While the state has been mired in the controversial gray wolf reintroduction that was voted in by slim margin in 2020, Colorado is getting ready to reintroduce the smaller, but less-controversial wolverine back into its wilds. The reintroduction is still some years out, though.
Colorado lawmakers passed bipartisan legislation to reintroduce the wolverines in 2024, with the prime sponsors of the bill calling it “completely opposite from the wolf reintroduction process.”
Wolverines are not related to wolves. Rather, they are the largest member of the weasel family.
The last wolverine killed in Colorado was in 1919. One GPS-collared male moved through Colorado in 2009, but wildlife officials say one hasn’t been seen since. Experts estimate that Colorado is home to 20 percent of the lower 48’s suitable habitat for wolverines. There are an estimated 300 to 400 wolverines living in the contiguous U.S.
Wolverines were wiped out in the U.S. by 1920 mainly due to humans. They had a historical range from Northern Canada to Colorado.
The largest concentrated population of wolverines in the U.S. is in Alaska, where there are roughly 5 wolverines per 1000 square kilometers.
The Colorado Parks and Wildlife Commission heard from biologists and experts on what reintroduction will look like on Thursday.
Robert Inman, Ph.D., Colorado’s leading wolverine expert, gave the presentation to the commission where he dived deeper into the history of the animal as well as the steps necessary for a successful reintroduction. Inman has been exclusively researching wolverines for 15 years and worked with the world’s foremost wolverine experts in Sweden.
Inman said wolverines were once native to Colorado. The recovery of wolverines from Canada into Montana, Idaho and Wyoming in the 1970s gave way for reintroduction elsewhere.
For more than 90 years, Inman said, there were no records of wolverines in Colorado until the GPS-collared male, “M56,” was spotted in Rocky Mountain National Park in 2009. One hasn’t been seen or documented since. He said that wildlife officials are “confident there’s not a population of wolverines” in Colorado.
Reintroduction has been on the table for more than 25 years when legislation was first introduced to have the wolverines be introduced alongside the Canadian Lynx. Lynx reintroduction in Colorado has been successful with reported reproduction occurring.
The fear of waiting to reintroduce the wolverine was, according to Inman, due to fear that the wolverine species would be introduced and then listed as an endangered species, meaning more regulations for wildlife agencies.
In 2023, the wolverine was listed as a federally threatened species and with that listing came the possibility for a federal 10 (j) experimental population. An experimental population is reintroduced to its native habitat to “advance species recovery by encouraging the reintroduction of imperaled species in a place where it would not be otherwise introduced.”
Then in 2024, lawmakers passed the Restoration of Wolverines Act.
Four things must occur in order for an experimental population to be brought to Colorado, Inman said. First, CPW must deliver a Wolverine Restoration Plan to the public and statewide stakeholders. Second, the CPW Wildlife Commission has to come up with a depredation compensation plan for livestock producers in Colorado. Third, CPW will have to deliver a communication plan to statewide stakeholders and county commissioners. That, Inman said, will be developed later this year. And fourth, the U.S. Fish and Wildlife Service must publish a 10 (j) rule designating wolverines in Colorado as a “non-essential, experimental” population.
THE ARCTIC HOARDER
Wolverines live their lives mostly at elevations above 10,000 feet. They prefer the high-altitude alpine timberline that ranges in elevation from 11,000 feet and above. Inman said that is where the animals will spend most of their time, which includes setting up food caches and dens.
Wolverines have a large home range compared to their body size. In the lower 48, wolverines average between 20 and 30 pounds, “like a corgi with long legs.” They occupy a space between 100 and 300 square miles, which Inman said is “off-the-charts large for a 30-pound animal.”
They “patrol” their home ranges regularly throughout the year, leaving scent marks. Wolverines are highly territorial and have naturally low densities in the areas they occupy.
For example, Inman said that the Yellowstone Study Area has a population of about 15 wolverines. Those 15 wolverines are spread out so four wolverines occupy an area of a thousand square kilometers.
There are about 30,000 square kilometers of habitat for wolverines in Colorado. That area, Inman said, would be adequate for about 100 to 120 wolverines, which he said is about where the historical numbers often averaged in Colorado.
Wolverines “take a chance” each year to have a litter of kits. Litter weaning success, Inman said, depends on the availability of food each year. If there’s a good food year, the chances of a weaned litter is high and adversely low if it’s a bad food year.
That’s where they get their nickname, “The Arctic Hoarder.”
“This species exists in a way that seems to be at the margins of what’s possible,” Inman said.
In a more scientific way, “The wolverine is morphologically, behaviorally, and demographically adapted to occupy a cold, relatively unproductive niche.”
Living at high elevations, burrowing deep in the snow to establish highly-guarded dens, and caching every scrap of food they can find makes the wolverine a sparse and rare animal. They mainly feed on carrion, or the leftovers of animals that have been preyed upon or died in the wilderness. They are a highly opportunistic species.
Wolverines disperse at a “landscape scale,” and again occupy large areas each year. When they are successfully weaned, they can make large movements.
When the time comes to bring animals to Colorado, one of their first stops will be in the San Luis Valley. The Frisco Creek Rehabilitation Center outside Del Norte will initially house the wolverines where CPW staff will monitor the animals for issues and disease.
According to the Colorado Sun, releasing wolverines into the wild will be in coordination with the Southern Ute and Ute Mountain Ute Tribes into one of three areas: Mountain regions north of I-70, between I-70 and U.S. HWY 50, or within the San Juan mountains south of U.S. HWY 50.
Introducing 15 wolverines per year for three years is the target goal for right now.
Western Canada topped the list of where the wolverines may come from, Inman said, but there are other areas that have populations of wolverines adequate for transfer. Ideal areas are where wolverines live with populations of mountain lions, adequate prey food, and large genetic diversity.
Ultimately, he said, it will come down to who is willing to contract with Colorado.
Captures will happen between November and January where pregnant females will be transported and released prior to their giving birth. Male captures could continue through April.
After wolverines are introduced the conversation then shifts to depredation. Colorado Parks and Wildlife is drafting a depredation plan for wolverines similar to that of mountain lions and black bears. There are no records of wolverines attacking or killing people.
He said that in Montana and Wyoming, where wolverines have lived for 75 years, livestock depredation by wolverines is “simply not an issue.” Bighorn sheep populations in those states have not been affected by wolverines.
“They are not likely to have a measurable impact on livestock or other wildlife,” Inman said. Buit he noted that depredation could happen on domestic sheep and that a fair compensation rule should be in place.
Climate change will have an effect on wolverines, but Colorado’s higher peaks may endure climate change for longer.
“We think wolverines can make it here in 21st-century Colorado,” Inman said.
