White-tailed jackrabbit

Appearance

The white-tailed jackrabbit is a large species of hare and the largest species called "jackrabbit", although two larger hares are found further north in North America. This jackrabbit has an adult length of 56 to 65 cm , including a tail measuring 6.6 to 10.2 cm , and a weight between 2.5 and 4.3 kg . From winter to spring, weight tends to increase due to pregnancy in females but decrease due to the stresses of reproductive competition in males. Thusly, females in Iowa went from averaging 3,600 g in winter to 3,800 g in spring and males from averaging 3,400 g in winter to 3,100 g in spring. At the northern most extremity of its range it can be almost twice as large as in the middle of it range. In Saskatchewan rare specimens have been recorded at over 9 kg . It has distinctive large grey ears with black tips which are chestnut brown and white on the inside and the long, powerful hind legs characteristic of hares. The back, flanks and limbs are dark brown or greyish-brown and the underparts are pale grey. The ear, from the notch, measures from 10 to 11.3 cm and the hindfoot measures 14.5 to 16.5 cm . The tail is white with a dark central stripe above. Females are slightly larger than males. In northern populations, this hare moults in the autumn and becomes white all over except for its ears. They generally make no sound but will emit a shrill scream if they are injured or caught.

Distribution

The white-tailed jackrabbit is native to western and central parts of North America. Its range includes British Columbia, Alberta, Saskatchewan, Manitoba and Ontario in Canada and Washington, Oregon, California, Nevada, Utah, Idaho, Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Wisconsin, Iowa, Missouri and Illinois in the United States. It is found in plains and prairie and in alpine meadows with scattered coniferous trees up to an elevation of about 3,000 metres in Colorado. The white-tailed jackrabbit is slightly larger than the black-tailed jackrabbit and where their ranges overlap, they are segregated by their habitat, as the former tends to live in higher altitudes and the latter in more arid lowland habitats.

Status

The white-tailed jackrabbit is assessed as being of "Least Concern" by the IUCN in its Red List of Threatened Species. This is because this hare has an extensive range and is fairly common across most of this range. The population size may be declining slightly but not at a rate that would justify listing this hare in a more threatened category.

In Wyoming however, it has become scarce in Grand Teton National Park where it has not been seen recently. Briefly reputed to have been extirpated in Yellowstone National Park where it was at one time abundant, it is now clear from observations, roadkilled specimens and historical records that white-tailed jackrabbits are still present in the park. The causes of the decline in populations in Wyoming is unclear.

Behavior

The white-tailed jackrabbit is nocturnal and lies up during the day in a form, a shallow depression in the ground hidden under vegetation, emerging at dusk to feed. The forms of this species range from 46 to 61 cm long, 20 to 30 cm wide and up to 20 cm deep. There are often discernible paths leading away from the form and others among the plants at often-visited feeding sites. In winter snow, the forms are interconnecting cave-like structures. This jackrabbit is a solitary species and feeds on grasses and other green plants, including cultivated crops. In southern Colorado, from summer through fall into winter, the diet varied from of 70% to 4% forbs, 43% to 4% grasses and 76% to 7% scrubs. During the winter its diet includes buds, twigs and bark feed on off of low shrubs. It tends to be more selective in its feeding habits than the black-tailed jackrabbit which disadvantages it where their ranges overlap. It has good eyesight, excellent hearing and sensitive whiskers and is probably able to detect olfactory clues as to whether another jackrabbit is ready to breed.

The breeding season is variable and depends upon latitude and environmental factors and extends from February to July in different parts of the range. Several males may compete aggressively for the attention of a female by charging at each other, leaping and jostling. Ovulation by the female takes place after copulation. The gestation period is about 42 days and in preparation for the birth, the female prepares a fur-lined nest under dense vegetation. A litter consists of up to eleven young although four or five is a more typical number. The leverets weigh about 100 grams and are precocial. They have their eyes open and are fully furred at birth and soon begin to move around. They start to forage at about two weeks old and are weaned at four weeks. They are sexually mature at about seven months but do not breed until the year after their birth.

Habitat

The white-tailed jackrabbit is native to western and central parts of North America. Its range includes British Columbia, Alberta, Saskatchewan, Manitoba and Ontario in Canada and Washington, Oregon, California, Nevada, Utah, Idaho, Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Wisconsin, Iowa, Missouri and Illinois in the United States. It is found in plains and prairie and in alpine meadows with scattered coniferous trees up to an elevation of about 3,000 metres in Colorado. The white-tailed jackrabbit is slightly larger than the black-tailed jackrabbit and where their ranges overlap, they are segregated by their habitat, as the former tends to live in higher altitudes and the latter in more arid lowland habitats.White-tailed jackrabbits influence the composition of the turf through their selective grazing activities. They are important prey species for various mammalian predators. Red and grey foxes occasionally capture one, though not many large adults. They are perhaps most important prey for mid-sized carnivores like the American badger , the coyote and the bobcat and small supplemental prey for larger ones like the mountain lion and the gray wolf . Snakes sometimes attack them and bird predators include eagles, hawks and owls. Golden eagles are the only avian predators large enough to regularly take full-grown white-tailed jackrabbit, though ferruginous hawks and great horned owls may occasionally take an adult though these latter two species and other largish raptorial birds typically attack young individuals. They attempt to evade detection by crouching in the vegetation where their cryptic colouration makes them difficult to observe. They may slink away but if detected, they bound away at speed, adopting a zigzag course. They can run at up to 55 kilometres per hour and leap up to 5 metres . As well as being caught by animal predators, they are also hunted and eaten by humans.