Squirrels of the World

Ictidomys parvidens 269

general references: Cothran 1983; Cothran and Hon-
eycutt 1984; Martinez et al. 1999; Millán-Peña 1998; Schwanz
2006; Valdez and Ceballos 1991, 2003; Young and Jones 1982.

Ictidomys parvidens (Erxleben, 1777)

Rio Grande Ground Squirrel

description: Rio Grande ground squirrels have an oliva-
ceous gray to light brown dorsum, with nine rows of white
to buff spots from the back of the head to the rump. The
snout and the chin are yellowish to ochre to cinnamon.
The white to pale buff eye ring is conspicuous. The sides
and venter are white to pale buff. The tail is grizzled black,
suff used and frosted with the coloration of the venter.

size: Female—TL 216–303 mm; T 80–124 mm; Mass 90–
152 g.
Male—TL 243–325 mm; T 80–130 mm; Mass 100–210 g.

distribution: The Rio Grande ground squirrel is found
in southern New Mexico and western Texas (USA) to Coa-
huila, Nuevo León, Tamaulipas, Durango, and Zacatecas
(México).

geographic variation: None.

conservation: IUCN status—not listed. Population
trend—stable. I. parvidens is not ranked by IUCN, because it

has only recently been recognized as a distinct species, dif-

ferent from its sister taxon, I. mexicanus. Mexican ground

squirrels are listed as a species of least concern.

habitat: Rio Grande ground squirrels inhabit grassy habi-

tats and grassy shrublands in arid regions. They can also be

found in human-maintained grassy habitats, such as ceme-

teries and golf courses.

natural history: This species is diurnal. In mild cli-

mates, Rio Grande ground squirrels may be active for much

of the winter; however, most hibernate in burrows for about

seven months, beginning in late July through September.

All males immerge by late August, whereas females may

stay aboveground until the fall. Juveniles enter hibernation

in September and October. Males emerge fi rst in March and

feed ravenously to increase their body mass, in apparent

preparation for mating opportunities with females that

emerge two to four weeks later. The mating season can be

delayed upon emergence and is prolonged (30–71 days) dur-

ing March and April. After a gestation of 28–30 days, a litter

of 2–10 young (average = 5–6) is born in the burrow; they

emerge 30–54 days later, in late May–August. The young are

weaned by August. Numerous short burrows are used for

temporary or escape cover. Burrows for maternity and hiber-

nation are as deep as 1.5 m and are more convoluted, with a

nest chamber and sometimes multiple openings. This spe-

cies is colonial in good habitat but relatively asocial, al-

though tolerant of home range overlap. The Rio Grande

ground squirrels traverse relatively small areas, generally

less than 90 m in diameter.

Ictidomys parvidens. Photo courtesy Troy L. Best.