Urocitellus armatus

206.

Uinta Ground Squirrel

Urocitellus armatus

French: Spermophile des Uinta / German: Uinta-Ziesel / Spanish: Ardilla terrestre de Uinta

Taxonomy. Spermophilus armatus Kennicott, 1863,

“In the foothills of the Uinta Mountains, near Fort Bridger, [Uinta Co.], Wyo[ming], [USA].”

This species is monotypic.

Distribution. SE Idaho, SW Montana, W Wyoming, and SC Utah (USA).

Descriptive notes. Head-body mean 223-5 mm (males) and 216-7 mm (females), tail mean 71-8 mm (males) and 69-2 mm (females); weight mean 394-9 g (males) and 347-3 g (females). The Uinta Ground Squirrel is small and has gray-totan dorsum, without visible spots or lines; venter is gray to buff. Tail is modest and brown to black, with pale frosting on edges and gray on its underside. Chromosomal complement is 2n = 34 and FN = 64. Karyotype consists of ten pairs of metacentric autosomes, six pairs of submetacentric autosomes, submetacentric X-chromosome, and acrocentric Y-chromosome.

Habitat. Large open meadows at high elevations near timberline. The Uinta Ground Squirrel can inhabit dry meadows and shrub-steppe communities and can be found in agricultural and rangelands.

Food and Feeding. The Uinta Ground Squirrel is a generalist herbivore, with grasses comprising most of its diet, but seasonal variation is reported. Immediately following emergence, 90% of the diet consists of grass leaves, but this food component later decreases when leaves of forbs and grass seeds are added. Sagebrush (Artemisia, Asteraceae) leaves, earthworms, and roots are also eaten. They will eat insects and scavenge animaltissue; infanticide and cannibalism have been occasionally reported.

Breeding. The Uinta Ground Squirrel inhabits burrows with a vegetation-lined nest chamber in which young are born. Males exhibit territorial behavior soon after emergence and scent-mark by rubbing their cheeks on the ground. Female distribution, however, often causes males to shift territories. Breeding occurs within ¢.30 days of emergence. Aggression between males—fighting, biting, and some vocalizations—is common during breeding season. Females are in estrus for less than one day, usually 2-3 days after emergence from burrows; mating occurs in burrows. Yearling males usually do not mate; yearling females can mate but may experience reproductive failure. The Uinta Ground Squirrel produces only one litter peryear, following a gestation of 23-26 days. Litter sizes are 4-6 young, usually less than initial numbers of embryos. Young are born in the beginning of May and typically emerge c.22 dayslater. After mating, females become aggressive and intolerant until their young are weaned.

Activity patterns. Uinta Ground Squirrels are diurnal. They often arouse from hibernation and emerge from burrows in April. Adult males emerge from burrowsfirst, followed adult females 1-3 weekslater and then yearlings appear. Immergence of adults can begin as early as late July, with juveniles entering hibernacula by the end of August. Movements, Home range and Social organization. Uinta Ground Squirrels live in loose colonies. Densities are high as 28 ind/ha. Vocalizations are involved in agonistic behavior, and alarm calls are used to warn of predators. Ground predators elicit a churr call; aerial predators cause distinctly different chirp call. Body mass is better than age to predictlitter size. Juvenile males disperse from colonies; females typically remain philopatric to their natal burrow.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Population trend of the Uinta Ground Squirrel is unknown. Locally considered to be a pest,it is sometimes removed by shooting, poisoning, or trapping. Sagebrush steppe habitat has been declining due to conversion to grazing and agricultural lands, alternative energy development, and human habitation.

Bibliography. Eshelman & Sonnemann (2000), Hannon et al. (2006), Hethcoat & Chalfoun (2015), Linzey & NatureServe (Hammerson) (2008al), Madan et al. (2001), Mateju & Kratochvil (2013), Oli et al. (2001), Skurski et al. (2013), Thorington et al. (2012).