Animal Diversity Web

Ge­o­graphic Range

White-tailed an­te­lope squir­rels are found in north­west­ern New Mex­ico, west­ern Col­orado, south­east­ern Ore­gon, north­ern Ari­zona, south­west­ern Idaho, Utah, south­ern Nevada, south­ern Cal­i­for­nia, and as far south as the south­ern Baja Cal­i­for­nia penin­sula. Of all Am­mo­sper­mophilus, white-tailed an­te­lope squir­rels are the most wide­spread in North Amer­ica; their gen­eral range is the Great Basin to Baja Cal­i­for­nia.

(Belk and Smith, 1991; Tomich, 1982)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

White-tailed an­te­lope squir­rels live in deserts and foothills. These areas are sandy, grav­elly or rocky, pro­vided the soil can be bur­rowed in to es­cape from ex­treme heat and preda­tors. Am­mo­sper­mophilus leu­cu­rus will use bur­rows of other ro­dents, such as kan­ga­roo rats, for shel­ter and will make nu­mer­ous bur­rows of its own within its home range. Com­mon habi­tats in­clude desert suc­cu­lent shrub, ri­par­ian, and wash areas. Am­mo­sper­mophilus leu­cu­rus also oc­curs in chap­ar­ral and grass­land.

(John­son and Har­ris, 2001; Belk and Smith, 1991)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• desert or dune
• chaparral

Phys­i­cal De­scrip­tion

Am­mo­sper­mophilus leu­cu­rus ap­pear quite sim­i­lar to other an­te­lope ground squir­rels. They have slightly longer legs and small, rounded ears. White-tailed an­te­lope squir­rels are whitish on their ven­tral sur­face. Their backs are brown to gray in color with two white stripes from the shoul­der to the hind end. The outer sur­faces of all legs are some­what more red­dish in color. The un­der­side of their tails are pure white and they have a sub­ter­mi­nal black band on the tail.

They range in total length from 188 to 239 mm and in tail length from 42 to 87 mm. They weigh from 96 to 117 grams.

The hair of the tail molts in the fall and the rest of the hair molts once in spring and then again in fall. White-tailed an­te­lope squir­rels have cheek pouches that they can carry food in. They also have ten mam­mae, slightly more than other ground squir­rels, which typ­i­cally have four to seven.

(Nowak, 1999; Belk and Smith, 1991; Tomich, 1982)

• Other Physical Features
• endothermic
• bilateral symmetry

• Range mass

  96 to 117 g

  3.38 to 4.12 oz

• Average mass

  105 g

  3.70 oz

• Range length

  188 to 239 mm

  7.40 to 9.41 in

• Average length

  211 mm

  8.31 in

• Average basal metabolic rate

  0.511 W

  AnAge

Re­pro­duc­tion

Males and fe­males are sex­u­ally ma­ture by the end of their first year. The breed­ing sea­son for A. leu­cu­rus is in spring, be­tween Feb­ru­ary and June. Usu­ally fe­males have one lit­ter per year with be­tween five and four­teen ba­bies per lit­ter. Lit­ter size seems to de­pend on the quan­tity of green veg­e­ta­tion avail­able to the mother. The young weigh about three or four grams at birth. Some­times a fe­male will have two lit­ters in one year. Ges­ta­tion time is prob­a­bly be­tween thirty and thirty-five days.

(John­son and Har­ris, 2001; Nowak, 1999; Belk and Smith, 1991)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• viviparous

• Breeding season

  February through June

• Range number of offspring

  5 to 14

• Average number of offspring

  8 or 9

• Average number of offspring

  8

  AnAge

• Range gestation period

  30 to 35 days

• Range weaning age

  65 (low) days

• Average age at sexual or reproductive maturity (female)

  1 years

• Average age at sexual or reproductive maturity (female)
  Sex: female

  365 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  1 years

• Average age at sexual or reproductive maturity (male)
  Sex: male

  365 days

  AnAge

Am­mo­sper­mophilus leu­cu­rus build nests for the young near the cen­ter of the bur­row. Nests are made from dry plant ma­te­ri­als and an­i­mal fur. When the young are born, they are help­less and with­out adult fur; their eyes and ears are closed. Young come out of the bur­row about one or two weeks be­fore wean­ing, at ap­prox­i­mately 2 months of age.

(John­son and Har­ris, 2001; Belk and Smith, 1991)

• Parental Investment
• altricial
• female parental care

Lifes­pan/Longevity

Av­er­age lifes­pan is not known, but one white-tailed an­te­lope squir­rel lived five years and ten months in cap­tiv­ity. The av­er­age lifes­pan for other mem­bers of this genus is typ­i­cally one year.

(Nowak, 1999)

• Average lifespan
  Status: captivity

  5.8 years

  Max Planck Institute for Demographic Research

Be­hav­ior

White-tailed an­te­lope squir­rels are di­ur­nal and ac­tive through­out the year. In order to stay cool, A. leu­cu­rus are most ac­tive in the morn­ing and late af­ter­noon and are not ac­tive dur­ing the hottest part of the day. When they for­age, they will stop in the shade in order to avoid heat from the sun. They will also lay flat in a bur­row with their stom­ach against the cooler ground to cool off. Most of the year they live alone in bur­rows, fe­males oc­cupy bur­rows with their young of the year. In the win­ter, sev­eral in­di­vid­u­als will live to­gether in a bur­row and hud­dle to­gether at night in order to con­serve heat. Am­mo­sper­mophilus leu­cu­rus form dom­i­nance heirar­chies when they en­counter other in­di­vid­u­als, but there is no ev­i­dence of ter­ri­to­ri­al­ity. Home ranges are usu­ally about six hectares.

(John­son and Har­ris, 2001; Nowak, 1999; Belk and Smith, 1991; Tomich, 1982)

• Key Behaviors
• motile
• sedentary
• solitary
• dominance hierarchies

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

Dur­ing the year, dif­fer­ent food sources make up the bulk of the diet. Dur­ing the spring, greens are widely avail­able, so they con­si­tute the bulk of the diet, or ap­prox­i­mately 60%. In the fall, when greens are not read­ily avail­able, they only com­prise about 20% of the diet. Seeds and fruits are the most im­por­tant food source in the fall, mak­ing up about 60% of the diet, and are not as im­por­tant in the spring, mak­ing up about 20% of the diet. In­ver­te­brates, mainly in­sects, make up the rest of their diet dur­ing the year. Com­pared to other an­te­lope squir­rels, A. leu­cu­rus was found to be more car­niv­o­rous. The use of ef­fi­cient kid­neys keeps water loss low, but they must have some suc­cu­lent plants or free water in their diet in order to sur­vive. For­ag­ing by A. leu­cu­rus oc­curs in trees and shrubs or on the ground. White-tailed an­te­lope squir­rels have cheek pouches in which they can store food until they re­turn to their bur­rows, where they will hoard the food, or put it into a cache, as do other squir­rels.

Com­mon foods eaten in­clude: seeds, green veg­e­ta­tion, in­clud­ing grasses, mesquite, aca­cia, yucca, ephedra Mor­mon tea, Joshua tree, evening prim­rose, storks­bill, black­brush and op­un­tia cac­tus, fruits, in­ver­te­brates, car­rion.

(John­son and Har­ris, 2001; Belk and Smith, 1991; Tomich, 1982)

• Primary Diet
• omnivore

• Animal Foods
• carrion
• insects

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit

• Foraging Behavior
• stores or caches food

Pre­da­tion

These an­i­mals are eaten pri­mar­ily by di­ur­nal, desert-dwelling preda­tors, some of which are listed here.

They an­i­mals tend to run away from preda­tors in­stead of seek­ing shel­ter. When they are run­ning away, they very sel­dom look back. This species has slightly longer feet than other an­te­lope squir­rel species, which en­able them to run faster. They can also es­cape into their bur­row if there is an open­ing nearby. (John­son and Har­ris, 2001; Belk and Smith, 1991)

• Known Predators

  • hawks (Accipitridae)
  • owls (Strigiformes)
  • kit foxes (Vulpes velox)
  • bobcats (Lynx rufus)
  • coyotes (Canis latrans)
  • weasels (Mustelinae)
  • snakes (Serpentes)
  • badgers (Taxidea taxus)

Ecosys­tem Roles

White-tailed an­te­lope squir­rels store seeds in food caches, pos­si­bly re­sult­ing in the dis­per­sal and ger­mi­na­tion of seeds.

(Belk and Smith, 1991)

• Ecosystem Impact
• disperses seeds

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

White-tailed an­te­lope squir­rels make good re­search sub­jects be­cause they can be eas­ily stud­ied.

(Nowak, 1999)

• Positive Impacts
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

White-tailed an­te­lope squir­rels can be­come both­er­some to farm­ers. This rarely hap­pens be­cause A. leu­cu­rus lives in deserts where there are very few farms. How­ever, in some areas they oc­ca­sion­ally cause trou­ble by bur­row­ing on farm­land and eat­ing crops.

(Nowak, 1999)

• Negative Impacts
• crop pest

Con­ser­va­tion Sta­tus

These an­i­mals are abun­dant in suit­able habi­tat through­out their range.

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  No special status

• US Federal List

  No special status

• CITES

  No special status

Other Com­ments

There are nine sub­species of A. leu­cu­rus in the United States.

(Tomich, 1982)

Con­trib­u­tors

Jen­nifer Nixon (au­thor), Uni­ver­sity of North­ern Iowa, Jim De­mastes (ed­i­tor), Uni­ver­sity of North­ern Iowa.

Ref­er­ences

Belk, M., H. Smith. April 12, 1991. *Am­mo­sper­mophilus leu­cu­rus*. Mam­malian Species: Spe­cial Pub­li­ca­tion of the Amer­i­can So­ci­ety of Mam­mal­o­gists, 368: 1-8.

John­son, V., J. Har­ris. "Cal­i­for­nia Wildlife Habi­tat Re­la­tion­ships Sys­tem" (On-line). Ac­cessed Oc­to­ber 22, 2001 at http://​www.​dfg.​ca.​gov/​whdab/​cwhr/​M067.​html.

Nowak, R. 1999. Walker's Mam­mals of the World 6th Edi­tion. Bal­ti­more and Lon­don: Johns Hop­kins Uni­ver­sity Press.

Tomich, P. 1982. Ground Squir­rels. Pp. 192-194, 196, 201 in J Chap­man, G Feld­hamer, eds. Wild Mam­mals of North Amer­ica: Bi­ol­ogy, Man­age­ment Eco­nom­ics. Bal­ti­more and Lon­don: Johns Hop­kins Uni­ver­sity Press.