Mohave Ground Squirrel (Spermophilus mohavensis)
General Distribution
Mohave ground squirrel is restricted to the northwestern Mojave Desert. The species is distributed sporadically from around Olancha in Inyo County south through the Mojave Desert portions of eastern Kern and Los Angeles Counties and east to the general vicinity of Victorville in San Bernardino County (U.S. Fish and Wildlife Service 1995). Mohave ground squirrels have been found at elevations up to 5,600 feet (1,707 meters) in some desert ranges (Best 1995).
Systematics
Mohave ground squirrel is one of 38 species in the genus Spermophilus. There are no recognized subspecies of this taxon (Hall 1981). The only congeners that occur within the same region are S. beecheyi and S. tereticaudus. A narrow zone of hybridization between S. tereticaudus and Mohave ground squirrel occurs at one disturbed site near Helendale in San Bernardino County (Best 1995).
Habitat Requirements
Mohave ground squirrels occur at elevations up to 5,600 feet (1,707 meters) and have been found in most of the habitat associations present within the species' 7,600-square mile (19,675-square kilometer) range (U.S. Fish and Wildlife Service 1995). Optimal habitats at lower elevations include open desert scrub, creosote-burrobush, and saltbush communities. Optimal habitats at higher elevations include Joshua tree woodland and monotypic blackbrush (Wessman 1977). Large alluvium-filled valleys with deep, fine- to medium-textured soils vegetated with creosote scrub, shadscale scrub, or alkalai sink scrub and with no desert pavement appear to be preferred habitats (U.S. Fish and Wildlife Service 1995). Mohave ground squirrels typically construct burrows in the sandy soils of desert washes (Best 1995), while steep slopes and rocky terrain are generally avoided (Zembal and Gall 1980).
Reproduction
Mating occurs shortly after emergence from estivation. A litter of four to six young is produced after a gestation period of 28–30 days. Successful reproduction appears to be correlated with rainfall, and reproduction may not occur in drought years (California Department of Fish and Game 1996). Young are born in burrow systems that may be up to 20 feet (6.1 meters) long and more than 3 feet (0.9 meter) deep.
Daily/Seasonal Activity
Mohave ground squirrels are diurnal and seasonally active. They tend to be less active when temperatures exceed 98.1 ° F (36.7 ° C) or drop below 88 ° F (31.1 ° C) (Bartholomew and Hudson 1960). They spend approximately 7 months of the year, typically August–February, estivating in burrows. Timing of estivation is apparently tied to accumulation of fat reserves, which varies in relation to environmental conditions and among sex and age classes (Bartholomew and Hudson 1960, U.S. Fish and Wildlife Service 1995).
Diet and Foraging
Mohave ground squirrels eat a wide variety of seeds, flowers, forbs, shrubs, grasses, fungi, and arthropods. Diet composition in a given year varies according to food availability (Best 1995, U.S. Fish and Wildlife Service 1995). Mohave ground squirrels often cache food in burrows for later consumption (Zeiner and others 1990, Zembal and Gall 1980).
Territoriality/Home Range
Mohave ground squirrels are territorial; home range size is 0.2-2.0 acres (0.1–0.8 hectares) (Best 1995, U.S. Fish and Wildlife Service 1995).
Predator-Prey Relations
Probable predators of Mohave ground squirrel include badger (Taxidea taxus), bobcat (Lynx rufus), coyote (Canis latrans), Mojave rattlesnake (Crotalus scutulatus), and various diurnal raptors (Best 1995).
Literature Cited
Bartholomew, G.A.; Hudson, J.W. 1960. Aestivation in the Mohave ground squirrel Citellus mohavensis. Bulletin of the Museum of Comparative Zoology 124: 193–208.
Best, T.L. 1995. Spermophilus mohavensis. Mammalian Species. 509: 1–7. Published by the American Society of Mammalogists. California Department of Fish and Game. 1996. The status of rare threatened and endangered annuals and plants of California: Combined annual report for 1993, 1994 and 1995. An addendum to the 1992 report. Sacramento, CA.
Hall, E.R. 1981. The mammals of North America. 2d ed. New York, NY: John Wiley and Sons.
Leitner, Phil. 1999. The Mysterious Mohave Ground Squirrel. Tortoise Tracks 19: 2 Summer 1999. [Homepage of Desert Tortoise Preserve Committee], [Online]. Available: http://www.tortoise-tracks. org/denizens/mgs.html.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment: Habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
U.S. Fish and Wildlife Service. 1995. Endangered and threatened wildlife and plants; 90-day finding for a petition to list the mohave ground squirrel as threatened. Federal Register Vol. 60 No. 173, p. 46569- 46571. September 7, 1995.
Wessman, E.V. 1977. The distribution and habitat preferences of the Mohave ground squirrel in the southeastern portion of its range. Sacramento, CA: California Department of Fish and Game Report. Contract No. S-1559.
Zeiner, D.C.; Laudenslayer, W.F., Jr.; Mayer, K.E., compiling editors. 1990. California's wildlife. Volume I: Mammals. Sacramento, CA: California Statewide Wildlife Habitat Relationships System, California Department of Fish and Game.
Zembal, R.; Gall, C. 1980. Observations on Mohave ground squirrel, Spermophilus mohavensis, in Inyo Co., California. Journal of Mammalogy 61: 347-350.
Information gathered from California DFG - California Interagency Wildlife Task Group