Squirrels of the World

350 Urocitellus armatus

sult, in U. armatus juvenile survival (about 30%) is observed
to be lower than adult survival (60%), and juvenile survival
is higher when the population density is lowest. During the
fi rst two years, when female body mass is correlated with
age, female survival exceeds that of males, but this pattern
can change in older Uinta ground squirrels. Body mass is
better than age for predicting litter size in this species. Den-
sities have been reported to be as high as 28 yearlings and
adults/ha. Juvenile males regularly disperse from colonies,
whereas females typically reside near their natal burrow.
Raptors, weasels (Mustela), badgers (Taxidea taxus), and coy-
otes (Canus latrans) are reported to prey on Uinta ground
squirrels. U. armatus is host to one species of Tricomonas, at
least one coccidian (Eimeria), fi ve species of fl eas (Neopsylla
inopina, Opisocrostis tuberculatus, Oropsylla idahoensis, Thrassis
pandorae, and T. francisi), and a nematode (Heligmosomoides
polygyrus).

general references: Eshelman and Sonnemann 2000;
Hannon et al. 2006; A. W. Linzey and Hammerson 2008b;
Madan et al. 2001; Oli et al. 2001.

Urocitellus beldingi Merriam, 1888

Belding’s Ground Squirrel

description: U. beldingi is a medium-sized ground squirrel

with a reddish brown dorsum and a cinnamon-colored

belly. The ears and legs are small, compared with other

ground squirrels; and the tail is short, fl at, bushy, and red-

dish below. The tip of the tail has banded tricolor hairs (red,

black, and white). Belding’s ground squirrel is distinguished

from other species of ground squirrels by the reddish ven-

tral surface of its tail and the lack of stripes or spots on its

back. U. beldingi is most closely related to U. armatus.

size: Female—HB 208.6 mm; T 63.1 m; Mass 265.2 g.

Male—HB 204.7 mm; T 64.9 mm; Mass 228.6 g.

Sex not stated—HB 197.5 mm; T 67.3 mm; Mass 287.4 g.

distribution: This species ranges from western Oregon

and southwestern Idaho south to northeastern California,

northern Nevada, and northwestern Utah (USA).

geographic variation: Three subspecies are recognized.

U. b. beldingi—northcentral California and extreme western

Nevada (USA). The reddish brown dorsum is darkest in

this subspecies.

U. b. creber—eastern Oregon, northeastern California, and

Urocitellus armatus. Photo courtesy Christopher M. Milensky.

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