Allactaga tetradactyla
four-toed jerboa

The species Allactaga tetradactyla can be found in northeastern Africa (in the Libyan Desert), Arabian Peninsula, and across southwestern and central Asia.

A. tetradactyla inhabits areas of clay deserts, semi deserts, and coastal salt marshes. It occupies four different kinds of simple burrows: temporary summer day burrows for hiding during the day, temperate summer night burrows for hiding during the night, permanant summer burrows used as a home for producing young, and permanent winter burrows for hibernation (Macdonald, 1984). Most of these burrows are only 60-150 cm deep. All burrows have side tunnels erupting at the surface, through which a jerboa can escape if they are threatened by a predator. A. tetradactyla often lines its nests with camel hair or their own belly hair (Nowak, 1991).

Allactaga tetradactyla is a small kangaroo-shaped animal with long, slender ears that are approximately the same length as their head. Their head and body length ranges from 90-263 mm and their tail length is approximately 142-308 mm. They have large eyes (a typical trait of nocturnal animals). Their hind legs are four times greater than their front legs, as is true of other jerboas. The 3 main footbones in their hind legs are fused into a single "cannon bone," which provides mechanical advantage for jumping (MacDonald, 1984 ). A. tetradactyla is the only species within the Jerboas that has four toes (hence the common name 4-toed Jerboa). It has only one small lateral digit (vs. the other species where there are either 2 outer toes or none at all). The sole of the hind foot has a tuft of stiff hairs, which acts as a steering mechanism while they leap. This hair also helps them to kick sand backwards while burrowing. There is another tuft of hair located on the opening of the ear that aids in keeping wind-blown sand from entering (Nowak, 1991). They have padded feet to help absorb and cushion from the shock of landing. A long tail balances the animal while resting and jumping, and it also acts as a brake during running (Hanney, 1975). The vertebrae of the neck region are short and expanded, and several are fused together. Jerboas have inflated bullae and the cheek teeth are rooted, high crowned and cuspidate (Nowak, 1991). They have velvety hair that is usually the same color as the sand they burrow in (sandy or greyish) and a white underbelly.

Little is known about the reproductive behavior of Allactaga tetradactyla except that there is a long breeding season that usually peaks corresponding with spring, summer, and fall. During this period, the male playfully chases the female until she stops briefly and copulation occurs. Sexual maturity in jerboa is reached after the first year (Bunker, 1997). The gestation period ranges from 25-42 days (Macdonald, 1984). There are an average of 3 annual litters consisting of 3-5 young per litter; however, a range of 1-8 young/litter has been recorded (Nowak, 1991).

This species is primarily nocturnal, but has been known to leave the burrow before sunset to feed. Usually there is just one jerboa per burrow unless a female is raising young. When the jerboa leaves its burrow in the late spring and summer, it often plugs the opening to keep the heat out and moisture in. This behavior maintains a suitable climate in its quarters during extremely hot times of the year. If it is too hot or too cold outside, they go into deep torpor, either estivating during hot or dry periods in the summer or hibernating for five months during the cold winter. During hibernation and sleeping periods, the jerboa lies on its side in order to better accomodate its long legs. During the mating dance, the male jerboa smacks the female on the snout, encircles her, and challenges her to take the mating position (Hendrickson, 1983). Jerboas walk with a slow bipedal movement, but when they are escaping from predators they leap in a zig zag pattern and often cover 1-3 meters per jump (Nowak, 1991).

Allactaga tetradactyla feeds primarily on seeds and succulent vegetation (especially plants with milky juices), but it also has been known to feed on insects. It does not drink water at all, but instead lives on metabolic water (produced by the chemical breakdown of food) (Macdonald, 1984).

Allactaga tetradactyla has been beneficial for controlling herbivorous insects that feed on agricultural crops. By preying on insects, jerboas keep the pest population low so the effect of insect predation on crops is reduced.

Jerboas have been known to be a plague carrier (Hanney, 1975).

Desert jerboas fluorish throughout the Palearctic, so they have no special status. However, the overall species richness of mammals fell significantly after the Gulf War in 1990, so one potential threat to A. tetradactyla is future warfare and pollution.

A. tetradactyla's basal metabolic rate is 68% less than that of the white rat. A temperature increase of 40 degrees C (104 F) kills white rats but only causes sleeping jerboas to salivate (Hendrickson, 1983). The lifespan of A. tetradactyla is less than two years.

Also, the known geological range of the Dipodidae is Pleistocene to Recent in North Africa (Nowak, 1991), suggesting that A. tetradactyla is a fairly recent species on the geological time scale.