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Photo by Dean Draper
Photo Copyright Dean Draper
Piute Ground Squirrel
Urocitellus mollis
NatureServe conservation status
Global (G-rank): G5
State (S-rank): S4S5
External links
General information
The Piute ground squirrel, Spermophilus mollis, is commonly found in the Great Basin and Columbia Plateau of Utah, Nevada, California, Oregon, Idaho, and Washington. The species is quite common throughout its range in Utah, where it is usually found in desert or grassland habitats.
The Piute ground squirrel eats grasses, seeds, crops, other vegetation, and sometimes meat. The species mates in late winter or early spring, and females produce a litter of five to ten young about 24 days after mating. The Piute ground squirrel is active during the day, but the species is not active year-round. In fact, Piute ground squirrels are often active only during the spring and the fall, becoming inactive during the hot dry summer and the cold winter. Because of its affinity for crops, the Piute ground squirrel can cause a great deal of agricultural damage in some areas.
Phenology
Emerges from dormancy in late winter or early spring (males before females) but returns to dormancy during May-July, when grasses dry out. May have separate period of activity in fall. Most active in the early morning (Rickart 1987).
Species range
Washington, north of the Yakima River and west of the Columbia River and, disjunctly, southeastern corner of Oregon, southern Idaho (Snake River Valley) southward through Nevada (except extreme southern Nevada), extreme eastcentral California, and western Utah.
Habitat
Mainly in high desert (sagebrush, shadscale, greasewood). In southwestern Idaho, highest densities were in winterfat-Sandberg's bluegrass communities, with intermediate densities in big sagebrush-dominated communities and lowest densities in shadscale communities; scarce in communities dominated by exotic annuals (Yensen et al. 1992). Generally occurs in well-drained soils, especially embankments. Often around desert springs and irrigated fields. Makes extensive burrow systems. Young are born in a nest chamber in an underground burrow.
Food habits
Main diet herbaceous vegetation (grasses, forbs, and exotic annuals), and seeds; may also eat some shrub parts and animal matter. Will often feed on crops. May climb bushes while foraging.
Ecology
Population density in southern Idaho was estimated at 3-32/ha, excluding juveniles; density estimates ranging up to 331/ha (including juveniles) may be inaccurate. Mean home range was estimated at 1357 sq m. May form colonies but families and individuals live separately. Compared to other ground squirrels, has high fecundity and low adult survivorship and is short-lived (Rickart 1988).
Reproductive characteristics
Breeds late January-early March, depending on locality. Drought may suppress breeding. Gestation lasts 24 days. Litter size typically is 5-10; 1 litter per year. Males mature as yearlings or as 2-year-olds; females breed as yearlings (Rickart 1987)
Threats or limiting factors
Decline in the late 1980s in the Snake River Birds of Prey Area in southwestern Idaho was due to widespread conversion of desert shrublands to exotic annual-dominated communities by wildfires (Yensen et al. 1992).
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
