Urocitellus mollis 359U. elegans is diurnal, and its activity is bimodal, with
peaks occurring in midmorning and evening. Vocalizations
include a combination of fi ve sounds but consist primarily
of two major calls: short and long “chirps.” The structure
and frequency of its vocalizations are distinguishable from
those of U. richardsonii, and hybrids between the two species
produce calls that are intermediate between those of their
parents. Males usually emerge a week before females.
Within fi ve days of emergence, females enter estrus for no
more than 24 hours. Litter sizes in the wild average 5.9,
which is relatively high for their adult body size. The young
emerge from the burrow 4–5 weeks after birth. U. elegans is
relatively asocial. Wyoming ground squirrels live in a col-
ony but reside individually in a burrow. Their social struc-
ture consists primarily of clusters of related females and ju-
veniles, usually organized in family units. Males disperse
after weaning. Agonistic behavior is relatively common and
limited primarily to the reproductive period. Adults hiber-
nate fi rst (in late July), whereas juveniles tend to enter hiber-
nation as late as September. The heaviest individuals—often
adult males—emerge fi rst, usually by early April. Although
laboratory studies suggest that food consumption, fat depo-
sition, and hibernation are controlled by endogenous fac-
tors, hibernation is also infl uenced by temperature and pho-
toperiod. Predators of Wyoming ground squirrels include a
minimum of eight species of mammalian carnivores and
two species of raptors—Goshawks (Accipiter gentiles) and
Red-Tailed Hawks (Buteo jamaicensis)—with ground preda-
tors exerting a particularly signifi cant eff ect on the survival
of U. elegans. At least four fl ea species and three tick species
are reported from Wyoming ground squirrels. Endopara-
sites include at least six coccidians (Eimeria), with patterns
of prevalence nearly the same as those for U. richardsonii. U.
elegans is aff ected by sylvatic (bubonic) plague, which can
cause severe mortality in its populations, as well as Colo-
rado tick-fever virus, to which this ground squirrel is re-
ported to develop some resistance. Because of its potential
threat to humans, livestock, and even agricultural crops, U.
elegans has been targeted for intensive removal eff orts.
general references: Seville and Stanton 1993; Yensen,
Mabee, et al. 2008; Zegers 1984.
Urocitellus mollis (Kennicott, 1863)
Piute Ground Squirrel
description: Piute ground squirrels have a uniform pale
smoke gray dorsum suff used with pinkish buff. The cheeks
and the hind limbs are washed with red to rust. The venter is
white to cream, washed with pinkish buff. The tail is grizzled
smoke gray above, with a cinnamon cast to the underside.
This species was formerly considered part of U. townsendii,
but it diff ers in having a chromosome count of 2n = 36.size: Female—Mass 121 g (82–164 g).
Male—Mass 154 g (107–205 g).
Both sexes—HB 213 mm (201–233 mm); T 52 mm (44–
61 mm).distribution: This species is found in the southeast cor-
ner of Oregon and the Snake River Valley (Idaho), south-
ward through extreme eastcentral California, Nevada, and
western Utah (USA).geographic variation: Three subspecies are recognized.U. m. mollis—California, Oregon, southern Idaho, Utah, and
Nevada portions of the species’ range (USA). It is inter-
mediate in size among the three subspecies.
U. m. artemesiae—Snake River plain, north of the Snake River
in central Idaho (USA). This is a small subspecies.
U. m. idahoensis—westcentral Idaho, northeast of the Snake
River (USA). This form is larger, and the pelage tends to
be more dappled. The tail is longer, broader, and darker.conservation: IUCN status—least concern. Population
trend—no information.