362 Urocitellus richardsoniiUrocitellus richardsonii (Sabine, 1822)
Richardson’s Ground Squirrel
description: Richardson’s ground squirrels have a fuscous
cinnamon to gray buff dorsum. The head and the neck are
ochraceous to cinnamon buff. The eye ring is white to buff.
The snout is often light gray. The lower sides and the venter
can be clay to buff to cinnamon. The tail is grizzled charcoa l
to black on the top and cinnamon buff to clay below.
size: Female—TL 291 mm (264–318 mm); T 70 mm (55–82
mm); Mass 120–590 g.
Male—TL 307 mm (283–337 mm); T 75 mm (65–88 mm);
Mass 290–745 g.
distribution: This species is found in the northern Great
Plains: in southern Alberta, southern Saskatchewan, and
southern Manitoba (Canada) south to Montana, North Da-
kota, northeastern South Dakota, western Minnesota, and
extreme northwestern Iowa (USA).
geographic variation: None.
conservation: IUCN status—least concern. Population
trend—stable.
habitat: U. richardsonii inhabits grasslands, pastures, fi elds,
and croplands.natural history: Richardson’s ground squirrels are diur-
nal, and they hibernate in burrows for six to eight months.
Adult males immerge in June, followed by adult females
soon after; juvenile females enter hibernation in August,
whereas juvenile males remain aboveground and reach
adult size as late as October. Emergence begins in March or
April, with adult males appearing aboveground fi rst, and
adult females about two to three weeks later. Mating occurs
three to fi ve days after the emergence of the females. Male-
male competition is intense during the two- to three-week
breeding season, and many males die as a result of injuries
and lost fat reserves. Females mate with several males, and
a copulatory plug forms after each mating. After a gestation
of 22–23 days, a litter of 3–11 is born within a grass-lined
nest chamber in the burrow. The young emerge from the
natal burrow at 28–30 days of age, are weaned within one to
two weeks afterward, and are sexually mature at 1 year.
Males disperse from their natal area during their fi rst year
of life; females remain in or near their natal area. Related
females within these kin clusters treat each other amicably,
but they chase unrelated individuals. Individuals hibernate
alone, but they may do so in the same burrow system. Bur-
rows consist of extensive networks of passages and en-
trances, with multiple chambers that extend to a depth of 1
m. Males will store seeds within the nest chamber to use in
preparation for the next spring’s mating season. The rigors
of the mating season result in male lifespans that rarely ex-
ceed 2 years, whereas females live up to 6 years. Principal
predators of this species are mustelids, canids, raptors, and
snakes. The alarm calls of U. richardsonii are a long shrill
burst that elicits vigilance for terrestrial predators, and a
short “chirp” that causes the animals to escape to cover inUrocitellus richardsonii. Photo courtesy Takeo Kawamichi.