296 Otospermophilus variegatusnatural history: O. variegatus is diurnal. Rock squirrels
hibernate in burrows for one to six months, and they may
remain active throughout the winter in mild weather. Males
emerge fi rst and, unlike many other ground squirrels, are not
yet ready to breed. After two to three weeks, females emerge
and are capable of breeding within about one week. The
breeding season lasts up to two months between March and
July, a prolonged period for ground squirrels. After a gesta-
tion of 30 days, a litter averaging 4.8 (range = 3–8) young is
born in the burrow; females may be able to have two litters
a year in mild climates, but evidence for this is scarce. Lactat-
ing females are known from May until October. The young
emerge at 8 weeks of age and are weaned after two to four
more weeks. Most juveniles grow slowly and do not reach
adult weight until midway through their second year of life.
Burrows are almost always found among rocks, boul-
ders, and trees that can serve as excellent safe locations;
however, rock squirrels have been reported to use arboreal
nests occasionally. Burrows are moderately complex, with a
few openings. The burrows are up to 6 m long and have a
nest chamber at a depth of more than 1.0 m. Rock squirrels
tend to be colonial, with several females in a colony. They
have overlapping home ranges and well-defi ned dominance
relations. Scent-marking is a signifi cant means of communi-
cation. Sociality is moderate (at best), with little interaction
between individuals despite considerable spatial and tempo-
ral overlap between adults. Natal philopatry is female bi-
ased, and all males leave their birthplace. The overlapping
home ranges of females (3.8–4.5 ha) are smaller than those of
males (7.9 ha).
Rock squirrels are primarily herbivorous, eating such
foods as buds, fl owers, nuts, fruits, cacti, tree seeds (acorns,
juniper berries) and cultivated crops (grapes and corn/
maize). However, they also often eat animal matter, such as
insects, earthworms, and small vertebrates. Rock squirrels
are very capable climbers and will forage in trees that are
laden with fruit. Their primary predators are raptors, ca-
nids, felids, and mustelids. O. variegatus has a stereotyped
response to snakes: the squirrels make a rapid approach, fl ag
the tail from side-to-side, and kick soil at the potential pred-
ator. Their alarm calls consist primarily of long and short
whistles that are diffi cult to locate. Rock squirrels typically
are not hunted; however, they are shot and poisoned for
removal in situations where they become pests. No major
conservation threats are known for this common and adapt-
able species.general references: Botello et al. 2007; Groves et al.
1988; Ortega 1987, 1990a, 1990b; Owings et al. 2001; Shriner
and Stacey 1991.Poliocitellus A. H. Howell, 1938
This genus has only one species.
Poliocitellus franklinii (Sabine, 1822)
Franklin’s Ground Squirrel
description: Franklin’s ground squirrel has a grizzled gray
coat with a yellowish wash on the rump and venter. Its tail
is long and bushy, but less so than the similar-sized Richard-
son’s ground squirrel (Urocitellus richardsonii); the Colum-
bian ground squirrel (U. columbianus) is more rusty in color.
With the exception of the yellowish wash in the pelage and
more rounded shoulders, P. franklinii resembles the eastern
gray squirrel (Sciurus carolinensis).
size: Female—HB 237.9 mm; T 128.1 mm; Mass 424.9 g.
Male—HB 232.4 mm; T 127.7 mm; Mass 461.2 g.
Sex not stated—HB 235.0 mm; T 136.0 mm; Mass 607.0 g.
distribution: Franklin’s ground squirrel is found in the
northern Great Plains: in parts of Canada and the north-