The white-tailed antelope squirrel (''Ammospermophilus leucurus'') is a diurnal species 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 ...

, scientifically classified in the order

Rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

ia and family

Sciuridae Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...

, found in

arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

regions of the

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

and the Baja California Peninsula of northwestern Mexico.

Distribution

The white-tailed antelope squirrel's geographical range extends north to south from southwestern Oregon to New Mexico, and east to west from western Colorado to Baja California, Mexico.Hall, E. R. 1946. Mammals of Nevada. University of California Press, Berkeley, 710 pp. Ammospermophilus leucurus - 1a

Home range and population density

This species of squirrel has an average

home range A home range is the area in which an animal lives and moves on a periodic basis. It is related to the concept of an animal's territory which is the area that is actively defended. The concept of a home range was introduced by W. H. Burt in 1943. ...

of , and utilizes approximately in its daily activities. Throughout much of the squirrel's range, especially in Utah, the population density fluctuates greatly, with periods of high density followed by periods of low density. Average population density also varies by season, with higher density in autumn relative to late spring.

Ecology

The white-tailed antelope squirrel is commonly spotted in arid habitats throughout the southwestern United States. Throughout this range, ''Ammospermophilus leucurus'' is omnivorous, feeding primarily on foliage (10%-60% of its diet), seeds (20%-50%), arthropods, and to a lesser extent, vertebrates (mainly lizards and rodents; predatory behavior by ground squirrels has been noted). In conjunction with being a predator, the white-tailed antelope squirrel is also prey to many larger animals, including raptors, various canids, and

snakes Snakes are elongated Limbless vertebrate, limbless reptiles of the suborder Serpentes (). Cladistically Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales much like other members of ...

. These squirrels are not only preyed upon by large predators, but they also fall victim to many diverse

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...

. These include various ticks, fleas, mites, lice, and a couple species of parasitic larvae. The Baby Chipmunk and the Carrot

Behavior

Antelope squirrels are active most during the cooler parts of the daylight hours, avoiding midday as much as possible. Although these animals live in hot and arid climates, the white-tailed antelope squirrel is diurnal, meaning heat gain from metabolic activity could be a problem. However, compared to direct exposure of heat from the sun, metabolic heat gain contributes little to the overheating of this species. This diurnal activity pattern may be attributed to predation patterns. Selective pressures may have led to this species avoiding nighttime activity due to increased predation by nighttime predators. This behavior is controlled by the squirrels' natural circadian rhythms, and research has shown these rhythms to be highly important in keeping these diurnal activity patterns intact.

Reproduction

Timing

White-tailed antelope squirrels' reproductive receptiveness in females and reproductive capability in males peaks in early spring. It only takes the squirrels one year to become sexually mature and begin reproducing; typically, antelope ground squirrels will produce one large litter per year.

Geographical variation

Geographical factors, and thus environmental factors, weigh heavily on ''Ammospermophilus leucurus reproductive cycle length and average litter size. Specifically, this variation is seen best when comparing the northern and southern extents of the antelope ground squirrels' distribution. In Oregon, which is the northernmost extent of the squirrels' range, reproductive cycles are relatively short, and the average litter size is 9.3. However, in Baja California, the southernmost extent of the squirrels' range, reproductive cycles last half of the year, and the average litter size is 5.9.

References

External links

{{Taxonbar, from=Q748208 Fauna of the Baja California Peninsula Fauna of the Southwestern United States Fauna of the Great Basin Fauna of the Colorado Desert Fauna of the Mojave Desert Fauna of Gulf of California islands Mammals described in 1889 Ammospermophilus Taxa named by Clinton Hart Merriam