An Animal of the High Desert -
Black-tailed Jackrabbit
Black-tailed jackrabbits (Lepus californicus) are common in
the western United States and northern Mexico. Early settlers called
them “jackass rabbits” because their ears resembled those of a
donkey (jackass). This name was later shortened to jackrabbit. There
are four species of jackrabbit in North America. The most common,
and the one seen most often in southeastern Idaho, is the
black-tailed jackrabbit.
Despite the name, the jackrabbit is actually not a rabbit, but a
hare. The largest of the North American hares, black-tailed
jackrabbits measure 18-24 inches long and their ears are 5-7 inches
long. Black-tailed jackrabbits, like all hares, are larger and more
slender than rabbits, have longer ears and legs, and their young,
called leverets, are born with fur and with their eyes open.
Because black-tailed jackrabbits prefer an arid habitat, they have
several adaptations that help them survive in a hot and dry
environment.
Black-tailed jackrabbits are mostly nocturnal. They live in open
habitat and run to escape predators rather than hiding in the woods
like the rabbit does. The jackrabbit’s large eyes are placed back on
the head so he can see in front, behind and overhead at the same
time. Their keen sense of hearing helps them be aware of their
surroundings and potential danger and they rely on their speed to
escape from predators such as coyotes, bobcats, foxes, horned owls,
hawks and snakes. When threatened, they first freeze, laying their
ears over their backs and blending their long, lean bodies into the
surroundings. If the vanishing act fails, they leap away in 20-foot
bounds at speeds up to 35 miles per hour. When trying to evade
predators, a jackrabbit moves in a zig-zag pattern.
The jackrabbit’s large ears also help the hare keep cool. The blood
vessels in the ears expand to allow the blood to cool before
re-entering the body. The jackrabbit can also decrease the blood
flow through its ears in the winter to stay warmer.
Jackrabbits do not dig burrows. Instead, they spend the hottest part
of the day resting in a bed scratched out at the base of a shrub or
in a clump of tall grass where the shade will protect it from the
heat. In the winter, a jackrabbit builds its nest under thick
foliage that protects it from harsh winds.
The black-tailed jackrabbit is an herbivore. In the summer they eat
mostly green plants and flowers that are high in water content, so
they do not require much water. They will also eat sagebrush and
cacti. In the winter, they don’t hibernate, and mainly eat shrubs.
Jackrabbits are constantly eating and consume large quantities of
food relative to their size. Fifteen jackrabbits eat as much food as
a large grazing cow in one day. In agricultural areas the jackrabbit
may become a pest to farmers by eating their crops.
Rabbit populations generally follow a cyclic pattern of high and low
population numbers. According to survey data, jackrabbit populations
on the INL appear to peak every 10 or 11 years. Populations increase
to great abundance and then suddenly decrease for unknown reasons,
but disease, food shortages or an increase in predators may
contribute. Their populations recover quickly, however, because they
are such prolific breeders. A female jackrabbit may bear three to
four litters per year with up to eight young per litter. Leverets
reach adult size and are able to breed in about seven to eight
months.
