Legislation calling for a wolverine recovery program is moving through the Colorado Legislature/NPS file

Wolverines, which, aside from a straggler that passed through Rocky Mountain National Park in 2009, have been missing from Colorado since the early 1900s, but an effort moving through the state's legislature could launch a recovery program for the ferocious carnivores.

"Reintroducing wolverines to Colorado offers a really significant opportunity to conserve the species," explained Megan Mueller, a conservation biologist with Rocky Mountain Wild, a nonprofit that works to protect and restore wildlife and wild lands in the Southern Rocky Mountain region. "The wolverine is also one of the last native species missing from Colorado. We've done a really great job with reintroducing a number of other species and so I think a lot of Coloradans would like to see wolverines back in the state."

Mueller, a guest on this week's podcast from the National Parks Traveler, said the Colorado Parks and Wildlife agency back in the 1990s began discussing efforts to recover wolverines, the largest member of the weasel family.

Once found across the northern tier of the United States and as far south as New Mexico in the Rockies and Southern California in the Sierra Nevada range, today small, fragmented populations of the reclusive animals can be found in Idaho, Montana, Washington, Wyoming, and northeast Oregon. Their homes are high in the mountains, where they travel ridgelines and avalanche chutes in search of animal carcasses they can scavange or prey they can kill. At times they'll even steal prey killed by another animal.

As the Traveler noted in a 2014 profile of wolverines, they "have a stocky and powerful muscular build, and a broad, round head that houses a short snout and forceful jaw. Between their aggressive, persistent personality and their bone-cracking jaw, wolverines are able to tear through frozen meat and with ease. Like other mustelids, they have a unique pair of molars in the back of their mouths that are rotated inward 90 degrees. This arrangement makes it much easier for them to tear chunks of meat from prey, even when the victim is frozen solid. While other mammals pack on the pounds in preparation for hibernation during the cold winter months, wolverines are well equipped for the coldest season. They have thick, dense fur, and wide, five-toed webbed paws that enable them to run on powdery snow effortlessly."

Legislating Recovery

The Colorado Legislature has been considering a measure that would give Colorado Parks and Wildlife the OK to move ahead with a wolverine recovery plan. The bill has gained approval from the state Senate and is expected to clear its final legislative hurdle in the House in the coming weeks. Helping nudge the legislation forward, according to Mueller, is a state law that requires the Colorado Legislature to approve reintroduction of any species that's protected under the Endangered Species Act. Just last fall the U.S. Fish and Wildlife Service listed wolverines as endangered, in large part due to climate change.

The animals depend on areas with deep snow through late spring. Pregnant females dig their dens into this snowpack to birth and raise their young. Snowpack is already in decline in the Western mountains, a trend that is predicted to worsen with a warming climate. Wolverine populations are also at risk from traps, human disturbance, habitat fragmentation and extremely low population numbers resulting in low genetic diversity.

Back in 2009 a dispersing male wolverine that had been fitted with a radio collar in Grand Teton National Park made its way south across Wyoming and into northern Colorado, where a photographer in the right spot at the right time captured an image of the animal in Rocky Mountain National Park. From there the wolverine reversed course and made it all the way north into North Dakota, where it was killed by a hunter.

"Males will often disperse long distances like that to find a mate. It's one of the other things I think is really amazing about wolverines, just their ability to cover huge distances," said Mueller when asked why a recovery program is necessary in light of that one wolverine's travels. "But the issue is that female wolverines tend to stay closer to where they were born. So they'll find a territory that's kind of close to where they were born or as close as possible to where they were born. They're not as likely to make those kinds of long-distance movements. We haven't had any documented evidence of a female wolverine in Colorado in 100 years, and the space that they have to disperse across is just incredibly inhospitable."

A few wolverines have managed to return to Mount Rainier National Park/Cascades Carnivore Project

Wolverines made the news in recent years with their appearance in Mount Rainier National Park in Washington state after long being missing from that landscape. Back in 2020 a female wolverine and her two kits were spotted in Mount Rainier, an event biologists hailed as evidence that the park once again can be a breeding ground for the species. A second litter of kits was spotted in the park in 2021.

"Mount Rainier's had a couple litters, I think now, which is amazing," said Elaine Leslie, who was the National Park Service's chief of biological resources before retiring. "But they've also been down in in Yosemite, North Cascades National Park, so you're seeing national parks as these areas with vast wilderness, which I think these animals need."

Park Service Support

Before she retired, Leslie was involved in Park Service discussions regarding wolverine recovery efforts. Since retiring she has remained in touch with colleagues in the Park Service who have been following the legislative developments in Colorado. In the past the Park Service has been interested in seeing wolverines back in Rocky Mountain and Great Sand Dunes national parks, said Leslie during the podcast.

"Restoration is one of our mandates," she explained, "and it's in our policy to look at at-risk species."

With the legislation working its way through the legislature, said Leslie, "it's just a matter of time. Everybody needs to wait for this process to move forward. I know that the [Park Service's] associate director for natural resource stewardship and science is aware of this. He was very supportive of our efforts way back when, so they're watching it."

But with climate change altering snowfall and warming winter temperatures, will Colorado's Rocky Mountains be able to serve as a refuge of sorts for wolverines?

"Colorado's mountains are higher in elevation then the mountains in much of the West of the wolverine's range in the lower 48," said Mueller. "And climate-change projections suggest that our mountains are likely to retain snowpack to a greater extent and farther into the future than some of the mountains in, for example, the northern Rocky Mountains up in Montana and Wyoming. Those projections make it look like there will be good habitat for wolverines moving forward into the future. It's always, of course, somewhat uncertain with climate change. Right? And I think predicting precipitation and snowpack is a little bit more challenging technically than predicting temperature changes with climate. So, there's some uncertainty there, but the best available science that we have suggests that wolverines should be able to do well in Colorado."

Rocky Mountain National Park has wolverine habitat/Kurt Repanshek file

Also helpful for any recovery effort, notes Rocky Mountain Wild, is that "94 percent of wolverine habitat in Colorado is on federal public land, and 68 percent of the habitat on those lands is in protected areas (designated wilderness areas, roadless areas, and wilderness study areas)." Overall, Colorado has about 7 million acres of wolverine habitat, said Mueller, and Colorado Parks and Wildlife has estimated that the state could support 100-180 wolverines.

"A lot of Colorado's mountains are protected as wilderness areas, roadless areas, national parks, and they all have excellent habitat for wolverines," she said. "So basically any mountain range in Colorado has habitat for wolverines."

While the wolverine legislation could gain full passage and the signature of Colorado's governor before Memorial Day Weekend, actual recovery of the species in the state won't happen overnight.

"They're planning a multi-year process to plan the reintroduction after the bill passes the legislature," Mueller said. "So that will include Colorado Parks and Wildlife updating and finalizing a technical plan for how to do the reintroduction. It will include a stakeholder process where Colorado Parks and Wildlife makes sure that stakeholders really support wolverine reintroduction in Colorado. And it will include some coordination with the U.S. Fish and Wildlife Service. So it'll take I'm guessing at least two or three years before we would see wolverines on the ground."

Where those wolverines come from has not been determined, though Alaska and Canada could provide some of the animals, both Leslie and Mueller said.

"We're pretty excited that we've gotten to this place," said Leslie. "I think it won't be a problem finding wolverines for the restoration project process. It'll be carried out over the course of years, so you're not just going to go and deplete a source in a certain area. You're going to be very careful about how you do that."