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Wolverines might be making a comeback

By Sharon Wootton
The Olympian

“With the camera techniques, we know there are three or four times more wolverines than have been detected by trapping alone. There are a lot more wolverines than we thought,” [wildlife biologist Keith] Aubrey said, but still fewer than 25 in the North Cascades.

The beauty of studying a little-studied mammal is the potential for making a difference. Keith Aubrey, wildlife biologist with the U.S. Forest Service's research station in Olympia, is having that opportunity.

Aubrey’s mammal of choice is Gulo gulo (gluttonous glutton), the wolverine. It resembles a small bear with a bushy tail but moves more like its relative, the weasel.

The North Cascades wolverine disappeared in the 1920s, but research suggests that wolverines are re-establishing a population in north-central Washington.

Aubrey initiated the first radio-telemetry study of wolverines in the contiguous U.S. Only five elusive wolverines have been trapped and released since 2005.

“We think the population is precarious under the best of circumstances,” Aubrey said.

For protection issues to be addressed, information about habitat is essential. Researchers found that the main habitat feature that accounted for the historical distribution of wolverines was spring snow cover.

Dens are located in snow tunnels, and the kits need the protection from predators and cold. Mid-April to mid-May is the end of the wolverines’ denning period.

“We’re also looking at the effect of warming on snow conditions,” Aubrey said.

Earlier snow melt means fewer areas are covered at the critical time, and those areas are more fragmented and isolated, probably affecting survival and limiting the wolverines range.

Also, a study of 533 dens in North America and Scandinavia showed that 98 percent of the dens corresponded with spring snow cover. Wolverines stay in or near snow 95 percent of the time.

The Washington wolverines are at the southern edge of the boreal forest that stretches north through Canada.

They are excellent winter scavengers with powerful jaws and teeth to eat frozen meat, broad paws for snow travel, thermal regulation to counter the cold and an incredibly strong sense of smell.

“They’re able to detect carcasses of goats or deer or elk in the winter, and capable of finding them under 6 feet of snow.”

Trappers decimated the historical wolverine population, in part because wolverines would eat the dead animals in the traps. It is illegal to trap wolverines in Washington.

In Scandinavia, wolverines are significant predators of reindeer. Rather than compensate herd owners, government pays the herders to locate wolverine dens.

“It’s a brilliant strategy. We know the locations of 500 wolverine dens in Sweden and Norway. We know of 60 to 70 in North America,” Aubrey said.

“The owners are compensated while providing invaluable data, and the reward is a disincentive to kill wolverines.”

High-tech tracking methods have created new data for the wolverines trapped in the areas of Hart’s Pass and Twisp. Data were collected by researchers on snowshoes and with cameras set near researcher-placed food above the snow.

“The wolverine looks up to decide how to reach the food, and the camera gets a clear picture of the throat and chest blazes. Each individual has a unique white blaze pattern,” Aubrey said.

“With the camera techniques, we know there are three or four times more wolverines than have been detected by trapping alone. There are a lot more wolverines than we thought,” Aubrey said, but still fewer than 25 in the North Cascades.

Technology also helped map 80 locations for wolverines in an area of about 730 square miles.

“They have a tendency to travel in a more-or-less circular or figure-eight routes, and often return close to the starting point,” he said of the monitored wolverines.

Aubrey’s research also calls into question the assumption that wolverines are solitary animals. “There is evidence that male groups will form and travel together. ... We’re still learning.”

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