Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Mohave Ground Squirrel as Endangered or Threatened
Notice Of 12 Month Petition Finding.
We, the U.S. Fish and Wildlife Service (Service), announce a 12-month finding on a petition to list the Mohave ground squirrel (Spermophilus mohavensis) as endangered or threatened under the Endangered Species Act of 1973, as amended (Act). After review of the best available scientific and commercial information, we find that listing the Mohave ground squirrel is not warranted at this time. However, we ask the public to continue to submit to us any new information that becomes available concerning the threats to the Mohave ground squirrel or its habitat at any time.
Table of Contents Back to Top
- FOR FURTHER INFORMATION CONTACT:
- SUPPLEMENTARY INFORMATION:
- Previous Federal Actions
- Species Information
- Species Description
- Nomenclature and Taxonomy
- Range and Distribution
- Abundance and Trends
- Food Habits
- Mortality and Predation
- Active Season and Dormancy
- Home Range and Movements
- Habitat Requirements
- Summary of Information Pertaining to the Five Factors
- Factor A: The Present or Threatened Destruction, Modification, or Curtailment of the Species' Habitat or Range
- Urban and Rural Development
- Off-Highway Vehicle Recreational Use
- Transportation Infrastructure
- Military Operations
- Energy Development
- Power Generation
- Solar Projects
- Wind Projects
- Geothermal Projects
- Utility Corridors
- Summary of Energy Development
- Livestock Grazing
- Climate Change
- Summary of Factor A
- Factor B: Overutilization for Commercial, Recreational, Scientific, or Educational Purposes
- Factor C: Disease or Predation
- Summary of Factor C
- Factor D: The Inadequacy of Existing Regulatory Mechanisms
- Local Land Use Ordinances and Processes
- State Laws and Regulations
- Federal Laws and Regulations
- Bureau of Land Management
- Department of Defense
- Environmental Protection Agency
- Other Federal Agencies
- Summary of Factor D
- Factor E: Other Natural or Manmade Factors Affecting the Continued Existence of the Species
- Direct Mortality
- Habitat Fragmentation
- Summary of Factor E
- Distinct Vertebrate Population Segment
- Markedly Separated From Other Populations of the Taxon
- Significant Portion of the Range Analysis
- Historical Range
- Current Range
- References Cited
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- Table 1—Federal Lands Managed for the Mohave Ground Squirrel or Its Habitat, and the Percent of the Species' Range1
DATES: Back to Top
The finding announced in this document was made on October 6, 2011.
ADDRESSES: Back to Top
This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R8-ES-2010-0006 and at http://www.fws.gov/ventura/. Supporting documentation we used in preparing this finding is available for public inspection, by appointment, during normal business hours at the U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, CA 93003. Please submit any new information, materials, comments, or questions concerning this finding to the above address.
FOR FURTHER INFORMATION CONTACT: Back to Top
Michael McCrary, Listing and Recovery Program Coordinator, U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office (see ADDRESSES); by telephone at 805-644-1766; or by facsimile at 805-644-3958. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION: Back to Top
Background Back to Top
Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.) requires that, for any petition to revise the Federal Lists of Endangered and Threatened Wildlife and Plants that contains substantial scientific or commercial information that listing may be warranted, we make a finding within 12 months of the date of receipt of the petition. In this finding, we determine whether the petitioned action is: (a) Not warranted, (b) warranted, or (c) warranted, but the immediate proposal of a regulation implementing the petitioned action is precluded by other pending proposals to determine whether species are endangered or threatened, and expeditious progress is being made to add or remove qualified species from the Federal Lists of Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition for which the requested action is found to be warranted but precluded as though resubmitted on the date of such finding, that is, requiring a subsequent finding to be made within 12 months. We must publish these 12-month findings in the Federal Register.
Previous Federal Actions
On December 13, 1993, the Service received a petition dated December 6, 1993, from Dr. Glenn R. Stewart of California Polytechnic State University, Pomona, California, requesting the Service list the Mohave ground squirrel as a threatened species. At that time, the species was a category 2 candidate (November 15, 1994; 59 FR 58982), and was first included in this category on September 18, 1985. Category 2 included taxa for which information in the Service's possession indicated that listing the species as endangered or threatened was possibly appropriate, but for which sufficient data on biological vulnerability and threats were not available to support a proposed listing rule. On September 7, 1995, we published our 90-day petition finding, which determined that the 1993 petition did not present substantial information indicating that the petitioned action may be warranted (60 FR 46569).
On September 5, 2005, we received a petition, dated August 30, 2005, from the Defenders of Wildlife and Dr. Glenn R. Stewart to list the Mohave ground squirrel as an endangered species in accordance with section 4 of the Act. It also requested that critical habitat be designated concurrent with the listing of the Mohave ground squirrel. The petition clearly identified itself as such and included the requisite identification information for the petitioners, as required in 50 CFR 424.14(a).
On April 27, 2010, the Service made its 90-day finding (75 FR 22063), concluding that the petition presented substantial scientific or commercial information to indicate that listing the Mohave ground squirrel may be warranted, announced the initiation of a status review of this species, and solicited comments and information to be provided in connection with the status review by June 28, 2010. This notice constitutes our 12-month finding regarding the petition to list the Mohave ground squirrel.
The Mohave ground squirrel is a medium-sized squirrel. Total length, including the tail, is about 9 inches (in) (23 centimeters (cm)), tail length is about 2.5 in (6.4 cm), and weight is about 3.5 ounces (104 grams). The upper body is grayish brown, pinkish gray, cinnamon gray, and pinkish cinnamon, without stripes or fleckings. The underparts of the body and the tail are silvery white and the tail is bushy (Grinnell and Dixon 1918, p. 667). The skin is darkly pigmented and dorsal hair tips are multi-banded. The Mohave ground squirrel has a winter and summer pelage (coat). In summer the pelage is coarser and shorter, the sides of the face paler, and the underbelly whiter than the winter pelage. The two sexes appear to be alike in color and measurements (Grinnell and Dixon 1918, p. 667).
Two other species of small ground squirrels occur within the range of the Mohave ground squirrel, the antelope ground squirrel (Ammospermophilus leucurus) and the round-tailed ground squirrel (Xerospermophilus tereticaudus). The three species are different in appearance. Although similar in size to the Mohave ground squirrel, the antelope ground squirrel is grayish brown in color, with a white side stripe and a black band on the underside of the tail near the tip (Ingles 1965, pp. 169-171). The round-tailed ground squirrel has a unicolored tail that is cylindrical or round and not bushy, and a larger body than the Mohave ground squirrel (Ingles 1965, p. 171). However, its skull is significantly smaller than that of the Mohave ground squirrel in 18 of 20 cranial characteristics (Best 1995, p. 508). Mohave and antelope ground squirrels occur sympatrically (occupying the same or overlapping geographic areas without interbreeding) in the same habitat (Aardahl and Roush 1985, p. 20), while round-tailed ground squirrels overlap only along the eastern edge of the Mohave ground squirrel's range (see “Nomenclature and Taxonomy” section below).
Nomenclature and Taxonomy
The scientific name of the Mohave ground squirrel was changed from Spermophilus mohavensis to Xerospermophilus mohavensis with the publication of a review of the available research on morphological, genetic, cytogenetic, ecological, and behavioral attributes in the genus Spermophilus (Helgen et al. 2009, p. 273).
The Mohave ground squirrel is a distinct, full species with no recognized subspecies. It was discovered in 1886 by Frank Stephens (Grinnell and Dixon 1918, p. 667) and described by Merriam (1889, p. 15). The type specimen is from near Rabbit Springs, San Bernardino County, California, about 15 miles (mi) (24.1 kilometers (km)) east of Hesperia (Grinnell and Dixon 1918, p. 667).
The closest relative of the Mohave ground squirrel is the round-tailed ground squirrel (Bell et al. 2009, p. 5; Helgen et al. 2009, p. 293). Until 1977, the ranges of these two species were thought to be adjacent to each other but not overlapping (Hall and Kelson 1959, p. 358). However, Wessman (1977, p. 10) determined that the eastern edge of the geographic range of the Mohave ground squirrel overlapped the western edge of the round-tailed ground squirrel (Wessman 1977, pp. 12-13). He identified several areas of contact between the two species and identified one area near Helendale, San Bernardino County, California, as a possible zone of hybridization between the species. He observed morphological characteristics of both species exhibited in a few of the squirrels captured there (e.g., long, narrow tail with white on the underside) (Wessman 1977, p. 13). However, in 2009, Bell et al. (p. 11) found no evidence of mitochondrial DNA introgression between the Mohave ground squirrel and the round-tailed ground squirrel, including the three individuals identified as backcross individuals based on allozyme (form of an enzyme that differs in amino acid sequence) and karyotypic (the shape, type, number, and order of a species' chromosomes) data from Hafner and Yates (1983). We are not aware of any information that would indicate hybridization occurs with the sympatric antelope ground squirrel.
Range and Distribution
The Mohave ground squirrel is endemic to the western part of the Mojave Desert, in portions of Inyo, Kern, Los Angeles, and San Bernardino Counties, California. It has one of the smallest ranges of any species of ground squirrel in North America (Hoyt 1972, p. 3). We define range as the geographical area within which a species may be found.
Aspects of the Mohave ground squirrel's biology and behavior make individuals of the species difficult to observe, trap, and count, which in part explains why the range of the species has increased over time (see below). Mohave ground squirrels are only active and above ground for part of the year (generally February through August) and therefore can only be trapped and observed during this time. They spend much of the year underground and in a state of dormancy (see “Active Season and Dormancy” section). The length of the active season and movements of Mohave ground squirrels may also be affected by rainfall amounts. The number of individuals in an area appears to decline during dry years, and movements and home range size shrink (Harris and Leitner 2004, p. 521). Thus, if traps are set during a dry year, the reduced movements of Mohave ground squirrels and reduced densities or local extirpations make it less likely that the traps are located when and where they will capture Mohave ground squirrels. Conversely, if traps are set during a wet year when home ranges are larger, the Mohave ground squirrel may avoid the baited traps because of the increased availability of forage.
Because most surveys for the Mohave ground squirrel have been only 1 year in duration, this limited survey duration makes it difficult to assess population trend for a species whose numbers, movements, and “trapability” can fluctuate greatly among years (Brooks and Matchett 2002, p. 171). These factors in combination have made it difficult to determine the boundaries of the species' range, its distribution within the range, and population trends (see “Abundance and Trends” section). This has been further complicated because the vast majority of the information currently available on the distribution and abundance of Mohave ground squirrels is based on the California Department of Fish and Game (CDFG) survey protocol, which has been known to not detect squirrels when other methods have shown them to be present (see “Abundance and Trend” section below).
In 1938, Howell (1938, p. 184) published a map of the range of the Mohave ground squirrel that included the western Antelope Valley to an area 15 mi (25.2 km) west of Barstow. In 1977, Wessman surveyed for the Mohave ground squirrel along much of its eastern boundary and found the species' range extended 1,152,000 ac (466,200 ha) farther east and south than previously reported (Wessman 1977, p. 4).
For this 12-month finding, the Service is defining the range of the Mohave ground squirrel as about 5,319,000 acres (ac) (2,152,532 hectares (ha)) (Service calculations) (see Map 1). The range is bounded on the south and west by the San Bernardino, San Gabriel, Tehachapi, and Sierra Nevada mountain ranges, although the species occurs in canyons in the eastern foothills of the Sierra Nevada up to 5,600 feet (ft) (1,706 meters (m)) (Gustafson 1993, pp. 56-57; Laabs 1998, p. 1). The range is bounded on the north and east by Owens Lake and the Mojave River/Lucerne Valley, respectively (Leitner 2008, p. 18). Howell (1938, p. 184) and Aardahl and Roush (1985, p. 3) included the Antelope Valley west of Palmdale and Lancaster in the range of the Mohave ground squirrel (see Map 1).
The range map in the petition did not include the western Antelope Valley because there are no definite records of the species in that area. However, for several reasons, we included the western Antelope Valley in our range of the Mohave ground squirrel. First, older reports and scientific papers on the Mohave ground squirrel included this area in the range of the species (e.g., Howell 1938, p. 184; Aardahl and Roush 1985, p. 3). Second, although portions of this area are now used for agriculture and livestock grazing, suitable habitat still remains and may be connected to currently occupied habitat to the east. Third, early museum collections of the Mohave ground squirrel did not record precise locality data and often used the closest town for reference such as “near Palmdale.” Frequently, the closest town was several miles away and the locality information vague. Fourth, recent visual observations of Mohave ground squirrels occurred southwest of Mojave (see Map 1) (Leitner 2008, p. 7). Thus, there is some indication that the Mohave ground squirrel may have occurred, and may continue to occur, in the western portion of the Antelope Valley. Although areas of natural habitat within the range of the Mohave ground squirrel have been lost or degraded from human activity (see Factor A), the boundary of the current range is larger than reported by Howell in 1938.
The range of the Mohave ground squirrel may be larger than defined by the Service, as there have been recent sightings beyond the area defined by the Service as the range of the Mohave ground squirrel. Although the Mohave ground squirrel has previously been reported at elevations up to 5,600 ft (1,706 m) in the canyons in the eastern foothills of the Sierra Nevada that open to the Mojave Desert (Gustafson 1993, pp. 56-57; Laabs 1998, p. 1), a biologist recently reported a Mohave ground squirrel about 10 mi (16.1 km) south of Weldon (see Map 1) in an interior valley in the Tehachapi Mountains (California Natural Diversity Database 2007). Another biologist sighted a Mohave ground squirrel in the Panamint Valley, which is about 5 mi (8 km) outside the northeastern edge of the range (see Map 1) (Threloff 2007 in litt., p.1), whereas Aardahl
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and Roush were unsuccessful in capturing a squirrel here in 1985 (Gustafson 1993, p. 56). We are not using these two sightings in our range calculations because they are anecdotal and fall outside the areas previously published about the range of the Mohave ground squirrel. Although we have not included these two sightings, they indicate that the range of the Mohave ground squirrel may actually be larger than previously indicated on range maps or currently defined by the Service.
Within its range, the Mohave ground squirrel has a patchy distribution (Hoyt 1972, p. 7), likely caused by differences in rainfall, terrain (Zembal and Gall 1980, p. 348), elevation, temperature (Gustafson 1993, pp. 56-57), and soils and vegetation (Harris and Leitner 2005, p. 189). The habitat requirements of the Mohave ground squirrel for feeding, breeding, and sheltering are not uniformly spaced throughout its range.
Leitner (2008, pp. i-A2) collected and analyzed 1,236 unpublished observations, field studies, and surveys from 1998 to 2007, including both positive and negative findings of trapping efforts using the CDFG survey protocol. These surveys were usually performed in association with proposed development, because the Mohave ground squirrel is listed as threatened under the California Endangered Species Act (CESA) (see Factor D, “State Laws and Regulations”). The survey effort has been heavily weighted to the southernmost portion of the species' range (Leitner 2008, p. 5), where most of the development in the range of the Mohave ground squirrel has occurred and is occurring (see Factor A, “Urban and Rural Development”). Approximately 67 percent of the surveys were conducted south of State Route 58 (SR-58) (see Map 1), and almost half of all surveys were in two areas in the southernmost part of the range of the Mohave ground squirrel: The Lancaster-Palmdale area and the Adelanto area. Almost all recorded observations of Mohave ground squirrels from 1998 to 2007 have been from Edwards Air Force Base (EAFB), which is south of SR-58 (see Map 1), or from the central and northern portion of the squirrel's range; only a few were observed in the southern end of the squirrel's range. However, much of the range of the Mohave ground squirrel has not been surveyed (Leitner 2008, p. 9).
Leitner (2008, p. 10) identified four areas that he labels as “core” areas for the Mohave ground squirrel. “Core” areas have the following criteria:
(1) The species has been present for a substantial period;
(2) The species is currently found at multiple locations; and
(3) There is a substantial number of adults representing a viable reproductive population.
Four areas that meet the above criteria are: (1) Coso Range-Olancha; (2) Little Dixie Wash; (3) EAFB; and (4) Coolgardie Mesa-Superior Valley (see Map 2). Leitner (2008, p. 1) also described four other population areas with multiple recent records of the species, although these areas are not known to have Mohave ground squirrels present for a substantial period: Pilot Knob, the Desert Tortoise Natural Area-Fremont Valley, Boron-Kramer Junction, and Poison Canyon (Leitner 2008, p. 34). Together these eight important population areas comprise about 606,000 ac (245,240 ha), or 11.4 percent of the species' range.
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Leitner has emphasized the importance of protecting and maintaining connectivity between these eight areas for the conservation of the Mohave ground squirrel (2008, p. 12). It should be noted, however, that these areas have been identified using the data available from limited surveys for the Mohave ground squirrel. Much of the range has not been surveyed (Leitner 2008, p. 9); therefore, unsurveyed areas may support additional important population areas for the Mohave ground squirrel. As an example of a recent discovery of an important population area, the Poison Canyon area was discovered during a 2006 survey for a proposed drainage improvement project along a State highway (Sapphos 2006, p. 3-1).
Abundance and Trends
Data on population abundance and trend for the Mohave ground squirrel are limited (Leitner 2008, p. 8). The behavioral characteristics of the Mohave ground squirrel make it difficult to determine its presence or abundance as it spends much of the year underground (see “Active Season and Dormancy” section below). Based on his observations, Burt (1936, p. 222) estimated the density of Mohave ground squirrels in the southern part of their range at 15 to 20 animals per square mi (5 to 8 animals per square km). Most subsequent studies cannot be readily compared with Burt (1936) because they did not estimate density of animals (i.e., they either reported the number of animals trapped or compared numbers trapped to individual trapping efforts (Hoyt 1972, p. 6; Recht 1977, p. 4; Wessman 1977, p. 4; Leitner 1980, pp. IV-26; Aardahl and Roush 1985, pp. 11-13; Scarry et al. 1996, pp. 12-17; Leitner 2001, pp. 13-18, 30-32).
The only location we are aware of where a population of Mohave ground squirrels has been studied in detail for several years is in the Coso Region in the northern portion of the species' range (Leitner 2005, p. 3). Trapping surveys for the Mohave ground squirrel at this location were conducted from 1989 to 1996 and from 2001 to 2005. However, the estimated population density was only reported for 1990 and for the period from 1992 to 1996 because of limited sample size in other years (Leitner and Leitner 1998, pp. A-3, A-6, A-8, A-9, A-12, A-15, A-18, and A-22). The number of Mohave ground squirrels that were captured varied from year to year, ranging from 10 squirrels trapped in 2003 to 78 in 1994 (Leitner 2005, p. 3). The number of adult Mohave ground squirrels trapped was higher per year during the period 1990-1996 than during the period 2001-2004 (Leitner 2005, p. 3).
Researchers have suggested that trends in protocol survey data over time could be used to evaluate the status of the species. Brooks and Matchett (2002) analyzed the data from 19 reported studies on the Mohave ground squirrel in 1918 and during the period 1970-2001. They suggested that the Mohave ground squirrel may be undergoing a long-term decline as indicated by the decreased trapping success since the mid-1980s (Brooks and Matchett 2002, p. 176). One possible reason for decline is that Mohave ground squirrel populations appear to be sensitive to both seasonal and annual rainfall patterns; for example, in dry years, reproduction the following spring may be unsuccessful, and population numbers and the area occupied by the species may decrease (Leitner and Leitner 1998, pp. 29-31; Harris and Leitner 2005, p. 520).
Gustafson (1993, p. 22) reported that prolonged periods of drought may result in the loss of Mohave ground squirrels in local areas, because no young may be born for one up to several years, and adult survivability is reduced by poor habitat conditions to the point where the population dies out. In general, the population dynamics of the Mohave ground squirrel appear to follow a contraction and expansion pattern, i.e., there are local extirpations of squirrel populations following drought years and recolonization of these areas with consecutive wet years (Harris and Leitner 2005, p. 189). During the last few decades, more consecutive years in the western Mojave Desert have been dry versus wet (Brooks and Matchett 2002, p. 175), suggesting a trend weighted toward extirpations rather than recolonizations. However, Brooks and Matchett (2002, p. 176) suggest that factors other than, or in addition to, rainfall amount and timing seem to be affecting Mohave ground squirrel abundance, such as trapping characteristics, trapping protocols, weather conditions, or site (habitat) characteristics.
Leitner (2001, pp. 30-31) conducted a similar comparison of trapping results at 11 sites in 1980, 1999, and 2000, and at 19 sites in 2004 (Leitner 2005, p. 5). The first study showed a positive correlation between rainfall and trapping success prior to 1991, but no correlation after that. Both studies reported that trapping success has declined and concluded that this indicated a possible decline in the distribution and abundance of the Mohave ground squirrel during this period, despite periods of above-normal precipitation (Leitner 2001, p. 32; Brooks and Matchett 2002, p. 176).
However, the survey protocol is subject to potential inaccuracies, such as yielding false negative results or undersampling the population (see also Factor D, “State Laws and Regulations” section). Mohave ground squirrels are difficult to trap (Hoyt 1972, p. 7), and they have been observed approaching traps but not entering them (Leitner 2009, pers. comm.). For example, in 2009, only one Mohave ground squirrel was trapped during two surveys conducted in the Fort Irwin western expansion area (Delaney and Leitner 2009, p. 9). However, the detection rate for a video detection system, which was used at the same time as the trapping was conducted, was much higher; the video system recorded nine Mohave ground squirrels compared to the one that was trapped (Delaney 2009, pp. 13-14).
The diet of the Mohave ground squirrel consists of leaves (Recht 1977, p. 75), flowers, fruits, and seeds (Leitner and Leitner 1992, p. 12; Gustafson 1993, pp. 77-83) from a variety of plants; they also feed on fungi (Burt 1936, p. 223) and arthropods (caterpillars) when available (Zembal and Gall 1980, p. 345). When available in spring, new, tender, green vegetation makes up nearly all of the diet of the Mohave ground squirrel (Best 1995, p. 6). The Mohave ground squirrel is also known to eat alfalfa (Best 1995, p. 5).
The Mohave ground squirrel forages on the ground, in the branches of shrubs, and, where present, in Yucca brevifolia (Joshua trees) (Johnson no date, p. 1). It caches food in its burrow for future use (Johnson no date, p. 1). It obtains water from its diet, but will drink water if available (Johnson no date, p. 1).
Recht (1977, p. 80) categorized the foraging strategy of the Mohave ground squirrel as a facultative specialist. Because the availability of food resources fluctuates seasonally and annually in the Mojave Desert, the Mohave ground squirrel specializes in certain food species for short periods, but changes the foods it consumes as their availability changes. For example, in March 1994, the diet of the Mohave ground squirrel in the northern part of its range was 90 percent shrubs, 10 percent forbs (i.e., any herbaceous plant that is not grass or grasslike), and less than 1 percent nonnative annual grasses (Schismus and Bromus) (Leitner et al. 1995, p. 45). By April, the Mohave ground squirrel's diet had changed to 60 percent shrubs, 35 to 40 percent forbs, and 2 percent grasses (Leitner et al. 1995, p. 48).
The quantity, variety, and nutritional quality of plant food sources available ultimately depend on the amount of rainfall from the preceding fall and winter (Aardahl and Roush 1985, p. 22). During drought years, there are few-to-no herbaceous native annual forbs available, and Mohave ground squirrels must then depend on shrub foliage for water and nutrition (Leitner and Leitner 1998, p. 20).
This foraging strategy provides efficiency and flexibility to maximize nutritional and water intake in a changing desert habitat (Recht 1977, p. 80). These abilities are needed, as the Mohave ground squirrel must increase its body weight in spring and early summer to sustain itself during the dormant period of mid-summer through winter (Leitner and Leitner 1998, p. 33).
Female Mohave ground squirrels can breed at 1 year of age if environmental conditions are favorable (Leitner and Leitner 1998, p. 28), while males do not breed until 2 years of age or older (Leitner and Leitner 1998, p. 36).
The Mohave ground squirrel mating season occurs from mid-February to mid-March (Harris and Leitner 2004, p. 1). Mohave ground squirrel males typically emerge from dormancy in February, up to 2 weeks before females (Recht pers. comm., as cited in Gustafson 1993, p. 83). Male Mohave ground squirrels defend a territory, which females enter for mating (Recht pers. comm., as cited in Gustafson 1993, pp. 83-84). Three to four females mate and remain in the male's territory for a day or so, before returning to their respective home ranges. After a gestation period of 29 to 30 days, the young are born in the female's burrow (natal burrow) from March to May, with a peak in April. Average litter size is about six (Burt 1936, p. 224; Recht pers. comm., as cited by Leitner et al. 1991, p. 63) and ranges from four to nine (Best 1995, p. 3). Parental care continues through mid-May, with juveniles emerging above ground at 10 days to 2 weeks of age (Gustafson 1993, p. 84). By early May, the juveniles are active above ground and can be captured in live traps.
Reproductive success appears to be strongly influenced by rainfall. In dry years, the Mohave ground squirrel's survival strategy appears to be to forego reproductive activity and concentrate on gaining weight and fat reserves in the spring and early summer to better survive the dormant period (Leitner and Leitner 1998, p. 32). For example, Mohave ground squirrels in the Coso Range failed to reproduce successfully in 1989, 1990, and 1994, which correlated with low fall and winter precipitation and a low standing crop of annual forbs. In each of the 3 years, precipitation during the period when it normally occurs in the region (September 1 to March 31) was lower than the long-term average for the same period (average of 3.3 in (8.5 cm) versus the average of 5 in (12.7 cm), respectively) (Leitner and Leitner 1998, pp. 18-19, 21, and 29). In years when reproduction does occur, females of all age classes (including yearlings) produce young (Leitner and Leitner 1998, p. 28).
Mortality and Predation
Mohave ground squirrels can live up to 5 years or longer (Leitner and Leitner 1998, p. 28). Mortality for juveniles is high during the first year and is disproportionately higher for males than females. As a result, the juvenile population contains significantly more females than males, and the adult female-to-male ratio averages about 2.6:1, but was reported to be as high as 7:1 in one population (Leitner and Leitner 1998, p. 36).
Information on the causes of mortality in the Mohave ground squirrel is limited. We are not aware of any information on diseases in the species. Although not based on direct observation, predators are believed to include coyote (Canis latrans), American badger (Taxidea taxus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo jamaicensis), prairie falcon (Falco mexicanus), common raven (Corvus corax), and rattlesnake (Crotalus sp.) (Boarman 1993, p. 2; Gustafson 1993, p. 88; Harris, pers. comm., as cited in Defenders of Wildlife and Stewart 2005, p. 15).
Mortality may also be caused by extended periods of low amounts of winter rainfall, which results in reduced availability of forage and water and increases the species' vulnerability to malnutrition, disease, and starvation. Gustafson (1993, p. 22) indicated that prolonged periods of drought result in the extirpation of Mohave ground squirrels in local areas as adult survival is reduced by poor forage conditions.
Active Season and Dormancy
The Mohave ground squirrel lives in burrows which it digs (Gustafson 1993, p. ix), and remains in burrows in a state of dormancy throughout much of the year. For the Mohave ground squirrel, dormancy is a physiological state that includes a reduced frequency of breathing, or apnea, reduced oxygen consumption, reduced body temperature (Bartholomew and Hudson 1960, pp. 195-197), and a reduced heart rate (Ingles 1965, p. 177). Mohave ground squirrels may be active from February to August (Bartholomew and Hudson 1960, p. 194), with dormancy usually beginning in July or August; emergence dates vary with elevation (Johnson no date, p. 1). In years when reproduction occurs, most adults are active through June, but all have entered dormancy by the end of July; in years with no reproduction, adults may enter dormancy as early as the end of April. In contrast, juvenile Mohave ground squirrels begin to forage outside their natal burrows by mid-May and do not enter dormancy until July at the earliest and as late as the end of August (Leitner and Leitner 1998, pp. 32, 38).
The period when dormancy begins varies annually. Dormancy does not appear to be an adaptation to avoid low temperatures; rather it appears to be an adaptation to seasonally restricted food and water (Bartholomew and Hudson 1960, p. 202). The initiation of dormancy appears to correspond to either the absence of available green vegetation or its abundance (Aardahl and Roush 1985, pp. 20-21). For the latter, the Mohave ground squirrel enters dormancy earlier as food abundance allows the animal to meet energy needs to sustain it through dormancy earlier (Harris and Leitner 2004, p. 521).
The principal source of energy for the Mohave ground squirrel during dormancy is stored body fat, although food is stored in burrows and may be consumed during the dormant period (Ingles 1965, p. 177; Recht 1977, p. 85; Johnson no date, p. 1). During more severe drought years, Mohave ground squirrels may enter dormancy with relatively low body weight, which likely affects survivorship of Mohave ground squirrels, especially juveniles, to the following spring (Leitner and Leitner 1998, p. 32).
Home Range and Movements
In general, juvenile Mohave ground squirrels have larger home ranges (at least twice as large) than adults, and adult males have larger home ranges than females (Aardahl and Roush 1985, p. 11; Best 1995, p. 6). Mohave ground squirrels are territorial and, throughout much of their active period, there is little overlap between home ranges (Recht 1977, p. 20). Best (1995, p. 6) observed that home ranges are separate until late June, with little evidence of territorial behavior. The home ranges are not static and may shift during the active season, and from year to year, in response to changes in food quality and quantity (Best 1995, p. 6; Harris and Leitner 2004, p. 520). Home ranges of juveniles form a cluster around the home range of an adult (Best 1995, p. 6), and adults exclude juveniles from those portions of the habitat with the densest vegetation (Best 1995, p. 6). Adult Mohave ground squirrels gain weight twice as fast as most juveniles, likely due to differences in resource quality between adult and juvenile home ranges (Recht 1977, p. 82).
Home range size varies with the reproductive period and rainfall levels and food availability (Harris and Leitner 2004, p. 1). During the mating season, the median male home range is much larger than the female home range, 16.6 ac (6.73 ha) compared to 1.8 ac (0.74 ha) (Harris and Leitner 2004, pp. 521-522). The females' home ranges are non-overlapping and noncontiguous, and each individual exhibits a high degree of site fidelity (Harris and Leitner 2004, p. 522). During the post-mating period, male home range size varies from 3.7 to 26.7 ac (1.5 to 10.8 ha), while female home range size varies from 0.72 to 4.69 ac (0.29 to 1.90 ha) (Harris and Leitner 2004, pp. 517, 521). Female post-mating home range size is larger than the mating season home range (Harris and Leitner 2004, p. 520).
An evaluation of different sequential survey results indicated that juvenile Mohave ground squirrels moved farther than adults (Aardahl and Roush 1985, p. 11), and long-distance movements were greater in males than in females. Among juveniles, the greatest long-distance movements between two sites for males (n = 15) was a mean of 4,987 ft (1,520 m) (range 360-20,440 ft (110-6,230 m)), and for females (n = 21) 1,657 ft (505 m) (range 344-12,670 ft (105-3,862 m)) (Harris and Leitner 2005, p. 188).
Both adult male and female Mohave ground squirrels vocalize during their active season, and have multiple types of calls (Delaney 2009, pp. 15-17). The purpose of these calls is unknown but may be linked to identifying home ranges.
The Mohave ground squirrel occurs in a wide variety of habitats in the western Mojave Desert (Wessman, as cited in Aardahl and Roush 1985, p. 22). They include Mojave creosote bush scrub, Mojave mixed woody scrub, desert saltbush scrub, blackbrush scrub, Mojave desert wash scrub, Joshua-tree woodland, and shadescale scrub (Gustafson 1993, pp. ix, 81; Bureau of Land Management (BLM) 1998, p. 1); Mojave creosote bush scrub is the preferred habitat of the Mohave ground squirrel (Aardahl and Roush 1985, pp. 22, 23). The Mohave ground squirrel has also been found in some areas used for agriculture (Gustafson 1993, pp. ix, 81; BLM 1998, p. 1).
Habitat features considered most suitable for the Mohave ground squirrel include areas with relatively flat topography, often located in large alluvial-filled valleys, containing fine-to-medium-textured soil with little or no rocks, and with the presence of a variety of native shrubs, including Larrea tridentata (creosote bush), Ambrosia dumosa (white bursage), and Atriplex spp. (saltbush) (Aardahl and Roush 1985, p. 9).
Soil characteristics are important, as the Mohave ground squirrel constructs burrows to escape temperature and humidity extremes and predators, and to give birth (Aardahl and Roush 1985, p. 23). The species is absent from very rocky areas and playas (i.e., a sandy, salty, or mud-caked flat floor of a desert drainage basin that is periodically covered with water) (Wessman 1977, pp. 7-9; Zembal and Gall 1980, p. 348). Rainfall must be adequate as it affects the quality and quantity of forage (Gustafson 1993, p. 57). Plant species diversity and the availability of native annual forbs are important to population stability and reproduction (Aardahl and Roush 1985, p. 22). The presence of a variety of shrubs that provide a reliable food source during drought years may be critical for a population to persist (Charis 2005, pp. 3-75).
The Mohave ground squirrel is considered to be absent, or nearly so, from dry lakebeds, lava flows, and steep, rocky slopes, although juveniles may disperse through such areas (Leitner, pers. comm., as cited in Laabs 1998, p. 3). Harris and Leitner (2005, p. 193) found that Mohave ground squirrels travelled through habitats considered marginal for permanent occupancy (e.g., contained rocky or gravelly soils, and elevation changes of hundreds of feet) but did not cross a playa barren of vegetation. Long-distance movement by juveniles through marginal areas may be critical for connecting local populations and recolonizing sites after local, drought-related extirpations (Harris and Leitner 2005, p. 1).
Summary of Information Pertaining to the Five Factors Back to Top
Section 4 of the Act (16 U.S.C. 1533) and implementing regulations (50 CFR part 424) set forth procedures for adding species to, removing species from, or reclassifying species on the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors:
(A) The present or threatened destruction, modification, or curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued existence.
In making this 12-month finding, information pertaining to the Mohave ground squirrel in relation to the five factors provided in section 4(a)(1) of the Act is discussed below.
In making our 12-month finding on a petition to list the Mohave ground squirrel, we considered and evaluated the best available scientific and commercial information. To ensure that this finding is based on the latest scientific information, we contacted species experts; land managers within the range of the Mohave ground squirrel; the CDFG; and others with expertise on the species, its habitat, and threats occurring, or likely to occur, within the range of the species. We conducted a search of the available published literature on the Mohave ground squirrel and collected unpublished reports on the species from resource agencies and others. Unpublished reports included regional field studies by State and Federal agencies and conservation groups, results of presence/absence surveys conducted prior to proposed development, and incidental observations reported by field biologists. In addition, we accessed information in the California Natural Diversity Database. This information, information provided by the public, and additional information and data in our files provided the basis for the status review for the Mohave ground squirrel. In making our 12-month finding, we considered and evaluated all scientific and commercial information in our files, including information received during the public comment period that ended June 28, 2010. The analysis of potential threats to the Mohave ground squirrel discussed below includes those identified in the petition and those identified in the information sources listed above.
In considering what factors might constitute threats to a species, we must look beyond the exposure of the species to a particular factor to evaluate whether the species may respond to that factor in a way that causes actual impacts to the species. If there is exposure to a factor and the species responds negatively, the factor may be a threat and, during the status review, we attempt to determine how significant a threat it is. The threat is significant if it drives or contributes to the risk of extinction of the species such that the species warrants listing as endangered or threatened as those terms are defined in the Act. However, the identification of factors that could impact a species negatively may not be sufficient to compel a finding that the species warrants listing. The information must include evidence sufficient to suggest that the potential threat has the capacity (i.e., it should be of sufficient magnitude and extent) to affect the species' status such that it meets the definition of endangered or threatened under the Act.
Factor A: The Present or Threatened Destruction, Modification, or Curtailment of the Species' Habitat or Range
The following potential threats that may affect the habitat or range of the Mohave ground squirrel are discussed in this section: (1) Urban and rural development, (2) off-highway vehicle (OHV) recreational use, (3) transportation infrastructure, (4) military operations, (5) energy development, (6) livestock grazing, (7) agriculture, (8) mining, and (9) climate change. Climate change is discussed under Factor A because, although climate change may affect Mohave ground squirrels directly by creating physiological stress, the primary impact of climate change on the species is expected to be through changes to the availability and distribution of Mohave ground squirrel habitat. In addition, commercial filming occurs on private and Bureau of Land Management (BLM) lands in the western Mojave Desert. The activities for creating motion pictures, television shows, and commercials may require travelling on unpaved roads and trails or cross-country use. However, in our review of the best available scientific and commercial information, we did not find information that indicates these filming activities have occurred, are presently occurring, or are likely to occur in the future within Mohave ground squirrel habitat, and therefore, we have determined that they are not a threat to the species.
Urban and Rural Development
The present and projected future growth of urban areas in the western Mojave Desert could adversely affect the Mohave ground squirrel. About 136,900 ac (55,426 ha), or 2.6 percent of the 5,319,000 ac (2,152,532 ha) range of the Mohave ground squirrel (see Background section), has been lost to urban and rural development (Defenders of Wildlife and Stewart 2005, pp. 19, 38). Loss of Mohave ground squirrel habitat has occurred from the construction of residential homes, commercial and industrial complexes, shopping malls, golf courses, airports and associated commercial and industrial development, roads, landfills, wastewater treatment facilities, prisons, flood management structures, and other facilities.
Most urban and rural development has occurred in valleys, flats, and gently sloping areas, which are the same types of areas most often used by Mohave ground squirrels. The greatest losses of Mohave ground squirrel habitat have occurred in, and adjacent to, cities including Palmdale, Lancaster, Victorville, Adelanto, Hesperia, Apple Valley, Barstow, and Ridgecrest, California (see Map 1). Smaller areas have also been lost at the towns of Hinkley, Boron, North Edwards, California City, Mojave, Rosamond, Inyokern, and Littlerock, and the unincorporated communities of Pearblossom, Phelan, and Pinyon Hills, California (see Map 1).
Most of this urban development has occurred in the southernmost portion of the Mohave ground squirrel's range on private land, generally south of SR-58 (see Map 1). More than 62 percent of the private land within the range of the Mohave ground squirrel is south of SR-58. The three cities with the largest developed areas within the range of the squirrel (i.e., Lancaster, Palmdale, and Victorville) occur in this area, as do several of the smaller towns listed above (see Map 1). Some of this area has also been converted to agriculture (see “Agriculture” section below), and there are areas that do not contain suitable habitat for the squirrel (e.g., dry lake beds). We estimate the portion of the range of the Mohave ground squirrel south of SR-58 to be 1,690,797 ac (684,244 ha), or about 31.8 percent of the range of the Mohave ground squirrel (see Background section for our range analysis). Urbanization in this area is mainly concentrated along the southern edge of the squirrel's range, and much of the area south of SR-58 is undeveloped.
Trapping results in the southern portion of the Mohave ground squirrel's range have generally been negative, especially in areas that are most heavily developed (Leitner 2008, p. 5). Mohave ground squirrels are currently known to occur in several areas south of SR-58, including one of the largest concentrations of squirrels on EAFB (see below). Recent records of the Mohave ground squirrel south of SR-58 and outside EAFB include two in the Victor Valley-Lucerne Valley area (Jones pers. comm., as cited in Defenders of Wildlife and Stewart 2005, p. 8), four records near Adelanto (Leitner 2008, p. 7), three records west and south of Barstow (Leitner 2008, pp. 7-8), and two records southwest of the town of Mojave (Leitner 2008, pp. 7-8).
The fact that trapping results south of SR-58 have generally been negative does not necessarily mean that the Mohave ground squirrel is absent from the area or the area does not provide habitat for the species (Leitner 2008, p. 9). Negative trapping results can occur for various reasons, including trap location, time of trapping, and food availability (Brooks and Matchett 2002, p. 172; Leitner 2008, p. 9) (see “Range and Distribution” section and Factor D, “State Laws and Regulations,” for further discussion of the survey protocol).
As discussed in the Background section, trapping surveys south of SR-58 have most often been conducted in areas where the squirrel has already been extirpated due to extensive urbanization, such as the Palmdale-Lancaster area in the southwestern portion of the range (Leitner 2008, p. 3). More importantly, large areas south of SR-58 have either never been surveyed or have been surveyed only 1-2 times (Leitner 2008, pp. 5, 9, 25). In addition, the trapping protocol that was used may not be the most effective method to determine the presence or absence of Mohave ground squirrels. Some scientists have identified potential problems with the protocol that raise questions about the accuracy of the current survey technique (Brooks and Matchett 2002, p. 172) (see Factor D, “State Laws and Regulations,” for further discussion of the survey protocol).
Federal lands comprise 28.5 percent of the area south of SR-58 (9.3 percent of the total range of the Mohave ground squirrel). One of the more important concentrations of Mohave ground squirrels south of SR-58 is on EAFB. The 307,435 ac (124,468 ha) EAFB encompasses about 18 percent of the area south of SR-58 (5.8 percent of the range of the Mohave ground squirrel) and contains one of the eight important population areas for the Mohave ground squirrel (Leitner 2008, p. 10; se Map 2 and Background section). EAFB is used primarily for testing and evaluating aircraft, and the impacts to Mohave ground squirrel habitat from urban and rural development are primarily confined to the small cantonment areas (see “Military Operations” section below for details).
In addition to the Federal lands on EAFB, there are more than 175,000 ac (70,820 ha) of Federal land managed by the BLM south of SR-58, all of which is not subject to the direct impacts of urbanization. These BLM lands include the southern part of the Fremont-Kramer Desert Wildlife Management Area (DWMA), which is managed for Mohave ground squirrel habitat. Urban and rural development will not occur on these lands (however, see “Off-Highway Vehicle Recreational Use,” “Military Operations,” and “Energy Development” sections below for a discussion on other activities that may affect these areas managed by EAFB and the BLM).
We expect that further urbanization of privately owned lands south of SR-58 will occur in the future. The population of the western Mojave Desert is projected to grow from 795,000 (in 2000) to more than 1.5 million people by 2035 (BLM et al. 2005, p. 244). Most incorporated cities and communities in the western Mojave Desert have general or community plans that describe their growth and development for the next 20 years or more. We estimate that about 475,000 ac (192,226 ha), or about 8.9 percent of the entire range of the Mohave ground squirrel, is incorporated. The majority (about 70 percent) of the incorporated land south of SR-58 occurs within the cities of Palmdale, Lancaster, Victorville, Apple Valley, Hesperia, Adelanto, and Barstow. Although these areas are already extensively urbanized, not all of the incorporated lands south of SR-58 are developed, and future growth is expected to occur in these areas. Under a worst-case scenario, all areas within the incorporated boundaries could be developed in the future.
We did not find any information on major proposed urban developments or new communities being planned in the unincorporated and rural lands south of SR-58, although the existing unincorporated communities will likely continue to grow. However, we expect that future development will most likely occur in areas that are already incorporated because of proximity to existing infrastructure. Although we cannot predict with any certainty what areas will be developed or when they may be developed in the next 20-30 years, even if all incorporated lands south of SR-58 were developed, more than 475,000 ac (161,875 ha) would likely remain under Federal ownership south of SR-58. Much of this land is in the Fremont-Kramer DWMA, which the BLM designated for management of Mohave ground squirrel habitat, and includes the important population area for the Mohave ground squirrel at EAFB (Leitner 2008, p. 10) (see Map 2). Except for possibly minor additions to the cantonment areas of EAFB, the Federal land south of SR-58 is not subject to urban and rural development.
About 3,648,830 ac (1,476,635 ha) or 68.6 percent of the range of the Mohave ground squirrel is north of SR-58. This area comprises the central and northern portions of the range of the Mohave ground squirrel. Most of this land has not experienced urban development; rather, urbanization is limited and concentrated mainly around Ridgecrest and California City. About 144,000 ac (58,275 ha), or 3.9 percent of the Mohave ground squirrel's range north of SR-58, is incorporated, almost all of which (90 percent) is within California City (BLM et al. 2005, chapter 3, p. 2). California City was incorporated in 1965, and although it is the third largest city in California in area, the population has grown to only about 14,120 in the 46 years since it was incorporated. Additionally, most of the incorporated area remains undeveloped. Given the slow growth rate of California City, we believe that much of the land within its incorporated boundaries will likely remain undeveloped.
Federal lands managed by the BLM and Department of Defense (DOD) make up about 80 percent (2,109,326 ac (853,617 ha)) of the range of the Mohave ground squirrel north of SR-58 (39.7 percent of the entire range). The BLM manages 438,364 ac (177, 400 ha), while the DOD manages 1,670,962 ac (676,217 ha). Most of the 1,110,443-ac (449,382-ha) China Lake Naval Air Weapons Station (NAWS) and the 33,359-ac (13,500-ha) Goldstone Deep Space Communications Complex (Goldstone Complex), managed by the National Aeronautical and Space Administration (NASA), experience little habitat disturbance. Seven of the eight Mohave ground squirrel important population areas are located north of SR-58, occur mostly or entirely on Federal land (see Map 2), and are not subject to urban development on Federal land. We do not expect any urbanization to occur on BLM land. Because of their missions, we anticipate minimal future urban development on the military bases; any development will likely be limited to the cantonment areas (see “Military Operations” section).
In summary, we recognize that some Mohave ground squirrel habitat has been lost to development within the range of the squirrel. Currently, about 2.6 percent of the range of the Mohave ground squirrel has been lost to development, and we expect that more of the range will be lost in the future, most likely adjacent to existing urban areas. A worst-case scenario would be that all incorporated land (about 8.9 percent (475,000 ac (192,226 ha)) within the range of the squirrel is developed. Although unlikely because of the expected slow growth of California City, even if this were to occur, 62 percent (3,300,000 ac (1,335,468 ha)) of the squirrel's range is federally owned, very little of which is subject to urban development. We estimate that about 57 percent of the Federal lands (EAFB, NAWS, Goldstone Complex, DWMAs, and Mohave Ground Squirrel Conservation Areas (MGSCA)) are managed, at least in part, for Mohave ground squirrel habitat (see Map 2, Table 1, and Factor D, “Federal Laws and Regulations”). The eight important population areas for the Mohave ground squirrel occur mostly or entirely within Federal lands managed in part for the Mohave ground squirrel, and are therefore not threatened with urban development. In addition, Leitner (2008, p. 9) has stated that additional populations of the Mohave ground squirrel may well exist because much of the range of the squirrel has never been surveyed or has only been surveyed 1-2 times, which may not be sufficient to determine the presence of the squirrel (Leitner 2008, p. 25). We conclude, based on this assessment, that urban and rural development does not currently pose a threat to the Mohave ground squirrel in relation to the present or threatened destruction, modification, or curtailment of its habitat or range, nor do we anticipate it posing a threat in the future.
|Management areas for the Mohave ground squirrel||Percent of Mohave ground squirrel range|
|Federal ownership||State/private ownership2within management area||Total area within management area boundary|
|1Species' range is 5,319,000 ac (2,152,532 ha) as calculated by the Service.|
|2State/private ownership is not specifically managed for the Mohave ground squirrel.|
|3Land ownership within designated boundary includes Federal, State, and privately-owned lands.|
|4Area of Critical Environmental Concern.|
|Mohave Ground Squirrel Conservation Area3||16.7||7.9||24.6|
|Department of Defense—Limited Use/Protected||27.0||0||27.0|
|Bureau of Land Management ACECs4(Fremont-Kramer Desert Wildlife Management Area, Superior-Cronese Desert Wildlife Management Area, Desert Tortoise Research Natural Area)3||13.6||8.5||22.1|
Off-Highway Vehicle Recreational Use
Off-highway vehicle (OHV) use is any use that includes driving a motorized vehicle off a paved road, including driving cross country and on existing dirt roads. OHV use has the potential to adversely affect the Mohave ground squirrel by crushing individuals (see Factor E, “Direct Mortality”) and their burrows (Bury et al. 1977, p. 16), damaging or destroying native vegetation, and compacting soils. Burrows are essential to the survival of the Mohave ground squirrel, as they provide protection from predation and the temperature extremes of the desert, are likely used to store food, and provide a safe location for reproduction and rearing young. Impacts to vegetation increase the exposure of the Mohave ground squirrel to predators, decrease available shade for thermoregulation, and increase soil temperature extremes, which adversely affect plant germination, growth (Boarman 2002, p. 47), and food availability. Compacted soils reduce the infiltration rate of rain, which means there is less water available for plants and seed germination (Boarman 2002, p. 46), reduce the root growth of established plants, and make it harder for seedlings to survive (Lovich and Bainbridge 1999, p. 316). With soil compaction, soil erosion from wind and water increases, nitrogen fixation is reduced, less organic material is available for plant growth, and seedling establishment is reduced (Lovich and Bainbridge 1999, pp. 315-316; Boarman 2002, pp. 45-46).
OHVs also transport nonnative annual seeds and plant parts from other locations. Their roads, trails, and tracks act as dispersal corridors for invasive annual plant species (Lovich and Bainbridge 1999, p. 313). These nonnative species suppress the growth of native annual forbs (Brooks 2000, p. 105), which are a source of food and water for the Mohave ground squirrel. Many native annual plants have a higher percentage of water and protein than nonnative plants (Oftedal et al. 2002, p. 344); however, we have no information on the Mohave ground squirrel's nutritional needs and their use of nonnative plants.
Other potential impacts of OHV use include: Noise, which can cause hearing loss in rodents (Lovich and Bainbridge 1999, p. 316) and may interfere with the Mohave ground squirrel's ability to detect predators and establish and maintain territories (Bury et al. 1977, p. 16); littering and dumping of garbage (BLM 2003, p. 31), which can attract Mohave ground squirrel predators (see Factor C, “Predation”); and increased fire sources (BLM 2003, p. 32), such as campfires and cigarettes, which can result in fires that destroy Mohave ground squirrel habitat.
In the western Mojave Desert, the BLM manages its lands for OHV recreation. The BLM has designated four open areas (i.e., OHV management areas) within the range of the Mohave ground squirrel as open to all OHV use, including cross-country use (BLM et al. 2005, chapter 3, pp. 242-243). The four OHV management areas within the range of the Mohave ground squirrel are: (1) Dove Springs (3,840 ac (1,554 ha)); (2) El Mirage (25,600 acres (10,360 ha)); (3) Jawbone Canyon (3,827 ac (9,642 ha)); and (4) Spangler Hills (62,080 acres (25,123 ha)) (BLM et al. 2005, chapter 3, pp. 243, 244; Service GIS data) (see Map 2). These four areas comprise 95,347 ac (38,586 ha) (BLM 2003, p. 31), or 1.8 percent of the range of the Mohave ground squirrel. Outside of these four areas, the BLM restricts OHV use to specific existing roads and trails, and cross-country use is prohibited (BLM et al. 2005, chapter 3, pp. 264-273). We are not aware of any plans on the part of the BLM to designate new OHV management areas in the future.
The impacts from OHV use to the Mohave ground squirrel and its habitat vary depending on the type of OHV activity, the designated land use, and the level of enforcement. The impacts to the Mohave ground squirrel and its habitat are greatest in open areas and high-OHV-use areas (e.g., staging areas for OHV events, camping areas), and less in areas where activities are confined to existing roads and trails.
Cross-country OHV use is restricted to the four management areas; however, the occurrence of off-route OHV use tends to extend or spill over into areas immediately adjacent to the management areas. Although the impacts to Mohave ground squirrels likely diminish with distance from the management areas, the BLM estimates that these “spill-over” zones, some of which are on private land, encompass an additional 150,239 ac (60,800 ha) (BLM et al. 2005, chapter 3, pp. 131, 132), or 2.8 percent of the range of the Mohave ground squirrel. This area, combined with the four designated OHV management areas, constitutes about 4.6 percent of the range of the Mohave ground squirrel.
The BLM has documented other areas not associated with the designated management areas where OHV use of designated routes is more frequent. The BLM estimates that these high-use areas include about 107,520 ac (43,512 ha), or 2 percent of the range of the Mohave ground squirrel (BLM et al. 2005, chapter 3, p. 133). When combined with the management areas and spill-over zones, about 6.6 percent of the squirrel's range is intensively used for OHV recreation. One of the more extensive high-use areas is the Rand Mountains area. To reduce OHV impacts in part of the Rand Mountains area, the BLM expanded the Western Rand Mountain Area of Critical Environmental Concern (ACEC) from 17,877 ac (7,235 ha) to 32,050 ac (12,970 ha), and closed the ACEC to OHV use except for 129 mi (208 km) of designated open routes, a 90-percent reduction in miles of open routes (BLM et al. 2005, chapter 3, p. 8). This resulted in a reduction of more than 14,000 acres (5,666 ha) of the high-use area in the Rand Mountains.
Although we are not aware of any estimates, the intensive and widespread OHV activity that occurs within the management and high-use areas has likely resulted in extensive loss and degradation of potential habitat for the squirrel. However, the status of the Mohave ground squirrel within these areas is not well known. Mohave ground squirrels have been trapped in the Dove Springs OHV Area, but not the Spangler Hills OHV Area (Leitner 2010, in litt.). Leitner suggests that the negative trapping results at the Spangler Hills OHV Area may be from an inadequate trapping effort in this large area. Thus, we cannot confirm that the Mohave ground squirrel occurs or does not occur at the Spangler Hills OHV Area. We are not aware of any information on the status of the Mohave ground squirrel in the other two management areas or the high-use areas.
In addition to the management areas and high-use areas, there are numerous single unpaved roads and trails within the range of the Mohave ground squirrel that are used by OHVs, including utility corridors. The potential direct and indirect impacts of roads are described above; however, road density and OHV use of these roads are much lower than in management areas. This lower use likely means potential impacts to the Mohave ground squirrel are less than in management and high-use areas.
We were unable to find information on the total number of miles of unpaved roads within the range of the Mohave ground squirrel. Based on a 2001-2002 inventory, the BLM estimated that 5,054 linear mi (8,134 km) of roads (including paved roads, unpaved roads, and trails) occur on BLM land in the western Mojave Desert. However, subsequent to that inventory, the BLM permanently closed 2,260 mi (3,637 km), or 45 percent of the roads and trails (BLM 2003, pp. 4-9). Most closures occurred in the DWMAs in Mohave ground squirrel habitat (BLM 2003, p. 396). DWMAs are ACECs where the BLM can limit or exclude surface disturbance, including use of roads and trails (see Factor D). In addition, the West Mojave (WEMO) Plan commits the BLM to an aggressive program of closed route rehabilitation (BLM et al. 2005, chapter 4, p. 7). The WEMO Plan is the BLM's resource management plan for the western Mojave Desert and amends the California Desert Conservation Area (CDCA) Plan. It also implements the Rand Mountains Fremont Valley Management Plan that reduces the number of open routes in the Rand Mountains by 90 percent (BLM et al. 2005, chapter 3, p. 8).
The BLM has implemented minimization measures to ensure that the different types of OHV uses occur within the appropriate designated management areas, roads, and trails, and thereby avoid the loss of additional Mohave ground squirrel habitat. These measures also allow for the eventual restoration of the habitat in areas where the roads and trails have been closed to OHV use (although restoration time from these impacts is believed to take several decades (Bury et al. 1977, p. 16; Lovich and Bainbridge 1999, p. 316)). These measures include signing closed routes, obscuring closed routes with vertical mulching, increasing public education, installing fencing and barriers, and increasing law enforcement (BLM et al. 2005, chapter 2, pp. 156-157, 163). In 2011, BLM is signing open routes, implementing a monitoring plan to determine compliance with route closures and whether any new illegal routes are being created, and implementing additional enforcement capability for the route network in the WEMO Plan area (U.S. District Court 2011, pp. 13-15). By 2014, the BLM will be preparing a revised OHV route network that complies with the Federal Land Policy and Management Act's (FLPMA) requirement to minimize damage to public resources and harassment and disruption of wildlife and habitat (U.S. District Court 2011, pp. 2, 13). These measures should reduce the impacts from OHV use on BLM land near management areas and on designated roads and trails in the range of the Mohave ground squirrel. However, the BLM's management actions for OHV use only apply to lands that they manage; they do not apply to State or private lands.
Part or all of 14 designated Wilderness areas (BLM et al. 2005, chapter 3, p. 9) are in the range of the Mohave ground squirrel. Under the Wilderness Act of 1964, roads, new structures, commercial activities, and use of motorized vehicles or equipment are prohibited within designated wilderness areas (BLM et al. 2005, chapter 3, p. 9). The acreage of wilderness area within the range of the Mohave ground squirrel and therefore closed to vehicle access and other forms of surface disturbance is about 253,000 ac (102,386 ha), or 4.6 percent of the range of the Mohave ground squirrel. Although portions of the wilderness areas include steep slopes and rocky substrates that would not provide suitable habitat for the Mohave ground squirrel, most of the wilderness areas are within the elevational range of the Mohave ground squirrel (BLM et al. 2005, chapter 3, p. 138) and provide connectivity among squirrel habitat.
DOD lands are closed to public access, and only persons with business on the military installations may enter. Because of the research, development, testing, and evaluation missions of EAFB and NAWS (see “Military Operations” below), vehicle access is restricted almost entirely to existing roads in those areas (EAFB 2008a, p. 102). However, EAFB has designated a 10,387 ac (4,203 ha) OHV recreation area on the base for use by base personnel (EAFB 2008a, p. 104), and Fort Irwin has an 82 ac (33 ha) OHV recreation area (Department of the Army 2003, p. 1). Although these activities may impact the Mohave ground squirrel and its habitat, the two areas comprise only 0.2 percent of the squirrel's range.
There are no State Vehicular Recreation Areas (SVRAs) in the range of the Mohave ground squirrel. SVRAs are operated and managed by the Off-Highway Motor Vehicle Recreation Division of California State Parks and provide trails, tracks, and other OHV recreational opportunities; interpretive and educational activities and publications promoting safe and responsible OHV recreation; public safety, including law enforcement and first aid; and resource management designed to sustain OHV opportunities and protect and enhance wildlife habitat, erosion control, revegetation, etc. (California State Parks 2011, unpublished information).
OHV recreation also occurs on private lands. Unauthorized OHV use on private lands includes illegal trespass, off-trail riding, illegal operation of non-street legal vehicles, and vandalism (Ciani 2011, p. 1). The Kern County Sheriff's Department is proposing to reduce unauthorized OHV use on private lands by expanding and enhancing current safety and enforcement efforts (Ciani 2011, p. 1). However, there is no information quantifying the degree or extent of the areas impacted by this unauthorized use, either in Kern County or anywhere else in the range of the Mohave ground squirrel. Additionally, although some authorized OHV activity may occur on private lands, we are unaware of any information on the degree or extent of impacts for authorized OHV activity on private lands.
OHV recreational use is likely to continue to increase in the future. The State's population is projected to grow from 34 million in 2000 to 46 million by 2020 (BLM et al. 2005, chapter 3, p. 244). The demand for OHV recreational opportunities is increasing, along with California's growing population (BLM et al. 2005, p. 244). However, the BLM has reduced the number of roads and trails available for OHV use and has not indicated that it has plans to designate additional OHV management or high-use areas in the range of the Mohave ground squirrel, and the expected increase in OHV use will mainly be limited to existing management or high-use areas.
In summary, OHV use is a popular recreational activity within portions of the range of the Mohave ground squirrel. Potential impacts of OHV use vary from none in wilderness areas, to substantial in management or high-use areas, depending on the type and intensity of OHV activity, the designated land use, and the level of enforcement. About 6.6 percent of the range of the Mohave ground squirrel, including BLM, DOD, and private lands, is classified as management areas, spillover zones, or high-use areas. Although Mohave ground squirrels have been reported in one of the four management areas, we have no information that indicates that the impacts from OHV use in these areas constitute a barrier to their movement. We presume the management areas are extensively degraded and provide little value to supporting populations of Mohave ground squirrels now or in the future; however, these areas occur in less than 7 percent of the range of the Mohave ground squirrel. Additionally, we have no information indicating that additional management areas will be designated for OHV use in the future.
In addition, the BLM has:
(1) No plans to designate additional high-use areas or roads and trails for the next few decades,
(2) Closed 45 percent of the roads and trails in the DWMAs and 90 percent in the western Rand Mountains, and
(3) Implemented actions to restore habitat in these areas (BLM et al. 2005 chapter 2, p. 167) and monitor compliance (such as increasing enforcement and minimizing damage to public resources and harassment/disruption of wildlife and habitat).
Areas of lesser use, such as existing unpaved roads and trails, can result in the loss of habitat, and vehicle activity can crush Mohave ground squirrels and their burrows; however, the significance of such losses is undocumented for the Mohave ground squirrel. Although miles of roads and trails exist, the habitat loss is essentially a narrow, linear band, the impacts of which are minor compared to that of a management or high-use area. Unpaved roads and trails do not result in the total fragmentation of habitat as they are not barriers to Mohave ground squirrel movement (Leitner 2010, in litt.).
OHV use of unpaved roads and trails also occurs on private land, and most of this use is probably not authorized by the land owner. However, we found no information on the extent of this type of OHV use on private lands. At least one county in the range of the Mohave ground squirrel has identified unauthorized OHV activities on private land as a natural resource and public safety problem and is seeking ways to reduce these activities through enforcement (Kern County Sheriff 2011, unpublished information).
Using the best available information, we have determined that OHV use is not a significant threat to the Mohave ground squirrel. We found no information that the transport and expansion of nonnative vegetation or potential impacts of noise and other indirect impacts are adversely affecting the Mohave ground squirrel. The impact of OHV use to the habitat of the squirrel mainly occurs in management, spill-over, and high-use areas, which comprise less than 7 percent of the range of the Mohave ground squirrel. Recreational OHV use is of minimal concern on DOD land due to restrictions, and because only 0.2 percent of the species' range overlaps with DOD recreational use areas. The BLM has closed a substantial number of roads and trails in the squirrel's range and is implementing measures to monitor and enforce these closures and to restore habitat in the closed areas. The BLM has no plans to establish additional areas for OHV use in the range of the Mohave ground squirrel. Therefore, we find that OHV recreational use on BLM land is not a significant threat to the Mohave ground squirrel. Although we do not have an exact estimate, less than 2 percent of the high-use area is on private land, and one county is pursuing enforcement options to address this unauthorized OHV use and its impacts on natural resources. In the future, we expect that OHV use will likely increase but will be limited to existing management areas and designated roads and trails. Therefore, based on our evaluation of the best available scientific and commercial data, we conclude that OHV recreational use does not currently pose a significant threat to the Mohave ground squirrel in relation to the destruction, modification, or curtailment of habitat or range, nor do we anticipate OHV recreational use posing a threat in the future.
Transportation infrastructure is a network of paved highways and roads. Although we were unable to find studies on the effects of transportation infrastructure on the Mohave ground squirrel, research on other animals has found that the presence of roads in an area may have a positive, negative, or no effect on animal abundance (Fahrig and Rytwinski 2009, p. 21).
Potential positive effects of roads include greater availability of forage plants adjacent to the roadway caused by precipitation runoff from the roadway and fewer predators near roadways because of the negative effects of roadways on larger mammals (Garland and Bradley 1984, p. 47; Fahrig and Rytwinski 2009, p. 21). Potential negative impacts from construction and operation may include mortality (see Factor E, “Direct Mortality”), barriers to movement and fragmentation (see Factor E, “Fragmentation”), and habitat loss and degradation (Gustafson 1993, pp. 23, 26; BLM 2003, p. 30; Leitner, pers. comm., as cited in Defenders of Wildlife and Stewart 2005, p. 22).
Mohave ground squirrels may be crushed by vehicles, and the presence of trash and other animals that are run over by vehicles (“road kill”) may attract common ravens and other predators to the road and nearby areas, thereby increasing the likelihood that Mohave ground squirrels adjacent to these sites would be vulnerable to predation (see Factor C, “Predation”). Some studies showed that roads produce an ecological “road-effect zone,” a zone over which significant ecological effects extend outward from a road (Forman and Deblinger 2000, p. 37). Besides road kill and loss of habitat, indirect effects of roads in the road-effect zone may include traffic noise, which many species avoid, and barriers to movements within a population, with potential demographic and genetic consequences (see Factor E, “Fragmentation”).
Roads alter habitat upslope and downslope by causing hydrologic and erosion effects (Foreman and Alexander 1998, p. 217), and promote the invasion of nonnative annual plant species (Brooks 2007, p. 154). Thus, the road-effect zone may interrupt horizontal ecological flows (e.g., animal movements, hydrology), alter landscape spatial patterns (i.e., the number, size, and arrangement of ecological pattern and ecological function and process), and change species distribution and abundance (Forman and Alexander 1998, p. 1). The interruption of hydrologic flows may have both positive and negative impacts on the habitat of the Mohave ground squirrel. The interruption may provide more water to upslope habitat, thereby increasing the amount and availability of forage. Conversely, the interruption may impede or prevent surface flow from reaching downslope areas, thereby decreasing the amount and availability of forage.
One major highway is planned within the range of the Mohave ground squirrel, the High Desert Transportation Corridor. This 63-mi (101.4-km) long east-west corridor would connect SR-14 in Palmdale with US-395 (Adelanto) and I-15 (Victorville), and would terminate on the southeast side of Apple Valley at SR-18 (see Map 1) (San Bernardino County 2011, unpublished information). The corridor would contain a highway with all, or portions, composed of freeway/expressway/tollway, and it may contain a high-speed rail line (Caltrans 2010a, p. 1). We estimate this project would result in the loss of 7,634 ac (3,089 ha), or 0.14 percent of the range of the Mohave ground squirrel.
The new highway would be located in the southern portion of the range of the Mohave ground squirrel, and south of the important population area on EAFB. The highway is planned to include areas currently developed for urban and rural use and agriculture, and thus, the loss of Mohave ground squirrel habitat would likely be less than the footprint of the proposed corridor. The project proponent may be required to mitigate for the loss of Mohave ground squirrel habitat as part of the permitting process under CESA (Jones 2011, in litt.) (see Factor D, “State Laws and Regulations”) and the WEMO Plan (see Factor D, Bureau of Land Management).
Although the new highway will likely have some effect on the habitat of the Mohave ground squirrel beyond what will be removed during road construction, we are not aware of any study on the extent of a potential road-effect zone or whether such a zone will have a positive or negative impact on Mohave ground squirrel populations, or how any impacts might change with variables, such as road width, traffic rates, and location. The extent of the road-effect zone varies, depending on the species being affected, location, habitat, road width, traffic density, and other factors. For example, the road-effect zone along one road in Massachusetts that passes through an area with many swamps and ponds varied from greater than 328 ft (100 m) to greater than 3,280 ft (1,000 m), and averaged 1,968 ft (600 m) (Forman and Deblinger 2000, p. 1). However, working in the high desert of southwestern Utah, which is similar to the environment in the west Mojave Desert, Bissonette and Rosa (2009, p. 27) found no clear road-effect zone for small mammals.
Although they did not conduct their study in desert areas, Adams and Geis (1983, p. 1) found instances where population abundance of some small mammal species was greater near roads because of their use of the adjacent habitat created or enhanced by the roadway (e.g., water collection, increased vegetation). In a creosote bush community in southern Nevada, Garland and Bradley (1984, p. 47) found the effects of roads on small mammals may differ in deserts when compared with mesic habitats. Roadsides receive runoff from pavement, which supports lush vegetation compared to adjacent habitat. They also found that round-tailed ground squirrels, a close relative of the Mohave ground squirrel, were more common near roadways (Garland and Bradley 1984, p. 54). In a review of the literature on the effects of roads on wildlife, Fahrig and Rytwinski (2009, p. 3) found that small mammals generally showed either a slightly positive effect from roads or no effect.
With so little known about the effects of roads on the Mohave ground squirrel and so many variations in the road-effect zone reported in the scientific literature, we employ a worst-case approach to our assessment of the impact of the new highway, in which we assume that there will be a road-effect zone associated with the new highway and that the impacts would be so severe as to eliminate all Mohave ground squirrel habitat within the zone. If such a zone were twice or even three times the width of the proposed highway, then at most the zone would result in the loss of an additional 22,902 ac (9,268 ha) of habitat, or an additional 0.43 percent of the range of the squirrel.
In total, construction of the proposed highway could result in the loss of less than 0.6 percent of the range of the Mohave ground squirrel, which includes potential impacts associated with a road-effect zone. However, the actual loss of habitat will likely be less because some areas have already been developed and mitigation will likely be required for the loss of habitat under the WEMO Plan and CESA (see Factor D, Bureau of Land Management and “State Laws and Regulations”). Within the DWMA, the mitigation ratio is 5:1 (see “Energy Development” section below).
In addition to the proposed highway, two existing highways within the range of the squirrel are planned to be modified. Areas of US-395 may be realigned and portions of SR-58 and US-395 would be widened within the range of the Mohave ground squirrel (Caltrans District 8 website, 2010b, unpublished information). For US-395, the proposed widening and realignment projects extend from the southern terminus at I-15 north to Kramer Junction (see Map 1). The US-395 projects occur within the southern portion of the range of the Mohave ground squirrel, well outside any of the important population areas for the squirrel. Some of the areas where the road will be widened have already been developed (e.g., Adelanto, Victorville, Kramer Junction, etc.) and would therefore not result in any additional loss of habitat. However, a portion is located in the Fremont-Kramer DWMA, which is managed for the Mohave ground squirrel (see Map 2). We estimate the proposed highway widening would directly impact an additional 1,600 ac (647 ha), or 0.03 percent of the range of the Mohave ground squirrel including the areas that have already been developed. If a road-effect zone exists for the Mohave ground squirrel, under a worst-case scenario, up to an additional 4,800 ac (1,942 ha) of habitat could be lost, or an additional 0.09 percent of the range of the squirrel.
For SR-58, the proposed widening projects extend from near Boron east to 7.5 mi (12.1 km) east of Kramer Junction (see Map 1). The project would occur in the southern portion of the range of the Mohave ground squirrel, well outside any important squirrel population area. Most of the proposed highway widening is located in the Fremont-Kramer DWMA (see Map 2); however, in the Kramer Junction area, impacts to the Mohave ground squirrel have already occurred from existing urban and rural development. The proposed highway widening is estimated to directly impact an additional 273 ac (110 ha), or less than 0.01 percent of the range of the Mohave ground squirrel, which includes the areas that have already been developed. Again, under a worst-case scenario, up to an additional 819 ac (331 ha) could be lost within the road-effect zone.
In total, road widening would result in the loss of about 7,492 ac (3,032 ha), or about 0.14 percent of the range of the Mohave ground squirrel, which includes potential impacts associated with a road-effect zone. However, the actual loss of habitat will likely be less because some areas have already been developed and mitigation will likely be required for the loss of habitat under the WEMO Plan and CESA (see Factor D, Bureau of Land Management and “State Laws and Regulations”); within the DWMA, the mitigation ratio is 5:1 (see “Energy Development” section below).
In summary, there are a few major highways and numerous roads within the range of the Mohave ground squirrel. There are plans to build a new east-west highway across the southern portion of the range of the Mohave ground squirrel and widen two existing highways, none of which will affect any of the important squirrel population areas. Combined, these projects would result in the direct loss of about 9,507 ac (3,738 ha) of habitat, or about 0.18 percent of the range of the squirrel. The actual amount would be less because some areas have already been developed and no additional habitat would be lost, and mitigation for loss of habitat would be required.
We acknowledge that roads may affect habitat beyond that lost during construction. This road-effect zone can have varying degrees of both positive and negative impacts on a species and its habitat, and the zone can extend various distances from the road depending on factors, such as the species being affected, location, habitat, road width, and traffic density. For squirrels and other small mammals, the road-effect zone tends to be neutral to slightly positive (Fahrig and Rytwinski 2009, p. 13). Although we do not have any information that such a zone exists for the Mohave ground squirrel or whether the impacts within the zone would be positive or negative, based on a worst-case scenario, an additional 28,521 ac (11,542 ha) of habitat or about 0.54 percent of the range of the squirrel could be lost. Therefore, based on a review of the best available scientific and commercial data, we find that transportation infrastructure projects likely to occur in the future could affect at most 0.74 percent of the range of the Mohave ground squirrel, and therefore do not pose a significant threat to the Mohave ground squirrel in relation to the destruction, modification, or curtailment of habitat or range. Note that other impacts that may be associated with roads, including mortality and habitat fragmentation, are discussed under Factor E.
The DOD manages about one-third of the range of the Mohave ground squirrel. Within the species' range, there are three major military bases—Fort Irwin and the National Training Center (NTC), EAFB, and NAWS.
Fort Irwin has three major management units; the National Training Center (NTC), the Goldstone Deep Space Communications Complex, and the Leach Lake Bombing Range. Fort Irwin's primary mission is training ground forces for combat, including the use of tanks, other tracked vehicles, and wheeled vehicles. Impacts from the training of ground forces and associated use of wheeled and tracked vehicles would be similar to impacts in OHV management areas (see “Off-Highway Vehicle Recreational Use” section above). In addition, Fort Irwin has a small cantonment area, which contains offices, housing, shops, restaurants, utilities, and other facilities. The impacts to the Mohave ground squirrel from the cantonment area would be similar to those described above under “Urban and Rural Development,” but on a very small scale. The Army has a proposal for both solar (14,000 ac (5,666 ha)) and wind (49 ac (20 ha)) (Department of the Army 2009, p. 33) energy projects within the boundaries of Fort Irwin (which also potentially includes the Goldstone Complex).
The NTC is about 642,558 ac (260,035 ha), with approximately 435,978 ac (176,435 ha) within the range of the Mohave ground squirrel. Located on the eastern edge of the range of the Mohave ground squirrel, we estimate that 8.2 percent of the range of the species is within the NTC boundary, which includes a recent expansion of Fort Irwin's southwestern boundary of 75,300 ac (29,745 ha) into an area that is within the range of the Mohave ground squirrel (see Factor D, Department of Defense, for additional discussion on the expansion area). Ground forces training is usually located on the flats and lower slopes of the NTC, which are the preferred habitat of the Mohave ground squirrel.
Prior to 1977, the Mohave ground squirrel was not known to occur on Fort Irwin. From 1977 to the early 1990s, Fort Irwin conducted surveys and found Mohave ground squirrels 40 mi (64 km) farther east than previously documented occurrences (Wessman 1977, pp. 11, 12). Krzysik (1994, p. 29) documented the impacts of ground forces training on the habitat of the Mohave ground squirrel, which included extensive losses of shrub cover, soil layers, and cryptobiotic soil crusts. Cryptobiotic soil crusts are collections of symbiotic bacteria, algae, fungi, and lichen that live on or slightly below the soil's surface and create a semipermeable soil surface or crust. They reduce soil erosion, promote and control water infiltration, regulate soil temperatures, catch and convert atmospheric nitrogen, accumulate organic matter, and facilitate native seedling establishment and growth (Boarman 2002, pp. 46 and 47), and thus aid in the maintenance of high-quality forage and habitat for the squirrel.
In the future, the 75,300 ac (29,745 ha) expansion area, some of which is likely Mohave ground squirrel habitat, will be used for ground forces training; impacts to the expansion area are expected to be the same as areas currently used for ground forces training. However, the entire area within the NTC is not used for ground forces training, as some of the terrain is not suitable for training and some areas are set aside as buffer zones to shield the training activities from civilian uses on lands adjacent to the base's boundary. Human access to the NTC is restricted, which precludes the use of the land for other forms of surface disturbance (e.g., OHV recreational use, urban and rural development, mining). Thus, while some areas are intensively used for ground forces training, others are not and remain undisturbed. Therefore, the estimated 8.2 percent of the range of the Mohave ground squirrel that is within the NTC is an overestimate of the portion of the species' range impacted by military training activities. In addition, Fort Irwin and the NTC have implemented mitigation measures for the Mohave ground squirrel to offset the impacts from the expansion area (see Factor D, Department of Defense). The location of the NTC does not appear to have an adverse effect on the movement of the Mohave ground squirrel between the Coolgardie Mesa and the EAFB important population areas (Bell 2006, pp. 43, 72) (see Map 2 and Significant Portion of the Range Analysis).
The 33,359-ac (13,500-ha) Goldstone Deep Space Communications Complex, which is operated by the National Aeronautics and Space Administration (NASA) for tracking and communication for space missions, is off limits to Army training activities, although a tank trail constructed in 1985 bisects most of the Complex. Little or no OHV use occurs within the Goldstone Complex, because there is no public access; personal staff vehicles are confined to paved and dirt maintenance roads, and military vehicles are restricted to the tank trail. Therefore, the Mohave ground squirrels within the Goldstone Complex are essentially protected from military training activities. This is 0.6 percent of the range of the Mohave ground squirrel.
The 91,182 ac (36,900 ha) Leach Lake Bombing Range is managed by the Air Force for live-bomb practice, and is off limits for ground use because of the high risk of unexploded ordnance. This area is 1.7 percent of the range of the Mohave ground squirrel; however, only a small portion of it is used for bombing practice. The remainder is managed as a buffer from human development in case a bomb misses its intended target. Although there are likely patches of Mohave ground squirrel habitat in the Bombing Range, their size, spatial arrangement, and degree of habitat quality are unknown because there is no ground access.
The 307,435 ac (124,468 ha) EAFB (see Map 1) is primarily used to test and evaluate aircraft. Additional activities include conducting and supporting tests of aerospace vehicles, evaluating flight and recovery of research vehicles, participating in developmental test and evaluation programs for the DOD and other government agencies, and operating the Air Force Test Pilot School (EAFB 2008b, pp. iii, 19). Because the emphasis at EAFB is training and testing in the air, the impacts to Mohave ground squirrel habitat are minimal and localized. Large areas of the base remain undeveloped and accommodate testing activities and buffers for these activities. These undisturbed and “off-limits” areas allow EAFB to conserve natural resources and minimize impacts to Mohave ground squirrel habitat.
Between 1993 and 2007, about 652 ac (264 ha) (about 0.2 percent of the base) of permanent land disturbance (e.g., urban development within the cantonment area) occurred at EAFB. EAFB recently announced plans to construct more than 3,000 ac (1,214 ha) of solar panels in the northwestern portion of the base to be energy self-sufficient; however, there is no timeframe for this project. Although this project would result in the loss of more Mohave ground squirrel habitat than has occurred in the past at EAFB (EAFB 2008b, p. iv), it is less than 0.06 percent of the range of the Mohave ground squirrel and has been sited to avoid: (1) The EAFB important population area; (2) areas with recorded occurrences of Mohave ground squirrels on EAFB; and (3) areas with likely connectivity to the south, east, and north where other important populations of Mohave ground squirrel are present (see Map 2). OHV use is strictly confined to designated areas on the base (see “Off-Highway Vehicle Recreational Use” section), while other activities that may affect Mohave ground squirrel habitat (e.g., livestock grazing and agriculture) are not allowed (EAFB 2008a, p. 73). The southeast portion of the base is designated critical habitat for the federally threatened desert tortoise, and the east boundary abuts the Fremont-Kramer DWMA, providing connectivity to this and other areas managed for the Mohave ground squirrel (see Factor D, Bureau of Land Management, and Factor E, “Fragmentation”). The Air Force has an active program on EAFB to minimize ground disturbing activities in desert tortoise habitat, which also benefits the Mohave ground squirrel (EAFB 2008a, p. 74).
The Air Force has conducted Mohave ground squirrel presence/absence surveys on EAFB since 1988, concentrating on 60 study plots distributed throughout the base that were established to monitor long-term trends of habitat quality and species diversity (EAFB 2008a, p. 74). Annual trapping studies have occurred since the mid-1990s based on funding availability (EAFB 2008a, p. 73). Mohave ground squirrels have been trapped in all years when trapping was conducted; these results indicate that the Mohave ground squirrel is relatively widespread on the base except for the northwest portion. Most observations have occurred in the east and south portions of EAFB (EAFB 2008a, p. 75). Although densities are not available with the methodology used on EAFB, one of the Mohave ground squirrel important population areas was designated here because the area meets the three criteria for a “core” area (Leitner 2008, p. 12) (see Map 2).
The 1,110,443 ac (440,695 ha) NAWS is located in the northern portion of the range of the Mohave ground squirrel (NAWS 2002, p. 6). The primary function of NAWS is to research, develop, test, and evaluate weapons systems for Navy, Air Force, Army, Joint Service, commercial, and foreign military weapons systems. NAWS also develops and tests airborne electronic warfare systems and performs aircraft weapons integration (NAWS 2002, p. 1). The Mohave ground squirrel has been studied for several years at the Coso Range in the northwest area of NAWS (see “Abundance and Trend” section) and has been documented at other locations throughout the base.
Impacts to the Mohave ground squirrel and its habitat on NAWS are similar to those described for EAFB in both type and magnitude. Similar to EAFB, large areas of NAWS remain undeveloped to accommodate aerial testing activities and to serve as buffers for testing activities. For example, NAWS tests unmanned aerial vehicles for which they need large areas of open space to fly these vehicles and test their control capabilities and buffers to ensure the safety of civilians outside the base. These large undisturbed and “off-limits” areas allow NAWS to conserve natural resources, including Mohave ground squirrel habitat, on much of the base.
Cattle grazing under BLM grazing leases no longer occurs on the base (BLM et al. 2005, chapter 4, p. 98). Feral burros and wild horses occur on NAWS. Impacts from burros and horses include loss of annual and woody perennial vegetation used by Mohave ground squirrels for forage, loss of cover from predators and thermal shade, and soil compaction from trailing (NAWS 2002, p. B-97) (see “Grazing” section below). However, NAWS and the BLM have an extensive burro removal program that has substantially reduced the impact of burros (BLM et al. 2005, chapter 2, p. 81).
In summary, Mohave ground squirrel habitat has been lost to military operations primarily from ground forces training. The largest area of loss is in the NTC, including the expansion area, with about 8.2 percent of the range of the Mohave ground squirrel within the NTC boundary. However, the NTC is on the eastern edge of the range of the Mohave ground squirrel (see Factor E, “Fragmentation”), and not all of the area within the NTC is impacted by ground forces training. Other locations on DOD land, such as the Goldstone Complex and much of EAFB and NAWS (more than 1,745,000 ac (706,180 ha)), are undeveloped and receive little-to-no surface impacts from military operations. Because of military security and the need for large areas of open space to test aircraft and weapon systems and buffer areas around the test areas, these areas become de facto conservation areas for Mohave ground squirrel habitat.
We found no information that the DOD is proposing to change its mission in the future and no information on proposals that would impact additional lands within military boundaries. The DOD manages about one third of the range of the Mohave ground squirrel. Although about 9 percent of the range of the squirrel is used for training and testing to meet the military's mission, we estimate that 27 percent of the range is managed under limited use or de facto habitat conservation for the Mohave ground squirrel (see Table 1). Therefore, after reviewing the best available scientific and commercial information, we conclude that military operations do not currently pose a significant threat to the Mohave ground squirrel in relation to the destruction, modification, or curtailment of habitat or range of the species, nor do we anticipate military operations posing a threat in the future.
Energy development includes two components, the power plant where energy production or generation occurs, and the transmission line that transports the energy to users. In the western Mojave Desert, power plants currently generate energy using both non-renewable sources (e.g., natural gas, etc.) and renewable sources (e.g., solar, wind, and geothermal) with several proposals to generate additional energy using renewable sources.
A total of 22 non-renewable and renewable energy power plants have been constructed within or near the range of the Mohave ground squirrel, including solar, wind, and geothermal facilities. These facilities are located in or near cities and communities in the range of the Mohave ground squirrel, including Little Lake, Tehachapi, Mojave, Cantil, Argus, Trona, Boron, Hinkley, Hesperia, Victorville, Oro Grande, Barstow, Daggett, and Newberry Springs (California Energy Commission (CEC) 2011 Web site). These non-renewable and renewable power plants produce energy by using water, geothermal, natural gas, biomass, wind, solar thermal, and coal, and they have ancillary facilities that require ongoing maintenance (such as pipelines, transmission lines, and roads). Impacts from the construction and operation of these existing facilities to the Mohave ground squirrel are similar to those described below for new renewable energy projects.
In addition, several applications have been submitted to Federal, State, and local agencies for the construction and operation of new renewable energy projects (e.g., solar, wind, and geothermal) and associated transmission lines, and for the expansion of existing renewable energy projects in the range of the Mohave ground squirrel.
Various Federal and State directives foster the increase in proposed renewable energy projects. The Energy Policy Act of 2005 requires the Department of the Interior to approve at least 10,000 megawatts (MW) of renewable energy on public lands by 2015. The American Recovery and Reinvestment Act of 2009 provides monetary incentives for utility-level renewable energy development that occurs through December 2011. Executive Order 13514 declares the reduction of greenhouse gases as a priority for Federal agencies, and Executive Order 13212 requires Federal agencies to expedite review of energy project applications. In addition, the Governor of California's Executive Order S-14-08 requires California electric utilities to obtain 33 percent of their power from renewable energy by 2020. These laws and directives mean that renewable energy projects will likely be located in the Mojave Desert in the future and possibly in the range of the Mohave ground squirrel.
The Department of the Interior has and continues to receive applications for utility-scale renewable energy projects on public lands, primarily in the western United States. As of November 2010 (Miller 2010, in litt.), the BLM had received 23 applications for solar and wind renewable energy projects in the CDCA, of which part or all of each project would be located in the range of the Mohave ground squirrel. These applications that are entirely or partly within the squirrel's range encompass an estimated 204,200 ac (82,637 ha) of BLM land. However, this is only a rough approximation, because at this point in the application process we cannot determine with any accuracy what areas fall inside or outside the range of the squirrel. Some proposed projects are located on both BLM and private land, but the amount on private land is not available at this time, and the location, size, and status of many of these proposed energy projects changes frequently. In addition, it is not likely that all of these proposed projects will be permitted (see discussion below under Solar Projects).
In addition to those applications on BLM-managed lands, several applications for solar and wind energy and transmission projects have been submitted to other agencies that manage lands in the Mojave Desert or that are privately owned. These include the DOD, Department of Energy, CEC, California Public Utilities Commission, and County planning agencies. At least a portion of many of these projects may fall within the range of the Mohave ground squirrel.
In response to the Federal and State initiatives to encourage renewable energy development and the several applications for permits for renewable energy projects, the Renewable Energy Action Team (REAT) was formed. Its members include the CEC, CDFG, BLM, Service, California Public Utilities Commission, California Independent System Operators, National Park Service, U.S. Environmental Protection Agency, and DOD. The REAT is developing the Desert Renewable Energy Conservation Plan (DRECP), which was mandated by California Executive Order S-14-08. This plan is a joint State Natural Communities Conservation Plan (NCCP) and Federal planning effort that will identify and provide measures necessary to conserve and manage natural biological diversity within the plan area while allowing compatible and appropriate economic development, growth, and other human uses (California Fish and Game Code section 2805(g)). This includes mitigation measures that will offset impacts to sensitive species that are addressed in the DRECP, including the Mohave ground squirrel.
Solar energy projects require a large, clear area for placing and maintaining photovoltaic panels or mirrors to produce energy and ancillary structures, including distribution lines to transport the generated energy to a high-voltage transmission line and provide power to the administration and operation facilities at the site; pipelines to supply water for administration and operation facilities and for the production of energy (e.g., washing mirrors and panels, generating steam to produce energy); and roads to access the project site, distribution line route, and pipeline route(s). Some of these ancillary structures are tens of miles long. In addition, some projects are obligated to provide energy on cloudy days. Therefore, a backup energy system may be constructed within the project site that uses non-renewable energy sources, such as natural gas or propane, to produce energy, which may require the construction of a pipeline to deliver the hydrocarbon fuel to the project site.
Solar energy projects are likely the most destructive renewable energy projects to Mohave ground squirrel habitat. Based on the past construction and operation of both solar thermal and photovoltaic solar energy projects in the Mojave Desert, the footprint of the project site is usually a large area, most of which is cleared and maintained free of vegetation, and the right-of-way for the transmission line and pipeline(s) includes a maintained access road for operation and maintenance. Solar energy projects are usually located on level or slightly sloping ground, which is characteristic Mohave ground squirrel habitat.
Adverse effects to the Mohave ground squirrel from construction and operation of solar plants include crushing animals and their burrows; loss of habitat for foraging, cover, and reproduction; increased levels of vehicle traffic that potentially result in the increased mortality of squirrels and increased predation; introduction of nonnative plants, especially along pipelines, transmission lines, and access roads; and altering habitat upslope and downslope, causing hydrologic and erosion effects.
There are two existing solar thermal power plants in the range of the Mohave ground squirrel, one near Kramer Junction and the second near Harper Dry Lake. These two facilities, both of which are located on private land, use solar trough or mirror technology, with backup natural gas as an energy source to produce power at night and on cloudy days. They cover an estimated 3,600 ac (1,457 ha), or 0.07 percent of the range of the Mohave ground squirrel, plus additional area for transmission lines, pipelines, and access roads. We are unaware of any information documenting impacts of these facilities on the Mohave ground squirrel population.
It is difficult to quantify the impacts of proposed solar energy projects on the habitat of the Mohave ground squirrel because of the uncertainty about their potential number, size, location, and jurisdiction. The DOD has proposed the development of 14,000 ac (5,666 ha) for solar energy production on Fort Irwin and 3,000 ac (1,214 ha) on EAFB. Although the average size of a solar project proposed on BLM land is about 7,000 ac (2,832 ha), the combined size of the three applications BLM has received that fall within the range of the Mohave ground squirrel was originally 9,686 ac (3,920 ha) (Miller 2010 in litt.). However, one of the three, the 3,883 ac (1,571 ha) Solar Millennium project, was recently cancelled after 2 years of environmental planning. It should be noted, however, that the cancellation of this project does not preclude another project proponent from submitting an application for solar development at the same site. The sizes of the two remaining projects are substantially different (5,325 ac (2,155 ha) versus 478 ac (193 ha)), which adds to the uncertainty about potential impacts on Mohave ground squirrel habitat. Ultimately, solar energy development on BLM land is likely to be limited within the range of the Mohave ground squirrel. Currently, none of the proposed solar energy projects are located in any of the eight important population areas for the Mohave ground squirrel.
The BLM is developing programmatic-level guidance for the development of solar energy projects and recently released a draft programmatic Environmental Impact Statement (EIS) for solar energy (BLM and DOE 2010). This draft EIS proposes four solar energy zones (SEZs) on 677,400 ac (27,414 ha) in the California desert. These SEZs are areas where the BLM would either make processing utility-scale solar energy project applications located in SEZs a priority or restrict solar energy project development to SEZs. None of the four proposed SEZs is in the range of the Mohave ground squirrel, and the EIS includes language and a map showing that BLM lands that are ACECs, DWMAs, or Mohave ground squirrel habitat are excluded from solar development. However, within the range of the Mohave ground squirrel, the map identifies scattered tracts of BLM land near the edge of EAFB and Victorville that have been identified as available for solar energy development (BLM and DOE 2010, p. 2). We note that this is a draft document, and the final document may be similar or different from the current EIS. Based on the currently available information, none of the proposed solar energy projects, the SEZs, or the scattered tracts of BLM land are within any of the important population areas for the Mohave ground squirrel.
Under the current WEMO Plan, which may extend to 2035, solar development within the range of the Mohave ground squirrel will also be restricted because the BLM has a maximum cumulative limit of 1 percent new surface disturbance of any kind for the MGSCA. One large solar project within the MGSCA would meet or exceed this 1-percent cap on any kind of surface disturbance. Although the 1-percent cap also applies to DWMAs, solar energy projects on BLM land in DWMAs are not likely to occur because of their designation as ACECs (see Factor D, Bureau of Land Management). The WEMO Plan also requires a mitigation ratio of 5:1 for lands within the DWMAs and the MGSCA for habitat lost from ground disturbance (BLM et al. 2005, chapter 2, p. 204). The mitigation generally involves acquisition of non-Federal land to add to the DWMAs and MGSCA, but mitigation measures other than habitat acquisition may be implemented to meet the 5:1 mitigation ratio. Outside of these areas, the mitigation ratio is 1:1 (BLM et al. 2005, chapter 2, p. 204, LaPre 2010). Once the DRECP is completed, the WEMO Plan would likely be amended to adopt this plan. The current delineation for the DWMAs and MGSCA are not likely to change with implementation of the DRECP.
BLM does not have jurisdiction over the permitting, development, and operation of solar energy projects on private land within the range of the Mohave ground squirrel and, therefore, does not have information on the number, size, and location of these projects. A project on private land may require approval from a County agency only, or from the County and the CEC. The applications received by these agencies are not always available to the public because of potential competition between energy developers, and as with BLM land, the number, size, and location of proposed solar energy projects changes frequently. However, we are aware of 21 proposed projects on private land within the range of the Mohave ground squirrel, which combined total 16,772 ac (6,787 ha), or about 0.3 percent of the range of the Mohave ground squirrel. Many of these projects are proposed for areas that were previously cleared and used for agriculture. None of these projects are located in any of the important population areas for the Mohave ground squirrel.
In summary, the impacts from construction and operation of a solar project in the range of the Mohave ground squirrel are similar to those described in the “Urban and Rural Development” section and are primarily loss of habitat. Two solar energy projects occur in the range of the Mohave ground squirrel, which combined are less than 0.1 percent of the range of the Mohave ground squirrel. The solar projects proposed on DOD land could comprise about 0.3 percent of the range of the squirrel. Three projects have been proposed on BLM land within the range of the squirrel, one of which was recently cancelled. The remaining two proposed projects make up about 0.1 percent of the range of the squirrel. Given the limitations for future development in the MGSCA and DWMAs, the BLM's current proposed position to either limit utility-scale solar energy development to SEZs or make projects located in SEZs a priority for processing over other projects, we expect that few solar projects will be approved and constructed on BLM land within the range of the Mohave ground squirrel within the foreseeable future.
We are aware of 21 proposed solar projects on private land, which combined are about 0.3 percent of the range of the Mohave ground squirrel. However, the locations for many of these projects primarily occur on lands previously cleared for agriculture. The combined total of existing and proposed solar projects make up no more than 0.81 percent of the range of the Mohave ground squirrel. It is unlikely that all of the proposed projects will be built, and none of them are located in any of the important population areas for the Mohave ground squirrel. Therefore, based on the best available scientific and commercial information, we conclude that solar energy development is not currently a significant threat to the Mohave ground squirrel in relation to the present or threatened destruction, modification, or curtailment of its habitat or range, nor do we anticipate it posing a threat in the future.
At wind energy project sites, wind turbine towers are scattered among hundreds or thousands of acres. The entire project site is not cleared of vegetation, rather an area at the base of each tower and the roads that provide access to the towers are cleared. Thus, the project area is crisscrossed with cleared areas, which are used during operation and maintenance. In addition to the roads, ancillary facilities include meteorological towers, a substation and an electrical collection system of buried electrical cables conveying electricity from the wind turbines to a substation, an operation and maintenance building, an electrical transmission line and associated tower structures to transmit the generated power to an existing high-voltage transmission line, and a “switching station” that connects the electrical components associated from the wind turbines to the high-voltage transmission line. Additionally, water and sewer lines are needed for an operations and maintenance building.
Adverse effects to the Mohave ground squirrel from construction and operation of wind energy projects include crushing animals and their burrows; loss of habitat for foraging, cover, and reproduction; increased levels of vehicle traffic that potentially result in the increased mortality of squirrels and increased predation; introduction of nonnative plants, especially along pipelines, transmission lines, and roads; and alteration of habitat upslope and downslope causing hydrologic and erosion effects. Although wind energy projects are usually similar in size or larger than solar energy projects, averaging about 8,725 ac (3,530 ha), they do not result in the elimination of all habitat within their perimeter as solar energy projects do. Habitat remains between the turbine pads and access roads. In addition, unlike solar projects, wind energy projects are frequently located on ridgelines, slopes, or in passes and would not likely be in areas with habitat characteristics preferred by Mohave ground squirrels. However, we have no information on how Mohave ground squirrel populations have been affected by currently operating wind energy projects or how they would be affected by the construction and operation of proposed wind energy projects.
Small patches of wind resources that are considered economically feasible to develop occur within the range of the Mohave ground squirrel (LM 2005, Appendix B, pp. 31-32), and some wind development is likely to occur. However, most of the large, commercially important wind fields in the Mojave Desert are to the west and south of the squirrel's range. So far, wind energy projects have been constructed on non-Federal land along the western edge of the Mohave ground squirrel's range in Kern County. Existing projects encompass about 4,900 ac (1,983 ha) or about 0.01 percent of the range of the Mohave ground squirrel (Waln 2011, p. 1). Wind turbines in this area have been placed mainly on hilltops and ridgelines, which are not generally suitable habitat for the Mohave ground squirrel.
It is difficult to quantify the impacts of proposed wind energy projects on the habitat of the Mohave ground squirrel. Applications have been submitted and withdrawn, and the size and location of the projects have changed after submission. It should be noted, however, that even if a project is cancelled, it does not prevent another project proponent from submitting an application for wind development at the same site. Recently the demand for energy sources from wind has been dampened by a reduction in the price of newly-found sources of natural gas and concerns over the future of renewable energy subsidies from Congress (Ball 2011, p. 2). As with solar energy projects, there is no single entity that is responsible for overseeing the development and operation of all wind energy projects in the Mojave Desert or within the range of the Mohave ground squirrel.
There is uncertainty in the development of future wind energy projects in the range of the Mohave ground squirrel. For example, only one wind project has been proposed on DOD land, a 49 ac (20 ha) project on Fort Irwin. In 2010, the BLM reported receiving 20 applications for wind energy projects totaling about 194,000 ac (78,509 ha) (Miller 2010, in litt.), although not all proposals occur within the range of the Mohave ground squirrel. The average project size is about 9,700 ac (3,925 ha), but sizes range from 160 ac (65 ha) to 45,385 ac (18,367 ha) (Miller 2010, in litt.). In contrast, in 2011 the BLM's list of wind energy applications (BLM 2011a, pp. 1, 3, and 4) did not include eight projects from the 2010 list. This change from 2010 was a reduction of about 86,000 ac (34,803 ha).
The total acreage of currently proposed wind energy projects that potentially occur in the range of the Mohave ground squirrel is about 107,347 ac (43,442 ha), or about 2 percent of the range of the species. In addition, the actual number of acres that fall within the range of the Mohave ground squirrel is likely to be far less because at this early stage in the proposal process the boundaries of each project are very generalized, and some of the current proposals overlap and some are partly outside the squirrel's range. In fact, requests for permits submitted to the BLM far exceed the 72,300 ac (29,259 ha) of economically developable wind resources that the BLM estimates occur on the lands they manage in the entire State of California (BLM 205, pp. 2-5). Most of the currently proposed wind energy projects on BLM land are located along the west and southeast edges of the range of the Mohave ground squirrel, and most are located on ridgetops and hillsides, which are not considered suitable habitat for the Mohave ground squirrel.
The BLM's wind energy program established policies, Best Management Practices (BMPs), and an Instructional Memorandum (IM 2009-043, December 19, 2008) to address the administration of wind energy development activities and identify minimum requirements for mitigation measures. These programmatic policies and BMPs would be applicable to all wind energy development projects on BLM lands. Site-specific and species-specific concerns, and the development of additional mitigation measures, would be addressed in project-level reviews, including National Environmental Policy Act (NEPA) analyses, as required (BLM 2005, Volume 1, Chapter ES, p. 4) (see Factor D below for a discussion of NEPA). For example, the BLM recommends establishing a policy by which right-of-way grants will not be issued for lands where wind energy development would be incompatible with specific resource values (BLM 2005, Vo