The North American wolverine (Gulo gulo luscus) is a survivor. It is called the Arctic Hoarder for good reason. This small mammal, a member of the weasel family, lives at high elevations where it’s cold and snowy. Wolverines scavenge for food in the summer and cache it away for winter. And they are returning to Colorado.
Senate Bill 24-171 or “Restoration of Wolverines” was introduced by former state senator Perry Will (now a Garfield County commissioner) in March of 2024 and had bi-partisan support. The bill became law two months later. The bill authorizes Colorado Parks and Wildlife (CPW) to reintroduce the North American wolverine in the state with certain conditions. As long as the wolverine remains on the federal list of threatened or endangered species, CPW must establish a final 10J rule designating the species as a non-essential, experimental population in Colorado — much like the federal 10J rule governing grey wolf reintroduction. Gulo gulo luscus is federally listed as threatened.
The Act also mandates that CPW develop a restoration plan, a livestock damage compensation rule and a communication plan before paws hit the ground.
At January’s CPW Commission (CPWC) meeting, Dr. Robert Inman, CPW’s wolverine coordinator, told the Commission that the wolverine is smaller than a wolf. “It’s the size of a beagle dog or a corgi with long legs,” he explained. He added that females weigh from 20 to 25 pounds and males weigh 30 to 35 pounds. “They live in the coldest parts of the Northern Hemisphere,” he added, making Colorado’s High Country a good match, particularly as cold-adapted species face a warming planet.
According to Inman, the animal was extirpated from Colorado in 1919 and disappeared from the lower 48 states the following year. From 1930 to 1970, wolverines returned to the Lower 48 but did not occur in Colorado until almost a century after it was last seen. “During 2009, a male wolverine named ‘M56’ was radio-tracked as he dispersed from near Grand Teton National Park south into Colorado,” he said. “This was the first record of a wolverine in Colorado in 90 years.”
CPW has not yet sourced the wolverines for reintroduction. “Overall, western Canada tops the list,” said Inman. “But there are many source areas that can provide wolverines that should be able to thrive here.”
The plan so far is to release 15 wolverines per year for three years. “Thirty wolverines over two years would be sufficient,” explained Inman. But issues like survival of young animals, called kits, and genetic viability could reduce the population. “We are planning to target a little more than that in case some of the vital rates don’t match Colorado or there are unanticipated issues.” He added that wolverines don’t move in packs, like wolves. Their home territories are large and they tend to stay there.
“In our Yellowstone study area, we estimated that there were 15 wolverines in an area about half the size of Yellowstone National Park,” he said. “That translates to about four wolverines per thousand square kilometers of habitat.”
He added that Colorado offers about 30,000 square kilometers of habitat and is capable of handling around 100 wolverines. “To understand how sparse wolverines are on the landscape and why it is so rare to see one, imagine the whole of Rocky Mountain National Park from north to south, east to west,” he said. “It’s 415 square miles and there’s room for four to five wolverines in the whole park.”
The wolverines will be released in alpine timberline areas north of I-70, in the high mountains south of I70 and north of Highway 50 and in the southern San Juan mountains.
As for livestock predation, Inman doesn’t see much of an issue there; wolverines tend to feed on smaller mammals like marmots. But domestic sheep share their habitat in Colorado. A livestock damage compensation rule is in the works.
Inman believes that bringing wolverines back to Colorado in the 21st century will work. “Wolverines may have been the first mammal to have been extirpated from the Lower 48,” he said. “This was a result of having no wildlife management laws at the turn of the century.” He added that poison bait is less of an issue these days and food for the wolverine is plentiful.
Seventy percent of habitat is in wilderness areas, which are roadless. Living in alpine habitat will also help ease the impacts of climate change. “Some people think that Colorado could actually be a climate refugia for the species,” he said.
You can find more information about CPW’s wolverine restoration project at www.bit.ly/CO-wolverines