Biologists found that a wolverine named Chewbacca, measured and collared by Cathy Raley, far right, Jeff Heinlen and others, ranged across 730 square miles. (U.S. Forest Service)
Considered a mere scavenger that robbed traps and ransacked cabins, the wolverine has recently earned respect and scientific attention. (Mike Hill / Woodfall / Photoshot / NHPA)
Wolverines inhabit the northernmost latitudes, where their snowshoe-like paws and thick coats are essential to survival. (Igor Shpilenok / Nature Picture Library / Minden Pictures)

The Way of the Wolverine

After all but disappearing, the mammals are again being sighted in Washington’s Cascade Range

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That’s the plan, at any rate.

“Mostly we get martens,” Rohrer says of the wolverine’s smaller cousin.

To see whether the wolverine really had re-established itself in the Pacific Northwest, Aubry, Rohrer and Fitkin laid three traps in 2006 and baited them with roadkill.

“We weren’t expecting much,” Aubry says. “We thought we’d be lucky if we caught even one wolverine.”

They caught two: a female, which they named Melanie, and a male, Rocky. Both were fitted with satellite collars and sent on their way. But Melanie’s collar fell off and Rocky’s was collected when he was recaptured a few months later. The second year, the crew collared three wolverines: Chewbacca (or Chewie, so named because he nearly gnawed his way through the trap’s wooden walls before the field crew could get to him), Xena and Melanie (again). The third year, they caught Rocky twice, and the fourth year they caught a new female, Sasha.

Data detailing the animals’ locations trickled in, and by March 2009 Aubry had an idea of the ranges for several wolverines. They were huge: Rocky covered more than 440 square miles, which sounds impressive until compared with Melanie, who covered 560 square miles. Both crossed into Canada. Yet their recorded travels were dwarfed by those of Chewie (730 square miles) and Xena (760 square miles)—among the largest ranges of wolverines reported in North America. More important, though, was that Aubry suspected Rocky and Melanie might be mates, and perhaps Chewie and Xena, too, given how closely their ranges overlapped. A mated pair could indicate a more stable—and potentially increasing—population.

Working with colleagues in the United States, Canada, Finland, Norway and Sweden, Aubry confirmed that the key to wolverine territory was snow—more precisely, snow cover that lasted into May. Every single reproductive den in North America, as well as about 90 percent of all wolverine activity in general, was in sites with long-lasting snow cover.

Scientists working in the Rocky Mountains then found that snow cover even explained the genetic relationships among wolverine populations. Wolverines interbreed along routes that go through long-lasting snow.

“We have a better sense of what they need, where they like to live,” Aubry says now of the wolverines in the North Cascades. “But no one can say with any certainty how many we have here.”

He points to a string of tracks running along the side of the road. “That 1-2-1 pattern, that’s classic mustelid. And look how big they are.”

About Eric Wagner

Eric Wagner has written for Smithsonian about cranes in Korea and sperm whales near Mexico.

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