Wolverine Declines Continue
Wolverines have disappeared from many parts of North America over the last century, and recent research shows that some of the remaining populations continue to plummet.
The ongoing declines are of particular concern since new evidence suggests that mountain-dwelling wolverines seldom travel between major ranges.
This means that many populations are biologically isolated and cannot expand in size or genetic diversity with immigrating animals.
In the 1800s, wolverines of the contiguous United States lived in the western mountains and the Great Lakes region. By the mid 1900s, their US range had shrunk substantially, and since 1995 they've only been located in portions of Washington, Idaho, Montana and Wyoming.
The fully isolated and genetically distinct wolverines of California's Sierra Nevada Mountains became extirpated by the 1930s. The eastern Canadian population may also have gone extinct, with the last confirmed sighting in 1978 in Quebec.
More recently, a subspecies, Gulo gulo vancouverensis, confined to Vancouver Island in British Columbia is now feared extinct. Across the island, large-scale forest harvesting has fragmented its habitat. According to records, 1992 was the last time a Vancouver Island wolverine was ever spotted.
On mainland BC, wolverines are estimated to number 3,520. They comprise part of the western Canada population that spans boreal and arctic regions. Western Canadian wolverines in 2003 probably totalled 15,000 to 19,000 animals. Their populations, however, have lately fallen in Alberta, Ontario and southern BC.
The same factors that have removed wolverines from much of their range - overharvesting and human encroachment into their habitat - continue to plague them. Wolverines suffer from unsustainable hunting and trapping in 21 percent of BC's population units. A 2005 study in western Montana found that licensed trapping largely contributed to wolverine population declines of 30 percent a year in four mountain ranges.
Research in BC's Columbia Mountains concludes that outdoor recreation and logging activities cause wolverines to avoid habitat. In this popular winter recreation region, wolverines stay away from areas used by heli-skiers or backcountry skiers. In summer, females also shun roads and recent logging.
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Environment Canada. 2006. Species at Risk. Wolverine Western Population.
John Krebs, Eric C. Lofroth and Ian Parfitt. 2007. Multiscale Habitat Use by Wolverines in British Columbia, Canada. Journal of Wildlife Management. 71(7): 2180-2192.
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