Family: Sciuridae, Squirrels view all from this family
Description Yellowish brown or buffy above, with 1 white stripe on each side; tail white below. L 9-10 1/2" (230-267 mm); T 2 5/8-3 1/8" (66-78 mm); HF 1 1/2-1 3/4" (37-44 mm); Wt 5 1/2 oz (155 g).
Similar Species White-tailed Antelope Squirrel is smaller and less buffy. Tail of Harris' Antelope Squirrel is black and white underneath.
Breeding Mates in late winter or early spring; 1 litter per year of 6-11 young born after gestation of 26 days. Average newborn weighs less than 1/4 oz (4.9 g).
Habitat Open, rolling, or hilly desert country and sandy washes; with shrubs in San Joaquin Valley, without shrubs in Kern County, California. Associated plants are orach, Mormon tea, ephedra, and juniper.
Range Kern, Kings, and w Fresno counties in southern California.
Discussion Nelson's Antelope Squirrel is most active in early morning and late evening, showing little movement at midday. It apparently does not hibernate, and there is no evidence that it estivates (becomes dormant during periods of high temperatures), although it often disappears from view in the hottest weather. Its pale coloration is an adaptation to the severe desert conditions in which it lives. Using its cheek pouches to transport food to the burrow, this species feeds on many different items as available. Green vegetation is a prominent food source in spring, while insects (June bugs, tenebrionid beetles, Jerusalem crickets, camel crickets, grasshoppers, and ants) constitute up to 90 percent of the diet from April to December. Seeds, particularly of grasses and Mormon tea, comprise 10 to 20 percent of the diet. This species also consumes vertebrates, mostly lizards and rodents. It climbs into shrubs to gather seeds or fruits, and may leap with grasshoppers until both come down at the same time and the insects can be captured. Most young are born in March and first appear aboveground in April, the only time of year when green vegetation is present. Weaning may begin before emergence from the nest, and is complete by mid to late April. Forming colonies of six to eight individuals, Nelson's Antelope Squirrels dig their burrows in loamy or alluvial soils (which often become brick-hard), as well as in sandy or gravelly soils. Very similar to those of kangaroo rats, these burrows have openings under shrubs and often honeycomb the sides of gullies. This squirrel is cautious in exiting from the burrow, relying on sounds more than visual cues. Like all antelope squirrels, it scurries about with its tail curled over its body, giving the impression of thistledown blowing over the ground. When the animal is alarmed, its tail twitches back and forth, not side to side. Its alarm call is a trill. Even though it is a desert species, Nelson's Antelope Squirrel cannot survive extremely high temperatures. If the animal is exposed to sun at 90°F (32°C), its actions become frenzied, and it froths at the mouth and then dies. The annual mortality rate of established adults is 60 to 80 percent, with summer the most critical period, although cold is also a problem. California Ground Squirrels may compete with Nelson's Antelope Squirrels, squeezing them out of their habitat, and kangaroo rats also will take over their burrows. Predators are American Badgers, Coyotes, and Kit Foxes, though land cultivation by humans is the biggest threat to this species. The state of California lists Nelson's Antelope Squirrel as a threatened species.
