Urocitellus beldingi 351northwestern Nevada (USA). The dorsal surface is light-
est in this subspecies.
U. b. oregonus—eastern third of the species’ range. The dor-
sum is buff y gray, with a faint wash of pale brown on the
dorsum and head.
conservation: IUCN status—least concern. Population
trend—stable.
habitat: Belding’s ground squirrel usually is found in
grassy meadows, sagebrush (Artemisia) communities, or a
combination of the two, at relatively high elevations in al-
pine and subalpine zones. It also frequently occupies agri-
cultural fi elds. This species’ preferred habitat includes open
mesic vegetation, often with a nearby water source. U. beld-
ingi appears to be limited by the availability of standing wa-
ter or vegetation with a substantial water content.
natural history: Belding’s ground squirrel is a generalist
herbivore, feeding primarily on grasses and forbs, but it also
consumes seeds later in the season as it prepares for hiber-
nation. The time invested in feeding increases through the
season in this diurnal ground squirrel. Animal matter is
eaten when available. Visual cues are important in foraging,
and the young appear to learn food preferences from their
mothers. Estimates of density vary from 1.2 to 304 animals/
ha, and density appears to be limited by the availability of
hibernacula. Males hibernate alone, and females often do so
in groups. Hibernation lasts longest for adult males; it is es-
timated to be 280 days at higher elevations and shorter at
lower elevations. Males emerge in the early spring and are
sexually active for about a month. Females emerge one to
two weeks after males, become sexually active within fi ve
days, and are collectively receptive for about two weeks.
Yearlings are the fi nal animals to emerge. Although the mat-
ing season lasts a few weeks, individual females are recep-
tive for only up to six hours on a single day.
Copulation occurs aboveground, and multiple paternity
of single litters appears to be common. Gestation lasts be-
tween 23 and 28 days; mean litter sizes (based on embryo
counts) diff er among sites but range between 5.8 and 7.4 for
adults and considerably less (4.8) for yearlings. Growth rates
for the young are similar to those of other species of Sper-
mophilus and Urocitellus. Females and their female kin defend
small territories around the burrow until the young are
weaned. Females are philopatric; juvenile males and re-
cently mated adult males disperse. Natal dispersal, as well as
related behavior that helps these squirrels prepare for dis-
persal, appears to be controlled by body condition (fat con-
tent) and mass, and it may be infl uenced by endogenous
time-keeping cues. Juveniles regularly engage in play behav-
ior, which may improve their motor skills and increase their
reproductive potential later in life. Infanticide is common in
Belding’s ground squirrels. It can result in the deaths of as
many as 30 percent of all juveniles, and it is most commonly
committed by yearling males (for food) and by adult females
soon after moving to a new colony.
Alarm calling is common in this species and most likely
evolved through kin selection. Two types of alarm calls are
produced: a short whistle that appears to be associated with
higher risks and faster predators, which usually causes
neighbors to retreat to their burrows; and a longer trill that
generally results in heightened vigilance. The development
of alarm calls in juveniles depends on their early experience
and is highly plastic. Young Belding’s ground squirrels are
able to discriminate between alarm calls within fi ve days of
emergence, but their responses to such calls are continually
refi ned for the next several weeks. Whistle calls appear to
develop fi rst. Belding’s ground squirrels produce scentsUrocitellus beldingi. Photo courtesy Phil Myers, Animal Diver-
sity Web, animaldiversity.org.