Antelope squirrels or antelope ground squirrels of the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

''Ammospermophilus'' are sciurids found in the desert and dry scrub areas of the southwestern United States and northern Mexico. They are a type of

ground squirrel Ground squirrels are rodents of the squirrel family (Sciuridae) that generally live on the ground or in burrows, rather than in trees like the tree squirrels. The term is most often used for the medium-sized ground squirrels, as the larger ones ar ...

and are able to resist

hyperthermia Hyperthermia, also known as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme te ...

and can survive body temperatures over .

Common characteristics

All the antelope squirrels share a common white stripe along the lateral sides from the shoulder to the hip similar to chipmunks. However, unlike chipmunks, these characteristic white stripes do not extend onto the head of the animals. The tails of antelope squirrels are often arched forward over their back. In the United States, these ground squirrels are found in the dry, desert like regions of the southwest. The different members of the genus ''Ammospermophilus'' have unique adaptations that allow them to overcome the extreme heat of the day and the low temperatures of the night. All antelope squirrels burrow into the ground for shelter, however not all are social creatures. Each antelope squirrel has a white ventral surface with little variation.

Species

The four unique species of the genus ''Ammospermophilus'' can be distinguished by some variations in size, weight, and appearance. There are currently five recognized

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

: All are somewhat similar in appearance and behavior. They are around in head-and-body length with a tail, and weigh . The tail is somewhat flattened. They have a single white stripe on both flanks and none on the face. They live in burrows, which they dig for themselves. They are diurnal, and do not

hibernate Hibernation is a state of minimal activity and metabolic reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is most ...

(though they become less active during the winter), so they are fairly easily seen.

Reproduction

The typical life span of a wild antelope squirrel is 2–4 years; although, in captivity they have been known to survive 11 years. Males and females are sexually mature by the end of their first year. The reproductive season last from February to March with typically one litter per year. Each litter contains between 5-14 young that will wean around 8 weeks and make their first appearance above ground. All antelope squirrels give birth to and nurse their young in burrows. However, they do vary in the way they dig the burrows. For example, the white-tailed squirrel digs shallow burrows under brush or will use the abandoned burrows of kangaroo rats. These squirrels are not monogamous and have been known to mate with multiple partners each breeding season.

Habitat

Antelope squirrels are commonly found in dry, shrubby areas of the southern United States into Mexico. These areas are sandy with rocky areas that provide soil that can be burrowed into for shelter and to escape the heat of the day. The temperatures in these regions can exceed during the day and require special adaptations by the ground squirrels to survive. During the night, temperatures in these desert and dry areas may dip below freezing which again requires adaptations to survive. There is very limited free-standing water supply. These regions can experience long bouts of drought. ''A. harrisii'' does not require surface water within its range but will drink on occasion from basins and bird-baths.

Diet

Ground Squirrels are important dispersers of seeds in the dry, shrubby deserts they live in. They participate in a behavior known as caching where seeds, fruits and vegetation are stored in burrows or hidden spots for consumption at a later time. The ground squirrels are omnivores and will feed on arthropods, insects, and carrion when these food sources are available. Their diets often rotate between green vegetation, fruits and seeds based on availability and season. All Antelope Squirrels carry their food in their cheek pouches for transport.

Behavior

''A. leucurus'' have larger feet than other antelope squirrels, which allow them to quickly evade and escape predators. They remain cool during the hot desert days by retreating to their burrows and limiting the majority of activity to the early morning and late evening hours. Some white-tailed squirrels have been known to sound shrill alarm calls when predators are nearby to warn relatives of incoming danger. ''A. nelsoni'' are able to function in temperatures up to and do not hibernate, however, they will lower their core temperature to within a few degrees of the ambient temperature of a burrow. Likewise, they will lower their activity level when food is scarce to preserve energy. ''A. interpres'' live in very hot, arid climates and so have adapted to laying flat (to maximize heat distribution) in a shaded spot against the cool ground. This allows for the Texas squirrel to be active during the hottest part of the day when most predators are inactive. ''A. harrisii'' are the only antelope squirrels who dig their own burrows instead of re-purposing burrows of other animals. They cool down by salivation and holding their tails above their heads to provide shade. They also flatten themselves on the ground to cool. During times of cold, they utilize cached seeds but also continue to forage.Pawnation: Antelope Ground Squirrel Adaptations
" accessed 5 January 2015.