Trapping Reform in Wyoming

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Wolverines in the Snowy Range? Biologists aim to find out.


Wolverines have been detected in western Wyoming mountain ranges. (National Park Service/FlickrCC)

When it comes to animals, not comic book characters, few wolverines are as famous as wolverine M56. Over the course of a few years, the badger-sized animal with claws meant for digging and teeth meant for ripping wandered from the Tetons to Rocky Mountain National Park in Colorado to North Dakota, where he was shot by a ranch hand unsure of the strange animal approaching his cows.

Wolverine M56 made headlines because his radio transmitter allowed biologists to track the epic journey, which spanned hundreds of miles. But those kinds of distances aren’t unheard of for one of the West’s rarest carnivores.

“Once they separate from their natal area and go on the search for a place to land, they can travel hundreds of miles in a few days, sometimes,” said Jeff Copeland, board member of The Wolverine Foundation and longtime wolverine researcher. “We’ve seen lots of animals do it, males and females.”

That’s why the Wyoming Game and Fish Department, along with biologists from Utah, Colorado, Washington, Oregon, Montana and Idaho, are coordinating to sample mountain ranges for wolverines every five years. In 2016 and 2017, biologists surveyed Wyoming’s western and central mountains, from the Wyoming Range to the Wind River Range to the Beartooths and the Bighorns, recovering hair samples and trail camera images of at least six unique wolverines. This year, scientists are resampling the same areas as before, and adding the Snowy Range in south central Wyoming. The likelihood biologists find wolverines in the Snowies is low, said Zack Walker, Game and Fish’s nongame supervisor, but not impossible.

“We think we’re in the leading edge of recolonization,” Walker said about wolverines moving from Montana down into Wyoming. “The interesting thing about fringe populations is that typically genetic diversity is lower than in the core, and so we’re making sure we keep all of our wolverines, but we also need an influx every couple generations from other areas.”

Trappers, ranchers and hunters rarely targeted wolverines the way they systematically annihilated wolves, mountain lions and grizzly bears. Wolverines, the largest member of the weasel family, can live at 8,000 feet in the winter and even higher in the summer. They seldomly wander near human habitation and, despite the namesake Marvel character, are not actually all that predatory. But habitat loss coupled with the poisoning campaign of the early- and mid-1900s in the western U.S. resulted in the nearly complete elimination of wolverines from the Lower 48 states.

Wolverines specialize in scavenging animal carcasses — elk, deer, bison, moose — and will occasionally kill something if it’s sick, weak or injured. So when ranchers and trappers placed cow carcasses on the landscape laced with poisons like 1080 and Strychnine, intending to kill wolves and bears, wolverines also died.

Our hope is that we continue to find them in more and more areas.

As soon as poisoning stopped, wolverine populations expanded again, slowly creeping down from Canada into Montana and Washington. From there, two distinct populations formed, with wolverines in Montana, Idaho and Wyoming carrying genetics from southern British Columbia, and those in the Cascades more genetically aligned with wolverines from northern Canada, Copeland said.

Because wolverines are notoriously hard to survey, population estimates are far from perfect. The U.S. Fish and Wildlife Service lists a 2013 population estimate of about 318 wolverines in the contiguous U.S., though it notes many caveats and states the estimate is “not a definitive population count across the western United States.” Many wildlife managers are now focusing more on whether wolverine habitat is occupied, instead of developing an actual population estimate.

Colorado hasn’t had a verified sighting of a wolverine since M56 made his walkabout in the mid-2010s, and California hasn’t had a verified sighting since one named Buddy wandered in and out of camera traps near Lake Tahoe beginning in 2008.

A trail camera captured this wolverine in the Wind River Range. (Wyoming Game and Fish Department)
But Copeland believes it’s only a matter of time before wolverines recolonize the high mountains of Utah and Colorado, and one path to the Colorado Rockies is through Wyoming’s Snowy Range.

Possible expansion
This year’s survey already looks promising, Walker said, at least in western Wyoming. Grainy trail camera images show wolverines climbing up a tree to a deer quarter hanging underneath a lure reeking with odors like skunk, beaver castor and fish oil. Size differences in the images may well indicate a male and female.

“We have more wolverine observations this go round than we did last,” Walker said. “And we have had multiple wolverines on the camera, which we’ve maybe never had before.”

Trapping an actual wolverine is as difficult as it sounds, which is why scientists have turned to cameras and smelly lures to observe the animals. When a wolverine climbs the tree to inspect the odor, a camera captures its likeness and a strategically placed wire brush snags a bit of hair.

A trail camera captured this wolverine in the Gros Ventre Range. (Wyoming Game and Fish Department)
Scientists then analyze the hair for DNA, which tells wildlife managers the creature’s gender, genetic lineage and unique signature, allowing them to count and then estimate individuals.

Wolverine experts like Copeland worry about the impact of climate change on the scrappy mustelids. Females build dens in 9 or even 12 feet of snow and only reproduce, on average, every other year. If snow takes longer to accumulate and melts earlier, mothers may feel forced to move their kits before they’re old enough to travel. The climate change question, coupled with concerns about low population levels, triggered a review by the U.S. Fish and Wildlife Service to potentially place the creature on the endangered species list. But in 2020, the agency said Lower-48-state populations are stable.

Walker worries about genetic diversity and connectivity with other populations. The more a population is isolated, the harder time animals have adapting to diseases or other changes in their environments. It’s part of the reason states continue to survey for the animals, to see if they are able to interact with others.

Left alone, Copeland believes they will spread into new areas, like wolverine M56.

“Our hope is that we continue to find them in more and more areas,” Walker said. “To know they’re expanding into available habitat in the state.”

Christine Peterson
Christine Peterson has covered science, the environment and outdoor recreation in Wyoming for more than a decade for various publications including the Casper Star-Tribune, National Geographic and Outdoor Life. She lives and reports from her home in Laramie. Contact her at, 307-797-0731 or @she.will.roam.

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