DENVER — Colorado wildlife officials have dusted off a drafted plan to reintroduce wolverines to the state, a proposal drastically different from the controversial but voter-mandated wolf reintroduction plan from last spring.
An early look at the drafted wolverine reintroduction plan was discussed at Wednesday's Colorado Parks and Wildlife (CPW) Commission meeting.
The plan will differ in many ways from the state's gray wolf reintroduction plan, which was approved in May 2023. Much of that is due to simple biology.
Unlike gray wolves, wolverines are solitary animals with enormous territories for each individual — up to 20 times as large as a bobcat's or coyote's — and therefore they only exist in low densities, CPW Species Conservation Unit Supervisor David Klute explained. They are "very effective scavengers" and throughout most of the year, they feed on carcasses of dead animals, he said. In the summers, they can also hunt rodents like marmots.
Wolverines were extirpated from Colorado in 1919 due to unregulated trapping and predator poisoning campaigns, and were listed as an endangered animal in Colorado in 1973.
Between 1979 and 1996, CPW completed 12 surveys searching for signs of both wolverines and Canada lynx, and found no evidence of any wolverines left in the state.
Today, Colorado has the largest expanse of wolverine habitat in the west that does not actually hold any of the animals — or at least none that are known. The state represents about 20% of estimated habitat for wolverines in the lower 48 states, Klute said. About 300 of the animals currently live in fragmented areas in the northern Rocky Mountains.
CPW said no known agency has attempted to reintroduce wolverines to a place where they previously existed.
Klute explained that CPW used data and information from experts to determine what a wolverine reintroduction would look like in Colorado. He told the CPW Commission on Wednesday that Colorado could hold a maximum of 100 to 180 animals if they mimic the same behavior as their original territories.
He listed out multiple benefits: 140 wolverines could bolster the western population of the species by 20% or more, and the reintroduction would restore a native species to its historical range. Bringing the animals back to Colorado could go a long way with improving their genetic diversity in the lower 48 states, and would enhance biodiversity, he said. In addition, Colorado's high country is projected to weather climate change better than other parts of wolverines' current range.
"Part of our mission as an agency is to perpetuate the wildlife resources of the state and in that sense, restoring wolverines represents part of our job and core purpose," he said.
Like the reintroduction of gray wolves, this plan calls to capture wolverines outside of Colorado and bring them to the state. However, this process is drastically different from the wolf release.
Based on a population viability analysis (PVA) and Sweden's data set of wolverine survival and breeding success, CPW Mammals Researcher Jake Ivan suggested that CPW should release 30 wolverines — 20 females and 10 males — over the first two years of the reintroduction effort.
The exact source for the wolverines is up in the air. They currently live in the "circumpolar," Klute said, which includes the northern parts of Asia and Canada, as well as Scandinavia and Alaska.
In a perfect world, Ivan said the transplanted wolverines would come from a place that has:
- Ecological similarity to Colorado (mountainous terrain instead of treeless tundra, which is another ecosystem wolverines inhabit)
- Similar predators to evade, like cougars
- Similar food sources, like marmots
- A high degree of genetic diversity in wolverines to avoid chances of inbreeding
When it comes to actually capturing the wolverines, CPW will follow the same steps it used in its 1997 Canada lynx reintroduction program, Ivan said. In that prior project, CPW paid people who live where wolverines exist — and are extremely familiar with hunting them — to capture the live animals. Staff will transport them to Colorado, where they will be temporarily held at the Frisco Creek Wildlife Rehabilitation Center south of Del Norte.
The center was built for the lynx reintroduction, but "engineered with an eye toward the future," Ivan said, and can house wolverines. The animals will undergo veterinarian exams, undergo any needed treatments and become acclimated to Colorado.
Ivan brought up a map that showed the primary wolverine habitat in Colorado and three possible release zones: one north of Interstate 70, one between I-70 and Highway 50, and one in the San Juan Mountains. All wolverines will be outfitted with a GPS collar prior to their release.
The first to go will be males and non-pregnant females, Ivan said. Experts strongly felt that the wolverines should be released directly into snowy dens pre-prepared by CPW. In addition to building the dens for the animals, CPW will discreetly provide food for them for at least the first few months, Ivan said. He explained that this will maximize their chances of survival and staying around the release location.
If any wolverines brought to Colorado are pregnant, they will spend extra time at the Frisco Creek Wildlife Rehabilitation Center to allow for the released males — which sometimes will eat offspring that are not his in the wild — to settle. CPW will place the pregnant females far from those males, Ivan said, and will also provide food for them.
A few conservation issues have been noted, though many have been addressed, Ivan said. That includes human-caused mortality, effects on other wildlife, climate change, winter recreation and livestock depredation, though the latter is "incredibly rare," he said. One aspect working in the animals' favor is that 94% of their ideal habitat is on public land, much of which is federally designated wilderness, he said.
The benchmarks for success in the wolverine reintroduction will line up with the benchmarks in the 1997 lynx restoration: evidence of breeding and births, young wolverines surviving at least one year, and evidence of those Colorado-born animals breeding and producing babies themselves.
The proposal to reintroduce wolverines to Colorado is not new — it's something the CPW has eyed since the late 1990s.
In those years, CPW — called the Colorado Division of Wildlife at the time — issued a publication titled "Draft Strategy for the Conservation and Reestablishment of Lynx and Wolverine in the Southern Rocky Mountains" and elected to focus on just one species at a time. The lynx was up. As of today, all benchmarks have been met, meaning that reintroduction was a success.
And so the idea of wolverines came around from the backburner, however it remained on hold while the state waited for a ruling on the animals' status.
That came in late November 2023, when the U.S. Fish and Wildlife Service announced its final rule to list the wolverines in the lower 48 as a threatened species under the Endangered Species Act. Officials wrote, "We have determined that the contiguous U.S. DPS (distinct population segment) of the North American wolverine is a threatened species due primarily to the ongoing and increasing impacts of climate change and associated habitat degradation and fragmentation."
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“Based on the best available science, this listing determination will help to stem the long-term impact and enhance the viability of wolverines in the contiguous United States," said Pacific Regional Director Hugh Morrison said the day of the announcement.
This move allowed CPW to look at getting a 10(j) designation for wolverines, which it can now do because of its listed status. Section 10(j) in the federal Endangered Species Act, which was also used in the gray wolf reintroduction process, allows the federal government to designate a population of a listed species — like the wolverines — as experimental if they are set to be released into natural habitat outside their current range, like Colorado.
The development of a 10(j) falls on the U.S. Fish and Wildlife Service, though CPW is a strong partner in this, CPW's Terrestrial Section Manager Brian Dreher explained.
More recently, Senate Bill 24-171, called "Restoration of Wolverines," was introduced in the Colorado Senate on March 4. If passed, it would authorize CPW to reintroduce wolverines to Colorado, with a few provisions, including waiting until the 10(j) rule has been published to designate the animals as an experimental and nonessential population in Colorado.
Directions on how to allow for compensation of livestock losses due to wolverine depredation is also included, though Dreher explained that there are extremely few documented cases of this in northern states in contemporary times.
The bill passed in the Senate on April 17 by a vote of 29-5. It was brought forward a few days later on April 22 in the House's Agriculture and Natural Resources Committee, where it passed 11-2. On Wednesday morning, the bill passed out of the House Appropriations Committee on a 6-4 vote and was referred unamended to the House Committee of the Whole, where it was heard on Friday morning.
It passed in the House on a vote of 51-13. It is now headed to Colorado Gov. Jared Polis' desk.
Senate Bill 24-171 is sponsored by Sen. Perry Will (R), Sen. Dylan Roberts (D), Rep. Barbara McLachlan (D) and Rep. Tisha Mauro (D).
