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Wolverine (Gulo gulo)

Habitat

Habitat Requirements

In a previous COSEWIC status report, Kelsall (1981) reviewed the available data and concluded that wolverine “habitat is probably best defined in terms of an adequate year-round food supply in large, sparsely inhabited wilderness areas, rather than in terms of particular types of topography or plant association…the animals are most abundant where large ungulates are common, and where carrion is abundant in winter from hunter kills, predation and natural mortality.”

Wolverines inhabit a variety of treed and treeless ecological areas, at all elevations. In mountainous areas adult females tend to use higher elevations and steeper terrain more than other sex and age classes, while adult males and subadults of both sexes make extensive use of low elevation habitats (Lofroth 2001). Lower elevation habitats are used more in winter (Landa et al. 1998). Adult females may be reducing the risk of predation on their kits by choosing the more rugged terrain (Golden, pers. com., 2003). High densities of wolverines occur in the mountainous areas of the Yukon Territory, Northwest Territories, British Columbia and Alberta, where habitats, prey species, and ungulates are most diverse and abundant (Boreal, Northern Mountain and Southern Mountain ecological areas). Viable populations of other large carnivores, as providers of carrion, may be important. In a study on wolves (Canis lupus) in the Yukon, wolverines frequently visited moose (Alces alces) and caribou (Rangifer tarandus) kills after wolves had left (Hayes, pers. com., 2002). There have been no field studies of wolverines on the arctic or Pacific islands, nor in Quebec, Labrador or the Prairie Provinces.

Wolverines have specific habitat requirements for den sites. Wolverine dens may be classified as natal or maternal, and multiple dens may be used in sequence (Copeland 1996). Dens are constructed either in boulders, under deadfall, or in snow tunnels (Magoun and Copeland 1998) at higher elevations, including tundra habitats. Dens or exposed sites may also be used for rendezvous between female and kits, and resting. Additional requirements are protection from predators such as golden eagles (Aquila chrysaëtos), bears (Ursus arctos and U. americanus) and wolves. Adequate insulating snow cover that persists throughout the denning period and proximity to kit rearing habitat are also important. Individual wolverines may reoccupy den sites or denning habitats for several consecutive years (Magoun 1985, Lee and Niptanatiak 1996).


Trends

Considerable wolverine habitat was lost or fragmented with the extensive settlement that occurred in the late 19th and 20th centuries at the southern edge of the range (van Zyll de Jong 1975). Losses were due primarily to human settlement, agriculture, and forestry. Most wolverine habitat was supplanted, and wolverine populations were reduced by hunting, trapping and poisoning, using poison baits directed at wolves. The removal of ungulates, an important winter prey base, also likely contributed to their extirpation. Reduced numbers of prey remains a significant threat to wolverine populations today, especially where mountain caribou (Rangifer tarandus caribou) herds are being impacted by forestry operations and overhunting. Much of the habitat lost during human colonization was not prime habitat (assuming low fur returns are correlated with populations and not effort), and numerical losses of wolverines may have been low.

Habitat fragmentation has resulted in isolated and threatened populations in the western coterminous United States (Banci 1994), and this process may be occurring in the Southern Mountain national ecological area of southern British Columbia and Alberta, and in northeastern Manitoba-northwestern Ontario (Kyle and Strobeck 2002). Across the range of wolverines, forestry, oil and gas and mineral exploration and development, and large hydroelectric reservoirs threaten habitat. Transportation corridors act as barriers to movement and essentially divide habitats and isolate populations (Austin 1998).

Both Kelsall (1981) and Dauphiné (1989) assumed that the relatively large number of parks and protected areas, which act as refugia from trapping and development in western Canada, had secured wolverine habitat in that area. However, human recreation, such as snowmobiling and other forms of snow travel, disturbs wolverines, particularly during the denning season in February-March (Heinemeyer et al. 2001). These activities are generally permitted and occur with great frequency both within and outside of protected areas. As well, trapping is permitted in many protected areas, and wolverines that range beyond protected area boundaries are vulnerable to trapping.


Protection/Ownership

Most of the wolverine’s range is on public or “Crown” lands although First Nations’ and Inuvialuit land claims have resulted in ownership of lands in the Yukon Territory, the Northwest Territories, Nunavut and British Columbia. Both Aboriginal and non-Aboriginal lands are subject to government-permitted land use activities.

Approximately 6% of the wolverine’s current range and 10% of the “high” relative density range in western Canada (Figure 3) is within parks and protected areas (Mulder, pers. com., 2003). The process of establishing parks and protected areas on Aboriginal lands is continuing.

Trapping is permitted, although it occurs infrequently, in many British Columbia provincial parks, in all national parks in the Yukon Territory, Northwest Territories, and Nunavut Territory, and in Wood Buffalo (Northwest Territories and Alberta) and Wapusk (Manitoba). Large, contiguous or connected blocks of suitable habitat are needed for wolverine conservation (Weaver et al. 1996). The establishment and maintenance of movement corridors between parks would strengthen wolverine population viability in the Southern Mountain ecological area of British Columbia and the western United States.

Most types of resource extraction or major habitat changes are not permitted in protected areas. However, recreational activities, such as snowmobiling and skiing which may disturb denning wolverines, are generally not restricted and transportation corridors bisect and penetrate parks. The Trans-Canada Highway, an impediment to the free movement of wolverines (Austin 1998), traverses Banff, Yoho and Glacier National Parks, and borders Revelstoke National Park.