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Geographic Range
The White-sided jackrabbit is found in a limited location in North America. Its range only extends from southern New Mexico to northwestern and central Mexico. The animal is actually considered threatened in New Mexico with its numbers in decline in recent years.
Habitat
White-sided jackrabbits inhabit high plateaus at high elevations, including the grassy plains of southwestern New Mexico and the open plains of the southern Mexican tableland. They avoid areas that are full of hills or mountainous. They prefer level lands full of grasses and also will avoid areas with that are full of trees and shrubs.
Description
White-sided jackrabbits have body lengths that range from 16 inches up to 30 inches long. Their tails will grow to lengths of 1 inch to 4 inches long. Their legs grow from 4 to 6 inches in the front and the back legs can grow from 6 inches to 12 inches long. The white-sided jackrabbits ears grow an astounding 2 to 6 inches when fully grown. The forepaws have five toes while the back paws have four. All toes end in sturdy claws. Some sexual dimorphism is present in this species; females are generally larger than the males.
The dorsal pelage of white-sided jackrabbits is short and coarse. The color is pale cinammon color heavily mixed with black. The underparts are white with traces of colored patches in front of the thighs. The tail has black hairs tipped with white on the upper surface and is all white on the underside. The sides are distinguishable from other species in that they are pure white, this is where they obtained their name. The rump and thighs are also white and lined with a few black hairs. A median black line concealed by sooty, brownish, and white-tipped hairs divides the rump. The limbs are white, but their outer surface is stained a buffy color. The gular pouch is also buffy while the sides of the neck and shoulders become more ochraceous in color. The head is a cream buff color, mixed with black, with whitish areas around the sides of the eyes. The ears are covered with short yellowish-brown hairs that are mixed with black anteriorly and white posteriorly. The apex of the ear is white-tipped. Below the apex of the ear is a tuft of black hair. The long fringes on the anterior edge of the ear are ochraceous buff while the fringes of the tip of the ear and posterior edge are white. The inner surface of the ear is almost bare except for a dusky spot on the posterior border. The nape is ochraceous buff in color.
The winter pelage of the white-sided jackrabbit is iron gray on the rump, back, and outside of the hind legs. The front of the hind legs and the tops of the feet are white. The front of the fore legs and top of the forefeet range from a pale gray to a dull iron-gray. The median black line of the rump is not strongly distinguishable and does not extend much further than the base of the tail. The top, sides, and tip of the tail are black while the underside is two-thirds white and one-third black. The top and sides of the head and back are dark-pinkish buff overlaid with black. The nape is usually black. The ears are dark bluff, black, and white. The front border of the ears are fringed with buff or ochraceous buff hairs, and the posterior border and tip are white. The underside of the neck is dark grayish bluff and the remaining underparts, including the flanks, are white
Reproduction
The breeding season of white-sided jackrabbits is a minimum of 18 weeks, occurring from mid-April to mid-August. The average number of young per litter is around 2. The young tend to have a soft, wooly coat in early life and attain sexual maturity at a rapid rate. Breeding in Lepus callotis does not begin within the first calendar year following their birth.
Behavior
Most activity of white-sided jackrabbits occurs during the night or at dusk, particularly on clear nights with bright moonlight. Their activity may be limited by cloud cover, precipitation, and wind, but temperature has little effect. The escape behavior consists of alternately flashing its white sides when running away. White-sided jackrabbits, when escaping, make rather long, high leaps. When startled by or alarmed by a predator, they leap straight upwards while extending the hind legs and flashing the white sides. In its resting position, a white-sided jackrabbit is camouflaged with its surroundings. The long hind legs and feet are adapted for speed, giving the animal lift and an ability to run in a zig-zag fashion that surpasses its pursuers. The long ears serve to locate sound as well as regulate temperature when they are raised like a fan to catch passing breezes in hot conditions. The eyes, like those of most nocturnal animals or animals that are active at dusk, are laterally arranged, giving them a complete field of vision (360 degrees). As a result, approaching danger can be perceived in advance.
A conspicuous trait of Callotis is its tendency to occur in pairs, usually one male and one female. They exhibit a pair bond that is most evident during the breeding season. After establishment of the pair bond, the male defends the pair from other intruding males. The purpose of such pair bonds may be to keep the sexes together in areas of low density. The members of the pair are usually within 15-20 feet of each other and run together when approached by intruders. The pair bond may not be broken during pregnancy.
Callotis construct and utilize shelter forms averaging 15 inches in length, 20 inches in width, and 7-8 inches in depth. The shelter form is usually located in clumps of grass and surrounded by dense stands of tabosagrass. White-sided jackrabbits may also occupy underground shelters, but this behavior is rare. Callotis forages by chewing and pulling grass blades near the ground until they are either uprooted or broken off. The food is ingested by chewing the grass that is sticking out of the mouth, with the head raised and the body sitting in a crouched position. The forepaws are not used in feeding except to brace against the ground as the grass is bitten off or uprooted. When eating certain nutgrass, however, the forepaws are used to excavate the bulbous tubers, leaving behind oval foraging depressions in which fecal pellets are often deposited.
Callotis has three types of vocalizations. The alarm or fear reaction consists of a high-pitched scream. Another sound, emitted by males in a pair when approached by an outside intruding male, is a series of harsh grunts until the intruder leaves or is chased away. A third vocalization, consisting of a trilling grunt is heard during the sexual chase of Callotis, however, it is not known which member of the pair makes this sound.
Food
The diet of white-sided jackrabbits consists primarily of grasses including buffalograss, tabosagrass, fiddleneck, wolftail, blue grama, vine mesquite, ring muhly, wooly Indian wheat, and Wright buckwheat. The significant non-grass item found in their diets was sedge nutgrass.
Human Interaction and Impact
Although many species of rabbit and hare are considered pests because they damage crops, fields, and orchards the white-sided jackrabbit is usually not considered a pest and has no known adverse conditions on human property.
Many species of rabbit and hare are also sought after their meat and fur. This is alos untrue of the white-sided jackrabbit and in fact, it is protected in most of its habitat region.
Conservation Efforts
The white-sided jackrabbit is considered endangered throughout its range in Mexico and southwestern New Mexico. Callotis commonly comes into contact with agriculture. As a result, the overgrazing of domestic livestock may be one of the factors contributing to its decline and the apparent replacement by Lepus californicus, which has been highly adaptable to these habitat changes. Prospects for the survival of the white-sided jackrabbit in many parts of its range are considered poor at best.
References
"Lepus callotis"