White-tailed Antelope Squirrel
These are the only small desert mammals active during the day in summer and late spring months. They cache food for for emergencies, although not as much as tree squirrels or chipmunks. Females bear from 3 to 9 young within about 28 days after mating. The males play no role in the rearing of the young.
DISTRIBUTION, ABUNDANCE, AND SEASONALITY
The white-tailed antelope squirrel is common to abundant in the deserts of California from
Mono Co. south to the Mexican border, and along the northeastern border of California in
Lassen and Modoc cos. Optimal habitats are
alkali desert scrub,
Fairly common in
desert succulent shrub,
habitats. Also occurs in mixed chaparral and annual
grassland (Miller and Stebbins 1964, Ingles 1965, Bradley and Mauer 1973, Honeycutt et al.
SPECIFIC HABITAT REQUIREMENTS
feeds on a variety of seeds, fruits, green vegetation, arthropods,
and carrion. In southern Nevada, greens were most important in spring (60% of diet), but less
important in autumn (20%); while seeds and fruits were most important in autumn (60%), but
less important in spring (20%) (Bradley 1968b). Important plant species include Mormon tea,
acacia, blackbrush, and grasses. Arthropods formed
30-35% of the diet in autumn (Bradley 1968b). Forages on ground and in shrubs and trees.
Carries food in cheek pouches and caches food.
Cover: Simple burrows are dug in friable soil, and are used for escaping predators and
extreme temperatures (Grinnell and Dixon 1919, Bartholomew and Hudson 1961, Bradley
1967). Individuals may have several burrows within their home range, and will use
abandoned burrows of other animals.
Reproduction: Nesting burrows are under shrubs and in the open, and may have 2 or 3
entrances. The burrow system generally extends less than 0.6 m (2 ft) below the surface. A
nest of dried vegetation and hair is constructed (Grinnell and Dixon 1919, Bradley 1967).
Water: Lives long periods without free water, taking moisture from food and minimizing
water loss through behavioral and physiological adaptations (Bartholomew and Hudson 1961,
Pattern: Prefers open areas in arid and semi-arid habitats; requires friable soil for
burrowing. Uses hard-surfaced, rocky, or gravelly soils in open areas with clumps of shrubs.
SPECIES LIFE HISTORY
Activity Patterns: Yearlong
activity. Peak activity is in summer and early fall, and is
greatly reduced in inclement weather. Hibernates in the northern parts of its range (Oregon
and Idaho), but is active yearlong in
Activity is greatest at temperatures
between 15-30°C (59-86°F). Depending on time of year, activity may be highest at midday,
or in the morning and late afternoon. Surface activity at Barstow begins 1.5 hrs after sunrise
and continues until 0.5 to 1.25 hrs before sunset (Karasov 1981). Daily energy expenditure
increased from April to October, and metabolic rate dropped at night (Karasov 1981). In
winter, reduces energy expenditure by 40% by huddling (Karasov 1983). With a constant
photoperiod in laboratory conditions, individuals showed an endogenous rhythm of testicular
development, but no circannual rhythms of body mass or water consumption (Kenagy 1981).
Changing photoperiod does not affect testicular rhythm, but there is a seasonal difference in
tendency to increase body mass (Kenagy and Bartholomew 1979).
Seasonal Movements/Migration: None.
Home Range: Home range estimates in Nevada varied from 1.4-9.4 ha (3-20.6 ac) (Allred
and Beck 1963a, Bradley 1967), with a mean of 6.7 ha (14.8 ac) (Allred and Beck 1963a), and
a daily fluctuation of 1.8 ha (4 ac) (Bradley 1967). This species can home from distances up
to 1.6 km (1 mi) (Bradley 1968a). Densities of 6-35 per km2 (0.4 mi 2) have been reported.
Territory: No data found. Presumably non-territorial. Forms hierarchies in small feeding
groups (Fisler 1976, 1977). Huddles in small groups in winter (Karasov 1983) for
Reproduction: Breeding season from February through June with a peak in births in April.
The litter size ranges from 5-14, with a mean of 9. Females may have 2 litters per yr, but 1 is
considered normal (Grinnell and Dixon 1919, Bradley 1967).
Niche: This small, diurnal omnivore is sympatric with the Mohave ground squirrel, which is
competitively superior, but lacks many of the behavioral and physiological adaptations of this
antelope squirrel that allow the latter to have yearlong activity (Bartholomew and Hudson
1961). Major predators probably include
(Grinnell and Dixon 1919).
California Department of Fish and Game. California Interagency Wildlife Task Group.