Refuge Notebook: Unveiling the secret lives of elusive wolverines, Part 2

Posted: Friday, November 19, 2010

Editor's note: This is the second of a two-part series. The first part appeared in the Nov. 12 Clarion.

During the winter wolverines are primarily scavengers of carcasses of large mammals. Carcasses of wolf-killed and winter-killed moose and caribou provide much of their food here in Alaska, but wolverines elsewhere scavenge the carcasses of other large ungulates (elk, deer, mountain goats and sheep).

Although they also prey on small mammals (such as Arctic ground squirrels, marmots, snowshoe hares, red squirrels) and birds (ptarmigan and grouse), and even spawning salmon during summers, it is believed wolverines probably cannot survive indefinitely by feeding only on small animals. Since wolverines have to compete with wolves, brown bears and other carnivores when scavenging large carcasses, they have developed a very pugnacious and belligerent demeanor. Wolverines have to be nasty and aggressive to be successful scavengers.

Wolverines travel long distances to find large carcasses, which tend to be widely scattered on the landscape; one male wolverine in Glacier National Park traveled more than 120 miles in a week. Wolverines also travel widely to patrol and place scent markings to dissuade other wolverines from taking over their large territories.

Wolverine territory size varies with sex and reproductive and social status, as well as habitat and prey density, but can range from 21 square miles (females with young) to 372 square miles (adult males).

The persistence and depth of snow cover are important components of wolverine habitat because wolverine kits are usually born in dens that females dig into deep snowdrifts to protect them from predators. Snow cover has to protect the denned kits until about mid-May. A recent analysis shows that the late-spring-melting-snow zone describes 90 percent of wolverine habitat throughout the world.

Although wolverines have not been radio-collared on the Kenai Peninsula, their annual harvest from trapping and hunting, distribution, population density and DNA structure have been studied by various researchers. In the mid-1990s former refuge pilot-biologist Bill Larned and I conducted aerial surveys throughout mountain habitat on the Kenai Peninsula during winter and mapped the distribution of wolverine tracks. On several occasions we meticulously followed the tracks until we observed the wolverine loping along in the snow.

In March 2004 an aerial population survey designed by Earl Becker and Howard Golden of the Alaska Department of Fish and Game using tracks in snow and conducted in a 1,675 square mile area in the northwestern Kenai Mountains resulted in an estimate of 12.8 wolverines or an average density of about 1 wolverine per 130 per square miles. This was lower than other average wolverine density estimates in Montana, Idaho, Arctic Alaska or the Yukon Territory where estimated wolverine densities ranged up 3 to 7 times higher using the same technique or radio telemetry, respectively. There are thus fewer wolverines on the Kenai Peninsula than there are brown bears, wolves, or lynx.

A 2005 study of wolverine DNA in northwestern America revealed that wolverines sampled on the Kenai Peninsula showed a disproportionate amount of mitochondrial genetic diversity (i.e. a unique mtDNA haplotype) compared to other North American wolverines, probably because of the island-like isolation of the Kenai Peninsula. The report concluded "...wolverines on the Kenai Peninsula and in southeastern Alaska may necessitate particular conservation emphasis." The report also noted that hunting and trapping pressure is a primary mortality factor for wolverines.

Wolverines everywhere face an uncertain future. To protect their kits in dens, wolverines depend on snow-cover until at least mid-May but glaciers are retreating and year-round snow cover is declining not only in Glacier National Park but here on the Kenai Peninsula. Because of their naturally low reproductive rate and low population density, any human-caused mortality adds to their natural mortality rate thus potentially jeopardizing wolverine populations. In its 2010 "Conservation Top 10 List" of worldwide conservation issues the International Wildlife Conservation Society listed the wolverine as one of North America's two species on which they are now focusing their attention.

After I left the Montana wolverine study in 1973 I doubted that I would ever again handle a live wild wolverine. But about 10 years ago while attending a Northern Furbearer Conference in Fairbanks I briefly held a young wolverine that was being raised for behavior research by Dr. Audrey Magoun. It vigorously squirmed and wiggled in my arms and as I looked into its dark, mysterious eyes I felt privileged that I had been given another chance to experience -- close up -- this wonderful elusive creature of the North.

Readers are encouraged to read the recently released book "The Wolverine Way" by Douglas Chadwick, and to log on to The Wolverine Foundation web site at:

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Ted Bailey is a retired Kenai National Wildlife Refuge wildlife biologist who has lived on the Kenai Peninsula for over 34 years. He maintains a keen interest in the Kenai Peninsula's wildlife and natural history.

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To report unusual bird sightings or hear what local birders have been seeing, call the Central Peninsula Bird Hotline at 262-2300. Previous Refuge Notebook articles can be viewed on the refuge website

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