Lepus californicus

Like other jackrabbits, the black-tailed jackrabbit has distinctive long ears, and the long powerful rear legs characteristic of hares. Reaching a length about 2 ft (61 cm), and a weight from 3 to 6 lb (1.4 to 2.7 kg), the black-tailed jackrabbit is the third-largest North American jackrabbit, after the antelope jackrabbit and the white-tailed jackrabbit. Additionally, the much more northerly Arctic hare and Alaskan hare are somewhat larger than the jackrabbit members of the hare genus. The black-tailed jackrabbit's dorsal fur is agouti (dark buff peppered with black), and its undersides and the insides of its legs are creamy white. The ears are black-tipped on the outer surfaces, and unpigmented inside. The ventral surface of the tail is grey to white, and the black dorsal surface of the tail continues up the spine for a few inches to form a short, black stripe. The females are larger than males, with no other significant differences.Although 17 subspecies are recognized, this number may be excessive. Using a cluster analysis of anatomical characters, Dixon and others found that black-tailed jackrabbit subspecies separated into two distinct groups that are geographically separated west and east of the Colorado Rocky Mountains and the Colorado River. They suggested only two infrataxa are warranted: the western subspecies L. c. californicus and the eastern subspecies L. c. texianus.The black-tailed jackrabbit occupies plant communities with a mixture of shrubs, grasses, and forbs. Shrubland-herb mosaics are preferred over pure stands of shrubs or herbs. Black-tailed jackrabbit populations are common in sagebrush (Artemisia spp.), creosotebush (Larrea tridentata), and other desert shrublands; palouse, shortgrass, and mixed-grass prairies; desert grassland; open-canopy chaparral; oak (Quercus spp.), and pinyon-juniper (Pinus-Juniperus spp.) woodlands; and early seral (succeeding each other), low- to mid-elevation coniferous forests. It is also common in and near croplands, especially alfalfa (Medicago sativa) fields.Male black-tailed jackrabbits reach sexual maturity around 7 months of age. Females usually breed in the spring of their second year, although females born in spring or early summer may breed in their first year. Ovulation is induced by copulation. The breeding season is variable depending upon latitude and environmental factors. In the northern part of their range in Idaho, black-tailed jackrabbits breed from February through May. In Utah, they breed from January through July, with over 75% of females pregnant by April. The Kansas breeding season extends from January to August. Breeding in warm climates continues nearly year-round. Two peak breeding seasons corresponding to rainfall patterns and growth of young vegetation occur in California, Arizona, and New Mexico. In Arizona, for example, breeding peaks during winter (January–March) rains and again during June monsoons.The black-tailed jackrabbit can occupy a wide range of habitats as long as diversity in plant species exists. It requires mixed grasses, forbs, and shrubs for food, and shrubs or small trees for cover. It prefers moderately open areas without dense understory growth and is seldom found in closed-canopy habitats. For example, in California, black-tailed jackrabbits are plentiful in open chamise (Ademostoma fasciculatum) and Ceanothus spp. chaparral interspersed with grasses, but does not occupy closed-canopy chaparral. Similarly, the black-tailed jackrabbit occupies clearcuts and early seral coniferous forest, but not closed-canopy coniferous forest.The black-tailed jackrabbit diet is composed of shrubs, small trees, grasses, and forbs. Throughout the course of a year, black-tailed jackrabbits feed on most if not all of the important plant species in a community. Growth stage and moisture content of plants may influence selection more than species. Shrubs generally comprise the bulk of fall and winter diets, while grasses and forbs are used in spring and early summer. This pattern varies with climate: herbaceous plants are grazed during greenup periods while the plants are in prereproductive to early reproductive stages, and shrubs are used more in dry seasons. Shrubs are browsed throughout the year, however. Most of a jackrabbit's body water is replaced by foraging water-rich vegetation. Jackrabbits require a plant's water weight to be at least five times its dry weight to meet daily water intake requirements. Therefore, black-tailed jackrabbits switch to phreatophyte (deep-rooted) shrubs when herbaceous vegetation is recovering from their foraging.The black-tailed jackrabbit is an important prey species for many raptors and carnivorous mammals. The black-tailed jackrabbit and Townsend's ground squirrel (Spermophilus townsendii) are the two most important prey species on the Snake River Birds of Prey Study Area. Hawks preying on black-tailed jackrabbits include the ferruginous hawk (Buteo regalis), white-tailed hawk (Buteo albicaudatus), Swainson's hawk (B. swainsoni), and red-tailed hawk (B. jamaicensis). The black-tailed jackrabbit is the primary prey of Swainson's, red-tailed, and ferruginous hawks on Idaho and Utah sites. Other raptors consuming black-tailed jackrabbits include the great horned owl (Bubo virginianus), burrowing owl (Athene cunicularia), golden eagle (Aquila chrysaetos), and bald eagle (Haliaeetus leucocephalus). A significant correlation exists between golden eagle and black-tailed jackrabbit reproduction patterns. In Colorado and southeastern Wyoming, black-tailed jackrabbits constitute 9% of nesting bald eagles' diet. Jackrabbits and cottontails (Sylvilagus spp.) combined form 9% of the diet of bald eagles wintering on national forests in Arizona and New Mexico.The black-tailed jackrabbit plays host to many ectoparasites including fleas, ticks, lice, and mites, and many endoparasites including trematodes, cestodes, nematodes, and botfly (Cuterebra) larvae. Diseases affecting the black-tailed jackrabbit in the West are tularemia, equine encephalitis, brucellosis, Q fever, and Rocky Mountain spotted fever. Ticks are vectors for tularemia, and infected ticks have been found on jackrabbits in the West. Jackrabbits infected with tularemia die very quickly.  This article incorporates public domain material from the United States Department of Agriculture document 'Lepus californicus'.