Wolverines could be coming back to Colorado as climate change alters habitat
The mountain devil can cross hundreds of miles of rough alpine terrain, tear into an elk carcass frozen for weeks and fend off predators several times larger than its 40-pound frame.
And the elusive species might be coming back to Colorado.
Wolverines — also called “mountain devils” and “skunk bears” — could be the next large mammal reintroduced in Colorado after wildlife officials implement the voter-mandated reintroduction of wolves by the end of the year.
How and when wolverines could be introduced here hinges on an upcoming decision from the U.S. Fish and Wildlife Service on whether the species should be protected under the Endangered Species Act. A decision is expected in the next few months and, depending on the way that goes, efforts to begin bringing in wolverines could begin again. Plans to reintroduce the species in Colorado have existed for more than a decade, but uncertainty around the federal listing decision kept wildlife officials from pursuing the effort.
“It was bouncing back and forth, lots of uncertainty there,” said Eric Odell, species conservation program manager at Colorado Parks and Wildlife. “Because of all that uncertainty, we put it all on the back burner.”
It helps that the state’s top leader has thrown his political weight behind the reintroduction effort.
“The governor continues to join so many Coloradans who share his enthusiasm for reintroducing the native wolverine, last spotted in 2009 in our state, to better restore ecological balance in wild Colorado areas,” Gov. Jared Polis’ spokesman, Conor Cahill, said in a statement. “The governor is hopeful that a successful wolverine reintroduction program will begin during his time as governor.”
Despite the name, wolverines are not related to wolves — they’re weasels, not canines. They wander widely through ranges that cover up to 600 square miles and can cover 15 miles in a day. They primarily feed on carcasses but will kill rabbits, rodents and — occasionally — livestock. They measure up to 18 inches tall at the shoulder and look like a small bear crossed with a badger crossed with a skunk.
Wolverines’ territory once spanned west from the Sierra Nevada in California to the Rocky Mountains. But the species was nearly exterminated from the lower 48 states by the early 1900s as large game herds decreased and ranchers and the federal government poisoned carcasses to kill off wolves, bears, coyotes and mountain lions. Wolverines, which number in the thousands in Canada and Alaska, have since reestablished populations in Washington, Montana, Idaho, Wyoming and Oregon, but have not come back to stay in Colorado.
Biologists estimate there are approximately 300 wolverines in the lower 48, mostly in Montana, Odell said. Colorado’s high snowy mountains are the species’ largest unoccupied territory and will only become more important as a warming climate shrink the snowpack the wolverines need for dens.
“There is a real role for Colorado to play in conservation here,” Odell said. “Wolverines really need Colorado.”
A threatened species?
Colorado wildlife officials first started considering reintroducing the wolverine during a raft trip in the 1990s, Odell said. They eventually decided to pursue lynx reintroduction instead.
But the agency returned to the idea in 2010 and completed a plan for reintroduction. Officials are taking a new look at that plan to see if it needs updates.
“We’ve started to dust that off and update that but it’s not ready for presentation to the (Colorado Parks and Wildlife Commission),” Odell said.
How the reintroduction plan is implemented depends on whether the U.S. Fish and Wildlife Service decides to list the species as threatened. Years of litigation over whether the species needed federal protection led a judge to mandate the service make a decision by Nov. 27.
Federal officials proposed listing the species as threatened in 2013 before changing their minds in 2014, citing robust populations in Canada and Alaska.
If the species is listed as threatened, state lawmakers will have to pass a bill allowing for the reintroduction of wolverines, Odell said. State wildlife officials will also have to coordinate more with federal officials on the reintroduction process and future management of the species.
If wolverines are not listed, Colorado Parks and Wildlife can move forward and start conversations with recreation groups, timber companies and other interested parties.
“It’s sort of a wait-and-see situation,” Odell said.
Climate change
The most significant stressor on wolverines in the coming years will be climate change, according to an analysis by the Fish and Wildlife Service.
Wolverines create high-altitude dens in the snowy mountains in the winter and raise their kits there to keep them warm and protect them from predators. Wolverine mothers need deep snow that lasts long into the spring months.
That type of snow will become rare in the American West as the climate warms. Wolverines will lose an estimated 30% of their habitat in the lower 48 states in the next 30 years and 60% of their habitat here in the next 70, according to the National Wildlife Federation.
Colorado’s mountains are predicted to retain their snowpack better than the lower-elevation mountains of Montana, Odell said. Colorado Parks and Wildlife biologists estimate there is enough suitable terrain in Colorado to support between 125 and 150 wolverines.
“The reliance of wolverines on snow and cold temperatures is pretty clear,” he said. “They seem to do better with springtime snowpack lasting.”
Natural wanderers
Colorado’s last wolverine lived here between 2009 and 2012 after traveling 585 miles over a few months from the northwest corner of Wyoming to the mountains west of Breckenridge, crossing two interstates, several mountains ranges and Wyoming’s vast and arid Red Desert.
M56 was the first wolverine seen in the state since 1919, but it didn’t stay put. It eventually wandered out of the state and was shot and killed on a ranch in North Dakota.
Data collected by the U.S. Fish and Wildlife Service shows that wolverines are moving back into some of their previous territories all on their own.
That’s why Colorado officials should wait for wolverines to reintroduce themselves instead of forcibly moving wolverines into the state, said Jeff Copeland, executive director of the Wolverine Foundation and a wildlife biologist who studied the species for more than 30 years.
Wolverines have moved back into all of the lower 48 states they previously occupied except Nevada, California and Colorado, Copeland said.
“Reintroduction is kind of happening on its own,” Copeland said. “The fact that we can see that and watch it is very exciting to me.”
Wolverines have been spotted recently in places where they hadn’t been for a century. In June, a young male was spotted three times in and near Yosemite National Park in California. Utah wildlife officials have confirmed several sightings.
The species’ rambling nature is what gives Copeland hope that a human-initiated reintroduction won’t be necessary in Colorado.
“It’s a very messy process,” he said. “It’s a last resort. It’s not the first choice because you’re going through a capture process, trying to capture these animals, transport them thousands of miles and then drop them off in completely new habitats and expecting them to live.”
Because wolverines do not live near each other, taking one or two will impact the ecosystem of that area, Copeland said.
But other advocates for the species said there is risk in waiting and hoping that wolverines reestablish themselves here. Even if a breeding pair make its way down south, more will have to follow to make sure there is enough genetic diversity, said Michael Robinson, senior conservation advocate at the Center for Biological Diversity.
“Colorado should do it on the principle that wolverines belong in Colorado,” Robinson said. “They’re part of the natural ecosystem and Colorado’s ecosystem can make a big difference.”
No other U.S. state has attempted to reintroduce the species, Copeland said. The only reintroduction he was aware of occurred in Finland.
Copeland said wolverines may not make a resurgence in Colorado during his lifetime, but he believes they will in the near future.
“I think it’s happening, I think that it’s incredibly fortunate that we recognize it and can watch it,” Copeland said. “Why do anything that can alter this natural process?”
Colorado wildlife officials have experience introducing other carnivorous mammals, like the lynx and black-footed ferret.
“There is real pride in restoring species to their native range,” Odell said.
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