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Lepus townsendii - White-Tailed Jackrabbit

Skull Pictures:               
Dorsal     Posterior mandible
Lateral     Ventral
Mandible

Physical Description:

The white-tailed jackrabbit is a relatively large hare with a leaner, lankier look than other hares and rabbits.  The pelage changes seasonally, in fact, it is the only jackrabbit that has two annual molts (Whitaker 1998).  Summer pelage ranges from dark brown to grayish-brown on the upper parts, while the under parts are a white or pale gray.  The pelage is thin and coarse with long guard hairs used for warmth.  White-tailed jackrabbits have long antenna-like ears that are colored gray on the anterior half of the outside, white on the opposing half, and a dark black patch extending to the tip. The tail, which gives the hare its common name, it white all year round with a dusky stripe on the dorsal side.  In northern or mountainous regions, there is a winter molt in which the animal is all white with some gray areas around the eyes and throat.  In more southern locations there may be a partial winter molt, in which the only the hare’s sides become white, or in some cases there may be no molt at all.

Lepus townsendii has extremely well developed hind legs allowing it a leaping distance of 12-16 feet and a sprinting speed up to 40 mph.   This is a great advantage considering the white-tailed jackrabbit favors open prairies, pastures, and grasslands as its habitat.

The only sexual dimorphism noticed in this particular species and the only notably difference between the two sexes is that the female is generally larger (Rogowitz 1991).

The dental formula is 2/1 0/0 3/2 3/3 = 28 (Martin 2001).  The first incisors are large are “rodent-like” and used for nipping plants.  The second incisors are small and the cheek teeth are hypsodant and rootless.

Distribution in Wisconsin:

The white-tailed jackrabbit is abundant throughout most of the Western United States including some Midwest states as well.  Fossil evidence of this species was found dating back to the early Holocene, which indicated that it was more prevalent than the similar species of black-tailed jackrabbits that have also been known to exist at that time (Wilson 1999).  Because white-tailed jackrabbits rarely enter wooded areas, it was originally absent from the heavily forested Great Lakes region.  However, since much of these forests are being converted into farmland, the white-tailed jackrabbit has spread through Minnesota and into Wisconsin (Kurta 1995).  However, this wasn’t the only introduction of this species into Wisconsin.  It was more than likely introduced in 1908 for sport.  In fact, it was quite common in counties including Barron, Clark, Eau Claire, Marathon, and Portage (Whitaker 1998).  Unfortunately, today it is extremely scarce and restricted to limited areas, mainly in the western part of the state.

Ontogeny and Reproduction:

Breeding season for the white-tailed jackrabbit begins in February.  Courtship between males and females is brief, lasting an average of 5-20 minutes (Kurta 1995).  It starts with small groups of males chasing females in the evening hours and consists of dashes, jumps, and circling activities that end in a brief copulation.  Most litters are born anywhere from April until early July after a gestation period ranging from 30 to 43 days (Wilson 1999).  Litter size ranges from 1 to 11 young (4 or 5 being the most common).  In northern climates, females bear one litter per year, as opposed to more southern climates where females may have 3 or 4 litters annually (Wesley 1993).  There is no nest to receive the young; however, they do create shallow depressions in the ground called “forms” in which they house the young. The young are born precocial and weigh approximately 90 grams.  They are well furred, with their eyes open and incisors protruding.  They have limited mobility within a half an hour after birth and begin foraging on their own at two weeks of age (Whitaker 1998).  Weaning occurs at one month of age and at two months the young are completely independent.

Ecology and Behavior:

White-tailed jackrabbits are nocturnal and partly crepuscular, feeding from sunset to sunrise. Its activity patterns are known to vary seasonally with changes in day length (Rogowitz 1997). This hare is a strict herbivore and in the summer feeds on various green vegetation and flowers such as clover, alfalfa, dandelions, or cultivated grains (Wesley 1993). They travel and forage along well-worn trails and obtain much of their water from their food. In the winter it resorts to shrubs dried grasses, or the twigs and bark of berry and fruit trees in order to survive.  Like most other rabbits and hares the white-tailed jackrabbit engages in coprophagy, which is the reingestion of soft fecal pellets.  This behavior enables them to assimilate more plant nutrients that are produced by bacteria in the caecum (Martin 2001).

Although the white-tailed jackrabbit is a very large hare, it is seldom seen.  This particular species is among the least social of all hares and tends to be solitary (Wilson 1999).  However, clusters of 3 or 4 individuals during the mating season are not at all uncommon (Whitaker 1998).  Daylight hours are spent resting in forms, which when possible, are dug near bushes or rocks.  During the winter season, however, cavities with connecting tunnels are dug in the snow often leading to popular feeding sites or other forms.

Lepus townsendii serves as prey for a number of predators, such as coyotes, foxes, hawks, badgers and many other carnivorous animals (Rogowitz 1991).  To escape such predators, these hares lie perfectly still with its ears up and alert to listen to the environment around it.  Often they can be approached quite closely before springing up and bounding away in a zigzag pattern (Kurta 1995).  White-tailed jackrabbits have also been known to enter water when cornered.  It swims by paddling with the two front feet and using the two back feet in a leaping motion (Whitaker1998).  In addition to animal predators, these hares also have humans to defend against.  Hunters use the assistance of dogs that have been trained to locate and flush the jackrabbit, making the hunt substantially easier. The white-tailed jackrabbit has been used widely for food and its fur is often manufactured into the linings and trimming of gloves and clothing. Automobiles also take a toll on the many jackrabbits that forage on grassy hills or prairies near roads and highways.  White-tailed jackrabbit populations are also controlled by diseases and parasites of many kinds, such as tularemia, Colorado tick fever, and infestations of botfly larvae (Wesley).

Remarks:

Lepus townsendii is officially endangered in British Columbia, Canada.  The last sighting of a white-tailed jackrabbit was in 1980 (Wesley 1993).  Competition with grazing animals reduced the population dramatically, mainly because there is a 50% overlap between the diets of grazing animals, such as cattle, and jackrabbits.  They are not as efficient of foragers as the black-tailed jackrabbit, so they were unable to find other food sources when the usual plant species were reduced.

The subspecies of Lepus townsendii include Lepus townsendii campanius which is found east of the Continental Divide and Lepus townsendii townsendii which is found west of the Continental Divide (Wilson 1999).  The white-tailed jackrabbit is often compared to a similar hare called the black-tailed jackrabbit (Lepus californicus).  White-tailed jackrabbits are larger in comparison although are more selective in the plant species it eats, which gives a competitive advantage to the black-tailed jackrabbit.  Distributions of the two species overlap, however black-tailed jackrabbits tend to be found in sagebrush and meadowland as opposed to white-tailed jackrabbits that prefer open grassland (Wilson 1999).

Literature Cited:

Kurta, A.  1995.  Mammals of the Great Lakes Region.  The University of Michigan Press.

Martin, R.E., R.H. Pine, A.F. DeBlase.  2001.  A Manual of Mammalogy with Keys and Families of the World.  Third Edition.  New York: McGraw-Hill Companies, Inc.

Rogowitz, G.L.  1997.  Locomotor and Foraging Activity of the White-Tailed Jackrabbit (Lepus townsendii).  Journal of Mammalogy 78(11): 72-1181.

Rogowitz, G.L. and M.L. Wolfe.  1991.  Intraspecific Variation in Life-History Traits of the White-tailed Jackrabbit (Lepus townsendii).  Journal of Mammalogy 72:796-806.

Wesley, W.M.  1993.  White-Tailed Jackrabbit.  Royal B.C. Museum.  <http://rbcm.gov.bc.ca/end_species/species/jackrab.html>.

Whitaker Jr., J.O. and W.J. Hamilton Jr.  1998.  Mammals of the Eastern United States.  New York: Comstock Publishing Associates.

Wilson, D.E. and S. Ruff.  1999.  The Smithsonian Book of North American Mammals.  Washington: Smithsonian Institution Press.

 
Reference written by Shannon Langness, Biol 378: Edited by Chris Yahnke.
Page last updated 4-27-04.

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