Major Life Events
Male black-tailed jackrabbit reach sexual maturity at about 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 its range in Idaho, black-tailed jackrabbit breeds from February through May. In Utah, black-tailed jackrabbit 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 gestation period ranges from 41 to 47 days. More litters are born in warm climates: the number of litters born each year ranges from two per year in Idaho to seven in Arizona. Litter sizes are largest in the northern portions of black-tailed jackrabbit's range and decrease toward the south. Average litter size has been reported at 4.9 in Idaho, 3.8 in Utah, and 2.2 in Arizona.
Female black-tailed jackrabbit do not prepare an elaborate nest. They give birth in shallow excavations called forms that are no more than a few centimeters deep. Females may line forms with hair prior to giving birth, but some drop litters in existing depressions on the ground with no further preparation. Young are borne fully furred with eyes open, and are mobile within minutes of birth. Females do not protect or even stay with the young except during nursing. Ages of weaning and dispersal are unclear since the young are well camouflaged and rarely observed in the field. Captive black-tailed jackrabbit are fully weaned by 8 weeks. The young stay together for at least a week after leaving the form.
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