JWM: In the Alaskan Arctic, where are all the wolverines?

A recent study found densities were a tenth of what researchers found 40 years ago

Wolverine densities on Alaska’s North Slope are far lower than the last survey revealed 40 years ago, raising concerns about what roles climate change, industrial development and human access may play in altering the remote Arctic tundra.

Seen from the air, wolverine (Gulo gulo) tracks crisscross the remote terrain, as do the tracks of their primary prey—caribou (Rangifer tarandus). “Traveling around the landscape, you get the impression that wolverines are all around,” said Tom Glass, a postdoctoral researcher at the University of Alaska Fairbanks. But as Glass investigated, he found a different story.

“This whole ecosystem has the potential to unravel if we encroach too much on the refugia that currently support wildlife,” said Martin Robards, regional director of the Arctic Beringia program for the Wildlife Conservation Society. He and Glass are co-authors on a study published recently in the Journal of Wildlife Management looking at wolverine densities and home ranges on the North Slope.

The region is undergoing dramatic changes. Due to climate change, snow is melting earlier, boreal wildlife is moving northward and willows are encroaching on the landscape. The human footprint is also growing, with expanding oil fields, new roads and increasing mining interest.

But while species of conservation concern like caribou and bowhead whales (Balaena mysticetus) are well researched in the North Slope, “to me, one of the species that stood out as understudied was the wolverine,” Robards said.

The disappearance of wolverines elsewhere in North America has brought a lot of attention. The species was listed as threatened in November in the Lower 48, and Colorado is laying plans to reintroduce wolverines in the hope that the Rockies can offer them a climate refuge. But their status in the north was less clear.

“In the Arctic, western scientists knew almost nothing about them—what they do, where they breed,” Robards said.

In a separate study in the July issue of JWM, another team of WCS biologists examined wolverines at two boreal forest sites in Canada—one in Red Lake, Ontario, and another in Rainbow Lake, Alberta. Considering the two sites together, they found the species was declining, due largely to fur trapping and vehicle strikes.

Wolverines are not considered threatened in Alaska, but they are of cultural importance. Alaska Natives line parka hoods with frost-resistant wolverine fur, and the mustelids remain widely hunted and trapped by both Alaska natives and others.

Previous research had found a range from extremely low densities to high densities at some locations in the Arctic. On the North Slope, wolverine space use hadn’t been studied since the early 1980s, when Audrey Magoun, then a PhD candidate at the University of Alaska Fairbanks, studied their home ranges and behavior. At the time, she found a robust 20 wolverines per 1,000 square kilometers in the Utukok Uplands, a similar landscape west of the current study. But had things changed? Was there a now conservation concern for these wolverines, too?

Biologists Tom Glass and Matt Kynoch replace a wolverine in the trap after fitting a collar, where it will recover from anesthesia prior to release. Credit: Peter Mather

Robards and Glass set out to find out. They placed bait to capture, collar and photograph wolverines to better understand their movements, ranges and densities across the Alaskan tundra.

“The main difficulty is the working conditions,” Glass said. The two went out in the winter, when wolverines are easier to find and the North Slope—a vast, treeless expanse between the mountains of the Brooks Range and the Arctic Ocean to the north—is more accessible by snow machines.

“Wolverines call pretty much that whole expanse home,” Glass said.

What they found surprised them. Despite the tracks across the landscape, wolverine densities were 10 times lower than those reported for the Utukok Uplands in 1984. They found roughly two wolverines per 1,000 square kilometers—among the lowest wolverine densities ever documented.

A male wolverine leaves the trap after being collared. Credit: Peter Mather

Researchers are left wondering why their densities are so low. “What was different between Audrey’s study and our study 40 years later?” Glass asked.

While their study doesn’t explore the causes, possibilities include climate-induced changes in vegetation and prey, increased industrial development, greater access for hunters on new roads or snow melting two weeks earlier than it did historically.

“That potentially means the kits are having to come out of their dens when they’re 10 or 11 weeks old rather than 12 or 13 weeks old,” Glass said. “These are the kinds of things nobody has studied.”

The population does not seem to be at risk yet, the researchers concluded, but the wolverine’s future in the region may be more precarious than conservationists once thought.

“We shouldn’t assume they’re totally safe,” Robards said. “One of the take-homes for me is, there’s maybe not a big window of safety for this species, particularly if they lose those large areas of refugia.”

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Header Image: A wolverine patrols the Brooks Range foothills in the midnight alpenglow of late April. Credit: Peter Mather