368 Xerospermophilus perotensishabitat: Perote ground squirrels live in hig h-elevat ion a rid
plains, open scrub, and rocky slopes, at elevations from
2200 to 2700 m.
natural history: This squirrel is diurnal. Perote ground
squirrels hibernate in burrows for a relatively short three
to four months each year, with individuals active for about
nine months (from March to November). Adult males
emerge before adult females and yearlings. Mating occurs
in April and May, and pregnant females are found in the
population from June to August. A litter of three to fi ve is
born in a burrow and begins emerging in mid-July. Most
adults have initiated hibernation by late September or
early October; juveniles may remain aboveground until
November. Their principal predators probably include
long-tailed weasels (Mustela frenata) and domestic dogs. Pe-
rote squirrels are not hunted or trapped. The major threats
to conservation of this species are habitat loss and frag-
mentation, due to the encroachment of agriculture and
grazing; however, X. perotensis does not frequent agricul-
tural fi elds. Only 30 percent of their potential habitat re-
mains untransformed. Perote ground squirrels in many
areas (82% of known localities) only remain in small frag-
ments along railways.general references: Best and Ceballos 1995; Sánchez-
Cordero et al. 2005; Valdez and Ceballos 1997, 2003.Xerospermophilus spilosoma
(Bennett, 1833)
Spotted Ground Squirreldescription: X. spilosoma have a gray to brown to cinna-
mon to reddish dorsum, with scattered small white to buff
spots of variable intensity. Spotted ground squirrels exhibit
considerable color variation, especially in their dorsal pel-
age. The venter is whitish to buff to cinnamon or pinkish
buff. The tail resembles the dorsum, but with fuscous black
toward the tip and a cinnamon core on the underside.size: Both sexes—TL 185–253 mm; T 55–92 mm; Mass 100–
200 g.distribution: X. spilosoma is found from southwestern
South Dakota south to southern Texas and west to Arizona
(USA), and from northcentral to central México.geographic variation: Thirteen subspecies are recog-
nized.X. s. spilosoma—Durango (México). See description above.
Xerospermophilus perotensis. Photo courtesy Juan Cruzado. X. s. altiplanensis—high plains of westcentral Chihuahua