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Harris's antelope squirrel
Head and body length is 137-168mm and tail length is 55-95mm. There
are no differences in external measurements between the sexes.
Harris antelope squirrels have long necks and slender bodies. The
tail is short and the ears are small. The body hair is mouse gray in
the winter and paler during the summer. Dorsal hairs are short and
somewhat coarse, but lay smoothly, giving the animal a glossy
appearance. Hairs on the undersurface are coarse and rigid. Winter
pelage is longer and softer than summer pelage. There is one white
stripe along both sides of the body from shoulder to rump. The
undersurface of the tail is mixed black and white. A white ring
encircles each eye, giving the Harris antelope squirrel a spectacled
appearance. The soles of the feet are heavily haired. The Harris
antelope squirrel carries its tail arched over its back.
Reproduction
Although mating can take place from December or January until June,
peak reproductive activity occurs from February-March. A vaginal
plug is formed after copulation. In females, the beginning of the
breeding season is marked by a swelling of the labia, enlargement of
the uterus, and opening of the vaginal orifice. In males,
spermatogenesis may begin as early as November and lasts until June.
The testes regress in size in June and July to less than 10% of the
February and March mass. Gestation lasts for about 30 days, and the
litter size may range from 5-14. The average litter size is 6.5.
Females give birth to only one litter per year. Newborns are naked
and the skin is pink and somewhat transparent. The young cannot
crawl, and their eyes and ears are closed. After 1 week, the dorsal
sides of the head and back are covered with black pigmentation. At 2
weeks, 2 pale stripes appear on the back. These stripes are covered
with white hairs in the adult. At 3 weeks, the claws are
well-developed and the lower incisors have erupted. At this age, the
young still cannot walk without falling over. Between 3 and 4 weeks,
the ears open and the young are fully covered with hair. The upper
incisors begin to erupt after 4 weeks. At this age, the young are
very vocal and frequently utter a trilling noise when disturbed.
When trilling, the young generally stand upright and shake all over.
Eyes open 29 to 34 days after birth. Running and other movements
improve a great deal after the eyes have opened. The young are
weaned 7 weeks after birth. The young first emerge from their
burrows between 4 and 5 weeks of age. Adult size is attained
approximately 217 days after birth. Males reach sexual maturity
during their first year. Females are sexually mature at about 10-11
months of age. The vagina does not open until the female is in heat.
Behavior
Harris antelope squirrels are diurnal. They have special adaptations
that allow them to be active even during the hottest hours of the
day. For example, they maintain their body temperature at a level
higher than that of any other nonsweating mammal (97-107 degrees F),
and they cool themselves through salivation. They are easily seen
scampering over rocky slopes in arid canyons and scurrying through
the bushy growth on broad, sandy plains. They do not hibernate.
Therefore, they store little body fat, and have little fluctuation
in body weight throughout the year. They are active above the ground
during each month of the year, except in the higher and colder parts
of their range. In these areas, they become inactive during the
winter, but they do not truly hibernate. Their ability to store food
allows for this winter inactivity. They are true ground squirrels,
living in burrows that they dig themselves. They have several
burrows within their home range of about 6 ha. One or more of these
burrows contains a nest, and the others are for retreat or escape.
The burrow is usually under a desert shrub, but is sometimes found
in the open. The centers of habitation are near rock-bound hills,
where safe shelters are easy to find. Harris antelope squirrels are
vigorous runners, with sharply delineated periods of activity and
rest. They run about the desert floor, stopping frequently to dig
things up from the ground. The antelope squirrel commonly sits
perfectly erect upon its hind feet. When disturbed, it runs with its
tail straight up in the air and utters chipperings as it hurries to
a nearby burrow. Before entering the burrow, it often stops, calls,
and stamps its forepaws. The alarm call is a trill that does not
change with sex, temperature, or season.
Harris antelope squirrels are never found abundantly. They are
solitary animals that come together for mating.
The Harris antelope squirrel has two molts during the year. The
spring molt occurs in May or June and the winter molt takes place in
October. Winter pelage is longer and softer than summer pelage,
which consists of coarse, closely spaced hairs. Juveniles first
appear above ground in summer pelage.
Food Habits
The Harris antelope squirrel is omnivorous. It feeds on seeds,
fruit, plant stems and roots, some insects, and carrion. It has
cheek pouches of considerable capacity. Suitable food supplies are
carried in the cheek pouches and stored in burrows, under rocks, or
in some other shelter.
In captivity they should be offered a complete diet of lab blocks, and rat or mouse
mix, with bits of fruit or veggies regularly. Cheerios or wheat
bread are great treats, in small quantities. Do NOT feed chocolate,
fried foods, salted foods, candy or junk food! They may enjoy
crickets and mealworms if they are captive bred, never feed wild
insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium
during nursing and growth due to demands on their systems at those
times, but take care not to overdo it. Water bottles should be used
to proved constant, clean water. Ceramic or stoneware food dishes
work well for keeping seeds or fresh foods off the floor, and a wire
mesh hopper that allows them to eat the lab blocks through without
extra waste.
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