"Extreme heat does not deter Harris's Antelope Squirrel from vigorous daytime activity. It is agile, scampering over sharp-spined cholla cactus without being pricked, and may sit on top of a cactus to look around. Antelope squirrels dig burrows, usually under desert shrubs such as mesquite, creosotebush, or palo verde, and eat mainly fruit and cactus seeds. Trapping studies indicate the species is found in low densities that vary seasonally. The squirrels are active year-round. They typically breed in December or January and have a litter of 5-9 young about a month later."

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Occurs below 1,350 meters elevation in the southwestern United States (Arizona and New Mexico) and adjoining portion of Sonora, Mexico. In the US, it occurs primarily in southern and western Arizona, where its range does not extend beyond the Colorado River. Found in a small area of southwestern New Mexico, specifically in the Peloncillo Mountains and near Redrock.

Harris antelope squirrels are found below 1,350m elevation in southwestern United States and northwestern Mexico. (Best et al. 1990)

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Southern Arizona and extreme southwestern New Mexico south into the northwest mainland of Mexico (Sonora). Below 1350 m.

Head and body length is 137-168mm and tail length is 55-95mm. There are no differences in external measurements between the sexes. Harris antelope squirrels have long necks and slender bodies. The tail is short and the ears are small. The body hair is mouse gray in the winter and paler during the summer. Dorsal hairs are short and somewhat coarse, but lay smoothly, giving the animal a glossy appearance. Hairs on the undersurface are coarse and rigid. Winter pelage is longer and softer than summer pelage. There is one white stripe along both sides of the body from shoulder to rump. The undersurface of the tail is mixed black and white. A white ring encircles each eye, giving the Harris antelope squirrel a spectacled appearance. The soles of the feet are heavily haired. The Harris antelope squirrel carries its tail arched over its back. (Best et al. 1990), (Nowak 1991)

Average mass: 126 g.

Length: 25 cm

Weight: 150 grams

Sexual Dimorphism: None

Length:
Average: 238 mm
Range: 216-267 mm

Weight:
Average: 122 g

Habitat and Ecology

Systems

• Terrestrial

The Harris antelope squirrel inhabits arid, sparsely vegetated plains and lower mountain slopes. It prefers rocky hills or rocky soils. (Nowak 1991)

Terrestrial Biomes: desert or dune

Comments: Low dry, sparsely vegetated desert; open areas in plains, valleys, canyons, and river bottoms. Saltbush-creosote bush- bursage, usually in areas with rocky soil or rocky slopes, but in sandy areas in some regions (see Best et al. 1990 for further details). In underground burrow when inactive. Burrow openings near or under bushes, in cactus thickets, or among rocks. May climb onto vegetation (Opuntia). Young are born in underground burrows.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

The Harris antelope squirrel is omnivorous. It feeds on seeds, fruit, plant stems and roots, some insects, and carrion. It has cheek pouches of considerable capacity. Suitable food supplies are carried in the cheek pouches and stored in burrows, under rocks, or in some other shelter. (Nowak 1991)

Comments: Diet includes fruit of cholla; seeds and fleshy fruit of barrel cactus; unripe seed pods of ocotillo; fruit and seeds of prickly pear; seeds of paloverde, wild gourd, and mesquite; meat; and green parts of plants (Hoffmeister 1986).

In southeastern Arizona, density ranged from 0.08 to 0.36 per ha; never abundant, occurs as scattered individuals (Best et al. 1990).

Comments: Diurnal, active throughout year.

Average lifespan

Status: captivity: 10.6 years.

Maximum longevity: 10.6 years (captivity)

Although mating can take place from December or January until June, peak reproductive activity occurs from February-March. A vaginal plug is formed after copulation. In females, the beginning of the breeding season is marked by a swelling of the labia, enlargement of the uterus, and opening of the vaginal orifice. In males, spermatogenesis may begin as early as November and lasts until June. The testes regress in size in June and July to less than 10% of the February and March mass. Gestation lasts for about 30 days, and the litter size may range from 5-14. The average litter size is 6.5. Females give birth to only one litter per year. Newborns are naked and the skin is pink and somewhat transparent. The young cannot crawl, and their eyes and ears are closed. After 1 week, the dorsal sides of the head and back are covered with black pigmentation. At 2 weeks, 2 pale stripes appear on the back. These stripes are covered with white hairs in the adult. At 3 weeks, the claws are well-developed and the lower incisors have erupted. At this age, the young still cannot walk without falling over. Between 3 and 4 weeks, the ears open and the young are fully covered with hair. The upper incisors begin to erupt after 4 weeks. At this age, the young are very vocal and frequently utter a trilling noise when disturbed. When trilling, the young generally stand upright and shake all over. Eyes open 29 to 34 days after birth. Running and other movements improve a great deal after the eyes have opened. The young are weaned 7 weeks after birth. The young first emerge from their burrows between 4 and 5 weeks of age. Adult size is attained approximately 217 days after birth. Males reach sexual maturity during their first year. Females are sexually mature at about 10-11 months of age. The vagina does not open until the female is in heat. (Neal 1965), (Best et al. 1990)

Average birth mass: 3.8 g.

Average gestation period: 30 days.

Average number of offspring: 6.8.

Average age at sexual or reproductive maturity (female)

Sex: female: 319 days.

In Arizona, breeds mostly in February or early March, also as early as December-January. Gestation probably lasts about 30 days. Litter size averages 6-7. Young fully haired at 3-4 weeks, first emerge from burrows at 4-5 weeks, weaned by 7 weeks. In southern Arizona, young were first observed in May; half-grown young observed in Sonora in late March. Apparently one litter per year, possibly sometimes two. Females sexually mature in spring following their birth.

In some parts of its range, the Harris antelope squirrel is losing habitat to agriculture and other human developments. It is considered threatened in the state of California. (Nowak 1991)

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Conservation Actions

Harris antelope squirrels can be a nuisance in irrigated areas because they raid crops and burrow through ditch banks. Some ground squirrels are suspected to be reservoirs of bubonic plague. (Nowak 1991)