Animal Diversity Web

Ge­o­graphic Range

Sper­mophilus ar­ma­tus are found only in a small area of the United States. Their range in­cludes south­west­ern Mon­tana, west­ern Wyoming, south­east­ern Idaho and north­ern cen­tral Utah.

(Whitaker 1996)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Sper­mophilus ar­ma­tus are found in the sage­grass moun­tain mead­ows of the west­ern United States. Here they bur­row in the soft soils. They can be found near tim­ber­line, in val­ley pas­tures, cul­ti­vated fields or along ir­ri­ga­tion ditches. They are also some­times found in lawns. They pre­fer moist habi­tats with lush veg­e­ta­tion and/or aquatic plants.

(Whitaker 1996, Mac­Clin­tock 1970)

• Terrestrial Biomes
• savanna or grassland

Phys­i­cal De­scrip­tion

Sper­mophilus ar­ma­tus are fairly large ground squir­rels with a body length of 280-303 mm and tail length 63 to 81 mm. Skull length is 46 to 48 mm. The Uinta ground squir­rels, as they are com­monly named, have mixed, brown-buff col­ored coats. Their sides are slightly paler and their un­der­bel­lies are pale buff to white. Their tails are black mixed with buff on top and bot­tom, with paler buff col­ored edges. The noses, ears and faces are more cin­na­mon col­ored. The ears are small and rounded with short fur.

(Whitaker 1996, Hall 1981)

• Other Physical Features
• endothermic
• bilateral symmetry

• Range mass

  284 to 425 g

  10.01 to 14.98 oz

Re­pro­duc­tion

The breed­ing sea­son be­gins im­me­di­ately after the end of hi­ber­na­tion in March or April. Dur­ing this sea­son males at­tract fe­males with calls and scent mark­ings. Scents are laid down by wip­ing their faces, which have apro­crine scent glands, against the ground. Breed­ing is also in part de­pen­dent on the so­cial rank of in­di­vid­u­als within the colony.

Fe­males give birth to one lit­ter per year usu­ally some­time in May. Ges­ta­tion length is 28 days. Young first emerge from bur­row, 24 days after birth. After this fe­male parental in­vest­ment is min­i­mal. First-year fe­males bear, on av­er­age, 4 to 5 yong per lit­ter, whereas older moth­ers bear 7 to 8 on av­er­age.

(Whitaker 1996, Balph 1984)

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual

Be­hav­ior

Sper­mophilus ar­ma­tus are bur­row­ers. In the win­ter these squir­rels hi­ber­nate, and in the sum­mer they aes­ti­vate (that is be­come dor­mant for the sum­mer). Adults begin aes­ti­va­tion in July whereas ju­ve­niles do not go into aes­ti­va­tion until later. By Sep­tem­ber the Uinta ground squir­rels can no longer be seen above ground. From aes­ti­va­tion they go di­rectly into the long pe­riod of hi­ber­na­tion, where they will re­main until March or April. This means that in­di­vid­u­als only re­main ac­tive above ground about three to three and a half months out of the year.

Pop­u­la­tion den­sity is high for ground squir­rels, around 23-28 in­di­vid­u­als per square hectare. S. ar­ma­tus live in ma­tri­lin­eal colonies. Males dis­perse as ju­ve­niles to other colonies. In­di­vid­u­als are ter­ri­to­r­ial though home ranges do over­lap. Fe­males es­pe­cially be­come ter­ri­to­r­ial and ag­gres­sive dur­ing preg­nancy. Males are quite ag­gres­sive dur­ing the breed­ing sea­son. Ag­gres­sion is in­di­cated by fights and warn­ing "chirps." "Chirps" are also used as mat­ing calls and as warn­ings to the colony of avian preda­tors. (Balph, 1984; Nowak, 1999; Whitaker, 1996)

• Key Behaviors
• fossorial
• diurnal
• motile
• sedentary
• hibernation
• aestivation
• social
• colonial
• dominance hierarchies

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

Sper­mophilus ar­ma­tus eat seeds, green veg­e­ta­tion, in­ver­te­brates and some ver­te­brates. They are often found near water, as they pre­fer suc­cu­lent plants. They are strong swim­mers and swim to re­trieve species of aquatic plants. Uinta ground squir­rels col­lect food for their pe­ri­ods of hi­ber­na­tion, dur­ing which they rely mostly on fat stores and some seeds stock­piled in their bur­rows. (Nowak, et al., 1987; Whitaker, 1996)

• Primary Diet
• herbivore
  • folivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

• Plant Foods
• seeds, grains, and nuts

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Like other ground squir­rels, Sper­mophilus ar­ma­tus can be de­struc­tive to crops, eat­ing veg­eta­bles and har­vest­ing seeds. Their win­ter stores of food con­sist al­most en­tirely of seeds, in­clud­ing a sig­nif­i­cant amount dug up from farm­ers' plant­i­ngs. (Nowak, et al., 1987)

Con­ser­va­tion Sta­tus

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Ali­cia LaValle (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Balph, D. 1984. Spa­tial and So­cial Be­hav­ior in a Pop­u­la­tion of Uinta Ground Squir­rels: In­ter­re­la­tion with Cli­mate and An­nual Cycle. Pp. 336-349 in J Murie, G Mich­ener, eds. The Bi­ol­ogy of Ground-Dwelling Squir­rels. United States of Amer­ica: Uni­ver­sity of Ne­braska Press.

CITES Sec­re­tariat, Oc­to­ber 12, 1999. "CITES" (On-line). Ac­cessed De­cem­ber 12, 1999 at http://​www.​wcmc.​org.​uk/​CITES/​eng/​index.​shtml.

Hall, R. 1981. The Mam­mals of North Amer­ica. New York: John Wiley and Sons.

Mac­Clin­tock, D. Squir­rels of North Amer­ica. New York: Van Nos­trand Rein­hold Co..

Nowak, R., H. Camp­bell, J. Chap­mann, A. Gard­ner, V. Geist. 1987. Wild An­i­mals of North Amer­ica. Wash­ing­ton D.C: The Na­tional Ge­o­graphic So­ci­ety.

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

Whitaker, J. 1996. Na­tional Audubon So­ci­ety Field Guide to North Amer­i­can Mam­mals. New York: Al­fred A. Knopt Inc..