et al. 2002, p. desert tortoises typically use more rolling alluvial fans dominated by 89). However, based on their presence shallow burrows that are more creosote bush (Larrea tridentata) and in El Pinacate and the general lack of susceptible to variation in ambient white bursage (Ambrosia dumosa) surveys in Mexico, the Sonoran desert temperatures and consequently females during all periods of the year; somewhat tortoise may potentially be found in this emerge earlier in the spring (as early as atypical for Sonoran desert tortoises in habitat in northwestern Sonora in low late February) than do males, who often other portions of its range (Lutz et al. densities. The extent of Sonoran desert remain dormant until the 2005; p. 22; Grandmaison et al. in press, tortoise distribution in northeastern commencement of the summer monsoon p. 4). In this habitat, Sonoran desert Sonora, an area characterized as a (AIDTT 2000, p. 7; Ernst and Lovich tortoises often used packrat middens transitional zone of foothills thornscrub, 2009, p. 547). Averill-Murray and Klug (organic debris piles constructed for tropical deciduous forest, and Madrean (2000, p. 66) and Bailey et al. (1995, p. nesting purposes which often are oak woodland, is poorly understood 367) suggest that shallow burrows may comprised of wood material, cactus (Bury et al. 2002, p. 89). account for responsiveness of females to pads, etc.) as shelter sites, especially warming periods in early spring for Burrow Use those with suitable canopy cover, an additional foraging opportunities to absence of cattle activity, and proximity Adequate shelter, often in the form of increase energy reserves for egg to roads and washes (Lutz et al. 2005, constructed burrows, is one of the most development, as shallower burrows are p. 22; Grandmaison et al. in press, p. 2). important habitat features for the more reflective of ground-surface Sonoran desert tortoises in Arizona Sonoran desert tortoise. Burrows are temperatures. Alternatively, cool, less generally occur within elevations from constructed under rocks and boulders, variable temperatures in deeper burrows 510 to 5,300 ft (155 to 1,615 m) (Barrett beneath vegetation, on semi-open selected by male Sonoran desert and Johnson 1990, p. 7; AGFD 2001, p. slopes, within the sidewalls of washes, tortoises may enhance sperm 4). According to the AGFD’s Heritage or by using rocky crevices which may or development and viability, as cooler Data Management system, 95 percent of may not be altered by the tortoise (Burge temperatures allow more sperm Sonoran desert tortoise observations in 1979, p. 44; 1980, pp. 44–45; Barrett production (Bailey et al. 1995, p. 367). Arizona have occurred at an elevation of 1990, p. 205; Averill-Murray et al. The season may influence the 904 to 4,198 ft (275 to 1279 m) (Zylstra 2002a, pp. 136–137, Grandmaison et al. locations and dimensions of burrows and Steidl 2009, p. 8). However, one in press, p. 14). Sonoran desert tortoises used by Sonoran desert tortoises in example of an extreme exception was a construct burrows in a variety of soil order to meet their behavioral and Sonoran desert tortoise observed at types including silt, silt with loose physiological needs (Barrett 1990, p. 7,808 ft (2,379 m) in a ponderosa pine- gravel, diatomite (a light-colored porous 205; Bailey et al. 1995, pp. 363, 366). dominated coniferous community in the rock composed of the shells of diatoms) Finally, particularly in hatchling and Rincon Mountain District of Saguaro and diatomaceous marl (a crumbly juvenile size classes, the burrow National Park in Pima County, Arizona mixture of clays, calcium and microclimate can affect the rate of water (Aslan et al. 2003, p. 57). The nearest magnesium carbonates, with remnants loss in desert tortoises, which results in road was 8.6 mi (13.9 km) away by trail of shells), and well-lithified (process behaviors (drinking pooled rain, and nearly 2,000 ft (610 m) lower in whereby loose particles are converted withdrawing into their shell, seeking elevation from the observed location of into rock) volcanic ash, as observed in long, deep burrows) to avoid lethal the tortoise, which strongly dismisses the lower San Pedro River Valley of dehydration in relatively hot, dry any notion that human activity was Arizona (Bailey et al. 1995, pp. 363– seasons (Wilson et al. 2001, p. 158; responsible for its location at such a 364). Burrows are used for Bulova 2002, pp. 184–186). high elevation (Aslan et al. 2003, p. 57). thermoregulation, nesting, and Other forms of shelter used by Sonoran desert tortoises in Mexico are protection from predators, and the lack Sonoran desert tortoise include packrat generally found at lower elevations, of suitable conditions for constructing middens, which are often shared with ranging from approximately 1,000 to burrows may be a limiting factor in other native , including other 1,640 ft (305 to 500 m) in elevation in Sonoran desert tortoise populations tortoises (Averill-Murray et al. 2002a, rocky outcrops in desertscrub and (Barrett and Humphrey 1986, p. 262; pp. 136–137; Lutz et al. 2005, p. 22; foothills thornscrub habitat (Bury et al. Bailey et al. 1995, p. 366; Zylstra and Grandmaison et al. in press, p. 2). These 2002, p. 89). As in Sonoran desertscrub Steidl 2008, p. 752). In fact, Sonoran shelter types provide less insulation habitat in Arizona, Sonoran desert desert tortoise population densities than earthen burrows and are therefore tortoises in Mexico often use shrubs as appear to be highly correlated with used for shorter duration, especially temporary shelter sites, and species available burrows, or potential burrow during the months with extremely hot such as mesquite (Prosopis spp.) and sites (Averill-Murray and Klug 2000, p. or cold temperatures. This was the most ironwood (Olneya tesota) may play 69; Averill-Murray et al. 2002b, p. 126). commonly used shelter site at Florence important roles in the natural history of Sonoran desert tortoises often use a Military Reservation. Sonoran desert tortoises in Mexico group of relatively closely-located (Bury et al. 2002, p. 100). Sonoran burrows as focal areas of activity in their Seasonal Behavior and Long-Distance desert tortoises in Mexico have not been home range. In doing so, they establish Movements documented in flatter areas between circular or slightly linear movement The Sonoran desert tortoise is diurnal mountain ranges (Bury et al. 2002, p. patterns, and may temporarily move on (active during daylight hours) but 89), although we presume they use these to another such cluster of burrows sometimes emerge at night in response areas to some extent for dispersal much within the same active season (Bulova to rainfall (Ernst and Lovich 2009, p. like they do in similar inter-mountain 1994, p. 140; Averill-Murray and Klug 544). Sonoran desert tortoises may be basins of Arizona. With the exception of 2000, p. 62; Lutz et al. 2005, p. 21). surface-active every month of the year, the El Pinacate Desert Bioreserve in Burrows influence a variety of but in the winter, surface activity is northwestern Sonora, Sonoran desert Sonoran desert tortoise behaviors and likely a response to thermoregulatory tortoises have not been documented physiological characteristics. During the needs or movements between burrows using the extremely arid Lower winter dormancy period (colder, winter (Averill-Murray and Klug 2000, p. 66).

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Temperature and precipitation are (Bailey et al. 1995, p. 367; Averill- understood, but are likely shorter than important predictors of Sonoran desert Murray and Klug 2000, p. 66). those of adults because of the complex tortoise activity (Meyer et al. 2010, p. The behavior and ecology of hatchling habitat of boulders and vegetation 11). Precipitation amounts and timing Sonoran desert tortoises is poorly (where they occur) may inhibit long- vary among the populations of desert understood because their small size distance movements (Van Devender tortoise. The lowest amount of rainfall makes them very difficult to observe in 2002a, p. 14). (usually during the winter) occurs in the the wild. Their scat is small, Gibbons (1986, p. 104) suspected that northwestern-most portion of the inconspicuous, and ephemeral, and long-distance movements by can species’ range, and gradually increases burrows used by individuals in this size be explained by: (1) Nest site selection; and becomes seasonally bimodal pattern class resemble those of other terrestrial (2) seasonal migration; (3) departure (rains in winter and summer) to the vertebrates in Sonoran desert tortoise from unfavorable habitat conditions; or south into the southern-most extent of habitat (Germano et al. 2002, pp. 271– (4) movement by males in search of the species range in northern Sinaloa, 272). This size class is thought to be the females. Averill-Murray and Klug (2000, most vulnerable, experiencing the Mexico (Germano et al. 1994, p. 76). p. 68) suggested that long-distance highest mortality rates (Morafka 1994, p. Sonoran desert tortoise surface activity movements may be interpreted as 161). random wanderings, infrequent travels largely mimics the warm-season Home range sizes of Sonoran desert precipitation pattern (Averill-Murray et to known sources of biological needs, tortoises vary with precipitation levels, explorations, adaptations for genetic al. 2002a, p. 139; Van Devender 2002a, contracting during wet years and p. 7). Like the Arizona populations, exchange, or for dispersal to other expanding during dry years in response suitable areas. Precipitation may Sonoran desert tortoises in Mexico seem to the availability of forage plants to be most active in late summer (Ernst influence the likelihood of long-distance (Averill-Murray and Klug 2000, p. 67). movements, especially in individuals and Lovich 2009, p. 544). Sonoran The home range of Sonoran desert approaching reproductive age in desert tortoises are approximately half tortoises may be as small as 6.4 ac (2.6 populations that experience above- as active during the spring as they are ha) but can vary widely, with males average precipitation for a 2- to 3-year in the summer, with females typically having larger home ranges than females period (AIDTT 2000, p. 8). Averill- becoming surface active to forage in late (Barrett 1990, p. 203; Averill-Murray Murray and Klug (2000, p. ii) stated, ‘‘A March, while males typically emerge and Klug 2000, pp. 55–61; Averill- large cohort of young tortoises that (but are not necessarily active) in late Murray et al. 2002a, pp. 150–151). In the experiences a relatively wet and April (Averill-Murray et al. 2002a, p. lower San Pedro River Valley, Meyer productive environment, with high 138). (1993, p. 99) found Sonoran desert survival, may provide the stock for The summer monsoon (occurring tortoise home ranges varied between 45 and 640 ac (18 and 258 ha) in size. dispersal between populations as they typically from late June through approach sexual maturity, in addition to September), characterized by both Sonoran desert tortoises are known to exhibit high fidelity to their home replacing aging adults within the local excessive heat and frequent ’’ ranges, with exception to dispersal population. Long-distance movements thunderstorms, is the peak activity by Sonoran desert tortoises observed by season for the Sonoran desert tortoise movements when they move to new areas (Zylstra and Swann 2009, p. vi). Averill-Murray and Klug (2000, p. 69) (Averill-Murray et al. 2002a, pp. 139– suggest the potential for metapopulation 140). During this period, new growth of They likely habituate to specific attributes of their home range, including (interrelated population dynamics perennial plants is initiated and annual the location of mates, water catchments, between regionally proximal plants germinate, providing forage for mineral licks, and burrow sites (Berry populations) relationships between tortoises (Averill-Murray et al. 2002a, p. 1986a, p. 113). local populations inhabiting regional 140). The onset of the summer monsoon Sonoran desert tortoises are known to hillsides. Habitat features may also triggers Sonoran desert tortoises to make long-distance movements between influence the Sonoran desert tortoises’ drink, flush their bladders, and populations in adjacent mountain ability to make long-distance rehydrate, establishing a positive water ranges. In an extreme example, Edwards movements. Dispersal of Sonoran desert and energy balance, and spurring et al. (2004, p. 494) tracked an adult tortoises between populations might be reproductive behaviors (AIDTT 2000, p. female Sonoran desert tortoise moving less likely through sparse desertscrub in 7). Sonoran desert tortoises have been 20 mi (32 km) between the Rincon and very hot, dry river valleys in the Lower observed to seek out rocks with surface of southern Colorado River subdivision of Sonoran depressions during summer months to Arizona (also see Zylstra and Swann desertscrub. Van Devender (2002a, p. drink puddled water from monsoon 2009, p. 10). During this long-distance 16) suggested that populations occurring storm events (Oftedal 2007, p. 23). movement, this tortoise encountered in the Eagletail, Maricopa, Sand Tank, Surface activity in Sonoran desert several barriers to movement that and similarly situated mountain ranges tortoises begins to wane as early as late required human intervention to might have existed in isolation for September and ends by mid-December overcome such as fence lines, railroad decades, if not centuries. as they prepare for hibernation. tracks, an interstate highway, and There are no data to evaluate long- Temperature and photoperiod (the several captures (including a temporary distance movements in populations that duration of daylight) are likely the cues adoption) by humans (Edwards et al. occur in Mexico. Although Sonoran used by Sonoran desert tortoises to 2004, p. 494). In another example, in the desert tortoises in Mexico are known to commence hibernation (Bailey et al. San Pedro Valley of southern Arizona, occupy slopes, arroyos, and bajadas, 1995, p. 367; Averill-Murray et al. a sub-adult Sonoran desert tortoise was they are infrequently observed using 2002a, p. 147). Periods of hibernation captured and marked in 1992. It was valley bottoms (Fritts and Jennings (typically from mid-November through recaptured in 2005 approximately 14 mi 1994, p. 52). Sonoran desert tortoise mid-February) in Sonoran desert (23 km) from its original point of populations in Mexico have been poorly tortoises appear to vary greatly among capture (Meyer et al. 2010, p. 18). studied, but we presume individuals populations and among years but appear Dispersal distances of hatchling make similar long-distance movements to correlate with seasonal temperatures Sonoran desert tortoises are not well between populations.

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Longevity Holycross 2006, p. 54; Oftedal 2007, p. type (forb or grass) were important Estimates of longevity in wild 21; Ernst and Lovich 2009, p. 562; predictors of nutritional quality versus a Sonoran desert tortoises vary Meyer et al. 2010, pp. 28–29, 44–48). Of plant being native or nonnative to a considerably from 30 years to over 100 the numerous nonnative plant species particular region. In summary, research has shown that forbs are more valuable years (Germano 1992, pp. 369–370; that have become established to Sonoran desert tortoise nutrition than 1994, p. 176; Zylstra and Swann 2009, throughout the range of the Sonoran grasses, and that native forbs are more p. vii). Using a growth equation to desert tortoise, only red brome (Bromus valuable than nonnative forbs in a dried extrapolate longevity in Sonoran desert rubens) and redstem filaree (Erodium state, which may be important in tortoises, Germano et al. (2002, p. 271) cicutarium) are frequently eaten and considered relatively important periods of drought. estimated that the average oldest ages Diets of Sonoran desert tortoises vary attained for Sonoran desert tortoises is nonnative species in the diets of Sonoran desert tortoises (Van Devender among populations in response to 62.2 years in females and 64.4 years in seasonal availability of plant species males; however, they admitted that et al. 2002, p. 183). However, physical injury to Mojave desert tortoises and in response to precipitation correlating age with size is problematic amounts (Martin and Van Devender in turtles. Zylstra and Swann (2009, p. resulting from consuming nonnative grass species (i.e., red brome and 2002, p. 31). In years of low winter vii) suspected that Sonoran desert rainfall, Sonoran desert tortoises are less tortoises may reach 80 to 100 years of cheatgrass (Bromus tectorum)) has been documented, and sharp seeds have been selective in plant species consumed age in the wild. Sonoran desert tortoises because there are fewer options, but in have been shown to live longer in the found lodged between the tortoises’ upper and lower jaw. This injury may years of high winter rainfall, Sonoran wild than those from the Mojave desert tortoises have exhibited highly population. adversely affect their foraging ability or become a source for infection (Medica selective foraging habits (Oftedal 2002, Bladder Physiology and Eckert 2007, p. 447). Though this pp. 205–206). During years when study focused on Mojave desert monsoon rains are light or irregular, The bladder in the Sonoran desert Sonoran desert tortoises consume dried tortoise is unique and serves an tortoises, this may affect all desert tortoises wherever these plant species plant material (Averill-Murray et al. important function in its survival. 2002a, p. 140). Within Saguaro National Sonoran desert tortoises are capable of occur (i.e., within the Sonoran Desert in Arizona). Park in southern Arizona, Sonoran drinking large amounts of water when it desert tortoises frequently ate annual is available, and may even construct Significant differences in the legumes in the spring (high in water water catchments by digging earthen nutritional quality of native versus content, low in potassium), and annual depressions, likely as an adaptation to nonnative forage for desert tortoises and perennial grasses (supplemented by the infrequent and unpredictable nature were not found by Hazard et al. (2010, prickly pear fruit (Opuntia of rainfall events throughout their range pp. 139–145). Nagy et al. (1998, pp. 260, engelmannii)) during the monsoon (Ernst and Lovich 2009, p. 546). The 263) compared the nutritional values of when ponding water can replenish bladder of Sonoran desert tortoises is a native and nonnative grasses (native: water reserves (Oftedal 2007, p. 17). In large and bilobed (divided into two Indian ricegrass (Achnatherum most years, Sonoran desert tortoises lobes) organ critical for withstanding the (Oryzopsis) hymenoides); nonnative: consume enough calories during the effects of seasonal and short-term Mediterrean grass (Schismus barbatus)) summer monsoon to fuel growth and drought because of its ability to store and forbs (native: desert dandilion store fat for the next year (Van Devender water, dilute excess dietary salts and (Malacothrix glabrata); nonnative: 2002a, p. 10). metabolic wastes, and reabsorb water redstem filaree), finding that the two Desert tortoises are uniquely into the bloodstream (Averill-Murray et grasses possessed similar nutritional vulnerable to changes in their potassium al. 2002a, p. 146; Ernst and Lovich value. The dry matter and energy levels (Oftedal 2002, p. 208). Because 2009, p. 545). In seasonal or short-term digestibility of the two grasses were potassium cannot be easily stored in the drought conditions, the concentration of much lower than those of the forbs, body, excess potassium must be urine in Sonoran desert tortoises allows providing little nitrogen, and tortoises excreted to avoid toxicological effects them to forage on dried vegetation by lost more water than they gained while (Oftedal 2002, p. 208). Therefore, reducing the dehydration effects of such processing grasses. The native forb was Sonoran desert tortoises that must forage types (Averill-Murray et al. more readily digestible than the forage on plants with high potassium 2002a, p. 146; Ernst and Lovich 2009, p. nonnative forb as dried mass, but the content must also flush their bladders 545). Water serves an important role in inverse was true as fresh mass (Nagy et more frequently and therefore risk a net flushing salts from the body of Sonoran al. 1998, p. 263). However, the native loss in metabolic water levels and desert tortoises and resetting the forbs provide significantly more subsequent dehydration (Oftedal 2002, electrolytic balance, preparing the nitrogen and water than the nonnative p. 209). Sonoran desert tortoise for the next dry forbs, which is important in maintaining The potassium excretion potential period (Averill-Murray et al. 2002a, pp. a positive water balance. Results of (PEP) is an index of water, nitrogen, and 140, 146). these feeding trials suggest that the potassium levels in a plant that relates proliferation of nonnative grasses to a desert tortoise’s ability to efficiently Diet, Foraging Behavior, and Potassium leading to the exclusion of forbs places excrete potassium. PEP is a critical Excretion Potential desert tortoises at a nutritional consideration for determining the value The Sonoran desert tortoise is an disadvantage. If, instead of eating to or risk of particular forage species herbivore, and has been documented to obtain a given volume of food, tortoises during times of drought or major eat 199 different species of plants, consume just enough food to satisfy perturbations to habitat, and for including herbs (55.3 percent), grasses their energy needs (as commonly noted comparing potential effects of forage (17.6 percent), woody plants (22.1 in other vertebrate groups), then the competition between tortoises and percent), and succulents (5 percent) native forbs provide the best nutrition. livestock. A positive PEP value for a (Ogden 1993, pp. 1–8; Van Devender et Nagy et al. (1998, p. 260) concluded that plant species (preferred by tortoises) al. 2002; pp. 175–176; Brennan and the life stage of the plant and the plant means there is more water and nitrogen

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in the food than is needed to excrete et al. 2010, p. 11). Sexual maturity and of 90.5 °F (32.5 °C) result in all females, potassium, and vice-versa for a negative first reproduction in female Sonoran and eggs incubated at the ‘‘pivotal’’ PEP value (Oftedal 2002, p. 215; Ernst desert tortoises occurs from 12 to 22 temperature of 88.3 °F (31.3 ° C) develop and Lovich 2009, p. 545). Sonoran years of age, or at 8.7 in (22 cm) in a 1:1 sex ratio (Rostal et al. 2002, p. desert tortoises have been documented midline carapace length, and 313). to selectively forage on high PEP plant reproductive activity is highly Predation species to minimize water loss influenced by winter and spring associated with metabolizing potassium precipitation (Averill-Murray and Klug As adults, Sonoran desert tortoises are (Oftedal 2002, p. 214; Ernst and Lovich 2000, p. 69; Averill-Murray et al. 2002b, relatively protected from natural 2009, p. 545). High PEP values can be p. 119; Bury et al. 2002, p. 100; predation because of their hard shells. found in certain species of primroses, Germano et al. 2002, p. 265). Females Mountain lions (Felis concolor) appear filaree, legumes, mustards, and spurges may store sperm for up to two years, to be the only natural predator in the (Ernst and Lovich 2009, p. 545). meaning that one season’s mating Sonoran Desert with the jaw strength Sonoran desert tortoises have been produces the following season’s clutch required to puncture or crack the shells found to be seasonally selective for high of eggs (Palmer et al. 1998, pp. 704–705; of adult Sonoran desert tortoises. PEP forage species, based on the Averill-Murray et al. 2002a, p. 141). However, mountain lion predation is abundance and diversity of plants and Female Sonoran desert tortoises may lay not known to contribute to elevated precipitation (Oftedal 2002, p. 223; one clutch of 1–12 eggs per year, usually mortality rates within monitored 2007, pp. 3, 22). around the onset of the summer rainy Sonoran desert tortoise populations In addition to herbivory, Sonoran season, although they may not produce (AIDTT 2000, p. 8; Meyer et al. 2010, p. desert tortoises are also geophagous; in a clutch every year (Averill-Murray 18; Riedle et al. 2010, p. 165). other words, they consume bones, 2002b, p. 295). Eggs hatch in September Dickenson et al. (2001, p. 254) recorded stones, and soil for additional nutrient and October (Van Devender 2002a, pp. 14 Sonoran desert tortoise mortalities in and mineral supplements, for 10–11; Averill-Murray 2002b, p. 295). the Little Shipp Wash and Harcuvar mechanical assistance in grinding plant The average clutch size is 3.8 to 5.7 monitoring plots from 1990–1994, five matter in the stomach, or to expel eggs, and in contrast to Mojave Desert of which were attributed to mountain parasites in the intestinal tract (Sokol tortoises, clutch size is not positively lion predation. Javelina (Tayassu tajacu) 1971, p. 70; Marlow and Tollestrup correlated with female body size predation on Sonoran desert tortoises was suspected in the San Pedro Valley 1982, p. 475; Esque and Peters 1994, pp. (Mueller et al. 1998, p. 313; Averill- of southern Arizona (Meyer et al. 2010, 108–109; Stitt and Davis 2003, p. 57; Murray 2002b, p. 299; Averill-Murray et p. 18). Other mammalian predators may Walde et al. 2007b, p. 148). Sonoran al. 2002b, p. 119). Late oviposition include badgers (Taxidea taxus), ring- desert tortoises are highly attracted to (deposition of eggs) dates recorded on tailed cats (Bassiriscus astutus), bobcats sites with exposed calcium carbonate the Sugarloaf study site in central (Felis rufus), skunks (Spilogale gracilis, and have been observed congregating at Arizona in 1998 and 1999 suggest that Mephitis mephitis, M. macroura, these sites year after year eating these eggs and hatchlings may occasionally Conepatus mesoleucus), kit foxes soils (Meyer et al. 2010, p. 11). Soil overwinter in nests (Averill-Murray (Vulpes macrotis), gray foxes (Urocyon condition and quality are important to 2002b, p. 299). Female desert tortoises the Sonoran desert tortoise, not only for cinereoargenteus), coyotes (Canis have been known to urinate on their latrans), and domestic dogs (Canis nutrients derived from eating soil, but nest sites before and after nesting; this also production and maintenance of familiaris) (Boarman 2002, p. 17; Ernst may be to aid in digging the nest, and vegetation that is consumed by tortoises and Lovich 2009, p. 563). might make it more difficult to dig up (Avery and Neibergs 1997, p. 13). Both golden eagles (Aquila Desert tortoises have been observed the nest after the soil dries, or possibly chrysaetos) and common ravens (Corvus eating scat from black-tailed jack to hydrate soils in contact with eggs as corvax) have been documented to prey rabbits, wood rats, collared peccaries, the rigid-shelled eggs of desert tortoises upon all size classes of Mojave desert and even desert tortoises. This behavior have been shown to uptake moisture tortoises in California (Berry 1985, pp. could possibly aid in the transfer of gut from the soil faster than it evaporates 1, 6–10). Such predation might also microflora such as bacteria or fungi or from the shell exposed to air (Patterson occur on Sonoran desert tortoises. The it could be used as a source of 1971, p. 199; Spotila et al. 1994, p. 112). greater roadrunner (Geococcyx additional nutrients (Walde et al. 2005, Female Sonoran desert tortoises that californianus) is also a suspected p. 77–78). Bostick (1990, p. 149) survive to reproductive age are believed predator on juvenile Mojave desert asserted that desert tortoises feed to produce as many as 85 eggs over the tortoises, based upon one field ‘‘primarily on dung’’ although this claim course of their lives, with perhaps two observation of roadrunner tracks next to was refuted in the literature (Boarman or three of those hatchlings surviving to a freshly killed individual (Berry 1985, 2002, pp. 27, 35, 38). Infrequent reproductive age (Van Devender 2002a, p. 11); such predation might also occur observations of sand, bird feathers, p. 11). on Sonoran desert tortoises. However, parts, and snake and lizard Desert tortoises exhibit environmental because avian predators rely exclusively skins have also been made during fecal sex determination, which means that on their vision to detect prey, we expect analyses of desert tortoises (Ernst and incubation temperatures during lower rates of avian predation on Lovich 2009, p. 560). embryonic development determine the Sonoran desert tortoises occupying sex of the tortoises. Higher incubation Arizona upland Sonoran desertscrub Reproduction temperatures produce more females and because the dense, complex habitat The Sonoran desert tortoise breeding lower temperatures produce more males structure likely limits birds’ ability to season begins with the summer (Spotila et al. 1994, pp. 109–111; Rostal detect tortoises. Habitat-associated monsoon when male-male combat over et al. 2002, p. 313). Incubation protection from avian predation may be receptive females can be observed, such temperatures at or below 86.9 degrees less pronounced where Sonoran desert as at sites with exposed calcium Fahrenheit (° F) (30.5 degrees Celsius tortoises occur in the sparser vegetation carbonate soils, where tortoise densities (° C)) result in the production of all male of the Lower Colorado River subdivision may be higher (discussed above) (Meyer desert tortoises, whereas temperatures of Sonoran desertscrub.

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Sonoran desert tortoises are most in 1987, AGFD and the U.S. Bureau of Sonoran desert tortoise was captured vulnerable to predation while in their Land Management (BLM) have and marked in 1992, and was not eggs or as hatchlings and juveniles established and maintained 17 plots in encountered again until 2005, when it predominantly because of their size and Arizona as long-term monitoring plots was incidentally observed undeveloped, softened shells (which do and have surveyed them in a somewhat approximately 14 mi (22.5 km) from its not adequately harden until irregular, but repeated fashion. Each original point of capture, 8 years after approximately 7 years of age) which plot has been surveyed between two and the conclusion of the study (Meyer et al. provide little protection and are easily nine times during this timeframe, with 2010, p. 18). Within the entire duration compromised. Higher mortality rates in 11 to 86 person-days (cumulative days of this study, approximately 30 percent the hatchling and juvenile age classes spent by researchers working on plots) of 577 marked Sonoran desert tortoises may also be partially due to their higher spent during each survey (AGFD 2010, were never recaptured, with only 15 metabolic rates, which necessitates p. 1). These long-term monitoring plots total carcasses found, indicating longer periods of surface activity to are located in six counties within potential emigration, long-term burrow obtain suitable amounts of forage. Arizona, and their locations were use, or difficulties in detecting Longer surface activity may cause chosen to represent Sonoran desert individuals in complex landscapes greater risk of detection by predators tortoise distribution in the State. (Meyer et al. 2010, p. 20). The amount (Morafka 1994, p. 163). Nest predation General monitoring objectives for the 17 plots are to document abundance, of time between recaptures of Sonoran levels may be high in some populations. desert tortoises can be significant; Seventy-five percent of Sonoran desert density, and changes of Sonoran desert tortoise populations across the State durations between recaptures of some tortoise nests suffered predation over a individuals in the San Pedro Valley two-year period at the Sugarloaf study using capture-recapture methods (Averill-Murray 2000, p. 3). Records of study were as high as 18 years (Meyer plot in Maricopa County, Arizona et al. 2010, p. 20). (Averill-Murray 2002b, p. 298). Gila demographic characteristics of each monsters (Heloderma suspectum) are a population, including sex ratios and Several authors have investigated how primary predator on tortoise eggs, and age/size structure as well as individual detectability may bias results of Mojave female Sonoran desert tortoises in the health and signs of disease within each desert tortoise monitoring. For example, process of oviposition will actively population were also recorded during Anderson et al. (2001, p. 583) studied defend the burrow and aggressively monitoring activities (Averill-Murray the degree to which field observers can pursue Gila monsters in attempting to 2000, p. 3). Monitoring protocols used meet the assumptions underlying line- drive them away (Barrett and Humphrey from 1987 to 2000 are summarized in transect sampling to monitor 1986, p. 262). Coachwhips (Coluber Averill-Murray (2000, pp. 3–7). populations of desert tortoises in The Sonoran desert tortoise is a flagellum) and gophersnakes (Pituophis Mojave desertscrub. They found that difficult species to monitor in the wild catenifer) have been reported when all Mojave desert tortoises are not because of its slow movement and consuming juvenile Sonoran desert detected along the centerline of the camouflaged appearance, especially in tortoises (Amarello et al. 2004, p. 178; transect route (which routinely occurs), the smaller hatchling and juvenile age Ernst and Lovich 2009, p. 563). biases in sampling data result classes. These factors can significantly Presumably, other snake species such as (Anderson et al. 2001, p. 583). Anderson hamper a surveyor’s ability to detect common kingsnakes (Lampropeltis et al. (2001, p. 593–596) noted that them in the field (Zylstra et al. 2010, p. getula) with generalized prey surveyor numbers and level of 1311). In addition, Arizona Upland preferences consume eggs or hatchling experience contribute to the reliability subdivision of Sonoran desertscrub of line transect methods. Freilich and Sonoran desert tortoises, but we did not (where Sonoran desert tortoise LaRue (1998, p. 594) experimentally find other examples in the literature. population densities are the highest) is For more detailed information on all tested the effect of personnel experience complex, often with many large aspects of Sonoran desert tortoise on Mojave desert tortoise survey boulders, somewhat dense vegetation, biology, see Barrett and Johnson (1990, outcomes in Mojave desertscrub. They and challenging topographic relief. pp. 1–95) and Bury and Germano (1994, Drought and emigration also affect the found that observers consistently pp. 1–212). reliability of data from Sonoran desert overestimated the number of desert Monitoring and Population Status tortoise population monitoring because tortoise burrows (falsely assigning other the tortoises may be inactive (in their animal burrows as those made by desert Monitoring and Statistical Analyses burrows) or have left the population tortoises), and found fewer desert We are unaware of any structured, (dispersed). In these cases the absence tortoises and scat than were actually long-term monitoring program for of observations might be mistaken as placed on test plots. Their results Sonoran desert tortoises in Mexico; mortality. Also, Sonoran desert tortoises indicated that experience played a therefore, we are unable to assess the can occur in low densities with little relatively small role in detecting Mojave current status or population trends in surface activity both seasonally and desert tortoises (Freilich and LaRue that part of the range. Therefore, we daily (Zylstra et al. 2010, p. 1311). 1998, pp. 593–594). In an effort to discuss only Arizona studies in this Alone or in combination, these factors, increase detections, some investigators section. in addition to a relatively short have tested the use of tortoise detection Twenty-eight individual Sonoran sampling period for such a long-lived dogs in Mojave desert tortoise desert tortoise populations in Arizona species, make subtle population trends monitoring projects (Cablk and Heaton have been studied since the mid-1970s difficult to distinguish and overall 2006, p. 1926; Heaton et al. 2008, pp. but few populations have been studied population trend analysis problematic. 476–477; Nussear et al. 2008, pp. 109– for more than a few years (Averill- Low detectability may have been 111). Because Sonoran desertscrub is Murray 2000, p. 1; Averill-Murray et al. responsible for long periods between more dense and complex than Mojave 2002b, p. 109). Monitoring plots (also recaptures of marked desert tortoises in desertscrub, detection is even more referred to as ‘‘plots’’) have varied from an 18-year desert tortoise study from difficult in Sonoran desert tortoise 0.2 to 1.5 sq mi (0.3 to 2.4 sq km) in size 1980 to 1997 in the San Pedro Valley, monitoring. Zylstra and Steidl (2009, p. (Averill-Murray 2000, p. 4). Beginning Arizona. For example, a sub-adult 16) found that line transect methods are

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not an efficient means with which to rangewide trends of the Sonoran desert used in our analysis of the status of and monitor Sonoran desert tortoises. tortoise. Averill-Murray (2000, pp. 12– threats to the Sonoran desert tortoise The seasonal timing of surveys and 13) identified problems with and is cited in this finding. For a more fluctuating influence of precipitation on extrapolating the results of the plot detailed analysis of the Boarman and Sonoran desert tortoise surface activity monitoring data to making range-wide Kristan (2008) report, see our ‘‘Review of also create problems with monitoring assessments outside of the plots. We Boarman and Kristan (2008)’’ provided populations and interpreting results. elaborate on these problems in our at http://www.regulations.gov (Docket Sonoran desert tortoises often become assessment of Boarman and Kristan Number FWS–R2–ES–2009–0032). inactive, residing in their burrows, (2008) below. during periods of seasonal or short-term Boarman and Kristan (2008, pp. 3–12) Survivorship and Population Densities drought. For example, in a multi-year analyzed mark and recapture data from in Arizona mark and recapture study of Mojave the 17 Sonoran desert tortoise long-term Viable populations in turtles usually desert tortoises in Joshua Tree National monitoring plots throughout Arizona require that both juvenile and adult size Park, Freilich et al. (2000, pp. 1487– that were surveyed on the average of classes have high survivorship (Averill- 1488) found that in years of below- once every 4 years from 1987 to 2006. Murray and Klug 2000, p. 70). Data on normal precipitation, desert tortoise Boarman and Kristan (2008, p. ii) the recruitment of juveniles into home ranges decreased, individual concluded that the Sonoran population Sonoran desert tortoise populations, and captures decreased, and the effort of the desert tortoise in Arizona their survivorship, are generally lacking required to find each tortoise nearly experienced statistically significant due to the difficulty detecting juveniles doubled; indicating the significant declines, at an annual rate of 3.52 in the field (AGFD 2010, p. 3). Data on influence of precipitation on the percent over the 20-year period; juvenile and adult survivorship in possible discrepancy between the equating to a cumulative 51 percent Sonoran desert tortoises require long- number of tortoises that can be observed decline in overall numbers during this term, repeated population monitoring, versus the number of tortoises that timeframe. which in turn, requires long-term, actually occur within a monitoring plot. We received several comments from reliable funding sources. Consequently, In an attempt to improve monitoring the public in response to our 90-day these data are conspicuously rare or protocols to account for such finding that addressed the Boarman and absent for most Sonoran desert tortoise complicating factors described above, Kristan (2008) report (AGFD 2010, pp. monitoring plots making population Averill-Murray (2000, pp. 7–13) 4–6; Carothers et al. 2010, pp. 5, 8–12; viability estimates for Sonoran desert critiqued the original protocols used for Ogden 2009, pp. 3–12, Smith 2010, pp. tortoise populations within Arizona long-term monitoring plots of Sonoran 4–5). Commenters criticized the method problematic at best. As expected for a desert tortoise populations in Arizona. and manner with which Boarman and long-lived species, survivorship in This work became the basis for several Kristan (2008) used statistical tests, as Sonoran desert tortoises (using data changes in monitoring protocols, well as the conclusions they made. generated from a few long-term beginning in 2000. Although line Significant concerns were noted with monitoring plots in Arizona) is transect methods have not been respect to the type of statistical tests generally high for adults but potentially implemented on Arizona’s Sonoran used by Boarman and Kristan (2008) lower for juveniles and hatchlings desert tortoise long-term monitoring because data were extrapolated beyond (Zylstra and Steidl 2009, p. 7). Where plots, the capture-recapture methods the statistical tests’ ability to avoid enough data from long-term monitoring currently used likely violate inherent biases (AGFD 2010, p. 4). plots or independent studies exist, assumptions about equal detection Problems associated with the statistical survivorship has been calculated for probability (all having the same confidence intervals for monitoring plot adults in the following plots or study probability of being captured during data used by Boarman and Kristan areas: Sugarloaf Mountain (96–98 every sampling occasion) (Zylstra and (2008) were also identified (Ogden 2009, percent), Florence Military Reservation Steidl 2009, p. 9). pp. 2–3). Also, monitoring plot data (88–97 percent), Little Shipp Wash (94– While monitoring of Sonoran desert used in Boarman and Kristan (2008, p. 97 percent), Granite Hills (94–97 tortoise populations in Arizona has been 20) were not designed to compare percent), and Eagletail Mountains (94– ongoing for several decades, attempts to population trends among individual 97 percent) (AGFD 2010, p. 2; Riedle et quantify temporal trends in abundance plots (Ogden 2009, p. 2). Carothers et al. al. 2010, p. 165). have been hampered by the data (2010, pp. 8–12) identified numerous Densities of Sonoran desert tortoises limitations discussed above (Zylstra and additional problems with the statistical among populations vary considerably. Steidl 2009, p. 5; Zylstra et al. 2010, pp. analysis provided by Boarman and In 2000, the density of Sonoran desert 1311–1317). Effective monitoring is Kristan (2008). Collectively, based upon tortoises, as determined by surveys on largely dictated by the objective of the comments received from the public as long-term monitoring plots and other monitoring, whether that objective is to well as our internal review, the number monitoring plots during the 1990s, detect changes in distribution, and magnitude of potential problems varied from 15 to 150 individuals per abundance, density, or survival. In associated with Boarman and Kristan’s square mile (2.6 sq km) (AIDTT 2000, addition, using existing plot data to (2008) statistical analysis call into pp. 5–6; Averill-Murray and Klug 2000, establish rangewide trends in Sonoran question the validity of their p. i). In the San Pedro Valley of desert tortoise populations is generally conclusions. After careful review of the southern Arizona, the average density of problematic because the current set of report and the questions raised by the Sonoran desert tortoise population monitoring plots does not represent a reviewers of the report, we decided that was 38 individuals per square mile random sample from the species’ entire the conclusions pertaining to overall (Meyer et al. 2010, p. 17). Stager et al. range in Arizona (Averill-Murray and Sonoran desert tortoise population (2010, p. 37) suspect that Sonoran desert Klug 2000, p. 25). Despite the history trends do not represent the best tortoise populations in Mohave County, and effort dedicated to monitoring available information and, therefore, we Arizona may be naturally lower due to Sonoran desert tortoise populations in did not use the report in this finding. limited burrowing habitat available to Arizona since 1987, there are limitations However, other information in the them to survive cold winters and hot of these data with respect to interpreting Boarman and Kristan (2008) report was summers.

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Periodic, Localized Declines in Arizona population may be stable, if not Act as including any subspecies of fish Populations returning to the previous 1987 level or wildlife or plants, and any distinct There are no records of actual (AGFD 2010, p. 3). population segment (DPS) of any extirpations of Sonoran desert tortoises The AGFD (2010, p. 3) and Hart et al. species of vertebrate fish or wildlife that from any of the monitored populations. (1992, p. 120) confirm Sonoran desert interbreeds when mature (16 U.S.C. However, periodic, localized, and tortoise populations declined from 1532(16)). We, along with the National sometimes substantial declines have initial population estimates (as Marine Fisheries Service (now the been documented in at least five of 17 demonstrated by density estimates and National Oceanic and Atmospheric monitored populations (Hart et al. 1992, relative carcass numbers) on three Administration—Fisheries), developed p. 60; Averill-Murray et al. 2002b, p. additional plots (Hualapai Foothills, the Policy Regarding the Recognition of San Pedro Valley, and East Bajada), 124; AGFD 2010, p. 4). Because of their Distinct Vertebrate Population Segments suspecting that drought conditions may life history, Sonoran desert tortoise (61 FR 4722; February 7, 1996), to help have played a role in the observed populations may be slow to rebound us in determining what constitutes a declines on these plots (Ogden 2009, pp. from declines (Howland and Rorabaugh DPS. The policy identifies three 12–13). An observed decline on the 2002, p. 340). The AGFD (2010, p. 4) elements that are to be considered Tortilla Mountains plot in 2001 may suggested that observed declines in regarding the status of a possible DPS. have been an artifact of low surface certain plots demonstrate localized, These elements include: (1) The activity in response to below-average discreteness of the population segment stochastic events and are not indicative precipitation, because an increase in in relation to the remainder of the taxon of population trends as a whole across carcasses was not detected (AGFD 2010, (group of similar biological organisms); the distribution of the Sonoran desert p. 3). (2) the significance of the population tortoise. Sonoran desert tortoise For detailed information on segment to the taxon to which it populations are particularly vulnerable monitoring and survey results from the belongs; and (3) the population to elevated mortality of adults. previous three decades for the Sonoran segment’s conservation status in relation Sustaining the adult, reproductive age desert tortoise in Arizona, see the to the Act’s standards for listing (i.e., class within Sonoran desert tortoise following reports: Schneider (1981), whether the population segment, when populations is important because Shields and Woodman (1987), Wirt treated as if it were a species, is mortality rates of juveniles are high and (1988), Woodman and Shields (1988), endangered or threatened) (61 FR 4722, because it takes a long time for a Holm (1989), Shields et al. (1990), February 7, 1996). The first two Sonoran desert tortoise to reach sexual SWCA (1990a; 1990b; 1990c), Hart et al. elements are used to determine if a maturity (Howland and Rorabaugh (1992), Murray and Schwalbe (1993; population segment constitutes a valid 2002, p. 339). The relatively higher 1997), Woodman et al. (1993; 1994; DPS. If it does, then the third element visibility of adult Sonoran desert 1995; 1996; 1998; 1999a; 1999b; 2000; is used to consider whether such DPS tortoises leaves them more vulnerable to 2001; 2002; 2003; 2004; 2005; 2006; warrants listing. In this section, we will human impacts like collecting or 2007; 2008; 2009), AIDTT (2000, pp. 5– consider the first two criteria shooting, and their tendency to move 6), Averill-Murray (2000, pp. 3–7), (discreteness and significance) to longer distances make them more Averill-Murray and Klug (2000, pp. 3– determine if the Sonoran desert tortoise susceptible to road mortality (Howland 25), Averill-Murray et al. (2002b, pp. is a valid DPS (i.e., a valid listable and Rorabaugh 2002, p. 340). 110–112), Walker and Wood (2002), entity). Our policy further recognizes it The largest population decline noted Young et al. (2002), and Zylstra and may be appropriate to assign different at any Sonoran desert tortoise Swann (2009). classifications (i.e., threatened or monitoring plot was observed on the It should be noted that an average endangered) to different DPSs of the Maricopa Mountains plot, where generation time for a Sonoran desert same vertebrate taxon (61 FR 4722). substantially more tortoise carcasses tortoise is 12–15 years and that were found than live tortoises in monitoring of Sonoran desert tortoise Discreteness successive years from 1987 through populations has only occurred for about Under the DPS policy, a population 1991 (Hart et al. 1992, p. 54; Averill- 30 years, representing approximately segment of a vertebrate species may be Murray et al. 2002b, p. 124). Regional two generations. Many threats described considered discrete if it satisfies either drought from 1984–1992 was a below have been potentially acting on one of the following two conditions: suspected cause of the die-off of Sonoran desert tortoise populations for (1) It is markedly separated from other Sonoran desert tortoises in the Maricopa many decades, longer than populations populations of the same taxon as a Mountains (Hart et al. 1992, p. 60; have been studied. Below, we discuss consequence of physical, physiological, Averill-Murray et al. 2002b, p. 124). the effects of various threats to ecological, or behavioral factors. However, in 1987, the estimated density individual Sonoran desert tortoises. Quantitative measures of genetic or of Sonoran desert tortoises on the However, due to limitations in morphological discontinuity (separation Maricopa Mountains plot was monitoring data, we are unable to based on genetic or morphological uncharacteristically high at 146 tortoises discern how Sonoran desert tortoise characters) may provide evidence of this per square mile (2.6 sq km), suggesting populations may have responded to separation. that the population may have been in these threats over time, or identify any (2) It is delimited by international the process of naturally correcting to long-term, historical trends in tortoise governmental boundaries within which carrying capacity (the state at which a populations. We have not observed any significant differences in control of population level is commensurate with extirpations among monitored exploitation, management of habitat, available resources) (AGFD 2010, p. 3). populations. conservation status, or regulatory Since 1991, the Sonoran desert tortoise mechanisms exist that are significant in population on the Maricopa Mountains Distinct Population Segment light of section 4(a)(1)(D) of the Act. plot has experienced relatively high We consider a species for listing Based upon available information, the survivorship and shown evidence of under the Act if available information international boundary between Mexico reproduction. No additional carcasses indicates such an action might be and the United States is not considered have been documented, indicating the warranted. ‘‘Species’’ is defined by the for delineation of discreteness because

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the edge of the DPS is not located at the between Plains of Sonora subdivision of are substantial among the three International Border and, therefore, will Sonoran desertscrub and Sinaloan populations of desert tortoise. not be addressed further. thornscrub habitats of central Sonora Divergence is 5.1–5.6 percent between The Colorado River and Rı´o Yaqui are such as in the vicinity of the Rı´o Yaqui the Sonoran and Mojave populations, two perennial rivers that form (Edwards et al. 2009, p. 8). 4.2 percent between the Sonoran and biogeographical barriers (a natural In addition to habitat differences, Sinaloan populations, and 5.1 percent barrier that prevents the migration of morphological differences have also between the Sinaloan and Mojave species) to movement of tortoises been documented among the three populations (Lamb and McLuckie 2002, between the Mojave and Sonoran desert populations of desert tortoise. Several pp. 74, 77). Considering geographic tortoise populations, and between the morphological differences in carapace distribution, genealogical depth, and a Sonoran and Sinaloan desert tortoise size and shape have been documented suite of other characteristics, the populations, respectively. The Colorado between the Mojave, Sonoran, and Mojave, Sonoran, and Sinaloan River, separating California and Sinaloan populations of desert tortoise: populations of desert tortoise are Arizona, comprises the northern and The carapace of the Mojave desert considered to be ecologically significant western boundaries of the Sonoran tortoise is the widest and tallest of the units (populations or groups of desert tortoise population as identified three, the Sinaloan desert tortoise populations historically isolated from in the April 2, 1990, final rule carapace is the most narrow and least one another, and thus representing deep designating the Mojave population of domed, and the carapace of the Sonoran phylogenetic (evolutionary development the desert tortoise (occurring north and desert tortoise is intermediate between of species over time) subdivisions west of the Colorado River) as a the two in those dimensions (Germano within species) (Lamb and McLuckie threatened species under the Act (55 FR 1993, pp. 324–325; AGFD 2001, p. 1). 2002, pp. 81–82). According to 12178; see final rule for a summary of Using eight independent shell mitochondrial DNA markers, the previous actions regarding the Mojave measurements, Weinstein and Berry Sonoran and Mojave populations appear population of the desert tortoise). The (1987, pp. 26–28) documented three to have diverged some 5 million years eastern boundary is the extent of the distinct phenotypes (physical ago (Lamb et al. 1989, p. 83; Lamb and range of the Sonoran desert tortoise appearances) in desert tortoise McLuckie 2002, p. 76). where desert habitats end and grassland, populations within the United States McCord (2002, p. 62) presented three chaparral, and mountain habitats begin, based on morphometric (body possible causes of the significant genetic which are areas that do not contain measurement) analyses: The ‘‘California’’ differentiation between Sonoran and desert tortoises. The southern boundary phenotype (Mojave population), ‘‘Beaver Mojave desert tortoises. First, genetic of the Sonoran desert tortoise DPS, as Dam Slope’’ phenotype (Mojave form in differentiation between Sonoran and considered in this finding, is the Rı´o Arizona), and the ‘‘Sonoran type’’ Mojave desert tortoises may have been Yaqui in southern Sonora, Mexico; (Sonoran population). Desert tortoises the result of differences in rainfall south and east of there, desert tortoises from southern Sonora and northern patterns between the winter-dominated are considered Sinaloan populations. Sinaloa in Mexico were not studied as rainfall pattern of the Mojave Desert and Potential threats to the Sinoloan desert part of this effort. the summer-dominated rainfall pattern tortoise are not evaluated as part of this Differences in reproduction strategies of the Sonoran desert. Second, genetic finding. between the Sonoran and Mojave differentiation between Sonoran and In view of this biogeographical populations of desert tortoises also Mojave desert tortoises may have isolation, significant ecological occur. Mojave desert tortoises lay up to occurred because the Sonoran desert divergence has occurred between the three clutches of eggs per year with tortoises may be represented as a relict Mojave and Sonoran populations of larger clutch sizes (more eggs), earlier in population (remnant survivor from the desert tortoise, largely due to significant the year (April to mid-July) (Wallis et al. past) of the tropical deciduous forest- differences in geology, vegetation types, 1999, p. 405) while those in the Sonoran evolved population of the Sinaloan and precipitation cycles where the population lay one clutch per year of population (based upon their general populations are distributed. Desert smaller size, later in the year (June absence in valley bottoms due to heavy tortoises in the Mojave population are through August) (Averill-Murray et al. flooding during summer rains, a most dense in the intermountain valleys 2002a, p. 141). These differences led phenomenon generally absent in the that have soil types favorable to the Averill-Murray (2002b, pp. 119–122) to Mojave Desert). Last, genetic differences construction of large, deep burrows the conclusion that Sonoran desert between Sonoran and Mojave desert (Bury et al. 1994, pp. 66–70). However, tortoises invest all reproductive effort tortoises may have resulted from their Sonoran desert tortoises reach into a single clutch which hatches at the mutual competition with the Bolson maximum densities in the rocky bajadas peak of forage and water availability and tortoise (Gopherus flavomarginatus), and hillsides of higher slopes, with abundance owing to late-summer another desert tortoise species which reduced densities in the intermountain rainfall. Whereas desert tortoises in the was widely distributed throughout valleys (Berry 1984, p. 434; AIDTT Mojave population (maturing at smaller Arizona in the Pleistocene, but which 2000; p. 4; Van Devender 2002a, p. 7; body sizes) (Berry et al. 2002a, p. 259) never occurred in California. The Brennan and Holycross 2006, p. 54; have higher clutch numbers to offset competing population Zylstra and Steidl 2008, p. 747). At the higher mortality from greater variability may have acted as a wedge between the southern end of the DPS, Edwards et al. in environmental conditions. Sonoran and Mojave populations, (2009, pp. 7–8) suggested that Sinaloan The Mojave, Sonoran, and Sinaloan driving them even farther apart, in a population of desert tortoise uses populations of the desert tortoise have process known as competitive Sinaloan thornscrub and tropical been found to have significantly displacement. deciduous forest habitats. These differentiated genotypes (genetic To explore the evolutionary track the different habitat types with differing characteristics) (Lamb and McLuckie three desert tortoise populations may soils and vegetation communities are 2002, p. 74; Van Devender 2002a, p. 24). have taken and the extent of their created by higher precipitation levels. Genetic distances, expressed as percent current genetic differentiation on the However, some level of gradation may sequence divergence (an estimate of landscape, Edwards et al. (2009, p. 8) occur in the vegetative transition zone percent difference in the genetic code), collected genetic samples from desert

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tortoises within three regions of Sonora, Lamb and McLuckie 2002, pp. 74, 77; from other populations of the species in Mexico: Twenty-two samples from near McCord 2002, p. 62; Van Devender its genetic characteristics. Alamos, Sonora (tropical deciduous 2002a, pp. 24–25; Van Devender 2002b, A population segment needs to satisfy forest in extreme southern Sonora), 19 p. 45; Zylstra and Steidl 2008, p. 747; only one of these conditions to be samples from near Ciudad Obrego´n Edwards et al. 2009, p. 8). considered significant. Furthermore, (foothill thornscrub in south-central We have reviewed the best available other information may be used as Sonora, south of the Rı´o Yaqui), and 14 commercial and scientific information appropriate to provide evidence for samples from two sites north of and find that the Sonoran population of significance. Hermosillo (Sonoran desertscrub in the desert tortoise as it occurs east and The current range of the Sonoran central Sonora). When they compared south of the Colorado River, south to the desert tortoise, as described in the genetic data with previously collected Rı´o Yaqui, in Sonora, Mexico, is discussion above pertaining to samples from Arizona, they found a discrete, under the Service’s DPS policy, discreteness, represents several hundred ‘‘continuum of genetic similarity’’ in from the Mojave and Sinaloan desert miles of occupied habitat spanning genetic samples taken from desert tortoise populations. We base this across an international border. This tortoises from the Hermosillo area of conclusion on ecological (habitat use), population segment is confined by two Sonora, Mexico, 528 mi (850 km) physiological (reproductive large perennial rivers: The Colorado northwest to the Kingman, Arizona area characteristics), morphological (shell River in its northern periphery when they compared genetic data with dimensions), and behavioral (seasonal (separating the Mojave and Sonoran previously collected samples from activity patterns) differences that are populations), and the Rı´o Yaqui at its Arizona (Edwards et al. 2009, p. 8). This further supported by analysis of genetic southern periphery (separating the confirms the similar genetic differences that concluded significant Sonoran and Sinaloan populations). relationships of Sonoran desert tortoises divergence has occurred among the These two rivers represent significant throughout the DPS. Genetic samples three populations. biogeographical barriers to genetic from the Ciudad Obrego´n region, exchange between adjacent population southward, showed clear genetic Significance segments and, therefore, preclude distinction and supported prior If a population segment is considered recolonization of this expanse of habitat evidence for a third distinct population discrete under one or more of the from adjacent populations, should the of desert tortoise, referred to as the conditions described in the Service’s Sonoran population of the desert Sinaloan population (Edwards et al. DPS policy, its biological and ecological tortoise become extirpated. Thus, the 2009, p. 8). The southern limits of desert significance will be considered in light loss of the Sonoran desert tortoise tortoise distribution in northern Sinaloa of Congressional guidance that the would constitute a significant gap of several hundred miles in the range are likely influenced by the growth of authority to list DPSs be used between the Mojave and Sinaloan disease-causing bacteria and fungi ‘‘sparingly’’ while encouraging the populations of desert tortoises, and may present in the soil of burrows, conservation of genetic diversity. In constitute as much as 40 percent of the exacerbated by the hot, humid, and wet making this determination, we consider total range occupied by desert tortoises conditions during tropical summer available scientific evidence of the as a whole, rangewide, which affirms its rainy seasons (Van Devender 2002b, p. discrete population segment’s 43). significance to the entire species. importance to the taxon to which it In addition, our evaluation of Evaluation of Discreteness belongs. Since precise circumstances are discreetness above found extensive Some biological similarities do exist likely to vary considerably from case to scientific support concluding that the among the three populations of desert case, the DPS policy does not describe Sonoran desert tortoise differs tortoise (Mojave, Sonoran, and all the classes of information that might significantly in its behavior Sinaloan). For example, some overlap in be used in determining the biological (reproduction, seasonal activity), habitat use occurs. It is well known that and ecological importance of a discrete ecology (habitat use and burrow Sonoran desert tortoises generally occur population. However, the DPS policy construction), morphology (physical on steep, rocky slopes and bajadas in describes four possible classes of characteristics), and genetics from either contrast to the Mojave desert tortoise, information that provide evidence of a the Sinaloan or the Mojave populations. which occurs primarily along the valley population segment’s biological and Because of these distinctions, the loss of bottoms. But to a lesser extent, Sonoran ecological importance to the taxon to the Sonoran desert tortoise population desert tortoises also use valley bottoms which it belongs. As specified in the would result in the permanent loss of a and Mojave desert tortoises also use DPS policy (61 FR 4722), this unique biological entity and would steep slopes and mountain bajadas consideration of the population diminish the natural variation within (Gardner and Brodie 2000, p. 51; segment’s significance may include, but the species as a whole. Averill-Murray and Averill-Murray is not limited to, the following: 2002, p. 16; Lutz et al. 2005, p. 22; (1) Persistence of the discrete Evaluation of Significance Grandmaison et al. in press, p. 4; Riedle population segment in an ecological We have reviewed the best available et al. 2008, p. 418). However, there are setting unusual or unique to the taxon; commercial and scientific data, and many more numerous and convincing (2) Evidence that loss of the discrete based on that review, we find that the data in the scientific literature to population segment would result in a Sonoran desert tortoise is significant to support the discreteness of the three significant gap in the range of a taxon; the continued existence of the taxon. recognized populations of Gopherus (3) Evidence that the discrete We base this conclusion on: (1) The agassizii, including differences in their population segment represents the only large geographic range of the Sonoran ecology, behavior, morphology, surviving natural occurrence of a taxon population, which is significant physiology, and genetics (Weinstein and that may be more abundant elsewhere as (approximately 40 percent) to the taxon Berry 1987, pp. 26–28; Germano 1993, an introduced population outside its as a whole; (2) a gap of several hundred pp. 324–325; Germano et al. 1994, p. 82; historic range; or miles that would result from the loss of AGFD 2001, p. 1; Averill-Murray 2002b, (4) Evidence that the discrete the Sonoran population, which would pp. 299–300; Berry et al. 2002a, p. 259; population segment differs markedly effectively bisect the species’ range; and

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(3) the behavioral, ecological, physical, in section 4(a)(1) of the Act is discussed a region that largely evolved in the and genetic distinctions among the three below. absence of invasive nonnative plants. desert tortoise populations. In considering what factors might These ecosystem-level changes cause constitute threats to a species, we must both direct and indirect effects on the Determination of Distinct Population look beyond the exposure of the species Sonoran desert tortoise and its habitat. Segment to a particular factor to evaluate whether Much of the available research on the Based on our review of the best the species may respond to that factor effects of nonnative plant species commercial and scientific information in a way that causes actual impacts to invasions and wildfire used in our available, the Sonoran population of the species. If there is exposure to a analysis has focused on Mojave desert tortoise is discrete from the factor and the species responds desertscrub habitats, largely due to the Mojave and Sinaloan populations and negatively, the factor may be a threat presence of the Mojave desert tortoise, significant to the species as a whole. As and, during the status review, we which is already listed as endangered. a result, we have determined that the attempt to determine how significant a However, Brooks and Matchett (2006, p. Sonoran population of desert tortoise threat it is. The threat is significant if it 158) suggest that research from the qualifies as a DPS and a listable entity drives, or contributes to, the risk of Mojave Desert is applicable to the under the Act. extinction of the species such that the Sonoran Desert when stating, ‘‘Both In the August 23, 2009, 90-day finding species warrants listing as endangered (Mojave and Sonoran deserts) occur at (74 FR 44335), we discussed a local or threatened as those terms are defined elevations above the hyperarid population of Mojave-genotype in the Act. However, the identification shrublands, are often positioned on the (genotype: genetic code) desert tortoises of factors that could impact a species lower slopes of mountain ranges, and (that also share Mojave phenotype (the negatively may not be sufficient to possess moderate woody plant cover.’’ physically-expressed genetic code) and compel a finding that the species Therefore, we used the information habitat-use characteristics with the warrants listing. The information must available from research on Mojave Mojave desert tortoise population) include evidence sufficient to suggest Desert habitats in our assessment of the occurring within the delineated Sonoran that these factors are operative threats effects of nonnative plants in the population in the Black Mountains area that act on the species to the point that Sonoran Desert. of western Mohave County, Arizona. the species may meet the definition of Nonnative perennial plants like This population is isolated from the endangered or threatened under the Act. buffelgrass, fountain grass, and threatened Mojave DPS that occurs In our review of the best scientific and Lehmann lovegrass were historically north and west of the Colorado River. commercial data available, we found introduced to the Sonoran Desert of The exact geographic extent of this numerous threats are impacting Sonoran Arizona as livestock forage and to Mojave-genotype in Arizona is currently desert tortoises or their habitat prevent soil erosion. For example, undefined and we expect there is throughout their range. Some of these buffelgrass was included in the interbreeding between desert tortoises threats occurred historically, some are nonnative plant species recommended with the Mojave and Sonoran genotype current, and some will continue into the for release by the Tucson Plant along the periphery of this population foreseeable future. As described in Materials Center of the Soil in the Black Mountains. Therefore, we detail below, these threats include Conservation Service until at least 1987 include this population of desert nonnative plant species and altered fire (Bahr 1991, p. 156). These nonnative tortoises as part of our status assessment regimes, urban and agricultural plant species subsequently became for the Sonoran desert tortoise in this development, barriers to dispersal and common and widespread in Sonoran finding. genetic exchange, off-highway vehicles, desertscrub in Arizona (Brooks and roads and highways, ironwood and Pyke 2001, p. 5). They have since Distinct Population Segment Five- colonized new areas, often taking Factor Analysis mesquite tree harvest, improper livestock grazing, undocumented advantage of disturbed soils, such as Section 4 of the Act (16 U.S.C. 1533) human immigration, illegal collection, those resulting from construction associated with roadways, power lines, and implementing regulations (50 CFR effects from field research and and railroad tracks (Bahre 1991, p. 155; part 424) set forth procedures for adding manipulation, predation from feral dogs, D’Antonio and Vitousek 1992, p. 65). species to, removing species from, or human depredation and vandalism, Construction and maintenance of roads reclassifying species on the Federal drought, and climate change. The effect and highways can also significantly Lists of Endangered and Threatened of habitat disturbances on Sonoran enhance the likelihood of nonnative Wildlife and Plants. Under section desert tortoises may differ among age plant invasions by increasing nitrogen 4(a)(1) of the Act, a species may be classes, but may be most significant to deposition in the soil, the dispersal determined to be endangered or hatchlings or juveniles (Tracy et al. potential of nonnative seeds, and threatened based on any of the 2006b, pp. 271–272). following five factors: adjacent soil moisture (Brooks 2007, pp. (A) The present or threatened Factor A. The Present or Threatened 153–154). Roadside ditches along destruction, modification, or Destruction, Modification, or highways are particularly important curtailment of its habitat or range; Curtailment of Its Habitat or Range. dispersal corridors for nonnative plant (B) Overutilization for commercial, species such as red brome and Nonnative Plant Species and Altered buffelgrass (Esque et al. 2002, p. 313). recreational, scientific, or educational Fire Regimes purposes; Mechanisms that allow the spread of (C) Disease or predation; The most significant modification to nonnative species generally pertain to (D) The inadequacy of existing Sonoran desert tortoise habitat is ground disturbance, but the plants may regulatory mechanisms; or associated with the ongoing invasion of also be spread by other mechanisms. For (E) Other natural or manmade factors nonnative plants in Mojave and Sonoran example, Smith et al. (2000, pp. 79–80), affecting its continued existence. desertscrub habitats, permanently and Brooks and Esque (2002, p. 337) In making this finding, information altering these ecosystems and causing a both found that elevated atmospheric pertaining to the Sonoran desert tortoise change in the frequency, duration, carbon dioxide levels, predicted as a in relation to the five factors provided intensity, and magnitude of wildfires in result of climate change (discussed in

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Factor E below), are likely to favor mustard (Brassica tournefortii), thistles Mohave, Yavapai, Gila, Pinal, and nonnative plant species, such as red (genera Centaurea and Cirsium), Cochise Counties (A–I, pp. 15, 28–30); brome, over native species in crimson fountaingrass (Pennisetum (6) Bull thistle (Cirsium vulgare) is desertscrub habitats. Increases in setaceum), natal grass (Melinus repens), one of the top 20 invasive plant species, atmospheric nitrogen deposition may and Lehmann lovegrass (Eragrostis at 3.1 percent of total reports, with 1,195 also be advantageous to nonnative plant lehmanniana) (Brooks 2001, p. 4; reports (p. 3); it reaches moderate species. Brooks (2003, pp. 344–345) Brooks and Pyke 2001, pp. 3, 5). densities in Yavapai and Gila Counties suspected that increasing human We are not aware of any good (A–I, p. 35); populations will lead to increased levels estimates of the number of acres of (7) Crimson fountaingrass is one of of atmospheric pollution and nitrogen desertscrub that have been invaded by the top 20 invasive plant species, at 2.6 deposition and stated, ‘‘Increased levels nonnative plant species, but Thomas percent of total reports, with 999 reports of soil nitrogen caused by atmospheric and Guertin (2007, Appendices I and II) (p. 3); it reaches high densities in Pima nitrogen deposition may increase the calculated the number of records by County, with moderate densities in dominance of invasive alien plants and county for many known invasive, Yavapai, Gila, La Paz, Santa Cruz, and decrease the diversity of (native) plant nonnative plants in Arizona that are Maricopa Counties (A–I, p. 61); and communities in desert regions, as it has harmful to Sonoran desert tortoise (8) Lehman lovegrass is one of the top in other ecosystems.’’ Sonoran desert habitat. These data illustrate general 20 invasive plant species, at 2.5 percent tortoise habitat may be particularly locations where certain nonnative of total reports, with 980 reports (p. 3); vulnerable to even minor increases in species are most common and describe it reaches high densities in Pima and soil nitrogen levels, because the ratio of which nonnative species are the most Cochise Counties, with moderate densities in Yavapai, Gila, Santa Cruz, increased nitrogen to plant biomass is reported in each area. Thomas and Maricopa, and Pinal Counties, but also higher compared with that of most other Guertin (2007, Appendices I and II) ecosystems (Brooks 2003, p. 344). This occurs in La Paz County (A–I, p. 45). reported the following for Arizona as of No spatial data were provided for suggests that even small changes in 2007 (relative number of reports of natal grass, but there were 191 nitrogen levels could result in ‘‘ ’’ ‘‘ ’’ densities being extremely high, high, observations (Thomas and Guertin 2007, ‘‘ ’’ ‘‘ ’’ substantial changes in the plant moderate, and occurs, all within the p. 10). community that supports Sonoran distribution of the Sonoran desert Buffelgrass has widely invaded desert tortoise habitat. tortoise): Arizona and northern Mexico since its The prevalence of nonnative grasses (1) Buffelgrass is the most-reported introduction in 1939 (Stevens and in many areas of Sonoran desertscrub nonnative plant species in Arizona, at Fehmi 2009, p. 379). While buffelgrass habitats has resulted in high amounts of 16.3 percent of total reports with 6,287 invasions are occurring and are poised flammable fuels in interspaces between reports (p. 3); it reaches extremely high to seriously impact the southwestern native plants that would otherwise be densities in Maricopa and Pima United States, the species has already free of vegetation. This situation serves Counties, with high densities in Pinal exacted significant tolls on Sonoran to promote the ignition and carrying of and Yuma Counties and moderate desertscrub communities in Sonora, wildfire (Brooks 1999, p. 13). In our densities in Santa Cruz and La Paz Mexico, because its expansion review of the best scientific data Counties, but it also occurs in Yavapai, continues to be facilitated through available, red brome, splitgrass (or Gila, and Cochise Counties (A–I, p. 60); intentional plantings and cultivation. Mediterranean grass, Schismus spp.), (2) Schismus spp. is one of the top 20 Consequently, the clearing of Sonoran and buffelgrass were considered the invasive plant species, at 2.4 percent of desertscrub and Sinaloan thornscrub in nonnative plant species that pose the total reports, with 919 reports (p. 3); it Sonora to plant pastures of buffelgrass greatest concern to the Sonoran desert reaches high densities in Maricopa, for livestock grazing creates a near tortoise and its habitat, because they are Pinal, and Pima Counties, with monoculture (area covered by a single thoroughly integrated into some areas of moderate densities in Mohave, Yavapai, plant species) that is highly prone to the desertscrub communities, and serve Gila, La Paz, and Yuma Counties, but it wildfires, and therefore represents a to promote and carry wildfire (Bahre also occurs in Santa Cruz County (A–I, substantial threat to the Sonoran desert 1991, p. 155; D’Antonio and Vitousek p. 69); tortoise in Mexico (Bury et al. 2002, p. 1992, pp. 65, 75; Brooks 1999, p. 13; (3) Red brome is one of the top 20 104; Walker and Pavlakovich-Kochi Brooks and Pyke 2001, p. 5; Brooks and invasive plant species, at 3 percent of 2003, p. 14; Van Devender and Reina Esque 2002, p. 337; Esque et al. 2002, total reports, with 1,152 reports (p. 3); 2005, pp. 160–161; University of p. 313; Van Devender 2002a, p. 16; it reaches high densities in Yavapai, Arizona 2010, p. 2). Buffelgrass has been Brooks and Matchett 2006, p. 148; Gila, Pinal, and Pima Counties, with planted in Sonora’s desertscrub lands DeFalco 2007a, p. 1; Zouhar et al. 2008, moderate densities in Mohave and since the 1950s and at least 5.5 million p. 157; Abella 2010, p. 1249; AGFD Maricopa Counties, but it also occurs in ac (2.2 million ha) of potential Sonoran 2010, p. 13). Red brome is known to La Paz and Yuma Counties (A–I, p. 24); desert tortoise habitat has already been carry wildfire in Sonoran desertscrub (4) Saharan mustard is one of the top converted into a near monoculture of habitat north of Tucson, natal grass is 20 invasive plant species, at 3.3 percent buffelgrass (Stoleson et al. 2005, p. 62). known to carry wildfire in desert of total reports, with 1,261 reports (p. 3); Buffelgrass has become established in grassland habitat south of Tucson to it reaches high densities in Maricopa, both the lower valley habitats and into Nogales, Arizona, and buffelgrass is Pinal, Pima, La Paz, and Yuma the granite boulder-strewn areas of known to carry wildfire in Sonoran Counties, with moderate densities in adjacent foothills, and has altered desertscrub and foothills thornscrub Mohave, Yavapai, and Gila Counties, historical fire regimes, regionally south of the international border to but it also occurs in Cochise County (A– converting large areas of Sonoran central Sonora (Esque et al. 2002, p. I, p. 21); desertscrub into habitat resembling the 316). Other nonnative plant species (5) Centaurea spp. had a total of 3– African savannah (Bury et al. 2002, p. identified in the literature as present in 318 reports (depending on species) (p. 104). Sonoran and Mojave desertscrub 9) and reaches high densities in Pima In Arizona, the Southern Arizona communities include Saharan (or Asian) County, with moderate densities in Buffelgrass Coordination Center

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(SABCC, a coalition of non-profit common from human sources such as number of fire starts has a greater organizations, Federal, State, and local burning trash, parking vehicles over dry potential of creating larger and more governments, conservation vegetation, fireworks, discarded destructive wildfires, especially where organizations, private businesses, and cigarettes, and accidental starts from they occur in remote, inaccessible areas individual citizens) reports dense stands backcountry recreationists (Esque et al. as a result of lightning strikes. of buffelgrass on public reserves, State 2002, p. 313). Human-caused wildfires Indirect effects of wildfires on and local lands, and private property, in desertscrub habitat are most common Sonoran desert tortoises are variable and including Saguaro National Park, near urban developments, major can be significant, including habitat Coronado National Forest, Bureau of roadways, and in areas where off- changes such as altered nutrient Land Management’s (BLM) Ironwood highway vehicle use is unregulated, availability and quality, loss of Forest National Monument, while lightning-caused wildfire in perennial plant species that are neighborhoods of Tucson, Sahuarita, desertscrub is typically located in more important as temporary cover from Marana and Oro Valley, and along remote wilderness areas (Brooks 1999, predators, loss of thermal refugia, roadsides throughout this region of p. 13). In central Sonora, ranchers altered tortoise behavior, shifts in biotic Arizona (SABCC 2010, p. 1) These areas intentionally set fires to maintain the community, pronounced desert tortoise are all within the distribution of the vigor of buffelgrass for livestock forage emigration from burned habitat, and Sonoran desert tortoise in Arizona. (Esque et al. 2002, p. 313). lower growth and reproductive output Brooks and Minnich (2006, p. 9) Numerous wildfires, varying in size, (Esque et al. 2003, p. 107; DeFalco 2006, stated that southwestern desert have occurred in recent times in many p. 5; McLuckie et al. 2007, p. 8). While ecosystems likely evolved in a fire areas throughout the Sonoran Desert a single fire in an area may or may not regime best described by ‘‘low intensity, including the: (1) Fire of produce long-term reductions in plant patchy burns and long fire return 1987 on the southern slopes of the Santa cover or biomass, repeated wildfires in intervals.’’ Wildfire capable of carrying Catalina Mountains; (2) Skyline (1992) a given area are capable of ecosystem itself in Sonoran desertscrub is a recent and Rock Peak (1993) fires in the San type-conversion from native desertscrub phenomenon in evolutionary and Tan Mountains; (3) Mother’s Day Fire of to nonnative annual grassland, and geological contexts and only became 1994 on the eastern slope of the Rincon render the area unsuitable for desert apparent recently in the Sonoran Desert Mountains (Esque et al. 2002, p. 323; tortoises (Brooks and Esque 2002, p. (Brooks and Pyke 2001, p. 5; Esque et 2003, p. 104); and (4) Cave Creek 336). Increased frequency in wildfires al. 2002, p. 312; Zouhar et al. 2008, pp. Complex fire of 2005 northeast of Cave caused by nonnative plant species 155, 160). From 1937 to 1986, only 1 Creek, Arizona, which burned 248,310 invasion increases light intensity at percent of all lightning-caused fires in ac (100,487 ha) of Sonoran desert ground level and soil nutrient the Rincon Mountains area of southern tortoise habitat; the largest wildfire ever availability, and reduces competition Arizona occurred in desertscrub habitat; recorded in Sonoran desertscrub in the from native perennial plants. These 5.6 percent occurred in desert grassland United States. changes further promote dominance by habitat (Bahre 1991, p. 126). While The BLM has kept records of wildfire nonnative plant species (Brooks and historical wildfires in desertscrub in Sonoran desert tortoise habitat. From D’Antonio 2003, p. 29). Wildfire in habitat were exceptionally rare, after 1990 to 2008, there have been 61 desertscrub habitats can reduce native successive years of above-average levels wildfires, affecting 21,977 ac (8,894 ha) and nonnative seed banks (Brooks and of precipitation, enough native fuels can in Category I Sonoran desert tortoise Draper 2006, p. 2). In Mojave develop to carry wildfire in desertscrub habitat; 285 wildfires, affecting 33,364 desertscrub, the effects of fire are most communities, such as happened south ac (13,502 ha) in Category II Sonoran pronounced under shrubs, where fire of Florence, Arizona in 1979 (Bahre desert tortoise habitat; and 508 can kill seed banks and reduce annual 1991, p. 141; Brooks and Esque 2002, p. wildfires, affecting 109,460 ac (44, 297 grass diversity, due to higher burn 336; Brooks and Minnich 2006, p. 9). ha) in Category III Sonoran desert intensity (Brooks 2002a, p. 1; 2002b, p. While increased precipitation enhances tortoise habitat (USBLM 2010, p. 9). In 1088). Microhabitat associated with plant growth and subsequently total, during the 1990–2008 period, shrubs in Sonoran desert tortoise habitat increases the likelihood for wildfire 164,801 ac (66,693 ha) of categorized is an important source of temporary starts in desertscrub habitat, drought and uncategorized Sonoran desert shelter and provides foraging can have an inverse effect with respect tortoise habitat has burned on BLM opportunities while tortoises are to certain nonnative plant species. Red lands (USBLM 2010, p. 9). Combining thermoregulating. brome, for example, is sensitive to the known area of habitat affected by Fires associated with nonnative plant drought conditions and, therefore, might fire on both BLM and other lands, an species have already affected Sonoran contribute to reduced fuel loads and estimated 1.5 percent of habitat in desert tortoise populations in Arizona. decreased fire frequency during long- Arizona has been adversely affected due The AGFD (2010, p. 13) reported results term drought (Brooks and Esque 2002, to wildfire in recent years; rangewide from an unpublished study after the p. 337), which might help to minimize this is estimated to be 0.8 percent, Edge Complex Fire of 2005 in the Four the likelihood of wildfires in areas although total acreage data on wildfires Peaks area on the Tonto National Forest, where red brome has formed a in Mexico are unknown and the total which indicated higher numbers of monoculture. Smith et al. (2000, p. 79) percentage of affected habitat is likely Sonoran desert tortoises (or their scat noted, ‘‘This shift in species higher because of the higher incidence were observed in unburned versus composition in favor of exotic annual of buffelgrass and lessened capacity to burned habitat), but they acknowledged grasses, driven by global [climate] fight wildfire in Sonora, Mexico. The that the study was preliminary and very change, has the potential to accelerate total area reported as burned is a limited in scope (AGFD 2010, p. 13). the fire cycle, reduce biodiversity and relatively small proportion of BLM In Sonora, Mexico, 5.5 million ac (2.2 alter ecosystem function in the deserts lands and has not likely been a million ha), representing an estimated of western North America.’’ significant impact to most Sonoran 22 percent of Sonoran desert habitat in Wildfire ignitions in the Sonoran desert tortoise populations in Arizona Mexico, or 11 percent rangewide, has Desert region historically resulted from so far. As the invasion of nonnative been planted to bufflegrass. This figure lightning but ignitions are now more plants continues to expand, the high still does not account for the land area

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where buffelgrass has become naturally ground or in shelter during a fire, become established. Mechanical established or the 11.9 million ac (4.8 weather, fire behavior, and shelter depth removal is one option that has been million ha) (or one-third of the land area (McLuckie et al. 2007, p. 8). The desert implemented on a small scale in some of the state of Sonora) that are suitable tortoise is most vulnerable to the direct areas, but is extremely labor intensive for future natural establishment of effects of wildfire when they are surface and not practical for treating large areas. buffelgrass (Stoleson et al. 2005, p. 62). active and away from primary cover Prescribed fire has been proposed as an Combining the current and predicted sites such as burrows, caliche caves, and alternative means to control nonnative number of acres converted to buffelgrass rock shelters, because these structures plant species invasions, but also carries in Mexico, 34 percent of the Sonoran reduce direct exposure to heat and obvious inherent risks to habitat and to desert tortoises’ habitat is lost or at risk smoke (Brooks and Esque 2002, p. 335). Sonoran desert tortoises (Brooks 2006, across its range. In the area of El Gravid (with fertilized eggs) female p. 31). Batamote, 29 mi (47 km) north of Sonoran desert tortoises may be more It is also important to note the Hermosillo, Sonora, buffelgrass has likely to perish from wildfire than other limitations of Sonoran desert habitat invaded Sonoran desert tortoise habitat tortoises because peak wildfire season with respect to post-disturbance (for in the adjacent foothills, which has led in Sonoran desertscrub occurs during example, after fires) regeneration (ability to wildfires that burned so hot that the the months of May and June. This is for native vegetation to recover). soil was scorched and the bedrock when reproductive females are actively Desertscrub regions receive low annual cracked (Esque et al. 2002, p. 321). foraging on spring growth to precipitation totals, and the plant In addition to impacts from fire, compensate for energy used in egg communities have correspondingly low Franklin and Molina-Freaner (in press, development; (Esque et al. 2002, pp. growth rates. Based on the type of p. 1) found that these large-scale 323–324; 2003, p. 106). disturbance, recovery time estimates conversions from desertscrub to Sonoran desert tortoises that survive range from 40 years to centuries (Abella grasslands in Sonora have reduced plant the wildfire itself may struggle to 2010, pp. 1271, 1273). Combined, these species richness by half, and reduced survive in post-burned Sonoran factors result in slow, post-disturbance tree and shrub cover by 78 percent, desertscrub habitat due to: (1) A recovery periods and it may take a long vastly affecting the ability of Sonoran reduction in forage and shade structure, time before any area becomes suitable desert habitat to meet the species’ such as packrat (Neotoma sp.) middens for Sonoran desert tortoises to thermoregulatory needs (that is, using and shrubs; and (2) increased visibility recolonize, if at all. The presence of vegetation as cover to regulate body to predators (which may be further nonnative species such as buffelgrass, temperature). These changes have increased in intermountain valleys cheatgrass, or red brome in disturbed resulted in substantial changes in where temporary shade, predator Mojave or Sonoran desertscrub may primary productivity (creation of avoidance, and available forage are further limit post-disturbance recovery, organic nutrients and the lowest level of particularly important in long-distance delay recovery, or prevent recovery the food chain, the plant community) movements in these dispersal corridors) altogether (Brown and Minnich 1986, p. and vegetation structure (the physical (Esque et al. 2002, pp. 325–326). 411; Brooks 1999, p. 18). structure of plant sizes and shapes as a The effects on Sonoran desert In our review of the best available mosaic on the landscape) which can tortoises of one particular fire were information, we have documented that affect the forage base and habitat studied in some detail. Within Saguaro nonnative plant species pose a suitability for Sonoran desert tortoises, National Park, the Mother’s Day Fire of significant threat to the Sonoran desert as well as lessened the feasibility of 1994 burned 340 ac (138 ha) of Arizona tortoise and its habitat, both in Arizona restoring native plant communities in Upland Sonoran desertscrub habitat that and Sonora, by promoting and carrying Sonora without aggressive land was occupied by Sonoran desert wildfire in an ecosystem that evolved in management (Franklin and Molina- tortoises, killing an estimated 11 percent its absence. Wildfires that are facilitated Freaner, in press, p. 1). Dense stands of of the tortoise population (Esque et al. by nonnative plant species invasions buffelgrass have also been shown to 2003, p. 105). To assess how Sonoran may have direct and indirect adverse physically disrupt tortoise movements desert tortoises used burned versus effects on tortoises and tortoise in the closely related Texas tortoises unburned habitat following this fire, populations. The threat from nonnative (Gopherus berlandieri) (Fujii and transmitters were attached to 12 plant species to the Sonoran desert Forstner 2010, p. 61), so this may also tortoises, 6 each in burned and tortoise occurs throughout the species’ be true for Sonoran desert tortoises. The unburned habitat within or adjacent to range and is expected to increase over grass can become so thick that the the Mother’s Day Fire footprint. time with the expansion of nonnative tortoises cannot walk through it, and the Surprisingly, no differences were plants. There is currently no viable grass may be too tall for the tortoises to observed in movement or activity solution to curbing this continued walk on top of it. patterns between tortoises in burned expansion across the landscape. This In addition to damaging Mojave and and unburned areas, nor were long-term threat also acts synergistically with Sonoran desertscrub habitat, wildfires effects of the fire on surviving tortoises other threats discussed in this finding. can directly injure and kill Sonoran noted over the 6-year study period desert tortoises. Wildfire may kill a (Zylstra and Swann 2009, p. 7). These Urban Development and Agriculture desert tortoise by incineration, by results indicate that different tortoise Human population growth results in elevating body temperature, by populations may respond differently to the disturbance or loss of Sonoran poisoning from smoke inhalation, or by wildfires and that numerous variables desertscrub or the conversion of land for asphyxiation (Brooks et al. 1999, p. 40; and factors are at work. urban and agricultural development. Brooks and Esque 2002, p. 335; One of the principal reasons that Arizona increased its population by 394 McLuckie et al. 2007, p. 7). Survival nonnative plants pose a significant percent from 1960 to 2000, and was rates of Sonoran desert tortoises may be impact to Sonoran desert tortoise habitat second only to Nevada as the fastest contingent upon several factors, is because few, if any, reasonable growing State during this timeframe including soil type, substrate, methods currently exist to control the (Social Science Data Analysis Network vegetation, tortoise activity during fire, ongoing invasion of these plants or to (SSDAN) 2000, p. 1). Since 1990, whether tortoises are active and above remediate areas where they have Arizona’s population has grown by 44

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percent. From 1960 to 2000, population Nogales, through Tucson, Phoenix, and people will one day live in this growth rates in Arizona counties where north into Yavapai County (called the development (Pinal County the Sonoran desert tortoise occurs have Sun Corridor ‘‘Megapolitan’’) is Comprehensive Plan 2009, p. 115). The varied by county but are no less predicted to have 8 million people by loss of 176,000 ac (71,225 ha) remarkable, and all are increasing: 2030, an 82.5 percent increase from constitutes a loss of 0.7 percent of Maricopa (463 percent); Pima (318 2000 (Gammage et al. 2008, pp. 15, 22– Sonoran desert tortoise habitat in percent); Pinal (54 percent); Santa Cruz 23). If build-out occurs as expected, it Arizona; rangewide, 0.34 percent. The (355 percent); Cochise (214 percent); will encompass a significant proportion Pinal County Comprehensive Plan Yavapai (579 percent); Gila (199 of the Sonoran desert tortoise (2009, p. 117) identifies many miles of percent); Graham (238 percent); Yuma distribution in Arizona, and will in new freeways and principal arterials in (346 percent); LaPaz (142 percent); and effect permanently isolate Sonoran the analysis area at build-out, which the Mohave (2,004 percent) (see SSDAN desert tortoise populations that occur on plan acknowledges may take over a half 2000). The population of Phoenix, either side of the Interstate 19, Interstate century to realize (Pinal County Arizona, grew 67 percent from 1980 to 10, and Interstate 17 corridors. Comprehensive Plan 2009, p. 115). The 2000 (Berry et al. 2006, p. 7). The land area permanently altered by effect of roads on Sonoran desert Urban expansion and human human activities from urban tortoises is discussed below. population growth trends in Arizona are development and agriculture has grown Additionally, the Maricopa County expected to continue into the future. to 13 percent of all land in the western Comprehensive Plan calls for growth Maricopa-Pima-Pinal county areas of United States, Lue et al. (2008, p. 1130). areas to the south and east of Chandler Arizona are expected to grow by as Lue et al. (2008, p. 1133) concluded that and Mesa, Arizona, which are within much as 71 percent in the next 15 years, in low-productivity habitat, such as the range of the Sonoran desert tortoise creating rural-urban edge effects across desertscrub habitats, slight human (Maricopa County Comprehensive Plan millions of acres of public lands disturbances can have pronounced 2002 (revised), p. 92). City currently supporting Sonoran desert effects. Significant urban development comprehensive plans within the range tortoise populations (AIDTT 2000, p. 10; occurs within intermountain valleys, of the Sonoran desert tortoise also call BLM files—Lands Livability Initiative). within or adjacent to occupied Sonoran for future growth areas. For example, In another projection, the population in desert tortoise habitat, which increases the City of Eloy has designated six such Arizona is expected to more than double the likelihood of effects along the rural- areas encompassing 15,520 ac (6,281 within the next 20 years compared to urban interface, and may also inhibit ha), mostly along the Interstate 10 the 2000 population estimate (U.S. movement of individuals between corridor (City of Eloy General Plan 2004, Census Bureau 2005, p. 1). Many cities populations on nearby hillsides or pp. 7–6 through 7–10). The loss of and towns within the distribution of the mountain ranges. Disturbances to 15,520 ac (6,281 ha) constitutes a loss of Sonoran desert tortoise have already Sonoran desert tortoise habitat on the 0.06 percent of their habitat in Arizona; experienced substantial growth during landscape can take many forms and rangewide, 0.03 percent. While much of the 8-year time span, 2000–2008: City of cover extreme distances. Roads, canals, this area has already been impacted by Avondale (118.3 percent); City of pipelines, and railroad tracks are development or irrigated agriculture, Buckeye (392.5 percent); Bullhead City examples of linear habitat destruction. any remaining dispersal habitat for the (20.3 percent), Town of Carefree (30.5 We discuss the potential effects of linear Sonoran desert tortoise will likely be percent); Casa Grande (56 percent); disturbances below in the section titled, negatively affected as development and Town of Cave Creek (44.2 percent); City ‘‘Development as a Barrier.’’ its associated infrastructure progress of Chandler (37.5 percent); City of Development pressure across Arizona into these areas. Coolidge (24.9 percent); City of El has slowed due to the recent economic Much of the past and projected Mirage (195.6 percent); City of Eloy downturn and decline in the housing development within the range of the (22.3 percent); City of Florence (20.3 market. However, development will Sonoran desert tortoise in central and percent); Town of Fountain Hills (23.2 likely continue in the future, although southwestern Arizona has occurred and percent); City of Gilbert (84.5 percent); perhaps at a slower pace than in the is expected to continue as a conversion City of Goodyear (203 percent); City of earlier part of this century. We also from agricultural uses to municipal Kingman (32.2 percent); Lake Havasu recognize that economic trends are uses. Land traditionally used for City (33.3 percent); City of Litchfield difficult to predict into the future. The agriculture is not occupied by Sonoran Park (34.2 percent); City of Mammoth most recent draft Pinal County desert tortoises, but has a comparatively (45 percent); Town of Marana (139.9 Comprehensive Plan (February 2009) minor effect on adjacent Sonoran desert percent); City of Maricopa (2,508 acknowledges that the county is in the tortoises. When these lands are percent); Town of Oro Valley (32.5 middle of the Sun Corridor Megapolitan converted to municipal uses, the effect percent); Town of Queen Creek (544.5 and proposes four shorter-term growth to adjacent Sonoran desert tortoise percent); Town of Saguarita (507.3 areas in defining where development populations increases human access, percent); City of San Luis (58.5 percent); will likely occur, or be encouraged to and use of adjacent undeveloped land City of Somerton (63.2 percent); City of develop, over the next decade, but does increases as a result of development of Surprise (187.3 percent); City of not discourage growth outside of these these former agricultural areas. Tolleson (43.2 percent); and, Town of areas (Pinal County Comprehensive The human population of Sonora, Youngtown (62.2 percent) (U.S. Census Plan 2009, p. 109). These four growth Mexico, doubled in size from 1970 (1.1 Bureau 2008, pp. 1–4). areas (Gateway/Superstition Vistas, million) to 2000 (2.2 million) (Stoleson This population growth has spurred a West Pinal, Red Rock, and Tri- et al. 2005, p. 54). The population of significant increase in urbanization and Communities) fall completely within Sonora is expected to increase by 23 development in these areas. Regional the range of the Sonoran desert tortoise. percent, to 2.7 million people, in 2020 development is predicted to be extreme The Gateway/Superstition Vistas growth (Stoleson et al. 2005, p. 54). In in certain areas within the distribution area alone encompasses 176,000 ac discussing threats to Sonoran desert of the Sonoran desert tortoise in (71,225 ha), or 275 sq mi (712 sq km), tortoise populations adjacent to, and Arizona. In particular, a wide swath of State Trust land, and it is anticipated stemming from, urbanization in Sonora, from the international border in that 800,000 to more than 1 million Mexico, Fritts and Jennings (1994, p. 53)

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stated, ‘‘Tortoise populations adjacent to lands (AGFD 2010, p. 7). A development ‘‘* * * as urbanization continues to large population centers such as consisting of 48,000 single family expand, (Sonoran desert tortoise) habitat Hermosillo, Guaymas, and Caborca homes, south of the Colorado River in will continue to be lost.’’ In a Global probably have experienced long-term western Mohave County, is also Information System exercise, we harm, including direct human currently being planned (THS 2009, p. calculated that currently, 75 percent of exploitation, habitat degradation, road 4; Mardian 2010, p. 1). potentially occupied Sonoran desert kills, predation by domestic dogs, and Because less area is being used tortoise habitat within Arizona occurs use as pets. However, we found currently for agriculture in the United within 30 mi (48 km) (a reasonable evidence of tortoise populations on States, habitat loss due to agricultural distance a person might travel to hillsides and mountain slopes near each development is more of a historical recreate outdoors on public land) or less of these cities, which suggests that some issue. However, impacts to Sonoran of a city or town with a population of tortoise populations have survived desert tortoise dispersal habitat within 1,000 or more. As the human population despite perturbations by humans.’’ valley floors from historical agricultural of Arizona grows and development Therefore, Sonoran desert tortoises may use and wood harvesting are still expands as expected, we assume that persist as depressed populations evident. The vegetation and soils of 100 percent of Sonoran desert tortoise adjacent to urban development, but many valleys in the Sonoran Desert populations will occur within 30 mi (48 without long-term population trend data were shaped by the periodic flooding of km) or less of a city or town with a for these areas, we are unable to know dynamic wash systems, which partially population of 1,000 or more, in the for how long. recharged a shallow, fluctuating foreseeable future. Tortoise populations Urban development has been groundwater table. Because of are being increasingly exposed to identified as a concern for Sonoran agricultural development, these valleys humans and human activities, and desert tortoise conservation in several no longer experience these defining therefore to numerous threats that areas within Arizona because of the processes and there has been a would otherwise be minimized or associated increase in human-based permanent loss of meso- and nonexistent. We discuss these types of threats to populations in close xeroriparian habitat which are known to threats and how they affect Sonoran proximity. Averill-Murray and Swann be corridors for movement by Sonoran desert tortoises and their habitat below (2002, p. 1) stated that urban desert tortoises (Jackson and Comus in Factors B, C, D, and E. development adjacent to the Saguaro 1999, pp. 233, 249; Lutz et al. 2005, p. Some forms of development are likely National Park in Pima County threatens 22; Riedle et al. 2008, p. 418). to increase. The interest in renewable the Sonoran desert tortoise via several Agriculture in Sonora, Mexico, has energy projects is expected to increase mechanisms including harassment and shifted from small-scale, local markets significantly in the future. Solar predation by feral or off-leash domestic toward large-scale agro-industry, with radiation levels in the southwestern dogs, illegal releases of captive Sonoran Sonora producing 40 percent of the United States, including Arizona, are desert tortoises and exotic species that country’s total wheat crop (Stoleson et some of the highest in the world, and may transmit diseases to wild Sonoran al. 2005, p. 59). While agriculture in interest in tapping into this source of desert tortoises, elevated mortality on Sonora is largely constrained to valleys potential energy is growing. Potentially roads, and illegal collection for pets. (along the Rio Sonora), many types of significant tracts of BLM lands in Averill-Murray and Swann (2002, p. 7) habitat used by Sonoran desert tortoises southwestern Arizona have been stated that mid- to large-scale have been cleared for agriculture, identified for possible solar energy development projects on the bajadas including Sonoran desertscrub, development, encompassing large and foothills of the Rincon, Santa Rita, thornscrub, and tropical deciduous percentages of Arizona’s valley Santa Catalina, Tortolita, and Tucson forest (Stoleson et al. 2005, p. 60). In bottomland in La Paz and Yuma Mountains has likely led to area-wide 1994, the total irrigated acreage in Counties and adjacent to or within the decreases in Sonoran desert tortoise Sonora was 128,000 ac; in 2004 that foothills of the Black Mountains of populations. However, no population figure rose to 530,509 ac (214,689 ha), western Mohave County, which could estimates for Sonoran desert tortoises an increase of 314 percent (AQUASTAT isolate Sonoran desert tortoise before development of these areas exist, 2007, p. 2). This constitutes an populations and affect genetic exchange and, therefore, population responses to estimated loss of 2 percent of Sonoran among regional populations in those development of these areas cannot be desert tortoise habitat in Mexico; areas (USDOE 2009, p. 1). Since most ascertained. rangewide, 1 percent. solar projects are in the early planning In addition to the Tucson The projected growth of the human stages and have yet to be officially metropolitan area, urban encroachment population in Arizona and northern approved by the BLM, we are unable to on Sonoran desert tortoise habitat Mexico and subsequent urbanization ascertain the amount of Sonoran desert occurs adjacent to the greater Phoenix discussed above is expected to place tortoise habitat likely to be impacted. metropolitan area, in the area around onerous demands on lands where the However, we acknowledge that large South Mountain and adjacent to the Sonoran desert tortoise occurs, areas within the distribution of the (AGFD 2010, p. increasing the need for infrastructure Sonoran desert tortoise in Arizona are 7). Sonoran desert tortoises are known associated with development, such as being considered for solar projects. or suspected to still occur in 12 of the power lines, power plants, pipelines, In one example, 12,100–15,100 ac 16 Maricopa County and City of landfills, roads, sand and gravel mines, (4,897–6,110 ha) of BLM, State, and Phoenix urban mountain parks and and removal of boulders for landscaping private land containing Sonoran desert reserves. The four parks where no (AIDTT 2000, p. 10). In addition, these tortoise habitat along the southern tortoise sign has been found in recent growth projections will increase human bajada of the Black Mountains in years are completely surrounded by visitation to formerly remote Sonoran western Mohave County, Arizona, has urban development (AGFD 2010, p. 7). desert tortoise habitat as urban-rural been identified for development of the Urban development has occurred interface expands, whereby increasing Sterling Solar Generating Facility within adjacent to five monitoring plots, but human-associated threats discussed in the next 4 to 6 years (Needle Mountain only the Hualapai Foothills plot is detail below (AIDTT 2000, p. 10). The Power, LLC 2010, pp. 4, 8, 11). At build- completely surrounded by developed AGFD (2010, p. 7) concluded that out, the Sterling Solar Generating

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Facility will consist of solar fields, the increased incidence of an array of intermediate gene flow still occurs, or power blocks, buildings, retention human activities or influences such as occurred recently, among isolated ponds, rainwater catch basins, off-highway vehicle use, facilitation of populations at the rate of at least 1 evaporation ponds, wastewater and the spread of nonnative plant species migrant per generation (12–15 years) water treatment facilities, water storage via soil disturbances, and increased (Edwards et al. 2004, p. 485). However, tanks, on-site housing, a substation, a wildfire ignitions. These threats act in thousands of acres of tortoise habitat visitors center, a substation and combination with other threats have been recently lost to large switching station interconnection with discussed elsewhere in this finding, residential developments in the foothills the Western Area Power Administration including ironwood and mesquite tree of the Santa Catalina, Tortolita, Rincon, power lines, and septic tanks (Needle harvest, livestock grazing, nonnative and in the greater Mountain Power, LLC 2010, p. 11). We plants and altered fire regimes, roads Tucson metropolitan area (Edwards et expect the construction of this facility to and highways, and undocumented al. 2004, p. 485). render at least 13,100 ac (5,300 ha) of human immigration and interdiction. The importance of allowing Sonoran desert tortoise habitat as movement of individual tortoises Development as a Barrier unusable because this type of between populations is observable by construction requires the complete Urban development, canals, and evaluating historical gene flow. Edwards grading (removal of vegetation) of the transportation infrastructure, such as et al. (2004, p. 485) used seven project footprint. It could, therefore, roads and railroads, disrupt ecological microsatellite DNA markers to examine significantly affect the Black Mountains processes, increase mortality in animals, the genetic relationships of tortoises in desert tortoise population, especially in promote the degradation, loss, and eight populations in southern and consideration of other effects acting in isolation of wildlife habitat, and cause central Arizona, in the vicinity of combination with those poised from the fragmentation of populations (Spang et Tucson and Phoenix. They also proposed housing development and al. 1988, p. 9; Saunders et al. 1991, pp. calculated migration rates among these highway construction in the immediate 23–24; Averill-Murray and Klug 2000, p. populations to estimate historical rates area (THS 2009, p. 4; ADOT 2010, p. 3; 68; Seiler 2001, p. 3; Howland and of gene flow, and, therefore, the Mardian 2010, p. 1). The estimated loss Rorabaugh 2002, p. 335; Edwards et al. importance of individuals moving of 13,100 ac (5,300 ha) constitutes an 2004, p. 496). Sonoran desert tortoise between populations (Edwards et al. estimated loss of 0.05 percent of their populations are island-like in their 2004, p. 485). Edwards et al. (2004, p. habitat in Arizona; rangewide, 0.025 distribution, meaning they are generally 496) found no evidence of recent loss of percent. concentrated on the bajadas and genetic diversity that would indicate Other solar energy development and hillsides of mountains, and less- genetic bottlenecking that could occur transmission corridors pose similar distributed within the valleys between from lack of mixing among Sonoran threats to the Sonoran desert tortoise as these areas. As a result, they may be desert tortoise populations in southern development and roadway projects (see particularly vulnerable to large-scale Arizona. However, the authors discussion below). An average utility- disturbances that affect the suitability of acknowledged that a small sample size scale solar facility to generate 250 intervening habitat (Spang et al. 1988, p. and small number of genetic markers megawatts of electricity would occupy 9). Factors that affect inter-population (alleles) used in their analyses would about 1,250 ac (500 ha) of land (BLM dynamics in Sonoran desert tortoises likely not detect this genetic effect. 2009a, p. 1), and would involve removal include distance between populations, Despite reduced mixing among of all vegetation within its footprint. physical size of habitat areas, sizes of populations, Sonoran desert tortoises Additionally, concentrating solar power source populations, and the ease of may be capable of maintaining small facilities requires liquids such as oils or which intervening areas can be crossed effective population sizes (still viable molten salts to create steam to power by dispersing individuals (Howland and populations, despite small size), even conventional turbines and generators, as Rorabaugh 2002, p. 335). with a low degree of genetic diversity well as various industrial fluids, such as The effect of potential barriers to (Edwards et al. 2004, p. 496). However, hydraulic fluids, coolants, and inter-population movements of Sonoran Edwards et al. (2004, p. 496) also stated, lubricants, all of which may present a desert tortoises (discussed above in the ‘‘Because effective population sizes of contaminant risk should these fluids Species Information section) is not Sonoran desert tortoises are small, leak onto the ground (Scott 2009, p. 12). equal across their range. The ability for dispersal events probably play an New transmission lines would need to the Sonoran desert tortoise to move important role in the long-term be built for these facilities, as well as among populations is also important for maintenance of these populations.’’ This roads to maintain the facilities, posing allowing shifts in their range in suggests that while dispersal and additional threats to the Sonoran desert response to climate change, and to movement of tortoises may be rare, they tortoise through the destruction or promote recolonization after fire or may be important events. Therefore, contamination of remaining habitat and other regional disturbances (Beier and barriers that prevent this movement increased potential for road-kill Majka 2006, p. 2). Dispersal of Sonoran could result in significant genetic mortality. desert tortoises between populations impacts, by preventing mixing of In conclusion, the literature through sparse desertscrub is less likely populations over the long term. documents that urban development and in very hot, dry valleys in the Lower The effect of urban barriers limits population growth in Arizona and Colorado subdivision of Sonoran inter-population movements of Sonoran Sonora has been remarkable, and no desertscrub and populations in desert tortoises resulting in ‘‘closed’’ information is available to suggest these mountain ranges, such as the Eagletails, populations. Experts believe that an trends will not continue into the Maricopas, and Sand Tanks, have likely isolated population of Sonoran desert foreseeable future. Sonoran desert been existing in isolation for a long time tortoises that experiences significant tortoise habitat is permanently lost (Van Devender 2002a, p. 16). declines in population size could not where urban development occurs. Genetic analysis of blood samples overcome losses simply through an Sonoran desert tortoises and their collected from Sonoran desert tortoises increase in reproduction, based on habitats that occur adjacent to in Saguaro National Park in Pima evidence of past gene flow (Edwards et developed areas are also threatened by County, Arizona, suggest that al. 2004, p. 496). Therefore, if a

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population were to experience a of receiving population; and disease in the event of population declines or catastrophic decline as a result of a screening, among other factors (Berry extirpations, and may lead to isolation stochastic event such as drought, the 1986a, p. 113; Field et al. 2007, pp. 232, and eventual genetic bottlenecking. This immigration of new tortoises from 237, 240, 242; Martel et al. 2009, p. 218). threat acts synergistically with other adjacent populations would be Translocated Mojave desert tortoises factors as discussed above. necessary for population recovery have been shown to settle at release Off-Highway Vehicles (Edwards et al. 2004, p. 496). Urban sites, travel in straight lines for barriers effectively prevent this substantial distances, or disperse up to Off-highway vehicle use may pose a immigration of new tortoises, resulting approximately 4 miles (6.4 km) (Berry variety of threats to the suitability of in closed, or isolated, Sonoran desert 1986a, p. 113). Translocated desert habitat within the range of the Sonoran tortoise populations, which are now tortoises may disrupt social hierarchies desert tortoise. Off-highway vehicle use evident within the metropolitan areas of in receiving populations by displacing in Sonoran desert tortoise habitat can Phoenix and Tucson. Mountains and residents or they may be displaced result in damage to soil, riparian areas, associated foothills with Sonoran themselves (Berry 1986a, p. 113). wetlands, water quality, and air quality. desertscrub habitat occur in these urban Howland and Rorabaugh (2002, p. 341) This damage occurs due to reduced areas, and although development within suggest that translocation of Sonoran vegetation cover and growth rates, soil this habitat has been restricted by desert tortoises may not be a viable tool compaction, diminished water zoning laws, development is still for conservation because most intact infiltration, diminished presence and allowed to virtually surround the bases Sonoran desert tortoise populations in impaired function of soil stabilizers of the mountains, isolating tortoise Arizona are currently considered (biotic and abiotic soil crusts), noise, populations. Examples of this relatively healthy, and likely occur at or wildlife habitat fragmentation, spread of development include the Union Hills, near carrying capacity. Mullen and Ross invasive plant species, and accelerated White , McDowell (1997, pp. 145–146) found that erosion rates (Boarman 2002, pp. 43–51; Mountains, Black Mountains, and South translocated Mojave desert tortoises Ouren et al. 2007, pp. 5, 11; USGAO Mountain Park in the Phoenix have a lower survivorship than resident 2009, pp. 10, 13; Vega 2010, p. 3). Off- metropolitan area and , individuals (especially when moved highway vehicle use in Sonoran desert Tucson Mountains, and Saguaro during the summer versus during the tortoise habitat can also potentially National Park West in the Tucson spring), but that negative effects affect Sonoran desert tortoises directly metropolitan area (Edwards et al. 2004, commonly associated with by crushing individuals or their burrows p. 496). Zylstra and Swann (2009, pp. translocations are generally short-lived (Boarman 2002, pp. 43–51). 10–11) remarked that the increasing (1–2 years). Off-highway vehicle use has grown negative effect of human-made barriers A 2004 population viability analysis considerably in Arizona. Between 21 on Sonoran desert tortoise movements for the Mojave desert tortoise and 56 percent of Arizona residents between populations may require recommended that a minimum of (depending on the county in Arizona) translocation (moving animals out of 50,000 individuals are required for a 50 consider themselves off-highway harm’s way into more secured areas of percent chance of persistence for 500 vehicle users as of 1999, and projected suitable habitat), or occasional years, yet extrapolation of Sonoran increases in population growth are augmentation of populations with desert tortoise population data from expected to increase recreation on tortoises from other populations, to southern Arizona suggest that most public lands, in particular off-highway remain viable. populations number less than 20,000 vehicle use (AIDTT 2000, p. 10). As of Translocation has been considered an individuals, with some as low as several 2007, 385,000 off-highway vehicles option, and implemented to some hundred (Edwards et al. 2004, p. 496). were registered in Arizona (a 350 degree for Mojave desert tortoise Because the average generation time of percent increase since 1998), and 1.7 conservation and recovery. In assessing a Sonoran desert tortoise is million people (29 percent of the the viability of translocation as a approximately 12–15 years and much of Arizona’s public) engaged in off-road recovery and conservation tool for the the urban development is relatively activity from 2005–2007 (Sacco, pers. Mojave population, concern has been recent, the full effect of developments as comm., 2007). Over half of off-highway expressed for potentially moving barriers to genetic exchange among vehicle users reported that merely tortoises into areas where threats to Sonoran desert tortoise populations driving off-road was their primary desert tortoise populations remain, cannot be fully assessed at this time activity, versus using the off-highway which could negate any conservation (Edwards et al. 2004, p. 486). Edwards vehicle for the purpose of hunting, value associated with the action. Our et al. (2004, p. 495) further cautioned fishing, or hiking (Sacco, pers. comm., (Mojave) Desert Tortoise Recovery that their estimates of gene flow are 2007). The BLM (USBLM 2001, p. 1) Office stresses that translocation of contingent on what occurred pre- stated that interest in off-highway tortoises should not occur under such settlement, and should not be taken as vehicle use has increased substantially circumstances, emphasizing the need to evidence that natural immigration or in recent years and cited several address threats which impact all emigration still occurs. reasons, such as urban growth in the tortoises regardless of origin. In conclusion, the literature west, improved capabilities of off- Translocation of desert tortoises has documents that urban development and highway vehicles in accessing received mixed reviews in the scientific population growth, roads and highways, previously inaccessible areas, and literature and, as noted, may not be a canals, railroad tracks, and other types greater public interest in unconfined viable option for the Sonoran desert of development threaten the Sonoran outdoor recreational opportunities. tortoise. There are several factors that desert tortoise by creating barriers to The Forest Service stated that ‘‘the must be considered in deciding whether movement in Arizona and, perhaps to a number of off-highway vehicle users has or not to translocate tortoises into new lesser extent, in Sonora, Mexico. The climbed sevenfold in the past 28 years, areas, including temporary or longer- creation of barriers affects the tortoises’ from approximately 5 million in 1972 to term holding conditions of tortoises; the genetic exchange capacity within and 36 million in 2000’’ (USFS 2009, p. 2). propensity for post-release, long- between populations, which in turn The Tonto National Forest, which distance movements; drought; the status affects their ability to recolonize habitat encompasses a considerable amount of

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Sonoran desert tortoise habitat, receives highway vehicle use, 48 percent as movement corridors within their home the highest off-highway vehicle use of limited-use, 4 percent as closed, and 16 ranges, placing individuals at greater any national forest nationwide, partially percent of lands have yet to be risk of mortality from collisions with due to its close proximity to the Phoenix designated (USGAO 2009, p. 7). These off-highway vehicles. Populations that metropolitan area. The Arizona State figures indicate that at least 80 percent occur in similar areas throughout their Land Department recently closed to off- of BLM lands allow for off-highway distribution may also be vulnerable to highway vehicle use many of their lands vehicle use in some capacity. However, mortality associated with collisions, or in Maricopa County (which includes we do not have specific information for previously discussed indirect effects to Phoenix), to control dust pollution, BLM off-highway vehicle use in their habitat from off-highway vehicle which appears to have shifted off- Arizona. The BLM is taking actions to use. highway vehicle access to the nearby help manage off-highway vehicle use on Effects of off-highway vehicle use on Tonto National Forest (USFS 2009, p. 2; their lands. Sonoran desert tortoises are likely to be USGAO 2009, p. 11). The Tonto Historically, competitive off-highway more significant within washes that National Forest has indicated that soil vehicle racing events have occurred on separate steep slopes and rocky bajadas erosion appears to be the most a comparatively infrequent basis in used by Sonoran desert tortoises, where significant result from off-highway Arizona. On BLM lands in Arizona, tortoises are known to frequent and off- vehicle use on their lands and identified these activities are generally restricted highway vehicle use often occurs ‘‘unmanaged recreation’’ (off-highway from March 31 to October 15, in (AGFD 2010, p. 13). For example, ‘‘rock vehicle use) as one of four key threats consideration of potential surface crawling’’ (technical off-roading usually to soil, water, and wildlife habitat activity of Sonoran desert tortoises with highly-modified, high clearance, (USFS 2009, p. 1; USGAO 2009, pp. 10, (USBLM 2010, p. 4). However, similar four-wheel drive vehicles), generally 13). considerations may not occur with occurs in boulder-strewn washes where Off-highway vehicle use is respect to these events on lands Sonoran desert tortoises are most likely widespread across Arizona, occurring managed by other agencies, thus making to inhabit. This activity may be on Forest Service, BLM, private, tribal, their lands more desirable for planning uniquely destructive to Sonoran desert and State Trust lands, and has been such events. For example, a Special tortoise habitat because: (1) It occurs on documented on all 17 Sonoran desert Land Use Permit application was steep slopes and rocky bajadas within tortoise monitoring plots. Pronounced recently submitted to the Arizona State Arizona Upland Sonoran desertscrub effects are found on the and Land Department for the establishment where populations reach their highest Wickenburg Mountains plots, which are of a semiannual competitive off- densities; and, (2) the intent of rock near urbanized areas (greater Phoenix highway vehicle race within Sonoran crawling is to aggressively challenge and Wickenburg, respectively) (AGFD desert tortoise habitat, slightly north of aspects of a given landscape that would 2010, p. 13). Tucson near Mammoth, Arizona (Vega otherwise clearly represent barriers to The Tonto National Forest has 2010, pp. 1–16). overland travel, which places habitat proposed to designate approximately Competitive off-highway vehicle and tortoises at greater risk. However, 800 mi (1,287 km) of roads as open for events can have a variety of detrimental rock crawling activity is presumed to be use, and close 280 mi (451 km) of roads effects on Sonoran desert tortoises or less popular an activity than more which are currently open (due to their habitat. Event courses have been conventional off-highway vehicle use significant resource damage). This is a found to create new destinations for and, therefore, likely affects a much net increase of 520 mi (837 km) of off- increased, year-long use, and smaller percentage of Sonoran desert highway vehicle trails and roads on the correspondingly greater impacts to local tortoise habitat. Tonto National Forest (USFS 2009, p. 3). Sonoran desert tortoise habitats and Bury (1987, p. 1) studied the effects of In addition, the Tonto National Forest higher incidence of illegal route off-highway vehicle use on Mojave has proposed the designation of five proliferation (Vega 2010, p. 3). The high desert tortoises in Mojave desertscrub more off-highway vehicle areas rates of speed associated with habitat. Some of his findings included a (representing 2,799 ac (1,132 ha) competitive off-highway vehicle events 60 percent reduction in perennial plant collectively, or 0.01 percent of its significantly increase the likelihood for cover, 1.3 desert tortoises per hectare habitat in Arizona) within Sonoran damage to burrows or other habitat (2.47 ac) in a control plot in which off- desert tortoise habitat on the Mesa and features (Vega 2010, p. 4). Lastly, event highway vehicles were excluded, versus Globe Ranger Districts (USFS 2009, p. spectators seeking good views have been 0.3 desert tortoises in an area used by 3). All other motorized travel not found to park their vehicles off-highway vehicles, and four times the specifically designated will be indiscriminately along the race course number of active burrows in the control prohibited by the Tonto National Forest without regard to vegetation and may plot versus the off-highway vehicle area except as authorized for dispersed crush Sonoran desert tortoises and their (Bury 1987, p. 1). Bury and Luckenbach camping access and big game retrieval burrows, or start wildfires if parked over (2002, p. 257) found that there were 1.3 (USFS 2009, p. 4). Because of the dry vegetation (Vega 2010, p. 5). times more live plants, 3.9 times more increase in off-highway vehicle access In his literature review, Boarman plant cover, 3.9 times the number of and subsequent use anticipated to occur (2002a, p. 50) found that, as of 2002, Mojave desert tortoises, and four times on the Tonto National Forest, associated most research on the effect of off- the number of active burrows in threats to the Sonoran desert tortoise highway vehicles had been performed undisturbed Mojave desertscrub as and its habitat on the Forest are in areas of high off-highway vehicle use compared to areas where off-highway expected to increase in scope and within the Mojave desert tortoise vehicles were used. We are not certain magnitude in the immediate future. distribution. As a result, there are fewer whether the areas studied by Bury BLM regulations require their lands available data for lightly-traveled areas (1987, p. 1) and Bury and Luckenbach be designated as open, limited, or closed (Boarman 2002, p. 50). (2002, p. 257) were unregulated, or to off-highway vehicle use (USGAO On the Florence Military Reservation, regulated areas with designated routes, 2009, p. 7). As of March 2009, the BLM Grandmaison et al. (in prep., p. 16) but similar effects to Sonoran desert has nationally designated approximately found that Sonoran desert tortoises use tortoises and their habitat can be 32 percent of its lands as open to off- infrequently traveled gravel roads as expected in areas of high off-road

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vehicle use in Sonoran and Mojave may crush or injure Sonoran desert the amount and quality of available desertscrub habitat within Arizona, tortoises (also discussed below). In forage vegetation for Sonoran desert particularly in areas of higher addition, we have documented the tortoises (Sharifi et al. 1997, pp. 844– accessibility (such as valley bottoms and tremendous growth in popularity of off- 845). lower foothills), such as the Florence highway vehicle use in Arizona, as well Construction of major highways Military Reservation in Pinal County as compliance deficiencies in off- planned in Arizona has the potential to (AIDTT 2000, p. 34; Lutz et al. 2005; p. highway vehicle licensing programs greatly affect certain Sonoran desert 22; AGFD 2010, p. 7; Grandmaison et al. (and therefore deficient fees collected tortoise populations. For example, the in press, p. 4). that are intended to fund enforcement Arizona Department of Transportation Brooks and Lair (2005, pp. 7–8) found and environmental mitigation) and (ADOT) has proposed rerouting State that, in Mojave desertscrub, off-highway enforcement programs (discussed above Route 95 through the southern and vehicle routes can cause a myriad of and below). This threat acts eastern bajada of the Black Mountains in effects including: (1) Altering synergistically with other threats Mohave County, Arizona (Jacobs precipitation runoff patterns which discussed herein. Considering the Engineering Group, Inc. 2009, pp. 24, promote increased erosion; (2) population growth estimates we have 33; ADOT 2010, p. 3; Goodman 2010, producing air-borne pollutants laden documented above for Arizona, we pp. 3–4). The proposed realignment of with heavy metals that affect habitat at believe that the popularity of off- State Route 95 is expected to pass distances ranging from 65 to 650 feet (20 highway vehicle use will continue to directly through 30 mi (48 km) of a to 200 m) from the road; (3) increasing grow, leading to an increase in severity Sonoran desert tortoise population (THS nitrogen deposition in soils, thereby and geographic extent of impacts across 2009, p. 4; Goodman 2010, pp. 3–4). We favoring nonnative plant invasions; and the distribution of the Sonoran desert expect this new four-lane highway to (4) providing a pathway for nonnative tortoise in Arizona over time. eliminate considerable amounts of plant species invasions. These impacts Sonoran desert tortoise habitat, become degrade Sonoran desert tortoise habitat Roads and Highways a significant source of mortality, and as well as their forage base. Foreman (2002, p. 35) estimated that threaten the continued viability of the Soil disturbance from off-highway at least 20 percent of land in the United Black Mountains habitat to support the vehicle use, development projects, and States has been ecologically affected by population of the Sonoran desert other activities can facilitate the roads. Roads and highways might also tortoise there, if appropriate mitigation invasion of nonnative plant species by adversely affect Sonoran desert tortoises measures are not enacted or are eliminating competition and creating a as they do Mojave desert tortoises. ineffective. rougher soil surface for seeds to lodge Studies of Mojave desert tortoises Both the ADOT and the Federal and germinate (Hobbs and Huenneke suggest that effects include providing Highways Administration participate in 1992, pp. 329–330). Motorized and human access to occupied habitat, the BLM’s tortoise mitigation program mechanical vehicles aid in the dispersal facilitating the spread of nonnative and provide funding for the acquisition of plants by transporting seeds of both plant species, altering movement of Sonoran desert tortoise habitat using native and nonnative plant species. Rew patterns, enhancing the genetic compensation rates prescribed for in the and Pollnac (2010, p. 2) found that fragmentation effect between BLM’s mitigation policy (ADOT 2010, p. trucks and sport utility vehicles driven populations of Sonoran desert tortoises 3). Compensation rates for disturbances off road in dry conditions can pick up by acting as barriers, and contaminating in Category I or II habitat are 3–6:1 and as many as 176 seeds from 50 mi (80 adjacent habitat (Boarman and Sazaki 2–5:1, respectively (USBLM 2009, p. km) of driving, and recreational off- 1996, p. 1; Forman and Alexander 1998, 18). To date, 584 ac (236 ha) of Sonoran highway vehicles can pick up as many p. 207; Boarman 2002, pp. 54–55; desert tortoise habitat have been as 200,000 seeds in 48 mi (77 km) of off- Edwards et al. 2004, pp. 495, 497; acquired through this program with road driving. Off-highway vehicles are Boarman and Sazaki 2006, p. 95; ADOT and Federal Highways generally transported via trailer from Andrews et al. 2008, pp. 127, 129–130; Administration. Another 98 ac (40 ha) site to site and may spread nonnative Rew and Pollnac 2010, p. 2). Roads that are scheduled to be acquired as a result plant species in subsequent uses. Off- act as barriers to genetic exchange of the proposed rerouting of U.S. highway vehicle use has also been between Sonoran desert tortoise Highway 95 through the Black shown to create edge effects along trails populations may increase the risk of Mountains of Mohave County (ADOT that generate dust, blanketing adjacent inbreeding depression and population 2010, p. 3). vegetation, and inhibiting plant growth extirpation (Boarman and Sazaki 2006, Considerable planning efforts for rates, size, and survivorship, all of p. 95). In one example, biological future road and highway development which affect the forage base and connectivity between Sonoran desert in Arizona have been afforded to the available cover for Sonoran desert tortoise populations of the Harquahala preservation of wildlife corridors, or tortoises (Ouren et al. 2007, p. 11). and Wickenburg Mountains is ‘‘linkages.’’ Linkage design plans have We have documented that off- significantly limited due to several been completed for several biological highway vehicle use poses a threat to barriers to tortoise movement including corridor areas in Arizona where the Sonoran desert tortoise and its highways U.S. 60 and U.S. 93, the Sonoran desert tortoises may be habitat in Arizona because it damages Burlington Northern Santa Fe Railroad, threatened by construction and soil, reduces vegetation cover and and urban development, and would be development activities that could growth rates, leads to soil compaction, further limited by the proposed become barriers to movement between diminishes water infiltration, Wickenburg bypass highways which are populations (Beier and Majka 2006, pp. diminishes the presence and impairs the in the planning phase (Beier et al. 1–81; Beier et al. 2006a, pp. 1–189; function of soil stabilizers (biotic and 2006d, p. vi). 2006b, pp. 1–151; 2006c, pp. 1–88; abiotic soil crusts), fragments habitat, The use of dirt or gravel roads by 2006d, pp. 1–97; 2006e, pp. 1–135). facilitates the spread of nonnative plant vehicles generates dust which may These linkage design plans are specific species, ignites wildfire, accelerates soil adversely affect physiological processes to both individual corridors that may be erosion, enhances the potential for of adjacent plants and reduce overall affected throughout Arizona, and to illegal collection (discussed below), and primary productivity, whereby affecting species (including the Sonoran desert

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tortoise) chosen as representative ‘‘focal recently (Bahre 1991, pp. 143–146). The Pressure for fuel wood and crafts species’’ in each individual assessment harvest of mature mesquites from materials has been so intense in Mexico (Beier and Majka 2006, pp. 1–81; Beier Mexico’s Sonoran desertscrub habitat south of Organ Pipe Cactus National et al. 2006a, pp. 1–189; 2006b, pp. 1– permanently alters desert ecosystems Monument that wood harvest, 151; 2006c, pp. 1–88; 2006d, pp. 1–97; because these leguminous (bearing seed especially ironwood, has been detected 2006e, pp. 1–135). pods similar to pea or bean plants) trees more than a third of a mile inside the In one example, a series of voluntary are important anchors for these systems boundary of the Monument, as supplies conservation recommendations were and their associated flora and fauna have been decimated south of the border proposed in Beier et al. (2006c, pp. 15– (Taylor 2006, p. 8). More than 200 plant (Suzan et al. 1999, p. 1499). The 16; 2006e, pp. 14–15) to mitigate effects and animal species depend on mesquite structure of Sonoran desert tortoise of major roadways, such as U.S. trees in northern Mexico for survival habitat in both washes and upland Highway 60 which traverses Sonoran and reproduction (American University habitats in the Monument boundary has desert tortoise habitat in Pinal and Gila Database 2010, p. 1). Mesquite and been affected by this harvest (Suzan et Counties, Arizona. However, the ironwood trees are ecologically al. 1999, p. 1499). Sonoran desert tortoise was not afforded important to Sonoran desert habitat as In conclusion, the literature consideration in all projects. For they serve as nursery plants (i.e., aiding documents that harvest of ironwood and example, Sonoran desert tortoise in dispersal, germination, seedling mesquite trees has degraded Sonoran populations in Rincon and Santa Rita development, and survival) for other desert tortoise habitat in Mexico, mountains in eastern Pima County, plant species used as forage for desert primarily, by the loss of organic matter, Arizona, are adversely affected by tortoises, and provide valuable shade for fixed nitrogen, and sulfur and soluble Interstate 10 and State Highway 83 temporary shelter sites for Sonoran salts, affecting overall habitat quality (known barriers to tortoise movement), desert tortoises (American University and quantity, which collectively and yet were not addressed in the Rincon- Database 2010, p. 2). In areas where indirectly affect the forage base and Santa Rita-Whetstone linkage design harvest has been concentrated, the loss protective cover for Sonoran desert plan (Beier et al. 2006a, pp. i–ii). In of mesquite trees results in the loss of tortoises in as much as 4 percent of its another example, the Sonoran desert organic matter, fixed nitrogen, and range in Mexico. This threat acts in tortoise was not afforded any sulfur and soluble salts, affecting overall combination with other threats that consideration in the Santa Rita- habitat quality and quantity (Rodriguez affect Sonoran desert tortoise Tumacacori linkage design plan, despite Franco and Maldonado Aguirre 1996, p. populations in Mexico discussed in this the likely adverse effects by Interstate 47). finding. 19, a known barrier to movement Livestock Grazing between populations located in the The demand for mesquite wood, used Santa Rita and the Atascosa-Pajarito- for cooking, has increased in the Sonoran desert tortoises, livestock, complex in Sonoran Desert region of northern and wild burros potentially share southern Santa Cruz County, Arizona Mexico; one million ac (400,000 ha) habitat throughout their distribution in (Beier et al. 2006b, pp. i–ii). While some have been cleared of mesquite to meet Arizona, with the exception of lands highways have associated structures these growing demands (American managed by the U.S. Fish and Wildlife that prevent or funnel tortoises to University Database 2010, p. 1). The Service or National Park Service. Wild underground crossings, several modification of one million ac burro herds range across millions of populations are still affected by barriers contributes to the degradation or acres of Sonoran desert tortoise habitat to movement from major roads and possible loss of 4 percent of tortoise in Arizona, predominantly on BLM highways that have no such structures. habitat in Mexico; rangewide, 2 percent. lands northwest of Phoenix, although In our review of the literature, we Ironwood trees are also being harvested the literature is generally lacking in have documented that roads and in the Sonoran desert of northern analysis of potential effects of wild highways pose a threat to Sonoran Mexico, where it is cherished for its burros on Sonoran desert tortoise desert tortoises in Arizona because they hardness and carving potential in Seri populations or habitat (AIDTT 2000, p. form barriers to movement, whether Indian artwork (American University 21). through direct mortality from vehicles Database 2010, p. 2). The accelerated The Mexican government has or from avoidance of roads by tortoises. rate of legume tree depletion for designated over 5 million ac (2 million The effects associated with barriers are charcoal and carvings in Sonora has ha) of Sonoran desertscrub for described in detail in the ‘‘Development affected the health of ironwood conversion into grasslands for livestock as a Barrier’’ section above. While populations and associated production (American University several roads or highways have communities (Suzan et al. 1997, p. 955). Database 2010, p. 1). Sonoran desert associated tortoise fencing and or This is evidenced by an increased tortoises are not found in grasslands, culverts to prevent road-kill of tortoises number of damaged and dying trees, as and this habitat type is not considered and facilitate safe movement, studies well as generally small size classes for suitable for the species. The loss of 5 have shown that these devices are often sampled areas (Suzan et al. 1997, pp. million ac (2 million ha) would not maintained and, therefore, become 950–955). In the Sonoyta region of constitute an estimated loss of 20 ineffective over time in achieving their northern Sonora, more than 478,000 ac percent of their habitat in Mexico; desired goal. This threat also acts (193,000 ha) have been affected by rangewide, 10 percent. Livestock synergistically with other influences deforestation related to charcoal grazing began to expand and modernize discussed herein. production, brick foundries, tourist in its extent and distribution in Sonora, crafts, and pasture conversion (Nabhan Mexico, in 1950, when land considered Ironwood and Mesquite Harvest and Suzan 1994, p. 64). The unsuitable for agriculture was The harvest of mesquite and modification of 478,000 ac (193,000 ha) subsequently used for livestock grazing ironwood trees for charcoal production contributes to the degradation or (Hawks 2003, p. 3). During this time, and use in wood carvings adversely possible loss of an estimated 2 percent new bulls were introduced throughout affects Sonoran desertscrub habitat in of their habitat in Mexico; rangewide, 1 ranching operations to improve herd Mexico, both historically and more percent. genetics, and artificial seeding of

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pastures also commenced at this time increase soil compaction and decrease include dietary overlap and competition (Hawks 2003, p. 3). By 1970, buffelgrass water absorption, thereby reducing for food resources, destruction of was the chosen seed for artificial range water availability to potential Sonoran vegetation structure used as temporary supplementation for a growing rural desert tortoise forage species and shelter sites, trampling of tortoises, livestock industry, and pastures were subsequently reducing available forage collapsing of tortoise burrows, altering seeded with the species throughout (Boarman 2002, p. 30). Oldemeyer plant species composition by facilitating Sonora, Mexico. In Sonora, buffelgrass (1994, pp. 100–101) commented that the invasion of nonnative plant species, has trended towards a monoculture in there remains much uncertainty on the and compaction of soil which may many areas, and changed the fire regime exact effects of livestock grazing on inhibit the construction of burrows to the detriment of native vegetation desert tortoises. Meyer et al. (2010, p. (Avery and Neibergs 1997, p. 13). (Hawks 2003, p. 4). We discuss the 42) suggested that the effects of Boarman (2002a, p. 32) as well as Hobbs threat of nonnative plant species such as livestock grazing on Sonoran desert and Huenneke (1992, p. 329) found that buffelgrass in the ‘‘Nonnative Plant tortoises should be placed in the context livestock grazing can import nonnative Species and Altered Fire Regimes’’ of a grazing regime, effective plant propagules (seeds and other plant section above. precipitation, habitat type, topography, parts that may propagate) into native Livestock stocking rates in Sonora Sonoran desert tortoise behavior, and vegetation and subsequent physical have been documented at 2–5 times the habitat requirements. Loeser et al. alterations in vegetation structure and recommended rate for resource (2007, pp. 93–96) suggested that soil disturbance, such as trampling by sustainability (Walker and Pavlakovich- climatic variation is key in determining livestock hoof-action, may increase Kochi 2003, p. 14; University of Arizona the ecological effects of grazing 2010, p. 2). Rorabaugh (2008, p. 25) practices in arid rangelands. germination rates of seeds through found that livestock grazing ‘‘*** is The effects of soil compaction on burying and compaction and provide probably the most widespread human desertscrub vegetation have been microsites for establishment of use of Sonora’s landscapes’’ and that analyzed. In Mojave desertscrub where nonnative plant species. rangelands in Sonora are often heavily Sonoran desert tortoises also occur, Avery and Neibergs (1997, p. 13) grazed, with effects most apparent Adams et al. (1982, p. 167) found that compared Mojave desert tortoise habitat during periods of drought. Livestock soil strength of drying compacted soils in both grazed and ungrazed areas production in Mexico is concentrated in increased at a greater rate than non- (where buffelgrass was not intentionally the northern states, and the numbers of compacted soils, and that even minor planted), and found no significant livestock have grown from 10 million in compaction produced similar effects to differences in annual plant cover, 1940, to 37.5 million in 1983, largely soil strength. Soil strength was found to biomass, or density between study due to the proximity to the United be inversely proportionate to production areas. The densities and individual States, the major importer of Mexican of summer annual grass species (Adams volumes of big galleta (Hilaria rigida), a cattle and beef (Stoleson et al. 2005, p. et al. 1982, p. 167). Plant species with perennial grass species, were greater in 60). In Sonora, 79 percent of agricultural taproots appeared more vulnerable to grazed habitat than within the grazing and rangelands are devoted to livestock the effects of soil compaction whereas exclosure (Avery and Neibergs 1997, p. production (Stoleson et al. 2005, p. 60). fibrous root systems common in 13). There was no significant difference Effects of poorly-managed livestock nonnative species such as Schismus in total cover of perennial plant species grazing observed in Sonora include spp. appeared less vulnerable, which within study plots (Avery and Neibergs changes in plant species composition indicates that root structure affects the 1997, p. 13). Avery and Neibergs (1997, and vegetation cover and structure, soil response of plant species and that plant p. 13) documented livestock nudging compaction, erosion, altered fire species respond differently to soil and rubbing Mojave desert tortoises, regimes, and nonnative plant species compaction, potentially favoring collapsing (potentially occupied) desert introductions and invasions (Stoleson et nonnative species in compacted soils tortoise burrows, and destroying al. 2005, pp. 61–62). (Adams et al. 1982, p. 174). vegetation shading actively used In the United States, however, While the Mojave and Sonoran desert permitted levels of livestock grazing tortoises differ to some degree in their burrows. The number of damaged and have been reduced to 10 percent of biology and behavior, research on undamaged burrows in grazed habitat historical levels (Bostick 1990, p. 149). livestock grazing effects on Mojave was equal, whereas the number of Potential effects of livestock grazing in desert tortoises or their habitat does undamaged burrows in ungrazed habitat desertscrub habitat received significant have applicability to Sonoran desert was significantly higher (Avery and treatment in the literature, with varied tortoises (especially where Sonoran Neibergs 1997, p. 18). Winter grazing scientific conclusions. Fleischner (1994, desert tortoises occupy Mojave appears to affect a higher proportion of p. 631) listed specific attributes of desertscrub habitat and by virtue of the actively used Mojave desert tortoise ecosystems, such as composition, arid-land commonality), representing burrows. Indirect effects from burrow function, and structure, as vulnerable to the best scientific information available. damage include increased risk of the effects of livestock management However, because Mojave desert tortoise mortality, increased energy through a variety of mechanisms tortoises typically occur in flat or costs, and altered activity time budgets including: (1) Decreasing the density gently-sloped terrain and construct as a result of the need to construct new and biomass of individual species, earthen burrows in soil, they may be burrows (Avery and Neibergs 1997, p. reducing species richness, and changing more susceptible to direct effects from 19). The potential for livestock to biological community organization; (2) livestock grazing. In comparison, damage Sonoran desert tortoise burrows interfering with nutrient cycling and Sonoran desert tortoises typically occur on lower slopes not reinforced with ecological succession; and (3) changing on steeper slopes and often construct granite boulders may be similar to the vegetation stratification, contributing to burrows that are reinforced by boulders findings of Avery and Neibergs (1997, p. soil erosion, and decreasing availability and, consequently, less susceptible to 18), as almost 200 Sonoran desert of water to biotic communities (Waser direct effects from livestock grazing. tortoise burrows were recorded as and Price 1981, pp. 409–410). In Mojave Observed effects of livestock grazing trampled during a survey of the East desertscrub, livestock grazing can within Mojave desert tortoise habitat Bajada plot in the Black Mountains of

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Arizona in 1997 (Woodman et al. 1998, positively correlated to distance to in Sonoran desert habitat, as livestock pp. 74–75). watering sites, while others, such as red are less likely to travel into rough, steep Some degree of overlap was observed brome, are negatively correlated (Brooks terrain, instead favoring valley bottoms in the forage plant preferences between et al. 2006, p. 139). Native plant species and water sources (AIDTT 2000, pp. 9, Mojave desert tortoises and livestock, cover and richness has been shown to 21). Effects from livestock grazing are with both preferring green annual decrease with increasing proximity to expected to be attenuated due to the species when available, and most livestock waters (Brooks et al. 2006, pp. relatively steep slopes and rugged overlap occurring during the spring 140–141). Brooks et al. (2006, p. 138) terrain often preferred by Sonoran (Avery and Neibergs 1997, pp. 18–19). state that these effects can be desert tortoises, but quantitative studies However, preferences began to diverge anticipated from 164 to 656 ft (50 to 200 have not been conducted to confirm this as spring and summer ensued, with m) from the edge of the watering site. assumption (AIDTT 2000, p. 9; Oftedal Mojave desert tortoises preferring dried Juvenile and adult Sonoran desert 2007, p. 26). Because of the generalized annuals, beavertail cactus (Opuntia tortoises were frequently observed by differences in habitat usage by livestock basilaris), and stems and dried flowers Meyer (1993, pp. 101–102) using salt (flats, ridge tops, and drainage bottoms) of silver cholla (Opuntia echinocarpa), licks provided for livestock. Frequenting and Sonoran desert tortoises (steep and livestock preferring California salt licks may benefit desert tortoises slopes and rocky bajadas), ecological jointfir (Ephedra californica) and big (especially hatchlings and small and dietary overlap is uncommon, but galleta grass (Avery and Neibergs 1997, juveniles), but likely increases risk of does occur to some degree (AGFD 2010, p. 18). We presume similar relationships being trampled by livestock because the p. 6). Where such overlap is significant, between preferred forage species of salt licks can attract higher in particular in periods of drought, the livestock and Sonoran desert tortoises concentrations of both livestock and effect of livestock use on Sonoran desert exist, because of their highly varied, and tortoises in actively grazed pastures. tortoise habitat may be considerable often opportunistic, foraging behavior as Based on the results of a study (AGFD 2010, p. 7). Sonoran desert they take advantage of both summer and conducted by Balph and Malecheck tortoises may also selectively avoid winter rainy seasons characteristic of (1985, p. 227), cattle avoid stepping on grazed areas. While Sonoran desert the Sonoran desert. This precipitation uneven surfaces. Desert tortoises will tortoises are generally known to use pattern affords Sonoran desert tortoises likely be perceived as an uneven ground steep rocky slopes and bajadas as their greater access to standing water and, surface, therefore, cattle may primary habitat areas, they occasionally therefore, the ability to forage on a more intentionally avoid stepping on them. occur in more flat terrain, such as the varied forage base, compared to the Neff et al. (2005, p. 87) compared the Florence Military Reservation, where Mojave desert tortoise. effects to soil geology, geomorphology, they are 35 percent less likely to use Studies have shown that livestock and geochemical characteristics of habitat where livestock grazing occurs grazing may result in varying effects on biological soil crusts that had been (AGFD 2010, p. 7). Grandmaison et al. plant species richness, composition, and disturbed, and the subsequent wind (in press, p. 2) examined microhabitat density of the Sonoran desert tortoise erosion due to livestock grazing, to an selection by the Sonoran desert tortoise forage base. Blydenstein et al. (1957, pp. ungrazed area in arid lands of on the Florence Military Reservation in 523, 525) found that vegetation density southeastern Utah. They found that south-central Arizona, and found that in some perennial species can be ‘‘* * * despite almost 30 years without tortoises most strongly selected for affected by livestock grazing in Sonoran livestock grazing, surface soils in the canopy cover, followed by an absence of desertscrub, while species composition historically grazed sites have 38–43 cattle activity and proximity to roads and annual plant species density were percent less silt, as well as 14–51 and washes. unaffected. Sixteen years of rest from percent less total elemental soil Of the 17 long-term monitoring plots, livestock grazing in the desert grassland magnesium, sodium, phosphorus, and evidence of some degree of habitat usage and oak woodlands in southeastern magnesium content relative to soils overlap with livestock has been Pima County in Arizona (at the extreme never exposed to livestock disturbances’’ observed on 12 plots. On several plots periphery of the Sonoran desert tortoise and 60–70 percent declines in surface (Arrastra Mountains, Bonanza Wash, range) showed increases in plant species soil carbon and nitrogen reserves (Neff West Silverbell Mountain, and Tortilla richness and significant increases in et al. 2005, p. 87). We are not certain to Mountains) extensive overlap with canopy cover for midgrass, shortgrass, what extent the loss of these surface soil livestock use has been documented in shrubs, and forbs (Brady et al. 1989, pp. nutrients may affect the forage quality or each year they were surveyed (AGFD 285–287). However, there was no quantity for Sonoran desert tortoises in 2010, p. 7). Heavy trampling and statistical difference in total vegetation arid habitat. Approximately 46 livestock destruction of Sonoran desert tortoise cover between grazed land and rested grazing allotments on the Tonto burrows has been documented on the land (Brady et al. 1989, pp. 285–287). National Forest partially or wholly Bonanza Wash plot. One Sonoran desert Features that attract livestock to overlap the potential range of the tortoise was crushed by livestock certain locations within an allotment Sonoran desert tortoise, with several trampling on the West Silverbell may have pronounced effects on desert rated as having impaired or Mountain plot, although such extreme tortoises and their habitat. Livestock unsatisfactory soil conditions (AIDTT reports of livestock-related direct effects watering, supplemental feeding, or salt- 2000, p. 37). on Sonoran desert tortoises are lick sites in desertscrub attract higher We observed several instances in the uncommon in the literature (AGFD use by greater densities of livestock in literature that discussed an inherent 2010, p. 7). arid environments. Effects to partitioning of land used by livestock Sonoran desert tortoises might desertscrub habitat are commensurate and that used by Sonoran desert compete with livestock for high-PEP with livestock use of these areas and tortoises. Livestock often take the paths plants (for review, see discussion of diet decrease with increasing distance from of least resistance and are unlikely to in the Species Information section these sources (Avery and Neibergs 1997, venture great distances from water. above) and therefore may place unique p. 19; Boarman 2002, p. 34). The density These behavioral traits of domestic competitive pressure on Sonoran desert of certain nonnative plant species, such livestock limit, to some degree, the tortoise populations (Oftedal 2002, pp. as Schismus spp., has also been potential effects from livestock grazing 235–236). Many high-PEP plant species

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are found primarily in the transition et al. 1990, p. 243). Increased soil were of unequal size, with the yearlong zone between areas where livestock and temperatures may impact the Sonoran light and moderate plots being the Sonoran desert tortoises compete desert tortoise in a variety of ways, such smallest. This could affect the number directly for these plant species, as noted as influencing changes in behavior, of tortoises observed but not likely the in several Arizona long-term monitoring lowering survivorship, and skewing the density of tortoises. Other variables that plots (East Bajada of the Black sex ratios of hatchlings (which are likely affected the analysis of Sonoran Mountains, Hualapai Foothills, Little determined by incubation temperatures; desert tortoise densities were Shipp Wash, , see Species Information, above). differences in vegetation, topography, San Pedro Valley), in addition to similar Bostick (1990, pp. 150–151) suggested soil types, and the location of tortoise observations from studies performed at that high desert tortoise densities are populations among study plots (Meyer , Saguaro National Park, and correlated with high livestock use, et al. 2010, p. 38). In addition, the Sugarloaf Mountain (Oftedal 2007, p. citing health examinations of Mojave ability to detect Sonoran desert tortoises 26). However, Oftedal (2007, p. 25) desert tortoises that existed in grazing is likely to increase with intensity of hypothesized that in situations where exclosures in northwestern Arizona. livestock use and a subsequent decrease winter precipitation is modest, high-PEP Bostick (1990, p. 149) also asserted that in ground cover, which could have plant species are in low abundance, and desert tortoises feed ‘‘primarily on further biased the number of nonnative annual grass species are in dung,’’ inferring that with more observations in the yearlong moderate high abundance, ‘‘the immediate effect livestock, there would be an abundance and heavy grazing study plots. Given of grazing (forage competition with of available tortoise forage. Bostick the results of these analyses, Meyer et Sonoran desert tortoise) would be [a] (1990, p. 151) summarized his al. (2010, p. 42) surmised that ‘‘tortoise reduction of overall forage biomass, not conclusions on the relationship between densities were affected by soil, [a] change in the quality of tortoise livestock grazing and desert tortoises topography and vegetation and had little diets. This suggests that cattle grazing with the following: (1) Desert tortoises or no relationship to livestock grazing or may be less damaging to tortoises in have coexisted with cattle for 300 years grazing systems.’’ years of modest rainfall.’’ In conclusion, in California and Mexico and at least Additional research examined effects Oftedal (2007, p. 26) found that ‘‘the 100 years elsewhere; (2) the highest of grazing regimes on fire behavior and high degree of diet selection that occurs tortoise densities known occurred at a wildlife and vegetation communities, during spring leaves (Sonoran) desert time when overgrazing by livestock was citing beneficial effects. Bahre (1991, p. tortoises susceptible to influences that the most severe ever known; (3) the 141) compared the relative frequency of may alter the abundance of the fewer the cattle on a range, the fewer the wildfires that occurred in the mid-1900s somewhat scarce high-PEP plants, and number of tortoises; and, (4) excluding (carried by nonnative plants), to fires in thus that may reduce the overall quality cattle for many years endangers the more recent times, and suggested that of the diet. Tortoises foraging in summer tortoise population. Boarman (2002, pp. mechanical fuel reduction by livestock appear less susceptible to the impacts of 27, 35, 38) refuted the conclusions made grazing might assist in reducing the livestock grazing.’’ Thus, seasonality and by Bostick (1990, pp. 149–151) that propensity of wildfires in Sonoran precipitation levels appear to affect the grazing benefits the desert tortoise. In desertscrub habitat. Loeser et al. (2007, likelihood of grazing to adversely affect addition, we found no information in p. 97) found that in Arizona grasslands ‘‘ the forage base of Sonoran desert the scientific literature that supported * * * some intermediate level of cattle the findings of Bostick (1990, pp. 149– grazing may maintain greater levels of tortoises, with spring being a period of 151). native plant diversity than the elevated sensitivity of Sonoran desert Some research has examined the alternatives of cattle removal or high- tortoises to livestock grazing where effects of various livestock grazing density, short-duration grazing tortoises and livestock spatially overlap. regimes to Sonoran desert tortoise practices.’’ Livestock grazing can influence the populations. Meyer et al. (2010, pp. 20– In an unpublished review of livestock microclimate at the ground surface. 26) compared the number and density of grazing literature, Holecheck (undated, Grazing may positively affect soil Sonoran desert tortoises in study plots p. 2) found that ‘‘* * * controlled temperature and, therefore, benefit exposed to four different livestock livestock grazing may enhance desert tortoise burrow temperatures grazing regimes: Yearlong light grazing rangeland vegetation by accelerating where burrows are not associated with (plot size 2,279 ac (922 ha)), yearlong plant succession, increasing plant boulders, but instead constructed in moderate grazing (plot size 3,254 ac diversity, increasing plant productivity, more open habitat such as underneath (1,317 ha)), yearlong heavy grazing (plot and reducing plant mortality during shrubs (Boarman 2002, p. 31). Field size 4,634 ac (1,875 ha)), and rest- drought. These positive impacts of research in Mojave desertscrub indicates rotation (plot size 4,758 ac (1,925 ha)). livestock grazing are most likely to that when the undergrowth beneath They found that the highest number and occur when grazing intensities are light shrubs is grazed, and the shrub itself is density of Sonoran desert tortoises (266 to conservative.’’ Holecheck (undated, p. minimally browsed or unaffected by total individuals; 36.89 individuals per 2) countered the unanimous findings of grazing, underlying soils may cool from square mile) was observed in the over 30 independent livestock grazing effects from wind and shade. Heavily pastures with yearlong heavy grazing as impact studies that documented that vegetated undergrowth traps heat and compared to rest-rotation (215 total controlled grazing increases increases soil temperature (Boarman individuals; 28.94 individuals per compaction, reduces infiltration, and 2002, p. 31). Alternately, heavily square mile), yearlong light grazing (52 increases erosion by claiming that ‘‘these browsed shrubs can increase soil total individuals; 14.61 individuals per impacts are generally of small temperatures (Boarman 2002, p. 31). square mile), and yearlong moderate magnitude and are ameliorated by Lower vegetative ground cover in grazing (47 total individuals; 9.23 natural processes that cause soil northern Sonora, as a response to individuals per square mile) (Meyer et formation, soil deposition, and soil livestock overgrazing, was found to al. 2010, p. 23). The study plots used for loosening.’’ increase soil and air temperatures above this comparison between the number Some local land management the levels found in adjacent grazed and density of Sonoran desert tortoises organizations are currently working on lands within the United States (Bryant and various livestock grazing regimes proactive conservations efforts to reduce

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potential impacts of ranching and other mi (225 km) of the border, from Recently, 33.5 mi (54 km) of permanent activities on the Sonoran desert tortoise. approximately Nogales west to the vehicle barriers were installed along the For example, the Winkelman Natural California State line. International international border within the Cabeza Resource Conservation District border fencing structures and barriers Prieta National Wildlife Refuge, which (WNRCD, a coalition of local livestock (especially the impenetrable pedestrian has likely reduced illegal vehicular ranchers and grazing lease permittees in fencing) along the Arizona-Sonoran access to the Refuge (SBBI Incorporated the Winkelman area of the lower San border pose population-connectivity 2010, p. 1). Pedro River in Arizona) has prepared a problems for the Sonoran desert Along the entire southern boundary of draft conservation plan for the desert tortoise, which depends on emigration the Buenos Aires National Wildlife tortoise within their area (WNRCD 2010, and immigration for genetic fitness of Refuge, a 7-mi- (11.3-km-) long pp. 1–13). This draft plan proposes regional populations. However, along pedestrian barrier has been constructed conservation and land management most of the border, just vehicle barriers (USDHS 2007, pp. 4, Figure 2–1). prescriptions for land managers in their occur, which allow tortoises to pass Because pedestrian barriers on the area as recommended by the Arizona through them, and do not pose a barrier border are generally well-fortified, Interagency Desert Tortoise Team. to movement (Cohn 2007, p. 96; Flesch complete barriers to terrestrial However, presently the draft plan has et al. 2010, p. 179; Audsley 2010, p. 5; movement, we assume that Sonoran not secured specific agreements with Sferra 2010, pers. comm.). The two desert tortoises in the larger juvenile land managers responsible for Sonoran primary types of barrier devices that and adult size classes are now desert tortoise habitat, and it lacks have been constructed, or are planned prevented from making trans-border financial commitments to carry out the for construction, are vehicle barriers and dispersal movements as a result of the recommended conservation actions. For pedestrian fences, the latter of which barrier construction in this area. example, Pinal County was identified as may be impenetrable to Sonoran desert The border region associated with the having responsibilities for conservation tortoises where the fence is buried into Tohono O’odham Nation in Pima actions but has since indicated that they the ground (Audsley 2010, p. 5; Sferra County, Arizona, was recently are unable to participate in the draft 2010, pers. comm.). Where pedestrian considered to have one of the highest plan (Pinal County 2010, p. 1). While fences are not buried completely and rates of attempted crossings, because it this draft conservation plan could bollard fences (barriers formed by a is relatively remote (Sferra 2010, pers. further Sonoran desert tortoise series of vertical posts) are installed, comm.). Currently, all but 3 mi (4.8 km) conservation in this area once all the Sonoran desert tortoises less than 4 in of the 70-mi (113-km) section of border necessary management and financial (10 cm) in width may be able to get between the Tohono O’odham Nation agreements are in place and the plan is through (Audsley 2010, p. 5; Sferra and Mexico is reinforced with a vehicle finalized, it currently provides limited 2010, pers. comm.). barrier (Lackner 2010b, pers. comm.). conservation benefit to the Sonoran Undocumented immigrants affect Vehicle barriers are not constructed desert tortoise. Sonoran desert tortoise habitat by where terrain is too steep or rocky, or In consideration of the literature trampling vegetation along well-used where vehicular access is considered presented above, we conclude that routes and cutting wood for campfires, impossible (Lackner 2010b, pers. grazing effects to the Sonoran desert which affects the quality and amount of comm.). The lands of the Tohono tortoise may occur but are likely limited forage and also reduces the number of O’odham Nation are predominantly in severity and scope in Arizona, temporary shelter sites for Sonoran classified as Arizona Upland Sonoran because habitat shared by livestock and desert tortoises (Averill-Murray and desertscrub. The lands presumably have Sonoran desert tortoises is not a Averill-Murray 2002, p. 29). Other significant numbers of Sonoran desert significant proportion in most areas in human activities along the international tortoises, although survey data are Arizona, and because livestock grazing border (off-road driving, high-speed generally scarce from that area. in Arizona is actively managed by land driving, accidentally setting fires from Along the Organ Pipe Cactus National management agencies (see Factor D). We cooking or purposefully for distraction Monument border with Mexico, vehicle also acknowledge that data generated of law enforcement personnel, and barriers exist across most of the from research on grazing effects to interdiction activities by the U.S. Border monument, and a potentially tortoises and their habitat are variable, Patrol, U.S. Immigration and Customs impenetrable pedestrian fence has been making it difficult to accurately assess Enforcement, and other enforcement erected in Arizona Upland Sonoran the risk of livestock grazing to the agencies) also impact Sonoran desert desertscrub on Monument Hill and Sonoran desert tortoise. However, due tortoises and their habitat (AIDTT 2000, along 4 mi (6.4 km) of the border at the to limited regulations affecting livestock p. 27; Marris 2006, pp. 338–339; Sayre Lukeville Port of Entry (Sferra 2010, management in Mexico, and the and Knight 2010, p. 347). pers. comm.). information we have examined on its Historically, border enforcement The comparison of 2009 and 2010 extent in Sonora, we conclude that policies and associated structures have apprehension rates of undocumented livestock grazing likely poses a threat to indirectly channeled undocumented immigrants reflects both the number of the Sonoran desert tortoise in Mexico. immigration pressure onto the Cabeza attempted illegal crossings and the We also acknowledge the potential for Prieta National Wildlife Refuge (Marris intensity of enforcement activities livestock grazing effects to act 2006, pp. 338–339; Cohn 2007, p. 96). within various regions of the Arizona- synergistically with other influences Analysis has shown there are about Mexico border, as well as areas north of discussed herein. 8,000 mi (12,875 km) of unauthorized the border (Lackner 2010a, pers. routes on the approximate 1,000 sq mi comm.). Within Sonoran desert tortoise Undocumented Human Immigration (2,600 sq km) refuge, mostly in habitat, significant increases in United States border-enforcement designated wilderness (McCasland apprehension rates have occurred in the efforts have significantly increased 2010, pers. comm.). These routes are following areas (percentage denotes along the United States-Mexico most likely attributable to illegal cross- change from 2009 to June 2010): Tohono international border in Arizona in border traffic and associated law O’odham Nation (18.37 percent); Organ recent years. Sonoran desert tortoise enforcement response by Border Patrol Pipe Cactus National Monument (63.8 habitat occurs along approximately 140 (McCasland 2010, pers. comm.). percent), and the Sonoran Desert

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National Monument (70.69 percent) However, these impacts are significant centuries, which hinders remediation (U.S. Border Patrol 2010, pers. comm.). where they occur. projects with respect to their ability to In other areas, the apprehension rates prevent population declines in Sonoran Summary of Factor A have substantially decreased over the desert tortoises in the short- or medium- same time period: Ironwood Forest Our analysis under Factor A term. Each of these impacts results in National Monument (¥47.18 percent), identified an array of threats to Sonoran significant cumulative threats to the Barry M. Goldwater Air Force Range desert tortoise habitat. The documented species’ habitat and, based upon our (¥32.02 percent), and the Cabeza Prieta invasion and purposeful cultivation of review of the best commercial and National Wildlife Refuge (¥13.19 nonnative plant species within the scientific data available, we conclude percent) (U.S. Border Patrol 2010, pers. distribution of the Sonoran desert that the present or threatened comm.). Over the same time period, and tortoise in the United States and Mexico destruction, modification, or in total, there have been 79,307 significantly increases the threat of curtailment of its habitat or range is an apprehensions made, compared to wildfire in an ecosystem that evolved in immediate threat of high magnitude to 71,775 apprehensions in 2009, which the absence of wildfire. This threat is the Sonoran desert tortoise, both now represents a 10 percent increase widespread and, although currently and and in the foreseeable future. (Lackner 2010a, pers. comm.). comparatively less significant in Arizona, is substantial in Mexico, and is Factor B. Overutilization for New border- and access-road Commercial, Recreational, Scientific, or construction has connected previously expected to increase in the future. When including the total land area adversely Educational Purposes remote and undisturbed habitat to the modified by ironwood and mesquite existing network of Arizona roads, Illegal Collection harvesting, an estimated 98 percent of providing vehicular access to areas the Sonoran desert tortoises’ habitat will In urban areas of Sonora, Mexico, previously only accessible by foot or on be lost or adversely modified in Mexico such as Hermosillo, desert tortoises horseback (Sayre and Knight 2010, pp. in the near future, or 47 percent of the have become increasingly common as 346–347; Sferra 2010, pers. comm.). An Sonoran desert tortoise’s habitat household pets. They have been mostly unintended consequence of these new rangewide. It is important to recognize obtained from the wild in adjacent areas roads is that they are used not only by that while nonnative plant species are (Bury et al. 2002, p. 103). The sale of U.S. Border Patrol, but by the public expanding their distribution on the desert tortoises in Mexican pet stores and illegal traffic, increasing the risk of landscape, Sonoran desert tortoise ended when the tortoise was listed as wildfires, invasions of nonnative plant populations have persisted in affected threatened in that country in 1994 (Bury species, alteration of erosion and water areas that remain unburned, for et al. 2002, p. 103). movement patterns (affecting infiltration decades. The effect of nonnative plants Sonoran desert tortoises are a closed and soil stability), and mechanical on Sonoran desert tortoise populations season species in Arizona (Commission damage to vegetation (Sayre and Knight is most significant after a wildfire has Order 43), and therefore cannot be 2010, p. 347; Sferra 2010, pers. comm.). occurred; effectively giving nonnative legally taken from the wild or possessed Many new roads along the border have species a distinct competitive advantage without special license. In Arizona, the included cattle guards built with over native vegetation, and threatening current possession limit for Sonoran enclosed concrete pits that have the a type-conversion in habitat. While we desert tortoises legally held in captivity, unintended consequence of acting as have found evidence of numerous i.e., either obtained prior to season lethal pit-fall traps for reptiles, such as wildfires in occupied desertscrub, the closure or obtained through the tortoise smaller size class Sonoran desert majority of occupied habitat that has adoption program, is one per person per tortoises (Sayre and Knight 2010, p. been invaded by nonnative plants has household (AGFD 2010, p. 12). The 347). not yet burned and remains suitable AGFD allows for disposition of lawfully Based on our review of the literature habitat for the tortoise. possessed tortoises by gift to another and communications with resource In addition, projections for human person in Arizona, or as directed by the experts and enforcement personnel, we population growth and urban AGFD (AIDTT 2000, p. 14). Despite conclude that Sonoran desert tortoises development throughout the species’ collection prohibitions in Arizona, the and their habitat, both near the range are likely to both pose significant Sonoran desert tortoise is a very international border and within problems for genetic exchange among common pet in Arizona corridors of heavy undocumented Sonoran desert tortoise populations as households and has been so for decades. immigrant travel and enforcement well as increase the degree and scope of The actual number of Sonoran desert interdiction, are threatened by these human interactions with tortoises and tortoises in captivity is unclear because activities. Specifically, off-road route occupied habitat, which threatens the there are no special licenses or permits proliferation, high-speed driving, road tortoise in a variety of ways. Currently required to possess Sonoran desert construction (providing new access to in Arizona, 75 percent of potentially tortoises, or laws that prohibit their formerly inaccessible areas), human occupied Sonoran desert tortoise habitat propagation in captivity (Jarchow et al. depredation of tortoises as food sources, occurs within 30 mi or less of a city or 2002, p. 289; Jones 2008, p. 69). Jarchow and barriers to tortoise movement town with a population of 1,000 or et al. (2002, p. 289) state that the created by pedestrian fencing are more, and considering future growth number of captive Sonoran desert recognized as having serious impacts to projections, it is likely that 100 percent tortoises in Arizona is so large that an Sonoran desert tortoise habitat. The of occupied tortoise habitat will be outright prohibition of their possession geographic scope of these threats is affected in the future. Livestock grazing is both impossible and impractical. relatively small on the landscape, in Mexico poses significant threats to The popularity of Sonoran desert restricted to the immediate border the Sonoran desert tortoise habitat there tortoises in captivity, as well as the region, and to undocumented immigrant due to ineffective livestock management various adoption programs around the migration corridors, such as that and continued overgrazing. Lastly, State, may unintentionally mislead the recognized through the Tohono desertscrub habitat that has been public into thinking that Sonoran desert O’odham Nation, extending through disturbed takes a very long time to tortoises are not protected, and may, Ironwood Forest National Monument. recover, on the order of decades or therefore, be collected from the wild

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(Grandmaison in press, p. 6). For most-frequently collected age class, Sonoran desert tortoise from a example, the area surrounding the which could be detrimental to population poses a higher threat to that Hualapai Foothills plot experienced populations, especially when population, because the survivorship of increased development in 2001, which reproductive females are collected. tortoises in this size class is the highest, may have increased human-tortoise Grandmaison (2010a, pers. comm.) and the odds of a given Sonoran desert interactions and possibly illegal stated, ‘‘Illegal collection of desert tortoise reaching this size class is collection. Declines in tortoise tortoises is a form of additive mortality believed to be comparatively low, encounters at this plot in 2001 and 2005 resulting from the impacts of roadways further adding importance to the may have, in part, resulted from illegal in tortoise habitat. Given that adult maintenance of adults within a collection due to that plot’s proximity to tortoises are the most likely population. The removal of an adult developed land (AGFD 2010, p. 7). demographic to be collected (i.e., they female from a population also removes Arizona’s regulations have no are easier to detect than juveniles or the opportunity for numerous clutches provisions requiring permits for hatchlings), and the sensitivity of of eggs. In addition, nearly one-third of possession of Sonoran desert tortoises, tortoise population growth rates to even all motorists who encounter a Sonoran which would aid in identification of small increases in adult mortality, desert tortoise will attempt to move it those tortoises that were in lawful illegal collection really needs to be off the roadway, which increases the possession before January 1, 1988. In considered when discussing the risk of bladder-voiding, which may addition, there may be incentive created cumulative impacts of roads.’’ place additional physiological stress on for the illegal release of captive tortoises While the actual collection of Sonoran moved tortoises and may decrease their into the wild because of the number of desert tortoises detected on roadways is survivorship. We also found data on tortoises breeding in captivity, and the one form of interaction, a higher collection and sale of Sonoran desert difficulty associated with finding percentage of motorists attempt to move tortoises in Mexico, which is likely less recipients of offspring within the legal Sonoran desert tortoises off the roadway of a threat in current times, due to the 24-month window (under Arizona’s when they are detected. Grandmaison prohibition of commercial sale and to Commission Order 42). This could (2010a, pers. comm.) found that 28 the demographic trend associated with result in a higher number of illegal and percent of all motorists passing a desert more people moving to urban areas, indiscriminant releases into the wild tortoise will move the tortoise off of the reducing the number of wild encounters (AIDTT 2000, p. 14). Edwards et al. road. While moving a Sonoran desert with tortoises in Mexico. (2010, pp. 801–807) conducted genetic tortoise off the roadway may be testing of 180 captive tortoises from considered well-intended, the stress to a Field Research and Physical Arizona to discern their genetic origin Sonoran desert tortoise that is created Manipulation (as Sonoran, Mojave, or a hybrid). They when it is handled may result in Field research and monitoring of wild found that 45 percent of sampled intestinal torsion (which can cause Sonoran desert tortoise populations has captive tortoises were not of strictly intestinal obstructions), or lead to the been ongoing since the 1970s, Sonoran origin, but rather either pure tortoise voiding its bladder. As producing invaluable information for Mojave, Sonoran-Mojave cross, or Texas discussed below, bladder voiding has wildlife and habitat managers to make tortoise (Gopherus berlandieri)— serious implications, potentially reasoned decisions with respect to Sonoran desert tortoise hybrids resulting in decreased survival, conservation planning. However, some (Edwards et al. 2010, p. 804). These data especially during late spring and early level of harassment or potential harm indicate there may be a risk of genetic summer in the Sonoran Desert, when from disease transmission or contamination of wild populations precipitation is usually rare or non- dehydration is inherent to hands-on when captives are released. Genetic existent (Grandmaison 2010a, pers. manipulation (such as collecting blood contamination can weaken the genetic comm.; in press, p. 11). samples, affixing radio transmitters, and fitness of a population and render it Although removal of Sonoran desert vulnerable to extirpation. In addition, as tortoises from the wild has clear conducting health assessments). documented in Factor C below, captive negative effects on wild populations, One of the more significant risks to Sonoran desert tortoises have been their popularity as household pets may Sonoran desert tortoises from the shown to have a higher incidence of provide some educational benefits to the handling of wild tortoises by researchers disease, and their release can place wild public. Jarchow et al. (2002, p. 310) is the increased potential for them to populations at risk. provided evidence for potential void water reserves stored in their Opportunities to collect Sonoran conservation benefits from Sonoran bladder. As a defense mechanism when desert tortoises often result from desert tortoises that are already in threatened, Sonoran desert tortoises incidental observations by motorists captivity by stating, ‘‘The captive may occasionally evacuate their while using dirt, gravel, or paved roads. population of desert tortoises provides bladders, releasing valuable water stores In a recent study, out of a total of 561 not only enjoyment to their custodians important for survival in their arid opportunities for motorist-Sonoran but, more importantly, opportunities for habitat, especially during drought years. desert tortoise interaction, 1.43 percent education of the public and increased Averill-Murray (2002a, p. 430) noted, resulted in attempted collection of a live awareness of the species among those ‘‘This water loss could result in serious decoy, and 7.4 percent attempted the who may never see a desert tortoise in health threats or compromise normal collection of an artificial Sonoran desert nature. Thus, the captive population behavior or physiology, especially tortoise decoy (Grandmaison in press, may play an important role in mustering during hot, dry summer months.’’ Water pp. 8–9). Combining the data, public support for conservation of their loss in Sonoran desert tortoises can also Grandmaison (in press, p. 11–12) found wild relatives.’’ result in reductions of reproductive that collection attempts varied with In conclusion, research suggests that output and survivorship (Averill- road type and approximately 1 in 12 (8 about 1 in 12 motorists in Arizona who Murray 2002a, pp. 430, 433–434). percent) motorists that detect a Sonoran detect a Sonoran desert tortoise will Averill-Murray (2002a, pp. 430, 434) desert tortoise in the wild may attempt attempt to collect it, and that the highest found that Sonoran desert tortoises that to illegally collect it. Adult tortoises are incidence of collection is within the urinated during field research handling the most conspicuous and are likely the adult age class. The removal of an adult had a 5–13 percent lower survival rate.

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Any kind of handling of tortoises those who want one as a household pet, mechanisms, including harassment and during field research or monitoring of through several channels within the predation by feral or off-leash domestic Sonoran desert tortoise populations captive population (discussed further in dogs, and illegal releases of captive during periods of excessive drought may Factor D). In addition, efforts are being Sonoran desert tortoises and exotic be stressful to the tortoises (Berry et al. made to educate the public about the species that may transmit diseases to 2002b, p. 436). Berry et al. (2006b, p. Sonoran desert tortoise, with an wild Sonoran desert tortoises. 436) recommended that scientists emphasis on leaving Sonoran desert Predation by Ravens working with wild desert tortoises tortoises in the wild when they are recognize abnormalities in behavior and observed. We believe these factors may Ravens and coyotes are known laboratory data as early warning signs of reduce the likelihood of illegal predators on Mojave desert tortoises, stress to modify, delay, or terminate collection. However, a recent scientific and possibly on Sonoran desert specific field protocols on stressed study found that one in 12 tortoises that tortoises, and are most likely to benefit populations. is detected by a motorist (mostly adult from anthropogenic subsidization Use of radio telemetry technology on tortoises) is illegally collected. We (Boarman 1993, p. 192; Boarman et al. desert tortoises may affect their expect that in the foreseeable future, 2006, p. 259). Ravens turn over behavior, survival, and reproductive incidence of collection will likely hatchling desert tortoises and pierce success, but available literature is increase as the human population grows through their soft plastrons, or pierce largely inconclusive (Boarman et al. and more people will use off-road trails, directly through their carapace, to 1998, p. 26). There is little doubt that with higher frequency, within occupied access their meat and organs. Ravens are radio telemetry studies have provided tortoise habitat. Scientists who conduct often less likely to emigrate long many insightful data on the biology and field research on and monitoring of wild distances to colonize would-be suitable behavior of Sonoran desert tortoises, Sonoran desert populations have areas, but subsidization from human and are therefore more of a benefit than identified the potential risk for bladder activities on the landscape create a potential threat. voiding and disease transmission during opportunities for rapid population Jacobson et al. (1992, pp. 238–239) field manipulation of tortoises, and have growth of ravens where they formerly reviewed the recommended procedures now built appropriate protocols in their did not occur (Boarman et al. 1995, for obtaining blood samples from desert field methodology to minimize these p. 1; Fleischner et al. 2008, p. 472). tortoises, including collection from the risks. Based on this information, we find Ravens, in particular, have been heart, jugular vein, brachial vein, that overutilization for commercial, identified as subsidized predators on ventral coccygeal vein, orbital sinus, recreational, scientific, or educational juvenile Mojave desert tortoises, and and trimmed toenails, and assessed the purposes, in the form of illegal possibly on juvenile Sonoran desert potential risks associated with each collection, is likely to threaten the tortoises (Boarman 1993, p. 192). Roads collection site. At a minimum, the Sonoran desert tortoise now or in the and power line rights of way attract collection of blood samples from desert foreseeable future. potential avian predators of Sonoran tortoises is considered relatively desert tortoises, such as ravens and red- invasive and is likely a source of Factor C. Disease or Predation tailed hawks that use power lines as temporary stress to the animal, Natural predation of Sonoran desert nesting and perching sites, and roads potentially leading to bladder voiding tortoises occurs as discussed previously can serve as sources of carrion (Knight and subsequent dehydration if fluid in the Species Information section and Kawashima 1993, p. 266). Raven levels are not replenished before release. above. Unnatural sources of predation, populations, and potential risk of However, we believe the majority of such as from feral, or off-leash dogs, predation of Sonoran desert tortoises by field researchers exercise appropriate human depredation for recreation or as ravens, are both higher with increasing caution when collecting blood samples food, and as an indirect result of human proximity to human development from Sonoran desert tortoises, and the land uses (referred to as subsidized (Kristan and Boarman 2003, p. 2432). literature does not indicate these predation) also occur. A subsidized Documented reports of raven procedures are an appreciable source of predator is one whose survival in a predation on Sonoran desert tortoises mortality for wild Sonoran desert particular area is facilitated by the are rare in the literature, however. One tortoises. availability of food, water, or other local rancher in southeastern Mohave Over the years, field protocols have potentially limiting resources made County, Arizona, reported an been developed and standardized to available by the presence of human observation of raven predation on a minimize risks to Sonoran desert activities in that area (Boarman 1993, p. Sonoran desert tortoise (Dieringer 2010, tortoises while they are being physically 192). Common examples of subsidized p. 1). Ravens have also been observed handled. These protocols are outlined in predators are coyotes and ravens. on the Four Peak monitoring plot on Averill-Murray (2000, p. 17) and Berry Human activity-related resources that several occasions, but their predation on and Christopher (2001a, pp. 433–434). provide basic biological needs for Sonoran desert tortoises within this plot We believe these field protocols have subsidized predators include such has never been documented (Murray minimized potential risks to individual things as roads, landfills, sewage and and Schwalbe 1997, p. 33). Mojave tortoises posed by researchers during septic ponds, open dumpsters, desert tortoises are most commonly their field work. agricultural fields, feedlots, parks, associated with valley bottomlands picnic areas, livestock waters, utility characterized by relatively open, sparse Summary of Factor B poles, building sites, and overpasses vegetation communities which may be We identified two possible (Boarman 1993, p. 193; Rosentstock et advantageous to a purely visual-based mechanisms for which the potential al. 2004, p. 3; Boarman et al. 2006, p. predator such as the raven. In Arizona overutilization of Sonoran desert 259; Webb et al. 2009, p. 72). Upland Sonoran desertscrub, where tortoises for commercial, recreational, For example, Averill-Murray and Sonoran desert tortoises reach their scientific, or educational purposes Swann (2002, p. 1) stated that urban peak population densities, habitat is a could occur: Illegal collection and field development adjacent to the Saguaro more complex mosaic of boulders and research. Many desert tortoises exist in National Park in Pima County threatens denser vegetation, which would hamper captivity, and are generally available to the Sonoran desert tortoise via several the ability of such predators to locate

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prey, in particular, small hatchlings. percent of the monitoring plots. Three over a 6-year time period exhibited Some exceptions include habitat within such plots occur within 1 mi (1.6 km) signs of gunshots. Many of these sparsely vegetated valley bottoms that of developed areas. Domestic dogs have observations occurred before the listing are used for dispersal between been observed attacking and chewing on of the Mojave desert tortoise, indicating populations on adjacent mountains or Sonoran desert tortoises in the Hualapai that tortoises may have been shot foothills, or similar, uncharacteristic Foothills and Bonanza Wash plots simply for misdirected recreational areas that maintain Sonoran desert (AGFD 2010, p. 12). Domestic dogs sport or entertainment, not from tortoise populations, such as the appear to be a significant problem, politically-driven motives (people Florence Military Reservation. The best which may be worsening, in the East disliking the protections of the Act). scientific and commercial data available Bajada plot, where in 1997, 53 percent Bury and Marlow (1973, p. 11) indicates that predation by ravens is of live tortoises, and in 2002, 78 percent described examples of Mojave desert significantly less of a concern for of live tortoises, exhibited injuries tortoise mortalities in California as a Sonoran desert tortoises than it is for associated with domestic dogs (AGFD result of shooting, including eight Mojave desert tortoises. 2010, p. 12). One citizen commented independent observations of shot In conclusion, although raven that in 1997 a purebred Rottweiler was Mojave desert tortoises along two miles predation has been identified as a observed roaming freely on the (3.2 km) of dirt road; an individual’s substantial threat to the Mojave desert Ironwood Forest National Monument confession of using juvenile desert tortoise, largely because of the relatively with an adult Sonoran desert tortoise in tortoises as skeet (aerial shotgun) open, valley bottomland where they its jaws. The tortoise was mortally targets; and a report of an individual occur, the risk to Sonoran desert tortoise wounded from a punctured carapace, lining up a total of 47 desert tortoises populations is relatively low. Very few suggesting that large, powerful domestic and shooting each of them with a observations of raven predation of dog breeds may be able to penetrate the shotgun. Sonoran desert tortoises in Arizona or carapace of adult tortoises and kill them Recreational firearms target practice Sonora have been documented in the (Coping 2009, p. 7). occurs in dispersed fashion throughout literature, leading us to conclude that Numerous signs of attempted Federal and State lands in Arizona raven predation on the Sonoran desert predation (consistent with those from within the distribution of Sonoran tortoise is not a concern. feral dogs), ranging from mild to severe, desert tortoises. Some reports of gunshot were observed in wild Sonoran desert deaths of Sonoran desert tortoises on Predation From Feral or Off-Leash Dogs tortoises examined in Sonora, Mexico these lands have been made (Hart et al. Feral dogs are known to interact with (Brown et al. 2006, p. 6). We are 1992, p. 120; AGFD 2010, p. 9; Jones numerous species of animals, including unaware of the locations where these 2010, pers. comm.). In some locations, desert tortoises and related species, and wild Sonoran desert tortoises were recreational firearms target practice is they may force Sonoran desert tortoises captured by Brown et al., but the highly conspicuous (as evidenced by to use their habitat in an unnatural proximity to human settlements, and large amounts of debris used as targets manner (Causey and Cude 1978, pp. 94– free-ranging domestic dogs (a common and left behind) in densely occupied 95; Lenth et al. 2008, pp. 222–223). The sight in Mexico) may have been Sonoran desert tortoise habitat, most risk of feral or off-leash dog predation responsible. notably in areas near urban population on Sonoran desert tortoises is expected In conclusion, the threat of feral dog centers, such as at Sugarloaf Mountain to be highest within the urban-rural predation exists in both Arizona and on the Cave Creek Ranger District of the interface (a likely source of Sonora, Mexico, and has been shown to Tonto National Forest. In this location, domesticated, feral dogs). be strongly correlated with distance to two incidences of shot Sonoran desert Jones (2008, p. 66) documented 35 urbanized areas in most cases. We found tortoises have been reported, although it separate incidences of harassment by numerous reports of observed or could not be determined whether these wild or domestic dogs in surveys suspected feral dog predation in the wounds occurred pre- or post-mortem conducted in high-use public lands literature, most in immediate proximity (Jones 2010, pers. comm.). Another adjacent to the urban centers of Tucson, to urban areas. Feral dog predation has incidence of shooting was reported in Phoenix, and Kingman, Arizona (Pima, been documented in approximately half the Hualapai Foothills monitoring plot Maricopa, and Mohave Counties, of the long-term monitoring plots in (Hart et al. 1992, p. 120). The AGFD respectively), based upon observed shell Arizona, and may be a significant cause (2010, p. 9) reported 13 separate damage. These incidences were of population decline in one plot. As incidences of vandalism on Sonoran positively correlated with increasing urbanization and human population desert tortoises on or adjacent to 7 proximity to urban centers. Also, three growth continues into the future, as different monitoring plots; several of the to five packs of presumably feral dogs described in Factor A, the incidence of Sonoran desert tortoises appeared to were observed in both the East Bajada feral dog predation of Sonoran desert have been killed by gunshot. monitoring plot in Mohave County and tortoises is expected to also increase. When studying Mojave desert in Saguaro National Park West in Pima tortoises, Berry (1986b, p. 129) found County (Jones 2008, p. 66). Researchers Human Depredation and Vandalism that the incidence of gunshot deaths is of Sonoran desert tortoises within the Human depredation (intentional likely to be higher in areas of greater Tucson Mountain District of Saguaro killing) of Sonoran desert tortoises has vehicular access and in proximity to National Park noted a high number of been documented to occur either as a urban areas. The potential effect of tortoises with injuries consistent with result of vandalism (most commonly via gunshot deaths on Sonoran desert dog attacks, attributing these gunshot) or as a source of food. The tortoise populations is not entirely observations to the close proximity of intentional shooting of Mojave desert known, but is likely most significant on this district to urban development tortoises in southern California was the adult size class, which is the most (Zylstra and Swann 2009, pp. 14–15). reported to be relatively common, at conspicuous, and this effect may act The AGFD (2010, pp. 11–12) reported least before the Mojave population was synergistically with other threats we that domestic dogs, their scat, and chew Federally listed. Berry (1986b, p. 127) have identified. Combined with the marks on, or trauma to, Sonoran desert found that 14 percent of 635 carcasses relatively low recruitment rate of tortoises have been reported in 47 taken from 11 sites in the Mojave Desert juvenile desert tortoises into adult size

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classes, adverse effects to survivorship In conclusion, direct human diseases that could affect wild Sonoran of populations adjacent to urban areas depredation on Sonoran desert tortoises desert tortoises (Howland and might be expected (Berry 1986b, p. 130). is most likely to occur via vandalism Rorabaugh 2002, p. 343). The release of Sonoran desert tortoises are (i.e., shooting) and utilization as a any captive reptile or amphibian is sometimes used as a food source in source of food. While the deliberate strictly prohibited by the AGFD. In a Sonora, and likely experience shooting of Sonoran desert tortoises has study investigating the relationship population declines where they occur been documented in Arizona, reports between exposure to M. agassizii and an adjacent to moderately sized settlements are comparatively rare, especially urban gradient of Greater Tucson, (Fritts and Jennings 1994, p. 52). Bury considering the amount of monitoring Arizona, Jones (2008, p. 36–37) found et al. (2002, p. 102) reported several and survey effort that has been afforded evidence to suggest a positive historical incidences of Sonoran desert to wild populations over the past correlation between the likelihood of tortoises being used as a source of food several decades. However, as the human testing seropositive for antibodies to M. by native peoples in Sonora, but less population continues to grow and agassizii (meaning a tortoise has been frequently in current times. According urbanization expands, we expect the exposed to URTD), and proximity to to 12 interviews at 6 ranches in central incidence of human depredation to urban centers. These results suggest that Sonora, 67 percent of local people increase. Sonoran desert tortoises have there may be a relationship between described Sonoran desert tortoises as been used for food in Mexico urbanization and this pathogen. declining. All but one interviewee historically, but these occurrences are Tortoises from suburban sites are 2.3 stated they have eaten Sonoran desert suspected to be comparatively rare in times more likely to test seropositive for tortoise meat at some point in their lives current times. Sonoran desert tortoises antibodies to M. agassizii than tortoises (Bury et al. 2002, p. 102). However, may also be captured by undocumented from other sites in the greater Tucson demographic trends in Sonora indicate immigrants as they pass through remote area. In fact, Sonoran desert tortoise the number of people living on ranches areas of Arizona, but increasing border- populations in the Rincon Mountains and ejidos (commonly owned lands enforcement activities are expected to (adjacent to Tucson, Arizona) had the used for agriculture and livestock reduce the number of undocumented highest prevalence of exposure to URTD grazing) have declined, while city immigrants entering Arizona in the of any sites tested in Arizona, with 72.7 populations have increased, potentially foreseeable future, reducing this risk. percent of sampled Sonoran desert tortoises identified as seropositive reducing the likelihood of Sonoran Upper Respiratory Tract Disease desert tortoises being used for food (Jones 2008, p. 93). The threats of mycoplasmosis (or Jones (2008, p. 60) also explored the (Bury et al. 2002, pp. 102–103). upper respiratory tract disease (URTD)), relationship between URTD and captive Sonoran desert tortoises have also and cutaneous dyskeratosis (shell and wild desert tortoises from high-use been documented as a food source for disease) were major factors in the listing public lands in Maricopa, Mohave and undocumented immigrants on their of the Mojave desert tortoise (Berry Pima counties, and found that captive journey through the Sonoran Desert of 1997, p. 91). Genetic analyses were desert tortoises are 1.8 times more likely Arizona, specifically in the Ironwood performed by Brown et al. (1994, p. to test seropositive for exposure to M. Forest National Monument. Coping 4580) on seven Mycoplasma organisms agassizii than wild tortoises (p. 65). (2009, p. 4) claims that by the time that were recovered from the upper Sonoran desert tortoises from Pima undocumented immigrants reach the respiratory tract of clinically ill desert County (wild and captive) had the Ironwood Forest National Monument, tortoises. These laboratory tests led to highest incidence of exposure to URTD many have been abandoned by their the discovery and subsequent species and were 5.4 times more likely to be guides and left without food, water, or description of Mycoplasma agassizii, seropositive for antibodies to M. a sense of direction, leaving them in the species of bacteria that causes upper agassizii than those from Mohave or intense desperation (Coping 2009, p. 4). respiratory tract disease in infected Maricopa Counties (Jones 2008, p. 65). In one instance on June 2, 1997, a small tortoises (Berry and Christopher 2001b, While clinical signs of URTD are group of undocumented immigrants p. 413). Although M. agassizii has been infrequently observed in wild Sonoran approached a resident living within the studied in Mojave and Sonoran desert desert tortoises in Arizona, Jones (2008, Ironwood Forest National Monument. tortoises, as well as gopher tortoises (G. pp. 37, 74) found that M. agassizii is The immigrants had a live Sonoran polyphemus), since the 1980s, its widespread among captive desert desert tortoise they had captured along origins are unknown. It may be a tortoises in Arizona, suggesting that the the way that had a rope tethered to its naturally occurring or an exotic captive population may be an important front leg. They told this resident that if pathogen. There are several potential reservoir of URTD-infected tortoises that they did not receive food from him, they routes of inoculation of vertebrates by can spread the disease to wild planned to eat the tortoise (Coping 2009, microbiota such as Mycoplasma spp., populations if unlawfully released or p. 5). In another reported observation, a including horizontal (transmission allowed to escape. livestock grazing permittee on the between individuals), vertical (passed Even though URTD appears to occur Ironwood Forest National Monument down from parent to offspring), and widely and has been documented in stated that he had seen immigrants environmental (passed from Sonoran desert tortoise populations, no carrying tortoises, ‘‘presumably with the environment to individual) (Belden and die-offs have been attributed to URTD in intent to consume’’ (Averill-Murray and Harris 2007, p. 536). Brown (2002, p. Arizona. Currently, URTD does not Averill-Murray 2002, p. 29). Indigenous 1340) states that direct contact with appear to be a source of mortality for communities of the Sonoran Desert infected individuals is the most likely Sonoran desert tortoise populations historically used Sonoran desert route of transmission. Brown (2003, p. (Hart et al. 1992, p. 120; AIDTT 2000, tortoises for food and medicine, and 1) stated that M. agassizii is not known p. 9; Averill-Murray and Klug 2000, p. their shells for ladles, dippers, bowls, to be transferred through the eggshell. 69; Dickinson et al. 2002, p. 256; and shovels (Nabhan 2002, p. 356). Disease may be spread to wild Howland and Rorabaugh 2002, p. 343; However, we have no information to populations as a result of the release of Jones 2008, p. 22; AGFD 2010, p. 9). suggest these uses have continued into captive native or nonnative tortoise Howland and Rorabaugh (2002, p. 343) modern times. species, which can be carriers of hypothesized that if disease does

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become a significant threat to Sonoran Cutaneous Dyskeratosis precise cause of death in many desert tortoise populations in the future, Cutaneous dyskeratosis, a shell situations. The literature documents their patchy distribution may limit the disease, was also a major factor that Sonoran desert tortoise populations spread of disease. However, because the considered in the listing of Mojave in proximity to urbanized areas are most captive population of desert tortoises desert tortoises. In populations of at risk of disease (as a result of released may serve as a reservoir of disease and Mojave desert tortoises exhibiting captives), because the captive because captives are unlawfully clinical signs of this disease, significant population (both in Arizona and released into the wild by the public, die-offs have been documented, some as Mexico) has a significantly higher monitoring wild tortoise populations high as 70 percent mortality rate percentage of seropositive tortoises and that occur near urban areas will (Jacobson et al. 1994, p. 69). Cutaneous tortoises that have acquired URTD. continue to be important (Howland and dyskeratosis may appear on the Cutaneous dyskeratosis has been Rorabaugh 2002, p. 343; Jones 2008, pp. carapace, plastron, and thickened scales documented in virtually all Sonoran desert tortoise long-term monitoring 6–7, 41, and 72–73). of the forelimbs, but is most often plots in Arizona, although no Sonoran An indirect effect of disease is that it apparent on the plastron (Jacobson et al. desert tortoises have been documented may also subject individuals to 1994, pp. 70–74). Potential causes of to have succumbed to this disease, and increased predation. Sonoran desert cutaneous dyskeratosis have not been we conclude that cutaneous tortoises that are exhibiting clinical confirmed, but may be related to dyskeratosis is not a substantial threat to signs of URTD may be more active deficiency diseases and environmental populations. Disease screening has been during winter months, in order to contamination (Berry 1997, p. 91). a regular component to field research increase their metabolism and elevate Cutaneous dyskeratosis has been and monitoring of wild Sonoran desert their body temperatures. This increase reported as more prevalent than URTD tortoise populations throughout their in surface activity might result in a within Sonoran desert tortoise range for many years, and has not greater chance of predation or human populations across Arizona. As of 2000, indicated that either URTD or cutaneous detection (Jones 2008; p. 105). Jones Sonoran desert tortoises infected with dyskeratosis pose a current threat to the (2008, p.103) found that periods of cutaneous dyskeratosis had been Sonoran desert tortoise. surface activity may increase in observed in every monitored clinically ill Sonoran desert tortoises; For additional information on disease population, with the exception of the in desert tortoises, or specific disease however, home range size did not differ Wickenburg Mountains plot (AIDTT data from monitored Sonoran desert between seropostive and seronegative 2000, p. 9; Averill-Murray and Klug tortoise populations, see Hart et al. tortoises (p. 103), so seropositive 2000, p. 69). However, noticeable (1992, p. 120); Berry (1997, p. 91); tortoises which are more active in population-level effects have not been Brown et al. (1994, p. 4580; 1995, p. winter months do not appear to be reported in any of the monitoring plots 350; 2002, p. 497; 2006, pp. 5–6); increasing the areas over which they (AIDTT 2000, p. 9; Averill-Murray and Jacobson et al. (1994, pp. 69, 70–74); move. Klug 2000, p. 69; AGFD 2010, p. 9). Of Schumacher et al. (1999, pp. 829–830); Wild Sonoran desert tortoises in the 36 individual Sonoran desert AIDTT (2000, p. 9); Averill-Murray and Sonora, Mexico, were tested for the tortoises sampled from the Little Shipp Klug (2000, p. 69); Berry and presence of antibodies to two Wash and the from Christopher (2001b, p. 413); Averill- Mycoplasma species, M. agassizii and 1990 to 1994, only 5 (all females Murray and Averill-Murray (2002, pp. M. testudineum, and were found to be presumed to be at least 30 years old) 16, 19, 26); Brown (2002, pp. 1340, generally unexposed (Brown et al. 2006, had signs of cutaneous dyskeratosis, and 1343; 2003, p. 1); Dickinson et al. (2001, p. 5). Twenty-seven of 28 wild Sonoran all lived through the end of the field pp. 254–256; 2002, pp. 256, 258, 260– desert tortoises were found to be study. This prompted Dickinson et al. 261; 2005, p. 841); Howland and seronegative, indicating they had not (2002, p. 258) to suspect that Sonoran Rorabaugh (2002, p. 343); Tracy et al. been exposed to Mycoplasma spp.; and desert tortoises might not be affected by (2006a, p. 1191); Belden and Harris one individual was serosuspect (a result this disease, although they (2007, pp. 536, 538); Wendland et al. indicating that the antibody level is acknowledged that more research was (2007, p. 1190); Jones et al. (2005, p. 1); intermediate between positive and necessary. As of 2000, the highest Boarman and Kristan (2008, p. 19); negative, and is considered incidence of cutaneous dyskeratosis (62 Jones (2008, pp. 6–7, 70, 93, 103, 105); inconclusive) for M. testudineum percent of individuals) was reported Zylstra and Swann (2009, pp. ix–x); and (Brown et al. 2006, p. 5). However, 11 from the East Bajada plot (AIDTT 2000, AGFD (2010, p. 9). of 21 captive Sonoran desert tortoises in p. 9). In Sonora, Mexico, 14 of the 28 Sonora, Mexico, tested seropositive for wild Sonoran desert tortoises examined Summary of Factor C antibodies, indicating exposure to M. exhibited clinical signs of cutaneous In review of the information agassizii; and four were serosuspect for dyskeratosis (Brown et al. 2006, p. 6). presented above, we conclude that exposure to M. testudineum. Ten In conclusion, disease has been predation from feral domestic dogs and, captive desert tortoises had M. agassizii documented as a serious threat to the to a lesser extent, human depredation isolated from nasal flushes, indicating a Mojave desert tortoise, and was a and vandalism, in combination with current infection, suggesting that primary cause for its listing under the other threats, threaten Sonoran desert disease may be more prevalent in the Act. The two most prevalent diseases tortoise populations, most notably as a Sonora captive population (Brown et al. that could affect Sonoran desert tortoise result of the expansion of urbanization 2006, pp. 5–6). Nearly all of the captive populations are URTD and cutaneous and associated increases in human desert tortoises exhibited mild to severe dyskeratosis. Researchers have activity in remote areas. We conclude clinical signs of URTD. Of the captive speculated that Sonoran desert tortoises this threat to be of moderate magnitude. tortoises, six had swollen or draining may be able to clear infections of M. Based upon our review of the available chin glands and four had evidence of agassizii, and no wild Sonoran desert literature, disease does not appear to be nasal discharge (Brown et al. 2006, p. 5– tortoises have been found to have died significantly affecting the status of wild 6). Once infected by URTD, tortoises from URTD in Arizona, although it is Sonoran desert tortoise populations. may ultimately die from the disease. nearly impossible to document the Therefore, we conclude that disease

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does not pose a significant threat to the importance of the habitat: (1) The BLM’s Desert Tortoise Mitigation Sonoran desert tortoise now or in the Maintaining viable populations, (2) Policy ‘‘establishes policy to mitigate for foreseeable future. resolvability of conflicts, (3) desert impacts to desert tortoises and their tortoise density, and (4) population habitats including compensation for Factor D. The Inadequacy of Existing status (stable, increasing, or decreasing) residual impacts that cannot otherwise Regulatory Mechanisms (AIDTT 2000, p. 16; USBLM 2010, p. 1). be mitigated. Mitigation, including Within its distribution in the United The BLM categorized habitat based compensation must be designed to meet States, the Sonoran desert tortoise upon its suitability for the desert the purposes of the Rangewide Plan, occurs on lands managed by a myriad of tortoise, with Category I being the most including maintaining viable Federal and State agencies and Native suited, and Category III the least, with populations as well as maintaining the American tribes, and on private lands. the goals of maintaining viable desert quantity and quality of Category I and State agencies, such as the Arizona tortoise populations in Category I and II II desert tortoise habitat’’ (USBLM Game and Fish Department (AGFD) or habitat, and limiting population 2009b, p. 1). Compensatory funds the Arizona Department of declines in Category III habitat to the derived from BLM’s compensation Transportation (ADOT), have either extent possible (AIDTT 2000, p. 16). policy are then used for a variety of direct management authority over the However, not all Sonoran desert tortoise conservation activities to lessen impacts Sonoran desert tortoise, or could habitat was included in this to Sonoran desert tortoises including potentially impact Sonoran desert categorization process. protective tortoise fencing, culverts for tortoise populations or habitat directly AIDTT (2000, p. 19) depicts the crossing, land acquisition, and research or indirectly in carrying out their distribution of the categorized habitat (AIDTT 2000, p. 19). Details of this intended missions. Internationally, the included in Arizona. In Arizona, there policy can be found in USBLM (2009b, Sonoran desert tortoise is listed in are 723,769 ac (292,899 ha) of Category pp. 1–45). Appendix I of the Convention on I Sonoran desert tortoise habitat, 2.6 The BLM implements various International Trade in Endangered million ac (1.1 million ha) of Category objectives and management actions Species of Wild Fauna and Flora II habitat, and 3.8 million ac (1.5 million through resource management plans (commonly referred as to CITES), which ha) of Category III habitat, totaling 7.1 unique to certain geographic regions of requires permits to transport individuals million ac (2.9 million ha) of BLM-managed lands (USBLM 2010, p. between member nations (Bury et al. categorized habitat (AIDTT 2000, p. 18). 3). Currently, there are eight individual 2002, p. 86; Howland and Rorabaugh The 1988 Rangewide Plan also resource management plans, some 2002, p. 348). Under the International indentified 14 different management recently issued and others up to 22 Union for Conservation of Nature’s ‘‘Red objectives the BLM has defined years old, representing the areas with List,’’ the desert tortoise (rangewide) is specifically for desert tortoise potential Sonoran desert tortoise habitat considered ‘‘vulnerable’’—meaning it management, each with its own (USBLM 2010, p. 3). The Phoenix faces a high risk of extinction in the itemized management action plan. Resource Management Plan, which medium-term (Rorabaugh 2008, p. 27). These management objectives include directs the management of In our review, we found that the the following categories: (1) Increased approximately 440,000 ac (178,000 ha) Sonoran desert tortoise is commonly awareness; (2) inventory and of Sonoran desert tortoise habitat, does considered in conservation planning monitoring; (3) cumulative impacts; (4) not contain district-specific where it occurs on public or tribal lands identification of endangered management actions, but incorporates in Arizona. Below we discuss how each populations; (5) coordination and management actions described in the agency or entity manages their land, or cooperation; (6) research and studies; (7) Strategy for Desert Tortoise Habitat otherwise considers the Sonoran desert management of tortoise habitat; (8) Management on Public Lands in tortoise in their planning activities. regulation of lands and realty actions; Arizona (USBLM 2010, p. 3). (9) regulation of off-highway vehicles; Approximately 1.1 million ac (455,000 U.S. Bureau of Land Management (10) regulation of livestock use; (11) ha) in the Yuma, Lake Havasu, BLM is very proactive in their regulation of wild horses and burros; Bradshaw-Harquahala, and Kingman conservation management, directly and (12) wildlife habitat management; (13) resource management planning areas indirectly, through three main predator control; and (14) management that were considered Sonoran desert mechanisms: (1) Sonoran desert tortoise of energy and minerals research and tortoise habitat have been designated as habitat categorization and compensation extraction (Spang et al. 1988, pp. 14–23; ‘‘priority habitats,’’ meaning that the (monies derived from adverse effects to AIDTT 2000, p. 18). BLM prioritizes management of wildlife Sonoran desert tortoise habitat for the In 1990, BLM’s Arizona State Office habitat over other multiple-use activities acquisition of new habitat, funding issued the policy titled Strategy for (USBLM 2010, p. 3). research, etc.); (2) resource management Desert Tortoise Habitat Management on The BLM can directly or indirectly planning; and (3) land designation. The Public Lands in Arizona, Instruction manage for the Sonoran desert tortoise BLM has developed numerous Memorandum No. AZ–91–16. It through the process of land designation, documents that outline how Sonoran outlined objectives and management such as Areas of Critical Environmental desert tortoise habitat management goals actions to be implemented, and also Concern (ACEC) and Wilderness Areas. and objectives are to be achieved and established the BLM Desert Tortoise In the case of ACECs, those values may accounted for in their land use Mitigation Policy, which was later pertain to specific species or habitats, or planning. reissued in 1999 (USBLM 2010, p. 2). In cultural or scenic values (AIDTT 2000, The BLM developed the document 2009, the BLM finalized the Desert p. 22). Sonoran desert tortoises were the titled ‘‘Desert Tortoise Management on Tortoise Mitigation Policy, in order ‘‘to impetus for the Poachie and McCracken the Public Lands: A Rangewide Plan’’ articulate mitigation policy including ACECs, while other ACECs benefit the (authored by Spang et al. 1988), and off-site compensation for the Sonoran Sonoran desert tortoise through broad created the designation of three desert tortoise and its habitat on public protections, such as in the Agua Fria categories of desert tortoise habitat lands managed by (BLM) in Arizona, in and Ironwood Forest National throughout the species’ range, using a consistent manner between District Monuments (AIDTT 2000, p. 22). four main criteria to indicate the and Field Offices’’ (USBLM 2009b, p. 1). Sixteen Arizona ACECs contain Sonoran

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desert tortoise habitat (AIDTT 2000, p. the BLM uses descriptive criteria that allotments that overlap Sonoran desert 22). ACEC designations facilitate the pertain to soil conditions, ground cover, tortoise habitat on the Coronado or minimization of surface-disturbing and erosion rates (USBLM 1997, p. 5). Prescott National Forests. With the activities, such as vehicular travel, The BLM generally prohibits mineral exception of livestock grazing, the camping, fire use, mineral extraction material sales (mining activities) in majority of land uses that have the activities, and grazing (AIDTT 2000, p. Category I and II Sonoran desert tortoise highest potential to affect the Sonoran 22). There are also 48 wilderness areas habitat, but requests are evaluated on a desert tortoise occur in districts adjacent managed by the BLM in Arizona, case-by-case basis (USBLM 2010, p. 3). to urbanized areas, such as the Santa including approximately 850,000 ac For example, in the Phoenix District, the Catalina Ranger District on the (344,000 ha) of Sonoran desert tortoise BLM has denied 11 such mineral Coronado National Forest (adjacent to habitat, through ‘‘reclaiming damaged material sales, while others have been the Tucson metropolitan area) and the areas, reclaiming old vehicle ways and denied in the Tucson District, to prevent Cave Creek and Mesa Ranger Districts routes, establishing campfire and potential impacts to Sonoran desert on the Tonto National Forest (adjacent camping policies to avoid resource tortoises and their habitat (USBLM to the Phoenix metropolitan area). impacts, establishing livestock grazing 2010, p. 4). While the Coronado National Forest use objectives with respect to desired In summary, the BLM considers the does not have specific management vegetation, setting objectives for wildlife Sonoran desert tortoise in its land policies for the Sonoran desert tortoise, habitat including the desert tortoise, and management planning and has denied two policies may serve its benefit: (1) setting prescriptions for wildfire’’ or altered projects which could ‘‘Provide habitat for wildlife populations (AIDTT 2000, pp. 22–23). In addition, adversely affect the Sonoran desert consistent with the goals outlined in the the BLM manages Sonoran desert tortoise or its habitat, specifically with Arizona and New Mexico Department of tortoise habitat in Wilderness Areas and respect to mining and livestock-grazing Game and Fish Comprehensive Plans National Monuments with an emphasis activities. However, we are not aware of and consistent with other resource on maintaining natural conditions and specific actions the BLM is taking with values;’’ and, (2) ‘‘Provide for ecosystem biological function of these areas respect to invading nonnative plant diversity by at least maintaining viable (USBLM 2010, p. 10). Approximately 22 species and subsequent wildfire populations of all native and desirable percent of categorized Sonoran desert concerns, vandalism of tortoises, feral nonnative wildlife, fish, and plant tortoise habitat falls under these dog predation, or management to species through improved habitat management prescriptions on BLM counter anticipated climate change. In management’’ (AIDTT 2000, p. 36). lands in Arizona (USBLM 2010, p. 10). addition and as discussed below, BLM In September 2005, Region 3 of the management of off-highway vehicle use U.S. Forest Service adopted a new Livestock grazing is the most on their lands is not protective of policy for rangeland adaptive widespread land-use activity permitted Sonoran desert tortoise populations. management (USFS 2007, pp. 1–34), on BLM lands, with 273 individual Therefore, we conclude that BLM called the Chapter 90 policy. Under this allotments covering approximately 6 management of the Sonoran desert policy, limits on timing, intensity, million ac (2.4 million ha), and 74 tortoise and its habitat is currently frequency, and duration of livestock percent of Sonoran desert tortoise inadequate. grazing are set in Allotment habitat in the U.S. on their lands U.S. Forest Service Management Plans. Monitoring and (Rosmarino and Connor 2008, p. 49). A adaptive management are key attributes policy was developed by the BLM’s The Sonoran desert tortoise is of the Chapter 90 policy and are Arizona State Office in 1994, addressing included on the U.S. Forest Service’s intended to ensure livestock grazing livestock use of upland vegetation Regional Forester’s Sensitive Species outcomes meet desired resource growth in response to significant winter List, which means it is evaluated in all conditions which include the needs of precipitation, ensuring adequate biological evaluations for activities and wildlife such as the Sonoran desert amounts of forage remained for the projects proposed within its habitat tortoise. The term ‘‘conservative use’’ in Sonoran desert tortoise (and other (AIDTT 2000, p. 35). Sonoran desert this policy is defined as forage species) before and after livestock use. tortoises occur on the Prescott utilization on key forage species These ‘‘ephemeral’’ pastures or (Bradshaw Ranger District), Coronado between 30 and 40 percent or less of allotments are permitted for 30 days of (Santa Catalina and Nogales Ranger annual forage production by weight for livestock grazing, with additional 30- Districts), and Tonto National Forests in herbaceous perennials, and 50 percent day extensions if monitoring concludes Arizona (Murray and Schwalbe 1993, p. or less on woody browse species (USFS adequate forage capacity exists (AIDTT 39). The Tonto National Forest manages 2007, pp. 26, 30). It is inherent in the 2000, p. 22). AIDTT (2000, p. 22) the most Sonoran desert tortoise habitat term ‘‘conservative use’’ that watershed viewed this grazing policy as a of the three National Forests in Arizona, conditions and vegetative ground cover ‘‘significant protective change that where they occur in the Cave Creek, will be optimized as appropriate to ensured forage for other animals, such Mesa, Globe, and Tonto Basin Ranger various range sites. At no time is as desert tortoises, and also ensured that Districts. excessive use considered acceptable. perennial plants would not be damaged Multiple land uses occur on these The goal is to achieve conservative use due to insufficient ephemeral growth.’’ National Forests, including recreation, in the uplands over successive years. In 1997, the BLM (USBLM 1997, pp. 1– camping, livestock grazing, and off- This strategy recognizes the importance 18) further developed standards and highway vehicle use. Approximately 46 of adaptive management, and may guidelines for livestock grazing and livestock grazing allotments on the include adjustments of timing, intensity, rangeland health. In upland sites, the Tonto National Forest partially or frequency, and duration of grazing to BLM standard is ‘‘Upland soils exhibit wholly overlap the potential range of reach resource objectives (USFS 2007, infiltration, permeability, and erosion the Sonoran desert tortoise, with several pp. 13–14). rates that are appropriate to soil type, rated as having impaired or Implementation monitoring of climate and landform (ecological site)’’ unsatisfactory soil conditions (AIDTT livestock grazing under conservative use (USBLM 1997, p. 5). To assess whether 2000, p. 37). We are not aware of the practices can be done using a variety of an allotment is meeting this standard, exact number of livestock grazing methods, and is designed to provide

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information that will enable decision- as results-oriented goals, strategies to 1999, the BLM tracked an increase of makers to practice adaptive achieve the goals, timeframes for greater than 20 percent of off-highway management by making necessary implementing strategies, or performance vehicle use within the range of the changes needed for plant development measures to monitor incremental Sonoran desert tortoise, and reported and recovery, and to assess physical progress (USGAO 2009, p. 16). 124 and 123 violations of improper improvements to allotments (USFS Limitations of the USFS’s strategic plan vehicle use Statewide in 1998 and 1999, 2007, pp. 16–17). Effectiveness have resulted from a general failure to respectively (AIDTT 2000, p. 10). The monitoring of conservative use practices address motorized travel designations BLM has only 195 law enforcement documents whether management on the ground, communicate with the officers nation-wide, which means that actions are having the expected progress public, monitor off-highway vehicle on average, each officer is responsible toward achieving resource-management trail systems, or enforce off-highway for overseeing approximately 1.2 objectives, and is used to track upland vehicle regulations (USGAO 2009, p. million ac (490,000 ha) of land, or 1,875 vegetative and soil condition over the 16). sq mi (4,856 sq km) (USGAO 2009, p. long term (USFS 2007, pp. 16–17). From In response to public concerns, the 38). Law enforcement of off-highway a short-term (within-year) perspective, BLM developed the ‘‘National vehicle use in the Arizona-Mexico wildlife habitat and watershed Management Strategy for Motorized Off- border region is further complicated by conditions are gauged by monitoring Highway Vehicle Use on Public Lands’’ increasing demands to address drug seasonal utilization on key forage (USBLM 2001, p. 9). This strategy smuggling and other border-related species during the grazing period. Due outlines action items that are to be issues (USGAO 2009, p. 39). To address to a warmer climate, variable implemented ‘‘as soon as practical’’ an inadequate law enforcement precipitation, and mild winters, (USBLM 2001, pp. 10–21). However, the presence, the BLM’s Phoenix District seasonal-utilization monitoring is U.S. Government Accountability Office has initiated an ‘‘ambassador program’’ important because the end of a (2009, pp. 17–18) found that ‘‘[d]espite which recruits volunteers to ‘‘educate particular growing season is not well- identifying numerous goals and users and promote safe, sustainable off- defined for all plant communities in strategies to achieve the goals, BLM’s highway vehicle use in the area’’ Sonoran desert tortoise habitat on Forest recreation plan does not identify any (USGAO 2009, p. 38). The use of signs Service lands. In review of this policy, timeframes for implementing the is a common method to enforce off- we conclude that implementation of the strategies or any performance measures highway vehicle regulations on Federal Forest Service’s rangeland management for monitoring incremental progress lands, but signs are often vandalized strategy is likely to retain physical * * *. Without performance measures (sometimes within 48 hours of their characteristics necessary to provide for and timeframes, the BLM cannot ensure installation), and must be frequently the necessary forage and shelter that it is making progress on achieving replaced (USGAO 2009, p. 40). requirements for Sonoran desert its goals in a timely manner.’’ In addition to wildlife management tortoise. The BLM generally prohibits (described below), the AGFD also In summary, the USFS considers the competitive off-highway vehicle events licenses, promulgates rules for, and Sonoran desert tortoise in all biological that could adversely affect Sonoran assists with regulatory enforcement of evaluations for activities and projects desert tortoises, from March 31 through off-highway vehicles use on public proposed within its habitat. The USFS October 15, but noncompetitive off- lands. In January 2009, the AGFD has developed a system of adaptive highway vehicle activities are evaluated created an off-highway vehicle decal management for livestock grazing on on a case-by-case basis, and mitigation program, designed to increase revenues their lands, using resource monitoring measures are implemented to reduce for off-highway vehicle enforcement, to indicate when changes in land potential impacts to Sonoran desert education, and signage on public lands conditions occur or prescribed use tortoises (USBLM 2010, p. 4). Although (AGFD 2009, p. 1). However, as of levels are unsustainable, preventing requests to permit rock crawling events November 2009, only 21 percent of all excessive harm to sensitive Sonoran (defined in Factor A, above) have been eligible off-highway vehicles and off- desert tortoise habitat. However, we are denied where they were proposed in highway vehicle owners in Arizona not aware of specific actions the USFS Sonoran desert tortoise habitat (USBLM were participating in the off-highway is taking with respect to management of 2010, p. 4), this activity still occurs vehicle decal program (AGFD 2009, p. invasive, nonnative plant species and outside of organized ‘‘events.’’ Rock 1). subsequent wildfire concerns, crawling is allowed where it might In review of off-highway vehicle vandalism of tortoises, feral dog adversely affect the Sonoran desert management on USFS and BLM lands in predation, or efforts to counter tortoise or its habitat (USBLM 2010, p. Arizona, we conclude that the current anticipated climate change. In addition, 4). status of law enforcement is inadequate and as discussed below, USFS Both the USFS and BLM acknowledge to protect Sonoran desert tortoises and management of off-highway vehicle on limited staff and financial resources for their habitat. We considered the their lands is not protective of Sonoran off-highway vehicle management following in making this conclusion: (1) desert tortoise populations. Therefore, (USGAO 2009, p. 37). Off-highway The documented adverse effects of off- we conclude that USFS management of vehicles that pass over undisturbed highway vehicle use on Sonoran desert the Sonoran desert tortoise and its desertscrub habitat may leave tracks tortoise habitat (see Factor A); (2) the habitat is currently inadequate. which are then noticed by others and propensity for off-highway vehicle users subsequently used until the trail is to illegally collect Sonoran desert Off-Highway Vehicle Management and mistakenly recognized as a designated tortoises in the wild (discussed in Enforcement on Public Lands route; this process is known as ‘‘route Factor B); (3) the significant, and While both the USFS and BLM have proliferation’’ (Brooks and Lair 2005, p. growing, use of off-highway vehicles in developed broad, strategic plans to 5). Illegal proliferation of roads and Arizona (discussed above in Factor A); manage off-highway vehicle use, these unauthorized use of off-highway and (4) the deficient level of law plans have been found to be missing vehicles has left persistent scars in the enforcement staff responsible for some key elements that could improve Sonoran Desert (Abella 2010, p. 1249). regulating the use of off-highway off-highway vehicle management, such In the Kingman area, between 1994 to vehicles on these lands discussed above.

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In addition, we accept the U.S. Force Base and Marine Corps Air U.S. Department of Defense lands are Government Accountability Office Station—Yuma, and is located in subjected to aircraft noise at similar finding that the USFS and BLM goals portions of Maricopa, Yuma, and Pima sound pressure levels, but we presume and objectives, intended to protect trust Counties (AIDTT 2000, pp. 32–33). The they are, because aircraft training occurs resources from damage associated with majority of military training exercises on these lands in Arizona. off-highway vehicle use, miss some key occur over the valleys where Sonoran In summary, the Barry M. Goldwater elements that could improve off- desert tortoise densities are low, leaving Range and Yuma Proving Ground highway vehicle management. the majority of Sonoran desert tortoise provide for considerable protection of populations unexposed to potential Ironwood and Mesquite Harvest Sonoran desert tortoise habitat on their threats from these exercises (AIDTT installations as a result of access To address ecological problems 2000, p. 34). Outside of training restrictions or through a permitting stemming from wide-ranging mesquite exercises, the public may access the program. The Barry M. Goldwater Range and ironwood harvesting in northern Barry M. Goldwater Range with a also created a management plan Mexico (discussed above in Factor A), permit, via designated routes (AIDTT specifically for the Sonoran desert the Arizona-Mexico Commission, and 2000, p. 34). tortoise in 1996. In addition, since these state government in Sonora, Mexico, The Florence Military Reservation lands are unlikely to be developed in made it illegal to cut and export these encompasses 25,752 ac (10,421 ha), and the future, these areas will likely be species (American University Database is jointly administered by the Arizona important in future Sonoran desert 2010, p. 4). Additionally, Mexico’s Army National Guard, the Arizona State tortoise conservation planning. Federal government has protected the Land Department, and the BLM (AIDTT However, the literature has documented ironwood tree, adding additional 2000, p. 34). As stated previously, the that current management on the monitoring and enforcement to protect Sonoran desert tortoise population on Florence Military Reservation is not remaining ironwood trees (American the Florence Military Reservation is adequate for protecting Sonoran desert University Database 2010, p. 4). Finally, unique among other populations across tortoises or their habitat. In discussion non-profit, bi-national groups are raising their range, because of the conspicuous under Factors A and B, we discussed awareness and funds to help stop these absence of boulder outcrops and use by several activities that occur in this area practices in Mexico (American tortoises of broad alluvial fans and which adversely affect the Sonoran University Database 2010, p. 4). We incised washes (Riedle et al. 2008, p. desert tortoise and its habitat. consider these regulations effective in 418; Grandmaison et al. in press, p. 4). reducing the harvest of ironwood and There is significant public access and U.S. Fish and Wildlife Service National mesquite in the future, but the land area multiple land uses allowed on the Wildlife Refuges already adversely modified by ironwood Florence Military Reservation, with no and mesquite harvesting, as discussed specific protections afforded to the Sonoran desert tortoises occur on in Factor A above, constitutes a current Sonoran desert tortoise (AIDTT 2000, p. several National Wildlife Refuges in threat to Sonoran desert tortoise habitat. 34). Sonoran desert tortoise home ranges Arizona. Sonoran desert tortoise populations are highest on the Kofa, U.S. Department of Defense overlap with concentrated military training areas on the Florence Military Buenos Aires, and Cabeza Prieta Three prominent Department of Reservation (Grandmaison et al. in National Wildlife Refuges, although Defense-administered lands maintain press, p. 1). When not used for military they also may occur in low densities populations of Sonoran desert tortoise: training, these areas serve as within the Cibola, Imperial, and Lake The Yuma Proving Ground, Barry M. recreational areas for camping, hunting, Havasu National Wildlife Refuges along Goldwater Range, and Florence Military and off-highway vehicle use, which the Colorado River (AIDTT 2000, p. 31). Reservation. The Yuma Proving Ground, cumulatively have degraded Sonoran The mission of the National Wildlife administered by the Department of the desert tortoise habitat by removing Refuge System is ‘‘ * * * to administer Army, encompasses 840,000 ac (340,000 vegetative cover, which in turn may a national network of lands and waters ha) in LaPaz and Yuma Counties of have led to reduced use of these areas for the conservation, management, and southwestern Arizona (AIDTT 2000, p. by Sonoran desert tortoises where appropriate, restoration of the 32). The majority of land on the Yuma (Grandmaison et al. in press, p. 4). fish, wildlife, and plant resources and Proving Ground is closed to public There are few data on the potential their habitats within the United States access year-round with the exception of effects of military operations to Sonoran for the benefit of present and future 133,000 ac (54,000 ha) that are open to desert tortoises on U.S. Department of generations of Americans’’ (AIDTT 2000, hunting access for 6 months per year. Defense lands, specifically with respect p. 31). Management on these National The relative inaccessibility of these to aircraft operations. However, Bowles Wildlife Refuges is largely protective of lands results in little disturbance to the et al. (1999, pp. 19–26) tested the Sonoran desert tortoises, as multiple use Sonoran desert tortoise and its habitat response of Mojave desert tortoises to activities such as livestock grazing and (AIDTT 2000, p. 33). In addition, the simulated aircraft sound and to sonic off-highway vehicle use are prohibited Yuma Proving Ground developed a booms associated with aircraft, in an (AIDTT 2000, p. 31). However, the U.S. management plan for the Sonoran desert attempt to ascertain potential effects to Border Patrol uses administrative roads, tortoise in 1996 (AIDTT 2000, pp. 33– wild desert tortoises that are exposed to which are closed to public use in these 34). We are uncertain whether or not such auditory stimuli within and areas, along the border region of the this management plan is effective in adjacent to aircraft flight paths and Buenos Aires and Cabeza Prieta Sonoran desert tortoise conservation on military training areas. They found that National Wildlife Refuges, which may the Yuma Proving Ground. Mojave desert tortoises could detect affect Sonoran desert tortoises or their The Barry M. Goldwater Range, used these sounds and had somewhat habitat in these areas. For further for aerial training exercises, is the subdued reactions ranging from discussion of the effect of U.S. Border largest contiguous portion of ‘‘freezing’’ all movements, to bladder Patrol operations on Sonoran desert Department of Defense lands in Arizona voiding (Bowles et al. 1999, pp. xxii- tortoises or their habitat, see the section (1.7 million ac, 690,000 ha), and is xxiv). We are not certain whether on Undocumented Immigration in jointly administered by the Luke Air Sonoran desert tortoise populations on Factor A of this finding.

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In summary, we conclude that the Arizona State Land Department plant species and subsequent wildfire regulations establishing the mission and Arizona State Trust Land, managed to concerns, vandalism of tortoises, feral management of the National Wildlife derive revenues for trust beneficiaries dog predation, or efforts to counter Refuge system are consistent with including educational, health, and penal anticipated climate change. Therefore, Sonoran desert tortoise habitat institutions, comprises 13 percent of all we conclude that Arizona State Land management, and are therefore adequate land in Arizona, much of which Department management of the Sonoran to protect the tortoise where it occurs on contains Sonoran desert tortoise habitat desert tortoise and its habitat is our lands. (AIDTT 2000, p. 15). In general, the currently inadequate. National Park Service mission of the Arizona State Land Arizona Game and Fish Department Department is to maximize economic The Arizona Game and Fish Sonoran desert tortoise habitat occurs return (AIDTT 2000, p. 16). The Arizona Department (AGFD) currently classifies on Organ Pipe Cactus National State Land Department has no broad the Sonoran desert tortoise as a Tier 1b Monument, Saguaro National Park, and management practices, policies, or ‘‘Species of Greatest Conservation Need’’ the Lake Mead National Recreation Area directives that pertain to Sonoran desert AGFD (2006, p. 485). A Tier 1b species (AIDTT 2000, p. 27). The National Park tortoise management, but does is one that requires immediate Service is mandated by law to ‘‘conserve coordinate with the AGFD on some conservation actions aimed at the scenery and the natural and historic projects to reduce potential impacts to improving conditions through objects and the wildlife therein and to the Sonoran desert tortoise (AIDTT intervention at the population or habitat provide for the enjoyment of the same 2000, p. 16). Four Sonoran desert level. Before April 28, 1989, the AGFD in such manner and by such means as tortoise monitoring sites occur partially allowed the collection and possession of will leave them unimpaired for the or fully on Arizona State Trust Lands: one lawfully captured Sonoran desert enjoyment of future generations’’ Granite Hills, Little Shipp Wash, tortoise per person (AIDTT 2000, p. 14). (AIDTT 2000, p. 26). The resource- , and Picacho After this date, under Commission management goals on National Park Mountains; two of these sites, Granite Order 43, the AGFD closed the season Service lands are broad in scope, and Hills (Pinal County) and Little Shipp on Sonoran desert tortoises, which include reducing ground disturbance, Wash (Yavapai County) are long-term prohibited the take of desert tortoises developing and implementing inventory monitoring plots (AIDTT 2000, pp. 5–6, from the wild, except under special and monitoring programs, assessing and 15). Other blocks of Sonoran desert permit (for example, scientific or mitigating resource disturbance, and tortoise habitat on Arizona State Trust educational) (AIDTT 2000, p. 14). developing environmental restoration Lands occur west of the Upper Burro Unless otherwise prescribed in title 17, and research programs (AIDTT 2000, p. Creek, Arrastra Mountain, and Tres it is unlawful to [t]ake, possess, 26). Livestock grazing and off-highway Alamos wilderness areas in Yavapai transport, buy, sell or offer or expose for vehicle use are not permitted on County and from the Tortolita to the sale wildlife except as expressly National Park Service lands. While the Tortilla Mountains in Pinal County permitted by this title’’ (ARS 17–309). It National Park Service has no specific (AIDTT 2000, p. 15). Recreation on State is also unlawful to release wildlife into provision for Sonoran desert tortoise Trust Lands is generally not monitored the wild except as authorized by the conservation on their lands, all wildlife and therefore may not be protective of Arizona Game and Fish Commission or inhabiting National Park Service lands Sonoran desert tortoises or their habitat. as defined in title 3 (see ARS 17–306). in Arizona, including the Sonoran The Arizona State Land Department is As a closed-season species, the desert desert tortoise, are protected, and considering restricting access to its tortoise cannot be taken from the wild possession or removal of wildlife is lands for purposes of conducting or possessed without special permit prohibited (AIDTT 2000, p. 26). wildlife studies. These access (Commission Order 43). As restricted restrictions may prohibit further live wildlife (R12–4–406), they cannot However, where National Park research due to numerous permit be imported, exported, or possessed Service lands are adjacent to urban requirements. These new policies are without special license or lawful areas, such as Saguaro National Park not yet in place and could be changed exemption. outside of the Tucson metropolitan area, prior to final issuance (Jody Latimer, Enforcement of the State closure on threats to Sonoran desert tortoises have ASLD, 2010, pers. comm.). If collection of Sonoran desert tortoises been documented. Averill-Murray and implemented as described by Latimer occurs when directly observed by law Swann (2002, p. 1) and Jones (2008, p. (ASLD, 2010, pers. comm.), these enforcement personnel, but the 66) documented threats such as proposed procedures and fees have the remoteness of many Sonoran desert harassment and predation by feral potential to limit Sonoran desert tortoise tortoise populations makes enforcement domestic dogs, releases of captive monitoring and research on Arizona strategies and techniques problematic Sonoran desert tortoises and exotic State Trust lands in the future through (AIDTT 2000, p. 14). Furthermore, species (that may transmit diseases), new monetary and procedural regulations regarding the collection or road mortality, and illegal collection of requirements. While these new policies possession of Sonoran desert tortoises tortoises, as affecting the Sonoran desert and regulations are not yet in effect, are poorly known to the public, tortoise population on Saguaro National even if they are implemented it appears emphasizing the importance of Park land. they will not address conservation and education efforts (AIDTT 2000, p. 14). In summary, we acknowledge that the management of the Sonoran desert The effect of illegal collection of mission and management of the tortoise and its habitat, and further, may Sonoran desert tortoises on wild National Park Service and their lands is have a negative effect by potentially populations in Mexico is largely consistent with Sonoran desert tortoise restricting important research needed unknown (see Factor B). habitat management, but where Park for conservation of the tortoise. The AGFD has led Sonoran desert Service land is affected by adjacent Furthermore, we are not aware of tortoise conservation in Arizona through urbanized areas, adequate regulatory specific actions the Arizona State Land research, guidance provided to the protections for the tortoise have not Department is taking with respect to public and other agencies, and been realized. management of invasive, nonnative cooperative conservation management

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on public lands. For example, the AGFD Sonoran desert tortoises; these measures buffelgrass for livestock grazing). In (2007a, p. 1) provides construction and are voluntary. 1988, the Mexican Government passed a development contractors with guidance, The AIDTT’s Memorandum of regulation that is similar to the National should a Sonoran desert tortoise be Understanding, signed in 1995, Environmental Policy Act of the United encountered within an area of a established specific objectives for the States (42 U.S.C. 4321 et seq.). This development. In addition, the AGFD team including: (1) Ensuring the Mexican regulation requires an (2007b, p. 1) also provides survival of the species; (2) preventing environmental assessment of private or environmental consultants guidance on loss of the species; and (3) improving government actions that may affect proper survey techniques and the quality of Sonoran desert tortoise wildlife or their habitat (SEDESOL 1988 considerations when surveying for habitat in Arizona, with the team to (LGEEPA)). Sonoran desert tortoises. AGFD (2006, function as an advocate for the Sonoran The Mexican Federal agency known pp. 485–487) described numerous desert tortoise (AIDTT 1996, Preface; as the Instituto Nacional de Ecologı´a management priorities with respect to AIDTT 2000, p. 2). A management plan (INE) is generally considered the mitigating potential threats facing the for the Sonoran desert tortoise Mexican counterpart to the U.S. Fish tortoise in Arizona. The completed in 1996 called for improved and Wildlife Service. INE is responsible recommendations outlined in these monitoring protocols, the for the analysis of the status and threats documents are recommended guidance, implementation of threat-minimization that pertain to species that are proposed voluntary in nature, and no reporting activities, and the creation of Sonoran for listing in the Norma Oficial requirements are mandated. Therefore, Desert Management Areas (AIDTT 1996, Mexicana NOM–059 (the Mexican we are uncertain whether project pp. 20–26). However, common equivalent to a threatened and proponents implement these criticisms of the 1996 plan include: (1) endangered species list), and if recommendations. Lack of meaningful goals and objectives; appropriate, the nomination of species (2) lack of political willpower without to the list. INE developed the Method of Arizona Interagency Desert Tortoise legal protection for the Sonoran desert Evaluation of the Risk of Extinction of Team tortoise; (3) failure to designate Sonoran the Wild Species in Mexico (MER), Desert Management Areas; and (4) poor which unifies the criteria of decisions As part of a multi-agency funding (AIDTT 2000, p. 2). on the categories of risk, and permits the collaborative project, the Arizona Collectively, these recognized use of specific information fundamental Interagency Desert Tortoise Team shortcomings hampered the to listing decisions. The MER is based (AIDTT) was formed in 1985 to implementation of threat-minimization on four independent, quantitative coordinate research and management of activities. In recognition of these criteria: (1) Size of the distribution of Sonoran desert tortoise populations in shortcomings, the AIDTT is currently in the taxon in Mexico, (2) state (quality) Arizona. Participating agencies in the the process of developing a State of the habitat with respect to natural AIDTT manage habitat, manage the Conservation Agreement, Assessment development of the taxon, (3) intrinsic species, or conduct research, and and Strategy with the goal of identifying biological vulnerability of the taxon, include the AGFD, Arizona State Lands reasonable, obtainable conservation and (4) impacts of human activity on the Department, U.S. Forest Service, BLM, goals and objectives that will contribute taxon. INE implemented use of the MER U.S. Bureau of Reclamation, U.S. to Sonoran desert tortoise conservation in 2006; therefore, all species previously Bureau of Indian Affairs, U.S. Fish and on public lands in a meaningful listed in the NOM–059 were, in many Wildlife Service, National Park Service, capacity. cases, based solely on expert review and U.S. Geological Survey, and several U.S. opinion. Specifically, until 2006, the Mexican Government (Secretaria de Department of Defense military listing process under INE consisted of a Medio Ambiente y Recursos Naturales) reservations (AIDTT 1996, Preface; panel of scientific experts who AIDTT 2000, p. 2). The AIDTT is co- Throughout Mexico, the desert convened as necessary for the purpose chaired by representatives from the U.S. tortoise is listed as ‘‘Amenazadas,’’ or of defining and assessing the status and Fish and Wildlife Service (Arizona Threatened, by the Secretaria de Medio threats that affect Mexico’s native Ecological Services Office) and the Ambiente y Recursos Naturales species that are considered to be at risk, AGFD. Since its inception, the AIDTT (SEMARNAT) (Bury et al. 2002, p. 86; and for applying those factors to the has collaborated in the development of Howland and Rorabaugh 2002, p. 348; definitions of the various listing numerous documents addressing SEDESOL 2008, p. 99). Threatened categories. conservation of the Sonoran desert species are ‘‘those species, or In summary, while the desert tortoise tortoise including ‘‘Survey Protocol for populations of the same, likely to be in is federally listed in Mexico, we have Sonoran Desert Tortoise Monitoring danger of disappearing in a short or documented significant threats to its Plots: Reviewed and Revised’’ (Averill- medium timeframe, if the factors that persistence in that country (see Factors Murray 2000a), ‘‘Status of the Sonoran negatively impact their viability, cause A and C) that are not controlled by the Population of the Desert Tortoise in the deterioration or modification of their listing, and therefore conclude that Arizona: An Update’’ (Averill-Murray habitat or directly diminish the size of regulations establishing management of 2000b), ‘‘Guidelines for Handling their populations continue to operate’’ the Sonoran desert tortoise in Mexico do Sonoran Desert Tortoises Encountered (SEDESOL 2008 (NOM–059–ECOL– not provide adequate assurances of its on Development Projects’’ (AGFD 2008), p. 5). This designation prohibits continued existence in that country. 2007a), ‘‘Desert Tortoise Survey taking of the species, unless specifically Guidelines for Environmental permitted, and also prohibits any Summary of Factor D Consultants’’ (AGFD 2007b), and activity that intentionally destroys or Numerous State and Federal entities ‘‘Recommended Standard Mitigation adversely modifies its habitat (SEDESOL have regulations or policies which Measures for Projects in Sonoran Desert 2000 and 2001 (NOM–059–ECOL–2001). implement management of either the Tortoise Habitat’’ (AIDTT 2008). However, activities that unintentionally Sonoran desert tortoise or its habitat Available online, the AIDTT (2008, pp. destroy or adversely modify their throughout the species’ range in 1–7) offers guidance on standard types habitat do not appear to be specifically Arizona. In Mexico, the species is of mitigation for projects that may affect prohibited (e.g., cultivation of currently listed as threatened. In our

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review of the available information on contaminants in surrounding areas as a (cancer-causing) and may also already each entity’s management policies and result of fugitive dust, contaminated occur in naturally-high levels in some regulations, we found numerous surface runoff, and other mechanisms areas of the American Southwest examples where the Sonoran desert consistent with contaminant fate and (Seltzer and Berry 2005, p. 263). tortoise is considered in management transport. Soil contamination within Because the Sonoran desert tortoise is actions and tortoise-specific mitigation ephemeral washes from leaching characterized as having a delayed sexual measures are mandated, or where land operations associated with mining maturation and a long generation time, activities that could appreciably activities has occurred throughout the potential effects from persistent, low- threaten Sonoran desert tortoise Sonoran Desert, and will likely continue level contaminants in the environment populations are prohibited. While to occur where these activities take include: (1) Mortality before several land managers and agencies in place. Sonoran desert tortoises that reproduction, (2) chronic accumulation Arizona actively consider the Sonoran forage in contaminated ephemeral of contaminants that may be transferred desert tortoise in their resource washes may ingest toxic constituents to offspring upon maturation, (3) planning, we found deficiencies in through soil or contaminated plant reduced size at maturity reducing management of off-highway vehicle use, matter, but we are not aware of any offspring quantity or quality, (4) delayed policies and procedures inconsistent specific reports of tortoises that became expression of fitness effects at the with Sonoran desert tortoise sick or deceased from this risk. The population level, and (5) delayed conservation, and some threats such as mining industry in Mexico is largely recovery of populations following invasive, nonnative plant species and concentrated in the northern tier of that abatement of fitness effects (Rowe 2008, subsequent wildfire concerns, country, with Sonora as the leader for p. 626). In several areas of the Sonoran vandalism of tortoises, feral dog generating copper, gold, graphite, Desert in Arizona and Sonora, Mexico, predation, or efforts to counter molybdenum, and wollastonite, as well mining operations and other human- anticipated climate change were not as the leader among Mexican States related activities can result in addressed by land management control. with the most surface area dedicated to remobilization and concentration of Lastly, significant threats we discuss mining (Stoleson et al. 2005, p. 56). The elemental toxicants in the air, on the above in Factors A and C are not being three largest mines (all copper) are soil surface, and on the surfaces of adequately addressed by land managers, found in Sonora (Stoleson et al. 2005, p. forage plants, both from ground including invasive, nonnative plant 57). The sizes of mines in Sonora vary disturbance and from long-range species and associated wildfire considerably, as do the known atmospheric deposition associated with concerns, vandalism of tortoises, feral environmental effects from mining- old copper smelter sites, coal-fired dog predation, and management to related activities (from exploration to power plants, and fugitive dust from counter anticipated climate change. long after closure), which include abandoned and active mining sites Although the Sonoran desert tortoise contamination and drawdown of (Seltzer and Berry 2005, p. 263; Rowe is considered a threatened species in groundwater aquifers, erosion, acid 2008, p. 628). The most likely routes for Mexico, we are not aware of mine drainage, fugitive dust, pollution exposure of Sonoran desert tortoises to conservation planning or enforcement of from smelter emissions, and landscape these types of contaminants are through regulations that has occurred because of clearing (Stoleson et al. 2005, p. 57). ingestion of contaminated soil or plant matter, or through inhalation of this status. Based upon our review of Rowe (2008, p. 623) investigated the information pertaining to threats in contaminated dust or particles, potential effects of persistent, low-level especially when a tortoise constructs or Mexico, it is unlikely that protections contaminants (e.g., heavy metals, afforded to the Sonoran desert tortoise modifies a burrow (Seltzer and Berry polychlorinated biphenols, 2005, p. 263; Hinck et al. 2010, p. 287). are adequate to ensure conservation for organochlorides) on long-lived the foreseeable future in Mexico. As a We have no specific records of Sonoran vertebrates (such as the Sonoran desert desert tortoises becoming sick or dying result, we conclude that the Sonoran tortoise). Cadmium and lead are of desert tortoise is threatened due the from this type of contamination; effects special concern due to their toxicity, from these contaminants can be inadequacy of existing regulatory and because they are persistent, significantly delayed and slow to mechanisms, in combination with the common environmental contaminants manifest. Also, few field researchers are other threats identified in this finding, (Martı´nez-Lo´pez et al. 2010, p. 671). sampling wild tortoises to test for both now and in the foreseeable future. Cadmium may affect turtle gonadal contaminant exposure. Factor E. Other Natural or Manmade development, and lead may affect an Conversion of habitat to large-scale Factors Affecting Its Continued individual tortoise’s susceptibility to agriculture has been concentrated in Existence infections and disease, because it may Sonora, Mexico, which has provided suppress its immune capacity. The latter sources of surface and groundwater Environmental Contaminants can potentially affect the spread of pollution such as salt intrusion due to Many sources of potential known diseases such as herpesvirus, agricultural water use extraction; contamination presently occur cutaneous dyskeratosis, and URTD municipal and agricultural discharges; throughout the distribution of the within and among affected populations and solid waste, including cast-off Sonoran desert tortoise. Copper mining (Martı´nez-Lo´pez et al. 2010, p. 671). As agrochemical containers, winery in the Sonoran Desert has occurred in stated previously, cutaneous residues, and hog farm muck (Nauman Arizona and adjacent Mexico for dyskeratosis is prevalent within most 2007, p. 1). The extent to which centuries, and many of these sites have populations of Sonoran desert tortoise Sonoran desert tortoises drink freely smelters (now decommissioned), which throughout their distribution in from perennial or intermittent streams is are former sources of airborne Arizona, but this disease has not been not known, but since tortoises are contaminants. In Arizona, historical or determined to currently be a significant opportunistic drinkers, we presume current large-scale copper mining threat to Sonoran desert tortoise they use streams as a source of water in operations exist in Pima, Pinal, Yavapai, populations. Another common addition to ephemeral pools generated Gila, and Mohave Counties, which are environmental contaminant is the heavy by precipitation events, and that they sources of low-level, persistent metal arsenic, which is carcinogenic may subsequently ingest such toxins.

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In conclusion and based upon our Alexander 1998, p. 213; Boarman 2002, within their home ranges (Grandmaison review of the best available scientific or pp. 54–55; Boarman and Sazaki 2006, p. et al. in press, p. 16). This suggests that commercial data, little is known of the 98; Dieringer 2010, p. 1). Anticipated low density Sonoran desert tortoise potential effect of low-level adverse effects of roads on Sonoran populations observed adjacent to environmental contamination on desert tortoise populations are likely heavily traveled roads may be the result Sonoran desert tortoises. We did related to the level of their use. For of mortality from vehicle collisions and ascertain that the risk of environmental example, Hoff and Marlow (2002, pp. illegal collection rather than road contaminants affecting Sonoran desert 451–454) found that the impact of roads avoidance behavior (Grandmaison et al. tortoise populations is most likely from on the prevalence of Mojave desert in press, p. 16). the presence of persistent, low-level tortoise signs (tracks, scat, etc.) was There appears to be a concerted effort toxicants such as heavy metals, commensurate with traffic volume— to mitigate the potential effect of several polychlorinated biphenols, and with the impacts more significant roads and highways on Sonoran desert organochlorides. However, potential adjacent to heavily traveled roads. tortoise populations and their habitat. effects of this type of environmental Mojave desert tortoise populations Barrier fencing (or tortoise fencing) and contamination are often delayed and showed depressed numbers within culverts along roads and highways are difficult to observe in long-lived species 1,300 feet (400 m) of highways in the recognized methods employed such as the Sonoran desert tortoise, Mojave Desert (Boarman and Sazaki throughout Arizona to reduce potential largely because of delayed sexual 2006, p. 98). Similar effects to Sonoran mortality through vehicle strikes of maturation and long generation times. desert tortoise populations might be Sonoran desert tortoises. Installing We did not find documentation of expected when heavily used roads are tortoise fencing along roads and population-level effects in Sonoran adjacent to, or are routed through, core highways minimizes the risk of road desert tortoises as a result of Sonoran desert tortoise habitat such as mortality of tortoises but may also environmental contamination. steep, boulder-strewn slopes within enhance the barrier effect between Therefore, we conclude that Arizona Upland Sonoran desertscrub populations by restricting long-distance environmental contamination of (Dieringer 2010, p. 1; Grandmaison movements (Boarman and Sazaki 1996, Sonoran desert tortoise habitat is not 2010b, p. 3). p. 3). Culverts that pass under roads and currently threatening populations; Sonoran desert tortoises move slowly highways may provide opportunities for however, we acknowledge that further and take a relatively long time to cross Sonoran desert tortoises to safely cross study is warranted to identify whether roads and highways, which may place roads and highways (Boarman and there is a risk for population-level them at elevated risk (Andrews et al. Sazaki 1996, pp. 3–4). impacts, and we recommend that land 2008, p. 124). However, we suspect that, The ADOT constructs and maintains managers consider collecting baseline due to their size and shape (particularly roads and highways that comprise soil data in areas that may be in the sub-adult and adult size classes), Arizona’s transportation system. It vulnerable. drivers may instinctively avoid striking routinely implements varied a crossing tortoise because of their conservation and mitigation actions Vehicle Strike Mortalities similarity to rocks, and the subsequent with respect to Sonoran desert tortoise We expect that the increased use of damage that hitting a ‘‘rock’’ could do to populations that may be affected by off-highway vehicles within Sonoran a vehicle. However, intentional vehicle these activities. The ADOT (ADOT desert tortoise habitat will increase the strikes of Mojave desert tortoises have 2010, pp. 2–5) listed numerous likelihood of encounters with Sonoran been reported (Bury and Marlow 1973, conservation measures including those desert tortoises which can result in a p. 11). While unpaved roads traverse 16 which address standard (voluntary and variety of potential outcomes for of the 17 Sonoran desert tortoise involuntary) mitigation measures, tortoises. According to the Arizona monitoring plots, the AGFD is only education, new construction design, Interagency Desert Tortoise Team aware of one instance of direct mortality habitat acquisition, native plant (AIDTT 2000, p. 10), ‘‘[a]n abundance of of a Sonoran desert tortoise from a restoration, nonnative plant control, anecdotal knowledge indicates that vehicle on a long-term monitoring plot, establishment of wildlife corridors, and contacts between people and wild on the East Bajada Plot (AGFD 2010, p. research that have been integrated into tortoises usually end to the detriment of 14). their road system planning, tortoises (e.g., collection, handling, Increased vegetation adjacent to construction, and improvement vandalism, crushing under vehicle tires, paved or heavily compacted roads activities. Tortoise-proof fencing and shooting).’’ resulting from increased water runoff adjacent to highways has been installed Averill-Murray and Swann (2002, p. may be beneficial to Sonoran desert along numerous routes throughout 1) stated that urban development tortoises, serving as a means to Arizona including 27.6 mi (44.4 km) adjacent to the Saguaro National Park in rehydrate them, but it may also attract along U.S. Highway 93 and 10.8 mi Pima County threatens the Sonoran them to these areas, indirectly (17.4 km) along State Route 85 (ADOT desert tortoise via several mechanisms, increasing the likelihood of adverse 2010, p. 3). Numerous, additional including elevated mortality on roads. interactions from: (1) Tortoises structures that assist Sonoran desert The high rates of speed associated with wandering onto the road, (2) vehicles tortoises to cross roads safely, such as competitive off-highway vehicle events pulling onto the vegetated shoulder of pathways, ramps, and culverts, have significantly increase the risk of direct the road and crushing tortoises, (3) been installed along the U.S. Highway mortality of Sonoran desert tortoises injury from grading or mowing 93 corridor and along a segment of the from vehicle collisions (Vega 2010, p. activities, (4) exposure to herbicides U.S. Highway 60 through the Tonto 4). applied to control growth of weeds National Forest (ADOT 2010, p. 3). Reptiles, including the Sonoran desert along the road shoulder, and (5) The ability of tortoise fencing to tortoise, may be particularly vulnerable increased potential for observation and prevent road mortality of Sonoran desert to roads due to the higher risk of collection by passers-by (Boarman 2002, tortoises is highly contingent on mortality as a result of vehicle strikes p. 55). As stated previously, Sonoran inspections and maintenance. Sonoran (Boarman and Sazaki 1996, p. 1; desert tortoises may use infrequently desert tortoise fencing along 10 mi (16 Boarman et al. 1997, p. 57; Forman and traveled gravel roads as travel routes km) of U.S. Highway 93 in Mohave and

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Yavapai Counties in Arizona, between consume, or become entangled with climatic patterns at regional and local mile markers 144 and 155, was shown balloons, exist. However, Averill- scales. to have major deficiencies, including Murray and Averill-Murray (2002, p. 29) At a regional scale, there is a broad 567 individual fencing breaches and posited that while balloons may affect consensus among climate models that instances of culvert undercutting, which individuals, they are unlikely to cause the area encompassing the southwestern diminish the effectiveness of these population-level impacts to Sonoran United States and northern Mexico will mitigation techniques (Grandmaison desert tortoises. get drier in the twenty-first century and 2010b, p. 3). Five Sonoran desert Illegal dumping in Arizona is that the trend towards a more arid tortoise road-mortalities were ubiquitous throughout the Sonoran climate is already under way (Seager et documented in 2008 in this stretch of Desert, but most concentrated in areas al. 2007). Evidence to support such highway, though none was documented adjacent to human settlements. These changes in temperature and rainfall in in 2009 (Grandmaison 2010b, p. 5). A relatively small but widely dispersed the southwest deserts is abundant. For rancher in southeastern Mohave County, piles of solid and potentially hazardous example, maximum summer Arizona, reported observations of waste may also serve as sources of temperatures in the southwestern Sonoran desert tortoises being killed on toxicological contamination of Sonoran United States are expected to increase U.S. Highway 93, particularly after desert tortoises in areas where ingestion over time in response to changes in the heavy rains, when adjacent tortoise of contaminated soils or plant matter climate system (Christensen et al. 2007, barrier fencing along the highway gets can occur. p. 887). Weiss and Overpeck (2005, p. washed out, allowing access of tortoises In conclusion, balloons and trash 2075) examined low-temperature data to the highway surface (Dieringer 2010, occur throughout the range of the desert over a 40-year timeframe from p. 1). Using radio-telemetry, tortoise. Trash piles are most numerous weather stations in the Grandmaison (2010b, p. 6) found that concentrated adjacent to human Sonoran Desert ecoregion of Arizona Sonoran desert tortoises with home settlements but helium-filled balloons and California, as well as the Mexican ranges within 0.62 mi (1 km) adjacent to can travel many miles away from cities States of Baja California, Baja California this stretch of Highway 93 did not cross or towns and be deposited in remote Sur, and Sonora. They found: the highway. However, additional habitat as they fall from the sky. We (1) Widespread warming trends in instances of Sonoran desert tortoise have documented that balloons in winter and spring, (2) decreased mortality on this and other major routes particular may pose health risks to frequency of freezing temperatures, (3) within the distribution of Sonoran Sonoran desert tortoises and are lengthening of the freeze-free season, desert tortoises undoubtedly occurs but encountered in monitoring plots and (4) increased minimum is rarely reported. although specific reports of tortoises temperatures per winter year. Such Many activities undertaken by the directly affected by balloons are rare in changes are likely to have widespread ADOT minimize the effect of roads and the literature. While effects can occur to impacts on Southwestern ecosystems. highways on tortoise populations. individual tortoises, the literature did While temperatures in the Southwest However, we have concern regarding not indicate that population-level effects are predicted to increase, rainfall the lack of ongoing maintenance of can be expected from such exposure. patterns will also be affected. The current, multi-year drought in the protection structures such as tortoise Climate Change barrier fencing. Therefore, we conclude western United States, including most that maintenance of tortoise protection There is unequivocal evidence that of the Southwest, is the most severe structures is not adequate to meet the the earth’s climate is warming based on drought recorded since 1900 (Overpeck desired objective of these structures in observations of increases in average and Udall, 2010, p. 1642). Numerous many areas, or to protect Sonoran desert global air and ocean temperatures, models predict a decrease in annual tortoise populations affected by heavily widespread melting of glaciers and precipitation in the southwestern used roads and highways in Arizona. polar ice caps, and rising sea levels United States and northern Mexico. (IPCC 2007, p. 4). Furthermore, the Solomon et al. (2009, p. 1707) predict Balloons and Trash Intergovernmental Panel on Climate precipitation amounts in the Helium-filled balloons are capable of Change (IPCC 2007, p. 7) summarized southwestern United States and dispersing great distances (greater than the likelihood of general future trends in northern Mexico will decrease by as 164 mi (264 km)) from their release several climatic variables, predicting: much as 9 to 12 percent (measured as points, and have been shown to make (1) Warmer and fewer cold days and percentage of change in precipitation up the largest percentage of litter types nights over most land areas, (2) warmer per degree of warming, relative to 1900 encountered in desert tortoise field and more frequent hot days and nights to 1950 as the baseline period). studies (Walde et al. 2007a, p. 148). over most land areas, (3) more frequent Christensen et al. (2007, p. 888) state, Desert tortoises are known to eat trash, warm spells/heat waves over most land ‘‘The projection of smaller warming over such as balloons, plastic, and other areas, (4) changes in precipitation the Pacific Ocean than over the garbage, which may kill them by patterns favoring an increased frequency continent, * * * is likely to induce a becoming lodged in the gastrointestinal of heavy precipitation events (or decrease in annual precipitation in the tract or by entangling the tortoise proportion of total rainfall from heavy southwestern USA and northern (Averill-Murray and Averill-Murray falls) over most areas, and (5) an Mexico.’’ In addition, Seager et al. (2007, 2002, p. 27; Walde et al. 2007a, p. 148). increase in the area affected by pp. 1181–1184) analyzed 19 models of Balloons and balloon string can also droughts. All of these changes are differing variables to estimate the future entangle the tortoise, sometimes leading caused by alterations in the energy climate of the southwestern United to induced amputation of an appendage balance within the atmosphere and the States and northern Mexico in response (Burge 1989, p. 7). Averill-Murray and Earth’s surface. The primary factors that to predictions of changing climatic Averill-Murray (2002, p. 27) reported 36 affect this balance are concentrations of patterns. All but one of the 19 models balloons found on Ironwood Forest greenhouse gases (mainly carbon predicted a drying trend within the National Monument in Pima County, dioxide), aerosols, land surface southwest (Seager et al. 2007, p. 1181). Arizona, indicating that opportunities properties, and solar radiation. These A total of 49 projections were created for a Sonoran desert tortoise to global climate changes will influence using the 19 models and all but 3

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predicted a shift to increasing aridity 394) found that because of their soils, leading to a decrease in soil (dryness) in the southwest as early as physiology, reptiles and amphibians are fertility (Ramanujan 2009, p. 1). Murphy 2021 to 2040 (Seager et al. 2007, p. sensitive to climatic changes, which et al. (in prep., p. ii) expect these 1181). While most climate change may result in effects to their responses in the vegetation community models predict less precipitation in the development, spatial distribution, and to adversely affect the quality of forage southwestern United States, a model interactions with other species. for Sonoran desert tortoises, leading to produced by the Hadley Centre for Specifically, egg development, sperm dietary nitrogen deficiencies. Climate Prediction and Research development, and sex ratios may be Desert tortoises are likely to be (HadCM2) predicted increased affected by climatic changes in affected by decreases in precipitation precipitation throughout most of the temperatures. Increased temperatures due to climate change. Rain is the single United States, and particularly in the may influence sex ratios within clutches most important climatic factor that southwest (Weltzin et al. 2003, p. 942). to favor females over males, which may drives desert ecosystems because it While there may be some uncertainty benefit populations as one male can ultimately determines recruitment rates, associated with the predictions of fertilize several females. However, if growth and reproduction rates, nutrient decreased rainfall in the arid deserts, temperatures rise too much, the effect cycling, and net ecosystem productivity, there is broad agreement that the overall could strongly select for female-only resulting in these ecosystems being the trend will be reduced precipitation. clutches, significantly skewing the sex most vulnerable to changes in In addition to increasing trends in ratio within populations, and posing precipitation levels (Weltzin et al. 2003, aridity, the timing of precipitation may long-term problems for reptiles such as p. 944; Huxman et al. 2004, p. 254; also be altered as a result of climate Sonoran desert tortoise populations Hereford et al. 2006, p. 25). Peterson change, which would result in (Walther et al. 2002, pp. 393–394). But (1996a, p. 1831) highlights the important changes in the vegetation as stated earlier, Sonoran desert importance of rain for desert tortoises: community within habitat of the tortoises build their nests in burrows ‘‘Energy acquisition and expenditure in Sonoran desert tortoise. The IPCC (2007, underground, thereby tempering the desert tortoises are strongly constrained p. 20) found that winter precipitation in effects of rising surface temperatures. by the contingencies of rainfall, both the southwestern United States is Sonoran desert tortoises may be indirectly through effects on availability predicted to decline by as much as 20 affected directly by regional climate and quality of food, and directly percent as a result of climate change, change. For example, increasing through reliance on freestanding water while summer precipitation may temperatures may cause desert tortoises for drinking, which is apparently increase slightly. Precipitation in to overheat (Ernst and Lovich 2009, p. necessary for achieving a net annual Mojave desertscrub occurs 544). Sonoran desert tortoises are energy profit.’’ Desert tortoises evolved predominantly during the cool-season vulnerable to overheating because they in arid conditions, and possess (winter) months but, depending on heat up 10 times faster than they can numerous physiological and behavioral location, it may also occur during the cool down, making them potentially adaptations to survive some degree of warm-summer months (Hereford et al. sensitive to temperature extremes drought (Schmidt-Nelson and Bently 2006, p. 29). Perennial plant species in associated with anticipated climate 1966, p. 911; Peterson 1996b, p. 1325; Mojave desertscrub are most affected by change (Ernst and Lovich 2009, p. 544). Christopher 1999, p. 365; Duda et al. changes in winter precipitation, as While climate change may directly 1999, p. 1188; AIDTT 2000, p. 4; Berry increases in winter precipitation affect the Sonoran desert tortoise, most et al. 2002b, pp. 443–446; Dickinson et increases germination and the of the impacts of climate change are al. 2002, pp. 251–252). Peterson (1996a, establishment of new plants (Hereford et anticipated to be indirect effects to the p. 1831) found desert tortoises have a al. 2006, p. 25). In contrast, decreases in tortoise caused by other changes in the very low field metabolic rate when winter precipitation substantially ecosystem that supports them. The compared to other desert reptiles, which increase mortality in perennial plants, following discussion describes may provide them an advantage in most notably in short-lived species anticipated indirect effects to the drought conditions. However, a (Hereford et al. 2006, p. 25). In addition, tortoise in response to predicted climate decrease in winter precipitation may decreasing winter precipitation has been change effects. disproportionately affect reproductive linked with a high mortality of drought- Changes in atmospheric carbon females because they are highly resistant shrubs in parts of the Sonoran dioxide and soil nitrogen levels are dependent upon springtime forage. A and Mojave deserts (McAuliffe and anticipated to affect the Sonoran desert decrease in winter precipitation is Hamerlynck 2010, p. 885). A reduction tortoise through responses observed in expected to adversely affect the quantity in winter precipitation could their forage base. The desert ecosystems and quality of their forage. This, in turn, significantly alter the plant inhabited by the Sonoran desert tortoise is likely to directly affect reproductive communities of the Sonoran and Mojave are also expected to be sensitive to output of Sonoran desert tortoise deserts. increased levels of carbon dioxide in the populations (Hereford et al. 2006, p. 25). Arid environments are especially atmosphere. Desert shrub cover may Persistent drought, and subsequent sensitive to climate change, because the increase with increasing carbon dioxide, changes in the tortoise forage base, can plants and animals that inhabit these but nonnative species may also respond affect blood chemistry and water areas are near their physical tolerances positively, out-competing native metabolism, reduce or eliminate the for temperature and water stress. Slight vegetation (Smith et al. 2000, p. 79; thymus and fat stores, and result in changes in temperature and rainfall, Loubimsteva and Adams 2004, p. 401), skeletal muscle and liver atrophy in along with increases in the magnitude thereby increasing the risk of fire. In desert tortoises (Berry et al. 2002b, pp. and frequency of extreme climatic addition, water and nitrogen are the 443–446; Dickinson et al. 2002, pp. events, can significantly alter species biggest constraints that influence 251–252). distributions and abundance (Archer biological productivity in desert Seasonal changes in rainfall may and Predick 2008, p. 23). In fact, ecosystems (Ramanujan 2009, p. 1). contribute to the spread of invasive warming effects may be particularly Predicted higher temperatures are species, such as Sahara mustard and severe for reptiles and amphibians. For expected to cause higher levels of exotic grasses, which are capable of instance, Walther et al. (2002, pp. 393– nitrogen to escape as a gas from desert explosive growth, and able to quickly

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out-compete native species (Barrows et San Pedro Valley (Meyer et al. 2010, p. identified shortcomings provide an al. 2009, p. 673). As explained in Factor 11). Localized cases of population incomplete picture of the status of the A, invasive species displace the native declines as a result of drought could be desert tortoise and its vulnerability to vegetation, reducing forage for tortoises, more common in the future, due to the effects of climate change. and increasing the threat of wildfires in decreasing rainfall caused by climate Weiss and Overpeck (2005, p. 2074) desert ecosystems, resulting in further change. disagreed with Galbraith and Price reduction of forage plants for the Another way to evaluate the threats to (2009, pp. 74–84). Accelerated increases tortoise. a species is the use of vulnerability in temperature projected as a result of Droughts, which are likely to be more assessments. The results of one climate change will potentially result in frequent and severe as a result of assessment, conducted by Galbraith and changes to the current geographical climate change, have been suggested to Price (2009, p. ii) concluded that the boundaries of the Sonoran Desert, as have caused in declines in local desert tortoise within the United States well as the distribution of associated Sonoran desert tortoise populations. was ‘‘highly vulnerable’’ to extinction as plant species (Weiss and Overpeck Periodic times of drought are not a result of climate change. The 2005, p. 2074). Specifically, Weiss and uncommon in the Southwest, and framework used by Galbraith and Price Overpeck (2005, p. 2074) predicted that tortoises have evolved with drought. (2009, pp. 80–82) considered numerous the current geographic boundary of the However, future drought conditions factors including: (1) Current population Sonoran Desert will contract in its may be more severe and long-lasting size and trends, (2) range trends, southeast portion and expand in (3) likely future stressor trends, (4) distribution and rise in elevation in the than previously recorded droughts individual replacement time, (5) likely eastern and northern portions, thus (Cook et al. 2004, p. 1016). The effects future vulnerability to stochastic events, potentially expanding areas of suitable of drought have been shown to have (6) future vulnerability to policy/ habitat for the Sonoran desert tortoise. significant population-level impacts on management change, (7) likely future Weiss and Overpeck (2005, p. 2075) and Mojave desert tortoises, as exhibited by vulnerability to natural stressors, (7) Galbraith and Price (2009, p. 80) agreed the observed declines in their physiological sensitivity to temperature that observed changes to the fire regime populations during years of drought- and precipitation change and to extreme of the Sonoran Desert favor nonnative induced reductions in annual plants weather events, (8) dispersive capability plant species, and may impede the (Longshore et al. 2003, p. 169). As stated and potential rate of increase, (9) habitat trajectory or degree of potential previously, Sonoran desert tortoises specialization, (10) likely event of future expansion of the Sonoran Desert. strongly benefit from the bimodal habitat loss due to climate change, (11) With the differences in predicted precipitation pattern characteristic of ability of habitats to shift in response to climate change under different the Sonoran Desert region, specifically climate change, and (12) dependence on scenarios, and the uncertainty of those from precipitation received during the temporal inter-relations and other effects on the tortoise, it is difficult to summer monsoon. However, the species. They summarized: ‘‘Over the come to a definitive conclusion as to the monsoon is characterized by highly- last three or four decades, these potential impacts of climate change on localized rainfall events of short populations (Mohave and Sonoran) have the Sonoran desert tortoise. All, none, or duration and high magnitude, and can come under high degrees of stress due a combination of these predictions may be spatially unpredictable. Therefore, largely to human activity (particularly actually be realized in the future within while some Sonoran desert tortoise urbanization and recreational intrusion) the distribution of the Sonoran desert populations may receive satisfactory * * * Climate change may be a tortoise, which adds uncertainty to how amounts of summer precipitation, significant new stressor, causing even the tortoise may respond to any given others may be exposed to reduced more habitat loss and exacerbating an combination of these predictions. For monsoon precipitation totals, and already difficult situation. Together, example, warmer average temperatures potentially zero precipitation in a given existing stressors and the direct and may affect the Sonoran desert tortoise year. This seems to have been the case indirect effects of climate change could positively by lengthening annual during the late 1980s in the Maricopa result in desert tortoises being put at surface-activity periods which may Mountains near Phoenix, Arizona. The even greater risk of population enhance reproduction potential and precipitous loss of 226 Sonoran desert reduction and extinction in their U.S. survivorship. Increased frequencies in tortoises in the Maricopa Mountains range.’’ heavy precipitation may provide more plot, which occurred between 1987 and Galbraith and Price (2009, pp. 79–80) opportunities for rehydration of 1990, is believed to have resulted from estimate that at least 20 to 50 percent of Sonoran desert tortoises and promote severe, localized drought, when no habitat today will not be available to the production of forage species, measurable rainfall occurred in that area desert tortoises by 2020 as a result of whereby reducing daily foraging periods in 1989. This indicates that even climate change and, to a much lesser to both avoid excessive high Sonoran desert tortoises may succumb extent, anticipated development. temperatures and, as a consequence, to excessive drought conditions However, in their analysis, Galbraith lessen predation risks. However, higher (Schwalbe 2010, p. 2). Subsequent and Price (2009, pp. 74–84) largely temperatures coupled with drought surveys have shown that survivorship disregarded the fact that the Sonoran conditions could also negatively affect within this population has improved, desert tortoise ranges into Mexico the Sonoran desert tortoise by and there is evidence that reproduction (which represents approximately half of increasing metabolism rates, foraging has resumed in this population. Also, a its total distribution), which should be needs, and associated foraging time, lack of additional carcasses found on factored into their vulnerability therefore increasing predation risk. the plot indicates that population analysis. They also often misapplied or Higher temperatures coupled with declines have stabilized, and the gave disproportionate influence to drought conditions could also reduce population might be rebounding (AGFD specific research on the Mojave desert forage availability of plant species that 2010, p. 4). Drought conditions also tortoise in addressing the desert tortoise depend on higher frequencies of apparently played a significant role in a in the U.S. as a whole. While we found precipitation events for growth (annual decline of new Sonoran desert tortoise certain attributes of Galbraith and Price plant species that respond to monsoon captures between 1988 and 1990 in the (2009, pp. 74–84) to be accurate, these storms).

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The temporal aspect of anticipated However, we are not able to quantify, threatened or endangered as those terms changes in climate and their effects on with certainty, how the direct and are defined by the Act. This does not the Sonoran desert tortoise and its indirect effects of climate change will necessarily require empirical proof of a habitat must be considered in context affect Sonoran desert tortoise threat; however, reasonably strong data- with the rate of evolutionary adaptation populations. Tortoise habitat may shift, based inferences are the minimum of the species. Skelly et al. (2007, native vegetation may change standard for considering a threat pp. 1353–1355) examined preferred depending on rainfall patterns, significant. The mere identification of temperature ranges and thermal increasing temperatures may affect the factors that could impact a species maxima, and suggested that some growth of native vegetation, the quality negatively is not sufficient to compel a species with short generation times and quantity of desert tortoise forage finding that listing is appropriate; we might evolve to meet the demands of a may be affected, precipitation patterns require evidence that these factors are changing climate. The Sonoran desert will likely affect desert vegetation, and operative threats that act on the species tortoise has much longer generation tortoises may experience physiological to the point that the species meets the times (approximately 12 to 15 years) effects that could result in changes in definition of threatened or endangered and may therefore be more vulnerable to reproduction and overall survival. We under the Act. the effects of climate change, because conclude that climate change may be a Despite the history of conservation they are unlikely to be able to rapidly significant stressor that exacerbates and management efforts afforded the adapt to environmental changes. current threats, both directly Sonoran desert tortoise in Arizona, our Specifically, we do not expect their (physiological effects to the tortoise) and review of the literature identified threats evolutionary processes to keep pace indirectly (habitat loss and to the Sonoran desert tortoise with the relatively fast-paced changes fragmentation). As such, climate change, attributable to all Threat Factors (A–E). predicted as a result of climate change in and of itself, may affect Sonoran The primary threats to the Sonoran in the near- or mid-term. desert tortoise populations, but the desert tortoise from habitat modification Perhaps the most important aspect of magnitude of the impacts to the Sonoran and destruction (Factor A) include the: projected changes in climate is the desert tortoise remains uncertain. (1) Current and ongoing invasion of relative irreversibility of these changes Climate change is not currently a threat nonnative plant species resulting in an into the future. Solomon et al. (2009, to the Sonoran desert tortoise, but it has unnatural, destructive wildfire regime p. 1704) state that the effects of climate the potential to be a threat in the in portions of the species’ distribution; change will be irreversible for foreseeable future. Impacts from climate (2) cumulative, anticipated indirect approximately 1,000 years, even if change in the future will likely effects to habitat and individual carbon emissions dropped to zero in exacerbate the current and ongoing tortoises from increased human activity current times, as a result of the threat of habitat loss caused by other tied to urbanization and human longevity of atmospheric carbon dioxide factors, as discussed above. and feedbacks associated with ocean population growth; (3) current and warming (Solomon et al. 2009, p. 1709). Finding anticipated creation of barriers to As required by the Act, we conducted genetic exchange among populations Summary of Factor E a review of the status of the Sonoran from urbanization and associated Our review of the best scientific and desert tortoise DPS and considered the infrastructure; (4) high and growing use commercial data available indicated that five factors in assessing whether the and popularity of OHV use in Sonoran Sonoran desert tortoises may be DPS is threatened or endangered desert tortoise habitat; (5) mesquite and vulnerable to the effects of throughout all or a significant portion of ironwood tree harvest in Mexico; (6) environmental contamination: Ingestion its range. We examined the best improper livestock grazing in Mexico; of trash, including balloons; and scientific and commercial information and (7) undocumented human substances from illegal solid waste available regarding the past, present, immigration and interdiction activities. dumps. However the literature did not and future threats faced by the Sonoran The primary threat to the Sonoran indicate these threats were currently desert tortoise. We reviewed the desert tortoise from overutilization for affecting populations and specific petition, information available in our commercial, recreational, scientific, or reports of affected individual tortoises files, and other available published and educational purposes (Factor B) is were rare. Vehicle strike mortalities unpublished information, and we illegal collection. The primary threat to have been documented, and may have consulted with species experts, land the Sonoran desert tortoise from some local sub-population effects in managers, and numerous stakeholders predation (Factor C) is the increase in close proximity to more heavily traveled including Federal, State, and Tribal feral or off-leash domestic dog predation roads and highways, but again, these agencies. and human depredation associated with effects are more localized and not In considering what factors might anticipated increases in urbanization rangewide, and thus do not appear to constitute threats, we must look beyond and human population growth. The have overall population-level effects. the mere exposure of the species to the Sonoran desert tortoise is also Further, while management and factor to determine whether the species threatened by the inadequacy of mitigation actions are being responds to the factor in a way that regulatory mechanisms (Factor D). In implemented, such as the construction causes actual impacts to the species. If our review of the available information, of barrier fences and culverts, these there is exposure to a factor, but no we found numerous examples where the devices are generally not maintained response, or only a positive response, Sonoran desert tortoise is considered in and appear to be ineffective in helping that factor is not a threat. If there is management actions and tortoise- to reduce these individual mortalities. exposure and the species responds specific mitigation measures are Climate change may also affect negatively, the factor may be a threat mandated, or where land activities that Sonoran desert tortoises. The combined and we then attempt to determine how could appreciably threaten Sonoran effects of global and regional climate significant a threat it is. If the threat is desert tortoise populations are change, along with the effects of long- significant, it may drive or contribute to prohibited. However, significant threats term drought, will play a role in the the risk of extinction of the species such we have identified in Factors A, C, and long-term persistence of the species. that the species warrants listing as E (primarily invading nonnative plant

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species and subsequent wildfire Sonoran desert tortoise habitat is within Guidelines’’ address the immediacy and concerns, vandalism of tortoises, feral 30 mi (48 km) or less of human magnitude of threats, and the level of dog predation, and climate change) are populations of 1,000 people or more. taxonomic distinctiveness. The system not being adequately addressed by land The factors that have resulted in the loss places greatest importance on the managers or other regulatory or degradation of habitat, or threaten the immediacy and magnitude of threats, mechanisms. The primary threats to the tortoise directly, are predicted to worsen but also factors in the level of taxonomic Sonoran desert tortoise from other in the foreseeable future as the footprint distinctiveness by assigning priority in natural or manmade factors affecting its of development and infrastructure descending order to monotypic genera continued existence (Factor E) include grows and human population growth (genus with one species), full species, the threats from vehicle strike mortality ensues. Some populations may and subspecies (or equivalently, distinct due to unmaintained structures disappear altogether, while others population segments of vertebrates). As intended to prevent tortoise mortality become smaller and more contracted; a result of our analysis of the best along heavily traveled routes through each of these scenarios exacerbates available scientific and commercial core Sonoran desert tortoise isolation and genetic and demographic information, we assigned the Sonoran populations. In addition, anticipated exchange. Therefore, we reasonably desert tortoise a Listing Priority Number effects from climate change are likely to anticipate that the Sonoran desert of 6, based on the high magnitude and exacerbate the ongoing threat of habitat tortoise DPS is in danger of extinction non-imminence of threats. One or more loss and degradation by other factors, in the foreseeable future throughout all of the threats discussed above are but we were unable to conclude that or a significant portion of its range. occurring in virtually every known climate change, by itself, currently On the basis of the best scientific and population throughout its range. These threatens the Sonoran desert tortoise. commercial information available, we threats are ongoing, and will continue to We have documented adverse effects of find that the petitioned action, to list the occur into the foreseeable future and, in many of these threats on existing Sonoran desert tortoise is warranted. In some cases (such as nonnative plant Sonoran desert tortoise populations, making this finding, we gave significant species invasions and climate change both historically and currently, and note deference to the irreversible effect of effects), are considered irreversible. Our that many threats act in synergistic threats as they are anticipated to occur rationale for assigning the Sonoran combination in their effects to the in the foreseeable future. We will make desert tortoise an LPN of 6 is outlined tortoise. The factors that are the primary a determination on the status of the below. drivers of these threats, such as species as threatened or endangered Under the Service’s LPN Guidance, urbanization, human population when we do a proposed listing the magnitude of threat is the first growth, and drought, are predicted to determination. However, as explained criterion we look at when establishing a increase in the foreseeable future. in more detail below, an immediate As a result of the numerous threats to proposal of a regulation implementing listing priority. The guidance indicates the Sonoran desert tortoise identified this action is precluded by higher that species with the highest magnitude above—which have occurred priority listing actions, and progress is of threat are those species facing the historically, continue today, and are being made to add or remove qualified greatest threats to their continued predicted to continue in the foreseeable species from the Lists of Endangered existence. These species receive the future—the tortoise has lost appreciable and Threatened Wildlife and Plants. highest listing priority. Threats to the amounts of habitat to the collective We reviewed the available Sonoran desert tortoise vary in their footprint of urban development, information to determine if the existing magnitude. We found the most agriculture, and infrastructure on the and foreseeable threats render the significant threats to the Sonoran desert landscape. Collectively, these land species at risk of extinction at this time tortoise to be the expansion of range and changes have not only destroyed former such that issuing an emergency increase in number of nonnative plant Sonoran desert tortoise habitat, but have regulation temporarily listing the DPS species, urban development and fragmented remaining populations, under section 4(b)(7) of the Act is associated human population growth in threatening long-term genetic fitness of warranted. We determined that issuing Arizona, and the highly popular and the tortoise and precluding their an emergency regulation temporarily growing use of OHVs in Arizona. These recolonization ability in the event of listing the species is not warranted for threats have both direct and indirect population extirpations. In Mexico, this species at this time because we effects to the Sonoran desert tortoise significant areas of former Sonoran have not documented any significant and its habitat. The area of land affected desert habitat have been significantly population extirpations. However, if at by nonnative species is widespread and, altered by the cultivation and natural any time we determine that issuing an although currently and comparatively colonization of invasive, nonnative emergency regulation temporarily less significant in Arizona, it is plant species, and in combination with listing the Sonoran desert tortoise is substantial in Mexico. It is also expected other threats, have likely greatly affected warranted, we will initiate this action at to increase in the foreseeable future in the viability of the Sonoran desert that time. both countries. When including the total tortoise in that country. land area adversely modified by Available monitoring data are not Listing Priority Number ironwood and mesquite harvesting, it is adequate to accurately determine how The Service adopted guidelines on projected that an estimated 98 percent the Sonoran desert tortoise historically September 21, 1983 (48 FR 43098) to of the Sonoran desert tortoises’ habitat responded to the loss of habitat or how establish a rational system for utilizing in Mexico (47 percent of habitat populations have individually available resources for the highest rangewide) will be lost or adversely responded to threats, but we are priority species when adding species to modified in the foreseeable future. reasonably certain that there are fewer the Lists of Endangered and Threatened Additionally, there is currently no Sonoran desert tortoises currently than Wildlife and Plants or reclassifying viable solution to the threat posed by historically, and that populations have species listed as threatened to the increase in nonnative plants on this become significantly fragmented over endangered status. These guidelines, landscape. The projected human time. Currently within Arizona, titled ‘‘Endangered and Threatened population growth and urban approximately 75 percent of potential Species Listing and Recovery Priority development throughout this DPS are

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likely to both pose significant problems of the Sonoran desert tortoise where urbanization that has already occurred for genetic exchange among Sonoran they occur. Some are acting currently in replaced agricultural land that was not desert tortoise populations. This will some areas, but not the whole DPS; usable Sonoran desert tortoise habitat. increase the degree and scope of human some threats are likely to expand Additionally, our evaluation of Sonoran interactions with tortoises and occupied geographically over time; some are desert tortoise population monitoring habitat, which threatens the tortoise in stabilized or even reducing in impact. data has not indicated that any a variety of ways that we discuss in Although we reviewed and discussed monitored population has been detail above. Currently in Arizona, 75 the numerous ways that individual extirpated and less than one-third of percent of potentially occupied Sonoran Sonoran desert tortoises are affected by monitored populations have shown desert tortoise habitat occurs within 30 various threats, there is currently no declines, indicating that impacts on mi (48 km) or less of a city or town with evidence that any existing population is Sonoran desert tortoise populations are a human population of 1,000 or more, threatened with extirpation in the near not currently imminent. These actual, and, considering future growth future. So while some of the threats are identifiable threats are covered in detail projections, it is likely that 100 percent happening now, impacts to tortoise under the discussion of Factors A of occupied tortoise habitat will be populations are not likely to be evident through E of this finding and currently affected in the future. The ever- in the immediate future. include habitat destruction, expanding human population in For example, we have documented modification, and fragmentation, Arizona is also likely to lead to that the invasion of nonnative plants is overutilization, predation from commensurate increases in OHV use. As most significant in Sonora, Mexico, unnatural sources, inadequate of 2007, 385,000 off-highway vehicles because of active planting for livestock regulatory mechanisms, and other were registered in Arizona (a 350 grazing purposes. However, while there natural and manmade factors. percent increase since 1998), and 1.7 were historic practices of planting The third criterion in our LPN million people (29 percent of the nonnative plant species as forage for guidance is intended to devote Arizona’s public) engaged in off-road livestock in the United States, these resources to those species representing activity from 2005 to 2007. We activities have ceased, leaving only highly distinctive or isolated gene pools identified significant threats from OHV slower, natural mechanisms to facilitate as reflected by taxonomy. The Sonoran use in Sonoran desert tortoise habitat, the expansion of nonnative plant desert tortoise is a valid taxon at the including habitat destruction, increased species in this country. Thus, DPS level, and therefore receives a illegal collection of tortoises, and comparatively less habitat area is lower priority than species in a significant problems with law significantly altered by nonnative plant monotypic genus. The Sonoran desert enforcement of OHV users. Despite distribution and abundance in Arizona, tortoise faces high magnitude, non- representing approximately half of the problems associated with OHV imminent threats, and is a valid taxon Sonoran desert tortoises’ range. management, several land management at the DPS level. Thus, in accordance Additionally, monitoring data indicate agencies responsible for Sonoran desert with our LPN guidance, we have that Sonoran desert tortoise populations tortoise habitat have plans to expand assigned the Sonoran desert tortoise an persist in habitat that is unburned, but OHV use on their lands. These three LPN of 6. where nonnative species have become major threats operate in combination We will continue to monitor the with other threats which, by themselves, established. As stated in Factor A, wildfire is an important trigger, capable threats to the Sonoran desert tortoise, might not be as serious, but acting of making nonnative-invaded habitat and the species’ status on an annual together, cause a more serious unsuitable for Sonoran desert tortoises. basis, and should the magnitude or the cumulative impact. These threats The majority of nonnative-invaded imminence of the threats change, we include improper livestock management Sonoran desert tortoise habitat remains will revisit our assessment of the LPN. in Mexico, illegal collection and release unburned in the United States; however Work on a proposed listing of tortoises, undocumented human we are less certain about the occurrence determination for the Sonoran desert immigration and associated interdiction of wildfire in nonnative-invaded habitat tortoise is precluded by work on higher activities, predation from feral or off- in Mexico. In both cases in Arizona and priority listing actions with absolute leash dogs, vehicle strike mortality from Mexico the ongoing conversion of statutory, court-ordered, or court- unmaintained, roadside mitigation habitats to nonnative grasses are not approved deadlines and final listing devices, and anticipated possible effects expected to impact tortoise populations determinations for those species that from climate change. In their totality, in the very immediate future. Therefore, were proposed for listing with funds these threats are high in magnitude the actual impacts on tortoise from Fiscal Year 2011. This work because of the amount of habitat that is populations from these and similar includes all the actions listed in the likely to be affected and the irreversible threats, such as climate change, are tables below under expeditious nature of the effect of these threats in more likely to occur in the mid- to long- progress. sensitive habitats that are slow to term future and are not considered Preclusion and Expeditious Progress rebound. imminent. Under our LPN Guidance, the second Also, many of the threats we discuss Preclusion is a function of the listing criterion we consider in assigning a above are linked to urbanization and priority of a species in relation to the listing priority is the immediacy of human population growth. In Arizona, resources that are available and the cost threats. This criterion is intended to we have observed significant and relative priority of competing ensure that the species that face actual, development and human population demands for those resources. Thus, in identifiable threats are given priority growth over the past several decades, any given fiscal year (FY), multiple over those species for which threats are but a weakened economy has slowed factors dictate whether it will be only potential or that are intrinsically growth in recent years. We documented possible to undertake work on a listing vulnerable but are not known to be that the Sun Corridor Megapolitan is proposal regulation or whether presently facing such threats. The expected to nearly double the human promulgation of such a proposal is threats are non-imminent because they population of southern and central precluded by higher-priority listing are not ubiquitous throughout the range Arizona by 2030. However, much of the actions.

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The resources available for listing ensure that some funds are available for refer specifically to the ‘‘to the actions are determined through the other work in the Listing Program (‘‘The maximum extent practicable’’ limitation annual Congressional appropriations critical habitat designation subcap will on the 90-day deadline for making a process. The appropriation for the ensure that some funding is available to ‘‘substantial information’’ finding, that Listing Program is available to support address other listing activities’’ (House finding is made at the point when the work involving the following listing Report No. 107–103, 107th Congress, 1st Service is deciding whether or not to actions: Proposed and final listing rules; Session, June 19, 2001)). In FY 2002 and commence a status review that will 90-day and 12-month findings on each year until FY 2006, the Service has determine the degree of threats facing petitions to add species to the Lists of had to use virtually the entire critical the species, and therefore the analysis Endangered and Threatened Wildlife habitat subcap to address court- underlying the statement is more and Plants (Lists) or to change the status mandated designations of critical relevant to the use of the warranted-but- of a species from threatened to habitat, and consequently none of the precluded finding, which is made when endangered; annual ‘‘resubmitted’’ critical habitat subcap funds have been the Service has already determined the petition findings on prior warranted- available for other listing activities. In degree of threats facing the species and but-precluded petition findings as some FYs since 2006, we have been able is deciding whether or not to commence required under section 4(b)(3)(C)(i) of to use some of the critical habitat a rulemaking. the Act; critical habitat petition subcap funds to fund proposed listing In FY 2010, $10,471,000 is the findings; proposed and final rules determinations for high-priority amount of money that Congress designating critical habitat; and candidate species. In other FYs, while appropriated for the Listing Program litigation-related, administrative, and we were unable to use any of the critical (that is, the portion of the Listing program-management functions habitat subcap funds to fund proposed Program funding not related to critical (including preparing and allocating listing determinations, we did use some habitat designations for species that are budgets, responding to Congressional of this money to fund the critical habitat already listed). Therefore, a proposed and public inquiries, and conducting portion of some proposed listing listing is precluded if pending proposals public outreach regarding listing and determinations so that the proposed with higher priority will require critical habitat). The work involved in listing determination and proposed expenditure of at least $10,471,000, and preparing various listing documents can critical habitat designation could be expeditious progress is the amount of be extensive and may include, but is not combined into one rule, thereby being work that can be achieved with limited to: gathering and assessing the more efficient in our work. In FY 2011 $10,471,000. Since court orders best scientific and commercial data we anticipate that we will be unable to requiring critical habitat work will not available and conducting analyses used use any of the critical habitat subcap require use of all of the funds within the as the basis for our decisions; writing funds to fund proposed listing critical habitat subcap, we used and publishing documents; and determinations. $1,114,417 of our critical habitat subcap obtaining, reviewing, and evaluating We make our determinations of funds in order to work on as many of public comments and peer review preclusion on a nationwide basis to our required petition findings and comments on proposed rules and ensure that the species most in need of listing determinations as possible. This incorporating relevant information into listing will be addressed first and also brings the total amount of funds we had final rules. The number of listing because we allocate our listing budget for listing actions in FY 2010 to actions that we can undertake in a given on a nationwide basis. Through the $11,585,417. year also is influenced by the listing cap, the critical habitat subcap, The $11,585,417 was used to fund complexity of those listing actions; that and the amount of funds needed to work in the following categories: is, more complex actions generally are address court-mandated critical habitat compliance with court orders and court- more costly. The median cost for designations, Congress and the courts approved settlement agreements preparing and publishing a 90-day have, in effect, determined the amount requiring that petition findings or listing finding is $39,276; for a 12-month of money available for other listing determinations be completed by a finding, $100,690; for a proposed rule activities nationwide. Therefore, the specific date; section 4 (of the Act) with critical habitat, $345,000; and for funds in the listing cap, other than those listing actions with absolute statutory a final listing rule with critical habitat, needed to address court-mandated deadlines; essential litigation-related, the median cost is $305,000. critical habitat for already listed species, administrative, and listing program- We cannot spend more than is set the limits on our determinations of management functions; and high- appropriated for the Listing Program preclusion and expeditious progress. priority listing actions for some of our without violating the Anti-Deficiency Congress identified the availability of candidate species. For FY 2011, on Act (see 31 U.S.C. 1341(a)(1)(A)). In resources as the only basis for deferring September 29, 2010, Congress passed a addition, in FY 1998 and for each fiscal the initiation of a rulemaking that is continuing resolution which provides year since then, Congress has placed a warranted. The Conference Report funding at the FY 2010 enacted level. In statutory cap on funds which may be accompanying P.L. 97–304, which 2009, the responsibility for listing expended for the Listing Program, equal established the current statutory foreign species under the Act was to the amount expressly appropriated deadlines and the warranted-but- transferred from the Division of for that purpose in that fiscal year. This precluded finding, states that the Scientific Authority, International cap was designed to prevent funds amendments were ‘‘not intended to Affairs Program, to the Endangered appropriated for other functions under allow the Secretary to delay Species Program. Therefore, starting in the Act (for example, recovery funds for commencing the rulemaking process for FY 2010, we use a portion of our removing species from the Lists), or for any reason other than that the existence funding to work on the actions other Service programs, from being used of pending or imminent proposals to list described above as they apply to listing for Listing Program actions (see House species subject to a greater degree of actions for foreign species. This has the Report 105–163, 105th Congress, 1st threat would make allocation of potential to further reduce funding Session, July 1, 1997). resources to such a petition [that is, for available for domestic listing actions. Since FY 2002, the Service’s budget a lower-ranking species] unwise.’’ Although there are currently no foreign has included a critical habitat subcap to Although that statement appeared to species issues included in our high-

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priority listing actions at this time, individuals, or 4 or fewer populations. overlap geographically or have the same many actions have statutory or court- Those species with the highest IUCN threats as a species with an LPN of 2. approved settlement deadlines, thus rank (critically endangered), the highest In addition, we take into consideration increasing their priority. The budget Heritage rank (G1), the highest Heritage the availability of staff resources when allocations for each specific listing threat rank (substantial, imminent we determine which high-priority action are identified in the Service’s FY threats), and currently with fewer than species will receive funding to 2011 Allocation Table (part of our 50 individuals, or fewer than 4 minimize the amount of time and administrative record). populations, originally comprised a resources required to complete each Based on our September 21, 1983, group of approximately 40 candidate listing action. guidance for assigning an LPN for each species (‘‘Top 40’’). These 40 candidate As explained above, a determination candidate species (48 FR 43098), we species have had the highest priority to that listing is warranted but precluded have a significant number of species receive funding to work on a proposed with an LPN of 2. Using this guidance, listing determination. As we work on must also demonstrate that expeditious we assign each candidate an LPN of 1 proposed and final listing rules for those progress is being made to add and to 12, depending on the magnitude of 40 candidates, we apply the ranking remove qualified species to and from threats (high or moderate to low), criteria to the next group of candidates the Lists of Endangered and Threatened immediacy of threats (imminent or with an LPN of 2 and 3 to determine the Wildlife and Plants. As with our nonimminent), and taxonomic status of next set of highest-priority candidate ‘‘precluded’’ finding, the evaluation of the species (in order of priority: species. Finally, proposed rules for whether progress in adding qualified monotypic genus (a species that is the reclassification of threatened species to species to the Lists has been expeditious sole member of a genus); species, or part endangered are lower priority, since as is a function of the resources available of a species (subspecies, distinct listed species, they are already afforded for listing and the competing demands population segment, or significant the protection of the Act and for those funds. Although we do not portion of the range)). The lower the implementing regulations. However, for discuss it in detail here, we are also listing priority number, the higher the efficiency reasons, we may choose to making expeditious progress in listing priority (that is, a species with an work on a proposed rule to reclassify a removing species from the list under the LPN of 1 would have the highest listing species to endangered if we can Recovery program in light of the priority). combine this with work that is subject resource available for delisting, which is Because of the large number of high- to a court-determined deadline. funded by a separate line item in the priority species, we have further ranked With our workload so much bigger budget of the Endangered Species the candidate species with an LPN of 2 than the amount of funds we have to Program. During FY 2010, we have by using the following extinction-risk accomplish it, it is important that we be completed two proposed delisting rules type criteria: International Union for the as efficient as possible in our listing and two final delisting rules. Given the Conservation of Nature and Natural process. Therefore, as we work on limited resources available for listing, Resources (IUCN) Red list status/rank, proposed rules for the highest priority we find that we made expeditious Heritage rank (provided by species in the next several years, we are progress in FY 2010 in the Listing NatureServe), Heritage threat rank preparing multi-species proposals when Program. This progress included (provided by NatureServe), and species appropriate, and these may include preparing and publishing the following currently with fewer than 50 species with lower priority if they determinations:

FY 2010 AND FY 2011 COMPLETED LISTING ACTIONS

Publication date Title Actions FR pages

10/08/2009 ...... Listing Lepidium papilliferum (Slickspot Peppergrass) as a Threat- Final Listing Threatened ...... 74 FR 52013–52064. ened Species Throughout Its Range. 10/27/2009 ...... 90-day Finding on a Petition To List the American Dipper in the Notice of 90-day Petition Find- 74 FR 55177–55180. Black Hills of South Dakota as Threatened or Endangered. ing, Not substantial. 10/28/2009 ...... Status Review of Arctic Grayling (Thymallus arcticus) in the Notice of Intent to Conduct Sta- 74 FR 55524–55525. Upper Missouri River System. tus Review for Listing Deci- sion. 11/03/2009 ...... Listing the British Columbia Distinct Population Segment of the Proposed Listing Threatened ..... 74 FR 56757–56770. Queen Charlotte Goshawk Under the Endangered Species Act: Proposed rule. 11/03/2009 ...... Listing the Salmon-Crested Cockatoo as Threatened Throughout Proposed Listing Threatened ..... 74 FR 56770–56791. Its Range with Special Rule. 11/23/2009 ...... Status Review of Gunnison sage-grouse (Centrocercus minimus) Notice of Intent to Conduct Sta- 74 FR 61100–61102. tus Review for Listing Deci- sion. 12/03/2009 ...... 12-Month Finding on a Petition to List the Black-tailed Prairie Dog Notice of 12-month petition find- 74 FR 63343–63366. as Threatened or Endangered. ing, Not warranted. 12/03/2009 ...... 90-Day Finding on a Petition to List Sprague’s Pipit as Threat- Notice of 90-day Petition Find- 74 FR 63337–63343. ened or Endangered. ing, Substantial. 12/15/2009 ...... 90-Day Finding on Petitions To List Nine Species of Mussels Notice of 90-day Petition Find- 74 FR 66260–66271. From Texas as Threatened or Endangered With Critical Habitat. ing, Substantial. 12/16/2009 ...... Partial 90-Day Finding on a Petition to List 475 Species in the Notice of 90-day Petition Find- 74 FR 66865–66905. Southwestern United States as Threatened or Endangered ing, Not substantial and Sub- With Critical Habitat. stantial. 12/17/2009 ...... 12-month Finding on a Petition To Change the Final Listing of the Notice of 12-month petition find- 74 FR 66937–66950. Distinct Population Segment of the Canada Lynx To Include ing, Warranted but precluded. New Mexico.

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FY 2010 AND FY 2011 COMPLETED LISTING ACTIONS—Continued

Publication date Title Actions FR pages

1/05/2010 ...... Listing Foreign Bird Species in Peru and Bolivia as Endangered Proposed Listing Endangered .... 75 FR 605–649. Throughout Their Range. 1/05/2010 ...... Listing Six Foreign Birds as Endangered Throughout Their Range Proposed Listing Endangered .... 75 FR 286–310. 1/05/2010 ...... Withdrawal of Proposed Rule to List Cook’s Petrel ...... Proposed rule, withdrawal ...... 75 FR 310–316. 1/05/2010 ...... Final Rule to List the Galapagos Petrel and Heinroth’s Final Listing Threatened ...... 75 FR 235–250. Shearwater as Threatened Throughout Their Ranges. 1/20/2010 ...... Initiation of Status Review for Agave eggersiana and Solanum Notice of Intent to Conduct Sta- 75 FR 3190–3191. conocarpum. tus Review for Listing Deci- sion. 2/09/2010 ...... 12-month Finding on a Petition to List the American Pika as Notice of 12-month petition find- 75 FR 6437–6471. Threatened or Endangered. ing, Not warranted. 2/25/2010 ...... 12-Month Finding on a Petition To List the Sonoran Desert Popu- Notice of 12-month petition find- 75 FR 8601–8621. lation of the Bald Eagle as a Threatened or Endangered Dis- ing, Not warranted. tinct Population Segment. 2/25/2010 ...... Withdrawal of Proposed Rule To List the Southwestern Wash- Withdrawal of Proposed Rule to 75 FR 8621–8644. ington/Columbia River Distinct Population Segment of Coastal List. Cutthroat Trout (Oncorhynchus clarki clarki) as Threatened. 3/18/2010 ...... 90-Day Finding on a Petition to List the Berry Cave salamander Notice of 90-day Petition Find- 75 FR 13068–13071. as Endangered. ing, Substantial. 3/23/2010 ...... 90-Day Finding on a Petition to List the Southern Hickorynut Notice of 90-day Petition Find- 75 FR 13717–13720. Mussel (Obovaria jacksoniana) as Endangered or Threatened. ing, Not substantial. 3/23/2010 ...... 90-Day Finding on a Petition to List the Striped Newt as Threat- Notice of 90-day Petition Find- 75 FR 13720–13726. ened. ing, Substantial. 3/23/2010 ...... 12-Month Findings for Petitions to List the Greater Sage-Grouse Notice of 12-month petition find- 75 FR 13910–14014. (Centrocercus urophasianus) as Threatened or Endangered. ing, Warranted but precluded. 3/31/2010 ...... 12-Month Finding on a Petition to List the Tucson Shovel-Nosed Notice of 12-month petition find- 75 FR 16050–16065. Snake (Chionactis occipitalis klauberi) as Threatened or En- ing, Warranted but precluded. dangered with Critical Habitat. 4/5/2010 ...... 90-Day Finding on a Petition To List Thorne’s Hairstreak Butterfly Notice of 90-day Petition Find- 75 FR 17062–17070. as Endangered. ing, Substantial. 4/6/2010 ...... 12-month Finding on a Petition To List the Mountain Whitefish in Notice of 12-month petition find- 75 FR 17352–17363. the Big Lost River, Idaho, as Endangered or Threatened. ing, Not warranted. 4/6/2010 ...... 90-Day Finding on a Petition to List a Stonefly (Isoperla jewetti) Notice of 90-day Petition Find- 75 FR 17363–17367. and a Mayfly (Fallceon eatoni) as Threatened or Endangered ing, Not substantial. with Critical Habitat. 4/7/2010 ...... 12-Month Finding on a Petition to Reclassify the Delta Smelt Notice of 12-month petition find- 75 FR 17667–17680. From Threatened to Endangered Throughout Its Range. ing, Warranted but precluded. 4/13/2010 ...... Determination of Endangered Status for 48 Species on Kauai and Final Listing Endangered ...... 75 FR 18959–19165. Designation of Critical Habitat. 4/15/2010 ...... Initiation of Status Review of the North American Wolverine in the Notice of Initiation of Status Re- 75 FR 19591–19592. Contiguous United States. view for Listing Decision. 4/15/2010 ...... 12-Month Finding on a Petition to List the Wyoming Pocket Go- Notice of 12-month petition find- 75 FR 19592–19607. pher as Endangered or Threatened with Critical Habitat. ing, Not warranted. 4/16/2010 ...... 90-Day Finding on a Petition to List a Distinct Population Seg- Notice of 90-day Petition Find- 75 FR 19925–19935. ment of the Fisher in Its United States Northern Rocky Moun- ing, Substantial. tain Range as Endangered or Threatened with Critical Habitat. 4/20/2010 ...... Initiation of Status Review for Sacramento splittail (Pogonichthys Notice of Initiation of Status Re- 75 FR 20547–20548. macrolepidotus). view for Listing Decision. 4/26/2010 ...... 90-Day Finding on a Petition to List the Harlequin Butterfly as En- Notice of 90-day Petition Find- 75 FR 21568–21571. dangered. ing, Substantial. 4/27/2010 ...... 12-Month Finding on a Petition to List Susan’s Purse-making Notice of 12-month petition find- 75 FR 22012–22025. Caddisfly (Ochrotrichia susanae) as Threatened or Endangered. ing, Not warranted. 4/27/2010 ...... 90-day Finding on a Petition to List the Mohave Ground Squirrel Notice of 90-day Petition Find- 75 FR 22063–22070. as Endangered with Critical Habitat. ing, Substantial. 5/4/2010 ...... 90-Day Finding on a Petition to List Hermes Copper Butterfly as Notice of 90-day Petition Find- 75 FR 23654–23663. Threatened or Endangered. ing, Substantial. 6/1/2010 ...... 90-Day Finding on a Petition To List Castanea pumila var. Notice of 90-day Petition Find- 75 FR 30313–30318. ozarkensis. ing, Substantial. 6/1/2010 ...... 12-month Finding on a Petition to List the White-tailed Prairie Notice of 12-month petition find- 75 FR 30338–30363. Dog as Endangered or Threatened. ing, Not warranted. 6/9/2010 ...... 90-Day Finding on a Petition To List van Rossem’s Gull-billed Notice of 90-day Petition Find- 75 FR 32728–32734. Tern as Endangered or Threatened. ing, Substantial. 6/16/2010 ...... 90-Day Finding on Five Petitions to List Seven Species of Hawai- Notice of 90-day Petition Find- 75 FR 34077–34088. ian Yellow-faced Bees as Endangered. ing, Substantial. 6/22/2010 ...... 12-Month Finding on a Petition to List the Least Chub as Threat- Notice of 12-month petition find- 75 FR 35398–35424. ened or Endangered. ing, Warranted but precluded. 6/23/2010 ...... 90-Day Finding on a Petition to List the Honduran Emerald Hum- Notice of 90-day Petition Find- 75 FR 35746–35751. mingbird as Endangered. ing, Substantial. 6/23/2010 ...... Listing Ipomopsis polyantha (Pagosa Skyrocket) as Endangered Proposed Listing Endangered 75 FR 35721–35746. Throughout Its Range, and Listing Penstemon debilis (Para- Proposed Listing Threatened. chute Beardtongue) and Phacelia submutica (DeBeque Phacelia) as Threatened Throughout Their Range.

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FY 2010 AND FY 2011 COMPLETED LISTING ACTIONS—Continued

Publication date Title Actions FR pages

6/24/2010 ...... Listing the Flying Earwig Hawaiian Damselfly and Pacific Hawai- Final Listing Endangered ...... 75 FR 35990–36012. ian Damselfly As Endangered Throughout Their Ranges. 6/24/2010 ...... Listing the Cumberland Darter, Rush Darter, Yellowcheek Darter, Proposed Listing Endangered .... 75 FR 36035–36057. Chucky Madtom, and Laurel Dace as Endangered Throughout Their Ranges. 6/29/2010 ...... Listing the Mountain Plover as Threatened ...... Reinstatement of Proposed List- 75 FR 37353–37358. ing Threatened. 7/20/2010 ...... 90-Day Finding on a Petition to List Pinus albicaulis (Whitebark Notice of 90-day Petition Find- 75 FR 42033–42040. Pine) as Endangered or Threatened with Critical Habitat. ing, Substantial. 7/20/2010 ...... 12-Month Finding on a Petition to List the Amargosa Toad as Notice of 12-month petition find- 75 FR 42040–42054. Threatened or Endangered. ing, Not warranted. 7/20/2010 ...... 90-Day Finding on a Petition to List the Giant Palouse Earthworm Notice of 90-day Petition Find- 75 FR 42059–42066. (Driloleirus americanus) as Threatened or Endangered. ing, Substantial. 7/27/2010 ...... Determination on Listing the Black-Breasted Puffleg as Endan- Final Listing Endangered ...... 75 FR 43844–43853. gered Throughout its Range; Final Rule. 7/27/2010 ...... Final Rule to List the Medium Tree-Finch (Camarhynchus pauper) Final Listing Endangered ...... 75 FR 43853–43864. as Endangered Throughout Its Range. 8/3/2010 ...... Determination of Threatened Status for Five Penguin Species ..... Final Listing Threatened ...... 75 FR 45497–45527. 8/4/2010 ...... 90-Day Finding on a Petition To List the Mexican Gray Wolf as Notice of 90-day Petition Find- 75 FR 46894–46898. an Endangered Subspecies With Critical Habitat. ing, Substantial. 8/10/2010 ...... 90-Day Finding on a Petition to List Arctostaphylos franciscana Notice of 90-day Petition Find- 75 FR 48294–48298. as Endangered with Critical Habitat. ing, Substantial. 8/17/2010 ...... Listing Three Foreign Bird Species from Latin America and the Final Listing Endangered ...... 75 FR 50813–50842. Caribbean as Endangered Throughout Their Range. 8/17/2010 ...... 90-Day Finding on a Petition to List Brian Head Mountainsnail as Notice of 90-day Petition Find- 75 FR 50739–50742. Endangered or Threatened with Critical Habitat. ing, Not substantial. 8/24/2010 ...... 90-Day Finding on a Petition to List the Oklahoma Grass Pink Or- Notice of 90-day Petition Find- 75 FR 51969–51974. chid as Endangered or Threatened. ing, Substantial. 9/1/2010 ...... 12-Month Finding on a Petition to List the White-Sided Jackrabbit Notice of 12-month petition find- 75 FR 53615–53629. as Threatened or Endangered. ing, Not warranted. 9/8/2010 ...... Proposed Rule To List the Ozark Hellbender Salamander as En- Proposed Listing Endangered .... 75 FR 54561–54579. dangered. 9/8/2010 ...... Revised 12–Month Finding to List the Upper Missouri River Dis- Notice of 12-month petition find- 75 FR 54707–54753. tinct Population Segment of Arctic Grayling as Endangered or ing, Warranted but precluded. Threatened. 9/9/2010 ...... 12-Month Finding on a Petition to List the Jemez Mountains Sala- Notice of 12-month petition find- 75 FR 54822–54845. mander (Plethodon neomexicanus) as Endangered or Threat- ing, Warranted but precluded. ened with Critical Habitat. 9/15/2010 ...... 12-Month Finding on a Petition to List Sprague’s Pipit as Endan- Notice of 12-month petition find- 75 FR 56028–56050. gered or Threatened Throughout Its Range. ing, Warranted but precluded. 9/22/2010 ...... 12-Month Finding on a Petition to List Agave eggersiana (no Notice of 12-month petition find- 75 FR 57720–57734. common name) as Endangered. ing, Warranted but precluded. 9/28/2010 ...... Determination of Endangered Status for the African Penguin ...... Final Listing Endangered ...... 75 FR 59645–59656. 9/28/2010 ...... Determination for the Gunnison Sage-grouse as a Threatened or Notice of 12-month petition find- 75 FR 59803–59863. Endangered Species. ing, Warranted but precluded. 9/30/2010 ...... 12-Month Finding on a Petition to List the Pygmy Rabbit as En- Notice of 12-month petition find- 75 FR 60515–60561. dangered or Threatened. ing, Not warranted. 10/6/2010 ...... Endangered Status for the Altamaha Spinymussel and Designa- Proposed Listing Endangered .... 75 FR 61664–61690. tion of Critical Habitat. 10/7/2010 ...... 12-month Finding on a Petition to list the Sacramento Splittail as Notice of 12-month petition find- 75 FR 62070–62095. Endangered or Threatened. ing, Not warranted.

Our expeditious progress also statutory timelines, that is, timelines a lower priority if they overlap includes work on listing actions that we required under the Act. Actions in the geographically or have the same threats funded in FY 2010 and FY 2011, but bottom section of the table are high- as the species with the high priority. have not yet been completed to date. priority listing actions. These actions Including these species together in the These actions are listed below. Actions include work primarily on species with same proposed rule results in in the top section of the table are being an LPN of 2, and, as discussed above, considerable savings in time and conducted under a deadline set by a selection of these species is partially funding compared to preparing separate court. Actions in the middle section of based on available staff resources, and proposed rules for each of them in the the table are being conducted to meet when appropriate, include species with future.

ACTIONS FUNDED IN FY 2010 AND FY 2011 BUT NOT YET COMPLETED

Species Action

Actions Subject to Court Order/Settlement Agreement

6 Birds from Eurasia ...... Final listing determination.

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ACTIONS FUNDED IN FY 2010 AND FY 2011 BUT NOT YET COMPLETED—Continued

Species Action

Flat-tailed horned lizard ...... Final listing determination. Mountain plover 4 ...... Final listing determination. 6 Birds from Peru ...... Proposed listing determination. Pacific walrus ...... 12-month petition finding. Wolverine ...... 12-month petition finding. Solanum conocarpum ...... 12-month petition finding. Desert tortoise—Sonoran population ...... 12-month petition finding. Thorne’s Hairstreak butterfly 3 ...... 12-month petition finding. Hermes copper butterfly 3 ...... 12-month petition finding.

Actions With Statutory Deadlines

Casey’s june beetle ...... Final listing determination. Georgia pigtoe, interrupted rocksnail, and rough hornsnail ...... Final listing determination. 7 Bird species from Brazil ...... Final listing determination. Southern rockhopper penguin—Campbell Plateau population ...... Final listing determination. 5 Bird species from Colombia and Ecuador ...... Final listing determination. Queen Charlotte goshawk ...... Final listing determination. 5 species southeast fish (Cumberland darter, rush darter, yellowcheek darter, chucky madtom, and laurel Final listing determination. dace) 4. Altamaha spinymussel ...... Final listing determination. Salmon crested cockatoo ...... Proposed listing determination. CA golden trout ...... 12-month petition finding. Black-footed albatross ...... 12-month petition finding. Mount Charleston blue butterfly ...... 12-month petition finding. Mojave fringe-toed lizard 1 ...... 12-month petition finding. Kokanee—Lake Sammamish population 1 ...... 12-month petition finding. Cactus ferruginous pygmy-owl 1 ...... 12-month petition finding. Northern leopard frog ...... 12-month petition finding. Tehachapi slender salamander ...... 12-month petition finding. Coqui Llanero ...... 12-month petition finding. Dusky tree vole ...... 12-month petition finding. 3 MT invertebrates (mist forestfly(Lednia tumana), Oreohelix sp.3, Oreohelix sp. 31) from 206 species peti- 12-month petition finding. tion. 5 UT plants (Astragalus hamiltonii, Eriogonum soredium, Lepidium ostleri, Penstemon flowersii, Trifolium 12-month petition finding. friscanum) from 206 species petition. 2 CO plants (Astragalus microcymbus, Astragalus schmolliae) from 206 species petition ...... 12-month petition finding. 5 WY plants (Abronia ammophila, Agrostis rossiae, Astragalus proimanthus, Boechere (Arabis) pusilla, 12-month petition finding. Penstemon gibbensii) from 206 species petition. Leatherside chub (from 206 species petition) ...... 12-month petition finding. Frigid ambersnail (from 206 species petition) ...... 12-month petition finding. —eastern population ...... 12-month petition finding. Wrights marsh thistle ...... 12-month petition finding. 67 of 475 southwest species ...... 12-month petition finding. Grand Canyon scorpion (from 475 species petition) ...... 12-month petition finding. Anacroneuria wipukupa (a stonefly from 475 species petition) ...... 12-month petition finding. Rattlesnake-master borer (from 475 species petition) ...... 12-month petition finding. 3 Texas (, Sphingicampa blanchardi, Agapema galbina) (from 475 species petition) ...... 12-month petition finding. 2 Texas shiners (Cyprinella sp., Cyprinella lepida) (from 475 species petition) ...... 12-month petition finding. 3 South Arizona plants (Erigeron piscaticus, Astragalus hypoxylus, Amoreuxia gonzalezii) (from 475 species 12-month petition finding. petition). 5 Central Texas mussel species (3 from 475 species petition) ...... 12-month petition finding. 14 parrots (foreign species) ...... 12-month petition finding. Berry Cave salamander 1 ...... 12-month petition finding. Striped Newt 1 ...... 12-month petition finding. Fisher—Northern Rocky Mountain Range 1 ...... 12-month petition finding. Mohave Ground Squirrel 1 ...... 12-month petition finding. Puerto Rico Harlequin Butterfly ...... 12-month petition finding. Western gull-billed tern ...... 12-month petition finding. Ozark chinquapin (Castanea pumila var. ozarkensis) ...... 12-month petition finding. HI yellow-faced bees ...... 12-month petition finding. Giant Palouse earthworm ...... 12-month petition finding. Whitebark pine ...... 12-month petition finding. OK grass pink (Calopogon oklahomensis) 1 ...... 12-month petition finding. Southeastern pop snowy plover & wintering pop. of piping plover 1 ...... 90-day petition finding. Eagle Lake trout 1 ...... 90-day petition finding. Smooth-billed ani 1 ...... 90-day petition finding. Bay Springs salamander 1 ...... 90-day petition finding. 32 species of snails and slugs 1 ...... 90-day petition finding. 42 snail species (Nevada & Utah) ...... 90-day petition finding. Red knot roselaari subspecies ...... 90-day petition finding. Peary caribou ...... 90-day petition finding.

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ACTIONS FUNDED IN FY 2010 AND FY 2011 BUT NOT YET COMPLETED—Continued

Species Action

Plains bison ...... 90-day petition finding. Spring Mountains checkerspot butterfly ...... 90-day petition finding. Spring pygmy sunfish ...... 90-day petition finding. Bay skipper ...... 90-day petition finding. Unsilvered fritillary ...... 90-day petition finding. Texas kangaroo rat ...... 90-day petition finding. Spot-tailed earless lizard ...... 90-day petition finding. Eastern small-footed bat ...... 90-day petition finding. Northern long-eared bat ...... 90-day petition finding. Prairie chub ...... 90-day petition finding. 10 species of Great Basin butterfly ...... 90-day petition finding. 6 sand dune (scarab) beetles ...... 90-day petition finding. Golden-winged warbler 4 ...... 90-day petition finding. Sand-verbena moth ...... 90-day petition finding. 404 Southeast species ...... 90-day petition finding. Franklin’s bumble bee 4 ...... 90-day petition finding. 2 Idaho snowflies (straight snowfly & Idaho snowfly) 4 ...... 90-day petition finding. American eel 4 ...... 90-day petition finding. Gila monster (Utah population) 4 ...... 90-day petition finding. Arapahoe snowfly 4 ...... 90-day petition finding. Leona’s little blue 4 ...... 90-day petition finding.

High-Priority Listing Actions 3

19 Oahu candidate species 2 (16 plants, 3 damselflies) (15 with LPN = 2, 3 with LPN = 3, 1 with LPN = 9) .... Proposed listing. 19 Maui-Nui candidate species 2 (16 plants, 3 tree snails) (14 with LPN = 2, 2 with LPN = 3, 3 with LPN = 8) Proposed listing. Dune sagebrush lizard (formerly Sand dune lizard) 3 (LPN = 2) ...... Proposed listing. 2 Arizona springsnails 2 (Pyrgulopsis bernadina (LPN = 2), Pyrgulopsis trivialis (LPN = 2)) ...... Proposed listing. New Mexico springsnail 2 (Pyrgulopsis chupaderae (LPN = 2) ...... Proposed listing. 2 mussels 2 (rayed bean (LPN = 2), snuffbox No LPN) ...... Proposed listing. 2 mussels 2 (sheepnose (LPN = 2), spectaclecase (LPN = 4),) ...... Proposed listing. 8 Gulf Coast mussels (southern kidneyshell (LPN = 2), round ebonyshell (LPN = 2), Alabama pearlshell (LPN Proposed listing. = 2), southern sandshell (LPN = 5), fuzzy pigtoe (LPN = 5), Choctaw bean (LPN = 5), narrow pigtoe (LPN = 5), and tapered pigtoe (LPN = 11)). Umtanum buckwheat (LPN = 2) 4 ...... Proposed listing. Grotto sculpin (LPN = 2) 4 ...... Proposed listing. 2 Arkansas mussels (Neosho mucket (LPN =2) & Rabbitsfoot (LPN = 9)) 4 ...... Proposed listing. Diamond darter (LPN = 2) 4 ...... Proposed listing. Gunnison sage-grouse (LPN = 2) 4 ...... Proposed listing. 1 Funds for listing actions for these species were provided in previous FYs. 2 Although funds for these high-priority listing actions were provided in FY 2008 or 2009, due to the complexity of these actions and competing priorities, these actions are still being developed. 3 Partially funded with FY 2010 funds and FY 2011 funds. 4 Funded with FY 2010 funds. 5 Funded with FY 2011 funds.

We have endeavored to make our becomes available. This review will from the Arizona Ecological Services listing actions as efficient and timely as determine if a change in status is Office (see ADDRESSES section). warranted, including the need to make possible, given the requirements of the Author(s) relevant law and regulations, and prompt use of emergency listing constraints relating to workload and procedures. The primary authors of this notice are personnel. We are continually We intend that any proposed listing the staff members of the Arizona considering ways to streamline determination for the Sonoran desert Ecological Services Office. tortoise will be as accurate as possible. processes or achieve economies of scale, Authority such as by batching related actions Therefore, we will continue to accept together. Given our limited budget for additional information and comments The authority for this section is implementing section 4 of the Act, these from all concerned governmental section 4 of the Endangered Species Act actions described above collectively agencies, the scientific community, of 1973, as amended (16 U.S.C. 1531 et constitute expeditious progress. industry, or any other interested party seq.). concerning this finding. The Sonoran desert tortoise will be Dated: November 23, 2010. added to the list of candidate species References Cited Rowan W. Gould, upon publication of this 12-month A complete list of references cited is Acting Director, Fish and Wildlife Service. finding. We will continue to monitor the available on the Internet at http:// [FR Doc. 2010–31000 Filed 12–13–10; 8:45 am] status of this DPS as new information www.regulations.gov and upon request BILLING CODE 4310–55–P

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