The Mysterious Wolverine

Megan Claflin is an environmental journalism student at Western Washington University, Flammable611@msn.com.

Trickster, shape shifter, thief — Native American folklore describes a variety of creatures with these characteristics. For the Navajo it is coyote, for northwest coastal tribes it’s raven, but members of North Cascades tribes name a different protagonist ­— wolverine.

Wolverines are revered as deviants by many cultures, assumedly due to their habits of scavenging food from other predators as well as humans. It’s common for wolverines to claw and chew their way through man-made barriers to retrieve food. “Skunk-bear” refers to the animal’s appearance and its habit of marking its claim with musk and urine; this has included the contents of tents, cabins and other dwellings. The wolverine’s Latin name, Gulo gulo, means gluttony, a reference to wolverine’s voracious appetite.

The wolverine is the largest terrestrial member of the weasel family mustelid. They occupy a wide range of habitats including tundra, taiga and forest zones of North America and Eurasia. Although wolverines tend to be labeled as creatures of northern wilderness and remote mountain ranges, their territories once extended as far south as Colorado and California.

Wolverines are stout in appearance with a broad, rounded head, small eyes and short, rounded ears. People fortunate enough to catch a glimpse of these elusive creatures often mistake them for a small bear or cub. A wolverine’s body is compact and muscular. Four short legs allow for swift movement and easy maneuvering amongst dense forest undergrowth. Each foot is complete with five clawed toes useful for climbing and digging.

Wolverines have powerful jaws, which allow the animal to crush bone, helpful for retaining all possible nourishment from carcasses. Typically adult males weigh 26 to 40 pounds while adult females range from 17 to 26 pounds.

A wolverine’s coat is typically a glossy, dark brown. Two pale stripes trail from the nape of the neck over the haunches to the base of the long, bushy tail. Their fur is resistant to moisture and frost, which led hunters to covet wolverine pelts during the early northwest fur trade and still today. Overtrapping coupled with loss of habitat may have led to decreased populations.

In the last decade, conservationists have proposed adding the wolverine to Washington’s threatened species list three times and each time the Washington Department of Fish and Wildlife (WDFW) rejected the proposal due to a lack of evidence.

Prior to 2005, the population of wolverines in Washington remained unknown. The little information available about these mysterious creatures comes from recovered fur, tracks and human and remotely-sensored camera sightings recorded with the United States Forest Service. Much like the grizzly bear, the wolverine is now viewed more as a legend than a living, breathing member of the North Cascades ecosystem.

In 2005, the U.S. Forest Service partnered with the WDWF to locate and monitor wolverine populations in the North Cascades range. The proposed five-year project is the first in Washington to study the distribution and ecology of one of North America’s rarest forest carnivores.

Wolverines occupy large territories and habitually remain distant from human activity and developments. These characteristics present a challenge to researchers who in response employ a variety of methods to identify probable wolverine habitat. A review of historical occurrence records and remote-camera and snow-tracking surveys supplied several credible locations for primary observation.

Researchers piloted the study in the Methow Valley Ranger District of the Okanogan-Wenatchee National Forest. Here, over four million acres reach north to the Canadian border, south to near the Columbia River, west into North Cascades National Park and east to the Methow and Okanogan River watersheds boundary.

During the fall of 2005 three live-capture traps were constructed near Hart’s Pass, the Twisp River drainage and Cutthroat Pass. A fourth trap was added in 2006 at Baldy Pass. The traps were built from native logs and baited with mule deer, beaver and salmon carcasses.

Wolverines are capable hunters; however, they commonly revert to scavenging as their primary method of securing food. Using their highly developed olfactory glands, wolverines locate carrion and are known to drive larger predators including bear and wolves away from a kill. It is this aggressiveness and tenacity that has earned the wolverine an undeserved reputation as a ferocious and vicious creature.

Over the 2005 and 2006 winter, the Baldy Pass trap proved unsuccessful and while the Cutthroat trap did capture a wolverine, the animal escaped before researchers returned. At Hart’s Pass, two wolverines were captured. The first was a juvenile female nicknamed Melanie, and the second an adult male dubbed Thor. Both animals were tranquilized to allow researchers to record their age, sex and condition as well as to collect tissue samples vital to genetic profiling.

The wolverines were fitted with radio-collars containing both satellite and standard VHF transmitters. Researchers intended for the received data to elaborate on the wolverines range; however, Thor’s collar failed shortly after his capture and Melanie’s collar presented additional complications. Programmed to be active for five hours each day so the battery life would extend one year, the cycle resulted in very few recorded satellite locations.

Researchers were able to modify the collars in 2006, when two additional wolverines were captured in the Twisp River trap: a male and female, named Chewbacca and Xena, respectively. Their collars were adjusted to be active for 48 hours, transmitting a signal every 60 seconds. The collars were then inactive for 24 hours before repeating the cycle. The satellite transmitters provided general location and movement data while the VHF transmitters provided location data on a more refined scale which enabled researchers to locate natal and maternal dens, and locate radio-collars if they were removed prematurely by the animal.

The same winter, Thor was photographed near Hart’s Pass using a remotely-sensored camera; however, biologists were unable recapture him and replace his malfunctioning collar. Melanie was recaptured in 2007, and researchers determined she was pregnant.

Wolverines breeding habits remain speculative although popular opinion supports that wolverines breed year-round taking advantage of hospitable conditions. Females are not sexually active until after their first summer while males reach sexual maturity during their second year. Males use their olfactory nerves to detect increased hormone levels in a female’s scent, thus knowing she is ready to breed. A wolverine pair will mate several times over a period of a few days and the males may remain near the female during breeding to fend off other potential suitors.

Like bears, wolverines exhibit delayed implantation, during which the development of the embryo is arrested in early stages. Females require secure dens, deep beneath snow pack. Often they will burrow underneath fallen logs or boulders. Gestations last an average of 30 to 40 days and litter sizes range from four to six. Increasing litter sizes with age is suspected, as it is common for mammals.

Kits, wolverine offspring, remain with their mother for several months after being weaned at seven to 10 weeks. Young wolverines grow quickly and by seven months reach adult size. Unfortunately, since learning of her pregnancy researchers have been unable to recapture Melanie and are thus unsure of the fate of her offspring.

As the Washington study completed its third year this past winter, success continued. An additional male was captured at Hart’s Pass and named Rocky. Adjustments to the radio-tracking collars proved beneficial. Preliminary data shows the captured wolverines inhabit large tracts of land ranging through the crest and eastern edge of the North Cascades extending into Canada. The wolverines appear to transverse their territories in a figure-eight pattern, which may increase their likelihood of locating food and mates.

Further examination of wolverine distribution has led researchers to theorize that decreased snow pack levels in April (a critical denning period) due to global climate change is causing the wolverine population to migrate north where conditions may be more suitable for breeding and rearing young.

Researchers involved with the Washington study plan to test this theory in the remaining two years as well as gain further insight into the habits and behaviors of these remarkable carnivores. A potential partnership with Canadian scientists will assist this process. §

• Roger Christopherson, biologist for North Cascades National Park Service complex.

• Distribution and Ecology of Wolverines in the North Cascades, J. Rohrer, K. Aubry, 2007.

• The Scientific Basis for Conserving Forest Carnivores: American Marten, Fisher, Lynx, and Wolverine, USDA Forest Service, 1994.