The snowshoe hare Lepus americanus, or "bush rabbit," as it is called throughout Canada, is one of our commonest forest mammals. It is shy and secretive, often undetected in summer, but its distinctive tracks and well-used trails ("runways" or "leads") become conspicuous with the first snowfall.

Large well-furred hind feet enable the snowshoe hare to move easily over the snow. In soft snow the four long toes of each foot are spread widely, increasing the size of these "snowshoes" still more. Another remarkable adaptation is the seasonal variation in fur color, from grey-brown in summer to almost pure white in midwinter. This alteration, brought about by a gradual shedding and replacement of the guard hairs twice yearly, is triggered by seasonal changes in day-length which affect the reproduction cycle and hence the moult. In the humid coastal zones of Washington, Oregon, and southwestern British Columbia where snow is infrequent, snowshoe hares remain brown throughout the year. The large ears, typical of most rabbits and hares, help to regulate body temperature and also to detect approaching enemies.

Geographic range and habitat

The snowshoe hare, found only in North America, is distributed throughout much of the Boreal Forest. The southern extensions of this forest, along the Appalachian Mountains in the east and the Rocky Mountains in the west, take the snowshoe at least as far south as North Carolina and New Mexico. To the north, it reaches the Arctic Ocean in the willow swales of the Mackenzie River delta.

The habitat of the snowshoe hare within the Boreal Forest varies greatly and is greatly affected by the type of forest and recency of fire. In eastern Canada and mountainous areas, the forest is predominantly coniferous (spruce and fir), whereas over large expanses of Alberta, Saskatchewan, and Manitoba the forest is mainly deciduous (aspen and balsam poplar). In either case, hare populations flourish if recurrent fires create situations where dense stands of young conifers or brushy deciduous growth provide abundant food and cover. When, in the absence of fire, forests have matured, hare numbers tend to be low; there, small isolated populations are usually associated with bog edges and other natural openings that may support patches of willow, alder, hazel, and other low-growing woody vegetation.

Snowshoe hares consume a variety of herbaceous plants during summer, including vetch, strawberry, raspberry, and fireweed. Their winter diet consists of small twigs, buds, and bark: maple, birch, rose, hazel, and willow are highly palatable deciduous species, whereas jackpine, white pine, larch, and cedar are favoured conifers.

Reproduction

Snowshoe hares are born fully furred, open-eyed, and capable of hopping about almost immediately. Such precociousness is characteristic of hares in general, and is in marked contrast to the behaviour of young rabbits, which are born naked and blind. Young snowshoes nurse only once a day, usually in the evening, and are self-supporting at three weeks of age. They weigh about 57 g at birth, gain 0.45 kg within a month, and reach an average adult weight of 1.4 to 1.8 kg at five months. Adult females tend to weigh slightly 57 to 114 g more than adult males.

Reproductive rates of the snowshoe hare vary geographically, being highest in the centre of its range (the three Prairie Provinces) and lower to the north (Alaska) and south (lake states, southern Ontario and Maritime Provinces). Snowshoes normally have four litters a year. However, because Alaskan hares have a maximum of only three litters annually, they produce fewer young, whereas in the southeastern part of the range, litter sizes are smaller.

Studies of snowshoe hare reproduction in Alberta over a 12-year period disclosed that litter size varied from one to nine; first litters of the year averaged only 2.8 young compared with 4.8 in later litters. There were major differences in yearly reproductive rates, with mean numbers of young per female ranging from 8 to 18. These annual differences mainly reflected variation in litter size and number of litters per year. The onset of breeding during any one year was closely synchronized within the hare population, but between one year and the next, breeding began as early as March 25 and as late as April 14. The gestation period for snowshoe hares in the wild was 35 days, with females remating within hours of giving birth. Thus successive litters tended to be born in groups at about 5-week intervals. In years when four litters were conceived, the last young were born from mid- to late August. There are, however, some authenticated records of births in September and even later.

Young snowshoe hares do not usually breed during their first summer, but occasionally a first-litter female will become sexually mature by mid-July and produce a litter in August.

Mortality

The snowshoe hare suffers from a great variety of infectious diseases -- viral, bacterial, and parasitic. It is also the victim of many kinds of mammalian and avian predators: among the most common are the lynx, red fox, coyote, mink, Great Horned Owl, and Northern Goshawk. The survival rate among first year hares varies annually from 3 to 40 per cent. Annual survival of adult hares is also highly variable, ranging from 12 to 50 per cent.

While disease and predation are often the immediate causes of death, their impact on hare populations seems to be greatly influenced by both weather and nutritional stresses. There is high mortality among young males, for example, when cool wet weather occurs during the first three weeks of life; increased mortality is likewise associated with prolonged periods of temperatures below -20�C in winter, and with food shortage during hare population peaks.

Population fluctuations

The spectacular cyclic fluctuations of snowshoe hare populations are well known in Canada. These remarkably regular fluctuations can be traced back over 200 years in the fur records of the Hudson's Bay Company and have been aptly termed the R-year cycle". The actual interval between successive peaks varies from 8 to 11 years and averages 9.6 years. During population peaks, hares often become extremely ahundant. Such a "rabbit high" occurred in central Alberta during 1970 when fall densities reached 3 500 to 6 500 animals per 2.6 km². The cycle is synchronized over broad areas, and a similar cycle affects grouse and subsequently certain predatory mammals and birds that depend heavily on snowshoe hares and grouse for food.

Recent recearch suggests strongly that peak hare populations interact critically with their overwinter food supply, and that losses due to predation become significant only after the hares have declined to well below peak densities. The first two or three years of cyclic decline are characterized by low adult survival, very low survival of young, reduced litter size and a shorter breeding season.

Movements and activity

The home range of a snowshoe hare, i.e., the area within which it normally lives, does not usually exceed 8 ha. Rain, snow or wind often markedly reduce their activity. During the daytime, hares rest quietly in sheltered spots called forms, but are very active between sundown and dawn. They seldom, if ever, dig burrows, but readily utilize those made by other animals.

A trail or runway is frequently used by several snowshoes as a travel-lane between feeding and resting sites. Squirrels, porcupines, skunks, and woodchucks also take advantage of these pathways, as do various mammalian predators. Major runways follow the same route in summer and winter; stems and leaves which begin to block such runways are quickly clipped off by the hares.

During periodic highs, snowshoe hares tend to disperse over winter from centres of dense population. At such times they may move 8 km or more. The great majority of these emigrants are juveniles or young born the previous summer.

Value to humans

The feeding habits of snowshoe hares sometimes conflict with human horticultural and silvicultural interests. During years of high population, hares commonly invade farms, damaging vegetable gardens and girdling fruit trees and ornamentals. Losses of seedling conifers in forestry plantations may be especially severe, and forest regeneration indefinitely delayed.

In some regions the snowshoe hare is hunted for sport, but elsewhere, as in western Canada, it is not regarded as a game animal. In Newfoundland (where it was introduced in the 1870s) thousands of snowshoes are snared annually for meat and sold in markets, whereas in the Prairie Provinces it would be difficult to give one away. This prejudice against eating hares apparently stems from the wide-spread belief that they harbour a mysterious disease which causes their cyclic decline. Aboriginal peoples, however, are not so gullible, and for many of them the snowshoe hare continues to be an important food source.

The fur of the hare is not durable and hence has little or no commercial value. The snowshoe's chief contribution to the fur trade is through its role as a principal food of such important furbearers as the lynx, red fox, fisher, and coyote.

The snowshoe hare is clearly one of the dominant herbivores and key prey species within the Boreal Forest, and as such accounts for much of this ecosystem's interesting and ecologically important diversity.

Reading list

Banfield, A.W.F. 1974. The mammals of Canada. University of Toronto Press, Toronto.
Cahalane, V.H. 1947. Mammals of North America. Macmillan, New York.
Keith, L.B. 1963. Wildlife's ten-year cycle. University of Wisconsin Press, Madison.
Seton, E.T. 1929. Lives of game animals. (Vol. 4, Part 21. Doubleday, Doran and Co., New York.
Soper, J.D. 1964. The mammals of Alberta. The Queen's Printer, Edmonton.


	Canadian Wildlife Service - Hinterland Who's Who series Reproduced with permission of the Minister of Public Works and Government Services Canada, 1999. Copyright � 1999 Environment Canada. All rights reserved. Last update: 19 January 1999

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