|The Mammals of Texas -
Thirteen-lined Ground Squirrel
Rodentia : Family Sciuridae : Spermophilus
Description. A small ground squirrel with
usually 13 alternating dark and light stripes, the dark
ones containing a series of squarish buffy spots, the
light stripes occasionally broken into spots; dark dorsal
stripes dark brown or black in color, the light stripes
continuous and buffy white; underside of tail russet at
base, shading to orange buff toward tip; lower sides
cinnamon buff; belly pinkish buff; chin white; ear small.
External measurements average: total length, 285 mm;
tail, 105 mm; hind foot, 40 mm. Weight of males averages
154 g (up to 212 g); females, 160 g (to 220 g).
Distribution in Texas. Known from
northern Texas and in a corridor extending from Tarrant
and Dallas counties in north-central Texas south to
Atascosa, Bee, and Calhoun counties along the Gulf Coast.
Habits. These squirrels are
typically inhabitants of short-grass prairies, but they
have invaded the tall-grass areas in Texas where they
live principally in pastures and along fencerows. They
live in burrows in the ground from which radiate
well-marked paths to the feeding grounds. In tall grass
the paths may become tunnels. In cultivated areas they
seem to prefer fence-rows and excavate their burrows near
fence posts. Occasionally, they usurp abandoned burrows
of pocket gophers or even those of prairie dogs. Their
own burrows are about 5 cm in diameter, have two or three
openings, descend to a depth of 10-115 cm, and may be 7 m
or more in length.
These squirrels are strictly diurnal
but their annual cycle of activity includes a very long
period of hibernation. In Texas, studies conducted by
Howard McCarley revealed that the period of hibernation
lasts about 240 days. Adults enter hibernation in July
and young-of-the-year in August or September. They emerge
from the middle of February to the first of March in the
Texas Panhandle. In southern Texas they have been
observed above ground as late as October 27 and as early
Their food is chiefly green grasses and
herbs in early spring but seeds, flower heads, and
insects contribute importantly to their diet as the
season advances. Grasshoppers are often conspicuous items
in their stomach contents, and often more than half of
the stomach contents consists of insects, including
grasshoppers, crickets, caterpillars, beetles, ants, and
insect eggs. They also eat mice and have been reported
capturing and eating small chickens. Quantities of dry
seeds stored in underground caches probably serve to
carry the squirrels through the period of scarcity
shortly after they emerge in the spring.
Mating activities begin about 2 weeks
after squirrels emerge from hibernation. The males are
sexually active for only 2-3 months which of necessity
restricts the length of the breeding season. Normally
only one litter is produced annually, but one study found
about 25% of the females observed in a marked population
produced two litters. The gestation period is 27-28 days.
The young vary in number from two to 13; the yearling
females produce the smallest litters. The young are
blind, hairless, and toothless at birth and weigh from 3
to 4 g each. By the eighth day they are dark dorsally; on
the 12th the stripes begin to appear and hair sparsely
covers the back; on the 26th their eyes begin to open.
The female then begins to wean them and at the age of 6
weeks they are entirely dependent upon their own
resources. They mature sexually at about 9 or 10 months
Where concentrated in pastures and
farming areas these squirrels may cause serious loss of
forage and crops, but their fondness for insects partly
offsets any damage they may do. On rangelands they
usually do no serious damage.
Photo courtesy of U.S. Fish and Wildlife Service.