Field Guide to Mammals
of Southern California
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Coachella Valley Round-Tailed Ground Squirrel (Spermophilus tereticaudus chlorus)
Coachella Valley round-tailed ground squirrel is found only in Coachella Valley in Riverside County, from San Gorgonio Pass to the vicinity of the Salton Sea (Ernest and Mares 1987). Occurrences of this species have been documented in Cabazon, Whitewater Station, Coachella, Mecca, Agua Caliente, and along the Coachella Canal near Box Canyon (Hall 1981). Elevation range for the species is from below sea level to 2,900 feet (900 meters) (Zeiner and others 1990). Elevation for the Coachella Valley round-tailed ground squirrel ranges from 455–2,000 feet (140–610 meters), from UC-Berkeley Museum of Zoology website for specimen records.
Thirteen species of ground squirrels are native to the Pacific states, most of which are easily distinguished from one another (Ingles 1965). Coachella Valley round-tailed ground squirrel, which is also referred to as Palm Springs round-tailed ground squirrel, is a subspecies of S. tereticaudus. Another subspecies, S. t. tereticaudus, also occurs in southern California (Hall 1981), potentially on National Forest System lands.
General habitat types that support round-tailed ground squirrel include desert succulent shrub, desert wash, desert scrub, alkali desert scrub, and levees in cropland habitat. The species prefers open, flat, and grassy areas in fine or sandy soils (Zeiner and others 1990). Coachella Valley round-tailed ground squirrel is found in sand fields and mesquite habitats and is often associated with hummocks or mounds. Burrows are generally located at the base of a creosote bush or a small hummock. Burrow entrances are several inches wide and lead to tunnels that are usually not deep nor more than 5–6 feet (1.5-1.8 meters) in length (Jaeger 1961).
Breeding season of round-tailed ground squirrel begins in late February and lasts through May or June. A single litter of 4–12 altricial young are born in March–April after a gestation of approximately 27–35 days. Lactation occurs for approximately 35 days, at which point the young are weaned. Young emerge from burrows in May, and males begin dispersing in June.
Round-tailed ground squirrel is crepuscular during the summer months and active during midday in fall and spring (Ernest and Mares 1987, Zeiner and others 1990). It enters a period of inactivity beginning in August or September and continues until January (Ernest and Mares 1987).
Diet and Foraging
Coachella Valley round-tailed ground squirrel feeds on leaves of desert plants, beans of mesquite, cactus fruit, ocotillo blossoms, agricultural crops, and occasionally small lizards or birds. They also consume insects and spiders, feeding both on the ground and climbing into shrubs and trees (Zeiner and others 1990).
Adult round-tailed ground squirrels are territorial during the breeding season; juveniles become territorial in July or August (Zeiner and others 1990). They maintain home ranges averaging 1.8 acres (0.74 hectares). Population densities exhibit an increase during periods of heavy rainfall. Drabek (1970) recorded densities of 2.1-16 individuals per acre (5.3-40 individuals per hectare) in Arizona. Densities in southern California are likely lower because the average rainfall is lower in southern California. According to one study, an average of 10-15 individuals per square mile (3.8–5.2 individuals per square kilometer) is a probable density estimate for this species (Jaeger 1961).
Predators of round-tailed ground squirrel include gopher snake (Pituophis melanoleucus), prairie falcon (Falco mexicanus), and domestic cat (Felis cattus) (Dunford 1977) coyotes (Canis latrans), badgers (Taxidea taxus) and ravens (Corvus corax) (Ernest and Mares 1987).
Coachella Valley Association of Governments. 2001. Coachella Valley Multiple Species Habitat Conservation Plan. May 29, 2001. [Online]. Available: http://www.co.riverside.ca.us/cvag/mshcp/index.htm.
Drabek, C.M. 1970. Ethoecology of the round-tailed squirrel, Spermophilus tereticaudus. Tuscon: University of Arizona. Unpublished Ph.D. dissertation.
Dunford, C. 1977. Behavioral limitations of round-tailed ground squirrel density. Ecology 58: 1254- 1268.
Ernest, K.A.; Mares, M.A. 1987. Spermophilus tereticaudus. Mammalian Species No. 274. The American Society of Mammalogists.
Hall, E.R. 1981. The mammals of North America. 2d ed. New York: John Wiley and Sons. Ingles, L.G. 1965. Mammals of the Pacific states: California, Oregon, and Washington. Stanford CA: Stanford University Press.
Jaeger, E.C. 1961. Desert wildlife. Stanford, CA: Stanford University Press. UC-Berkeley Museum of Zoology website. Specimen records at that museum by county. [Online]. Available: http://elib.cs.berkeley.edu/mvz/.
Zeiner, D.C.; Laudenslayer, W.F., Jr.; Mayer, K.E.; White, M., eds. 1990. California's wildlife. Volume III: Mammals. Sacramento, CA: California Statewide Wildlife Habitat Relationships System, California Department of Fish and Game.
Information gathered from California DFG - California Interagency Wildlife Task Group