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COSEWIC assessment and update status report on the wolverine Gulo gulo in Canada

Update
COSEWIC Status Report
on the
Wolverine
Gulo gulo

Eastern population
Western population

in Canada
2003

Species Information

Name and Classification

The wolverine, Gulo gulo (Linnaeus, 1758), was formerly known as Gulo luscus in North America; however, New and Old World forms have been shown to be conspecific (Kurtén and Rausch 1959). Four subspecies are recognized in North America (Hall 1981), two of which occur in Canada; Gulo gulo luscus, found across Canada, Alaska and the northwestern United States, and Gulo gulo vancouverensis, found on Vancouver Island. Banci (1982) found little evidence for classifying the Vancouver Island population as a distinct subspecies; however, it has undergone a high degree of isolation since the Pleistocene, and is still recognized as a distinct subspecies (Nagorsen 1990, Resources Inventory Committee 2002). A complete study of variation throughout the species’ range has been recommended (Nagorsen 1990).


Description

The wolverine is the largest terrestrial mustelid in North America and resembles a small bear in appearance more than a weasel (Figure 1). It has long, glossy coarse fur, which varies from brown to black, often with a pale facial mask and yellowish or tan stripes running laterally from the shoulders, crossing just above the tail. Some individuals have a white patch on the neck and chest. It has a large head, broad forehead, short stout neck, short stocky legs, and a heavy musculature. The feet are large, ears short and the tail is long and bushy. The skull structure is robust, allowing it to crush bones and frozen carcasses. Wolverines are sexually dimorphic with adult females ranging in size from 7.5 to 11 kg and males weighing 12 to 16 kg (Banci 1994, Copeland 1996, Lofroth 2001, Peterson 1966). Total length averages about 1 m, with the average tail length being 23 cm. Its general characteristics are described by Wilson (1982), Hash (1987), and Pasitschniak-Arts and Larivière (1995).


Figure 1: Illustration of Gulo gulo

Figure 1: Illustration of Gulo gulo.


Nationally Significant Populations

The original COSEWIC status designation for wolverine was “Rare” (equivalent to “Special Concern” prior to 1990) (Kelsall 1981). In 1989, two geographically separated populations were delineated, the eastern population of Quebec and Labrador, and the western population of northwestern Ontario, Manitoba, Saskatchewan, Alberta, British Columbia, Northwest Territories and Yukon Territory. The eastern population was assigned the status of “Endangered” and the western population was “Vulnerable” (equivalent to “Special Concern” from 1990 to 1999) (Dauphiné 1989).

The eastern population was isolated from the western population in historical times (Dawson 2000), and densities have declined from low levels to possible extirpation (Fortin et al. 2002). There is a draft recovery plan in place (Fortin et al. 2002).

Similar geographic isolation has occurred for the Vancouver Island, Pitt Island (north coast of British Columbia) and some or all of the arctic island sub-populations. Gene flow among these and other sub-populations has not been studied. Recent studies by Kyle and Strobeck (2001, 2002) have shown genetic structuring of wolverine sub-populations in Manitoba-Ontario, southern British Columbia (Revelstoke sample) and Idaho, suggesting varying degrees of isolation from the once panmictic Canadian population. There has been no evidence of wolverines on Vancouver Island since 1992 and the population and/or subspecies may be extirpated (Lofroth, pers. com., 2002).

The Southern Mountain national ecological area (see COSEWIC national ecological area map http://www.cosewic.gc.ca/cosewic/images/ecomap.gif) sub-population is vulnerable to habitat fragmentation and subsequent decreased viability. Genetically distinct populations occur in the United States and Scandinavia, due in part to population fragmentation (Kyle and Strobeck 2001, Walker et al. 2001). Wolverines from near Revelstoke, British Columbia have differentiated from the continuous northern population due to a barrier to gene flow, although not to the degree of the Idaho population (Kyle and Strobeck 2002).