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Wolverines stage comeback in Northwest, but for how long?

One of the rarest mammals in North America is staging a comeback here in the Northwest. Wildlife biologists have tracked wolverines on mountainsides where they haven't been seen in many decades. But several new studies also suggest the recovery could be short lived if mountain snowlines retreat due to global warming.

If this story were a movie, we could call it: "To Catch a Wolverine." It's set in winter in Washington's northern Cascades, though it could just as well take place in central Idaho. It's an action drama with a cast of determined wildlife biologists on snowmobiles.

We'll have John Rohrer play himself, a district biologist for the Okanagan-Wenatchee National Forest. His prop is a dead deer head to lure elusive wolverines:

"They're in this winter environment that we think is so harsh and so inhospitable, and they're loving it.”

Cut to Rohrer checking one of 11 live capture traps set up in the high country east of the Cascade Crest. He's assisted by state Fish and Wildlife biologist Scott Fitkin. Both men have worked with all sorts of interesting critters, but hold a special reverence for the wolverine:

"These are the most charismatic animals I've worked with over 20 years in my career. They have a lot of personality. They're certainly individuals. Each one is a little different in the way they react to us. They're a very beautiful animal. Everything about them is just interesting," says Fitkin.

They're also really rare. Yet until recently, this movie couldn't have bee made at all.

Trapping and deliberate poisoning more or less wiped out the wolverine from the contiguous United States. But now wolverines have moved down from Canada to reoccupy their historic ranges.

Rohrer and Fitkin are into their sixth season in pursuit of the elusive scavengers. Captures are few and far between. Fitkin videotaped the most recent one: a wolverine they named "Rocky" displays what Fitkin calls typical "bad-ass" attitude.

When the field crew catches a wolverine, they attach a GPS tracking collar and set the animal free again. Study leader Keith Aubry can monitor the signals from his desk at the Forest Service's Pacific Northwest Research Station in Olympia. Aubry says the wolverine's rebound appears fragile:

"The populations are not dense and they're not reproducing rapidly. So it's a precarious situation."

Aubry has a science journal paper in the works about this. He says global warming poses the biggest threat to wolverines. Why's that? Wolverines need long-lasting snow cover to dig the snow caves in which they give birth.

"The denning period, weaning, occurs about in mid-May. They need snow cover that persists to mid-May to provide these dens for the kits. If snow starts melting early, the den could start collapsing," says Keith Aubry.

The Forest Service is funding a parallel study in central Idaho. But in Idaho, the wolverines aren't the only ones being tracked.

The research team led by biologist Kim Heinemeyer is asking snowmobilers and backcountry skiers to voluntarily carry GPS tracking units too. That lets Heinemeyer see whether human recreation affects the wolverines:

"It's a very complicated question that we're trying to answer. While we have resident animals in the landscape and some of them have successfully denned we believe, we don't know the potentially more subtle interactions that may happen between winter recreation and wolverines."

In December, the U.S. Fish and Wildlife Service classified wolverines as a candidate for endangered species protection. Wolverines are also listed as a threatened species in Oregon. There haven't been any recent confirmed sightings in the state.

The non-profit Wolverine Foundation just launched an aerial and remote camera survey of the Wallowa Mountains in northeast Oregon to find out if wolverines have reestablished there.

Correspondent Tom Banse is an Olympia-based reporter with more than three decades of experience covering Washington and Oregon state government, public policy, business and breaking news stories. Most of his career was spent with public radio's Northwest News Network, but now in semi-retirement his work is appearing on other outlets.