Family: Sciuridae, Squirrels view all from this family
Description Upperparts buff in summer, gray in winter; 1 narrow white stripe on each side. Underparts white. Underside of tail pure white, with black-tipped hairs forming narrow black border. Upperside of tail has 1 black band. Ears small. L 7 5/8–9 3/8" (194–239 mm); T 2 1/8–3 3/8" (54–87 mm); HF 1 3/8–1 5/8" (35–43 mm); Wt 3–5 1/2 oz (85–156 g).
Similar Species Very similar Nelson’s Antelope Squirrel is larger and more yellowish. Harris’ Antelope Squirrel has tail that is black and white underneath. Mohave Ground Squirrel lacks stripes.
Breeding 1 litter of 5–14 young born in early spring; sometimes a second litter later in the year.
Habitat Deserts and foothills, from valley floor to juniper belt; hard, gravelly surfaces. Associated with sage, greasewood, shad scale, and creosote bush (Larrea).
Range Southeastern Oregon and sw Idaho south to s California; east through s Nevada, Utah, and n Arizona to w Colorado and nw New Mexico.
Discussion The most widespread member of its genus in North America, the White-tailed Antelope Squirrel is most active in midmorning and late afternoon, with a lull during the heat of the day. During winter, it is active throughout midday, spending much time basking in the sun. It hibernates in northern parts of its range, but may or may not hibernate in more southerly areas. This species, like other antelope squirrels, runs fast, with its tail held over its back, and exposing its white underparts. Usually foraging on the ground, but sometimes in yuccas or cacti, it feeds on green vegetation, seeds, insects, and vertebrate flesh, in descending order of importance. Green vegetation, especially evening primrose and storksbill, makes up the largest part of this animal’s diet from December to May; it eats seeds, particularly those of ephedra, yucca, and opuntia, all year, but in smallest quantities in March and April. Grasshoppers contribute to the diet in spring and summer, beetles in autumn, and vertebrates all year, probably as carrion. The White-tailed Antelope Squirrel usually lives in burrows, but may also take up residence in rock crevices or abandoned burrows of other animals, often kangaroo rats. Burrows are about 18 inches (450 mm) deep, their entrances under shrubs or in the open. Inside are food caches and, near the center of the system, a nest measuring about 5 to 8 inches (130 to 200 mm) in diameter. It uses available material to build a nest, which may incorporate grasses, fur, and bark. Many burrows throughout the home range allow refuge from danger and from heat. Escape burrows are shorter than home burrows, with no nest or food caches. The White-tailed Antelope Squirrel forms dominance hierarchies, which are maintained by visual and tactical cues. Young animals may lie on the ground and face off with one another, and then proceed to box or wrestle until dominance is established. This sparring is accompanied by growls, chattering, and chirps. Greetings are by oral or nasal touching. This species mates between February and June. The mating season peaks in February and March in southern Nevada, though in California it apparently takes place entirely within a two-week period. This desert creature has several adaptations to survive in extreme heat. When exposed to critical temperatures, it will enter a burrow and crawl on the floor with its sparsely furred belly in contact with the ground, which quickly draws out excess heat. While out of the burrow, this species uses available shade or shades itself with its tail, and climbs into bushes where the airflow is greater.
