Colorado's wolverine reintroduction bill signed into law — what this means and how it differs from wolf plan

Posted at 6:38 AM, May 21, 2024

LOVELAND PASS, Colo. — Colorado Gov. Jared Polis has signed a bill to authorize the restoration of wolverines to the state after they were extirpated from Colorado in 1919.

Polis signed Senate Bill 24-171, titled "Restoration of Wolverines," on Monday afternoon.

The bill, which was introduced in the Colorado Senate on March 4, allows Colorado Parks and Wildlife (CPW) to reintroduce wolverines to Colorado, with a few provisions, including waiting until a rule is published to designate the animals as an experimental and nonessential population in Colorado. SB 24-171 authorizes $750,000 from the Species Conservation Trust Fund to implement this reintroduction beginning in the 2024-25 state fiscal year.

Since 2000, isolated individual wolverines have been reportedly spotted in Colorado, but the state does not have a known established breeding population, the U.S. Fish and Wildlife Service (USFWS) said in a 2023 report.

USFWS wolverine dens and habitats
Wolverine observations (2009–2023) and dens (2000–2022) from various sources (State wildlife agencies, U.S. Forest Service, National Park Service, and others), and modeled wolverine habitat core areas. Natal dens are those used during parturition, maternal dens are those used after the natal den and before weaning, and unknown den status indicates a confirmed den as either a natal or maternal den.

As of 2023, only one wolverine was confirmed to have been spotted in the last century in Colorado, USFWS wrote in a separate 2023 report. That wolverine crossed into Colorado from Wyoming before ultimately traveling to North Dakota, where it was shot and killed in 2016.

"While a significant amount of modeled core habitat has been identified for wolverines in Colorado, no wolverines are currently known to occur there and there have been no verified wolverine observations in the last seven years," the report reads.

SB 24-171 aims to change that — slowly, but surely.

The bill passed in the Senate on April 17 by a vote of 29-5 and passed in the House on a vote of 51-13 on May 3. It was sponsored by Sen. Perry Will (R), Sen. Dylan Roberts (D), Rep. Barbara McLachlan (D) and Rep. Tisha Mauro (D).

A brief history of wolverines in Colorado

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.

wolverine map.jpg
These maps show where wolverines lived in the United States between 1827 and 1960 on the left, and between 1995 and 2005 on the right.

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, CPW Species Conservation Unit Supervisor David Klute explained during a CPW Commission meeting in early May.

About 300 of the animals currently live in fragmented areas in the northern Rocky Mountains but "high-resistance habitats, anthropogenic features, and highways" can create a barrier if those animals started to head farther south, the USFWS said.

Wolverines are sometimes mistaken for small bears because they have a broad head, rounded ears and a stocky body, but unlike bears, they have a long, bushy tail. They are typically brown with yellow-brown stripes along the sides of their body and forehead, CPW said. Full grown wolverines can reach 25 to 35 pounds and are 3 to 3.5 feet long.

Because they are solitary creatures, they only come together to breed, and the females give birth to just two to three cubs in the winter. Reproductive success is low, CPW said. The animals usually survive less than 15 years in the wild.

Their natural predators include bears, mountain lions and wolves.

How is this different from the wolf reintroduction?

Following the introduction of the bill on March 4, immediate concern arose about the reintroduction of yet another predator that had been previously pushed out of the state. In December 2023, the controversial but voter-mandated gray wolf reintroduction process began with the release of 10 wolves in Summit and Grand counties. It has left many ranchers concerned and frustrated as CPW has confirmed nine wolf depredations on livestock since the release.

However, the Wolverine reintroduction plan will differ in many ways from the state's wolf reintroduction plan, which was approved in May 2023.

Much of that is due to simple biological differences between the two animals.

Unlike 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, Klute said. CPW said female wolverines in the Yellowstone Region have an average range over 150 square miles and males have an average range of nearly 500 square miles.



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They are "very effective scavengers," Klute said, and do not chase down elk, deer and other ungulates (hoofed animals) like wolf packs do. As opportunistic feeders, wolverines eat small rodents, rabbits, porcupines, ground squirrels, marmots, birds and eggs, fish and plants. They also scavenge for deer and other larger ungulates, most of which were killed by other predators, though they will go after that type of bigger prey if it is weak, ill or trapped in the snow.

Wolverine attacks on livestock are "incredibly rare," CPW Mammals Researcher Jake Ivan told the commission. This was echoed by the USFWS, which wrote in a 2023 Federal Register report that unlike the wolverine population in Eurasia, wolverines in the United States rarely prey on livestock.

"During our extensive literature review in preparing the 2023 wolverine SSA (species status assessment) report addendum, we discovered only two instances of wolverine depredation in the United States since our 2018 SSA report; one wolverine that had depredated sheep in Utah, and another that was caught in a chicken coop in Washington."

Read more from this SSA report below.

Even so, like the wolf reintroduction plan, this wolverine plan will include directions on how to allow for compensation of any livestock losses due to wolverine depredation, CPW said. As of now, the allocation for payments to livestock owners is estimated at at least $10,000.

Click here to report a wolverine sighting on CPW's website.

What would a wolverine introduction look like?

CPW collected data and information from experts to determine what a wolverine reintroduction would look like in Colorado.

It found that Colorado could hold a maximum of 100 to 180 wolverines if they mimic the same behavior as their original territories.

Klute said 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 handle climate change better than other parts of wolverines' current range.

Wolverine 2

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 and wolverine data from Sweden, Ivan suggested that CPW should release 30 wolverines — 20 females and 10 males — over the first two years of the reintroduction effort.

Exactly where those animals will come from remains up in the air at this point. They live across Canada and Alaska, with smaller populations in Montana, Idaho and Wyoming.

In a perfect world, Ivan said the transplanted wolverines would come from a habitat 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

CPW will follow the same steps it used in its 1997 Canada lynx reintroduction program to capture the wolverines, Ivan said: The department plans to pay people experienced with hunting wolverines to capture them live, and then CPW staff will transport them to Colorado, where they will be temporarily held at the Frisco Creek Wildlife Rehabilitation Center south of Del Norte. The animals will undergo veterinarian exams and any needed treatments while they become acclimated to Colorado.

This is also different from the wolf plan, where the animals were captured out of state and then released in Colorado as quickly as possible.

Once the acclimatization is complete, the wolverines will be released in three possible zones: one north of I-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.

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When it comes to the actual release, CPW staff will bring the males and non-pregnant females out first. 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 of the captured wolverines 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 theirs — to settle in their new habitat. CPW will then place the pregnant females far from those males, Ivan said, and will also provide food for them.

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.

No known agency has attempted to reintroduce wolverines to a place where they previously existed, CPW said.

The road to the wolverine reintroduction

This plan is something the CPW has eyed since the late 1990s.

In those years, CPW — then called the Colorado Division of Wildlife — issued a publication titled "Draft Strategy for the Conservation and Reestablishment of Lynx and Wolverine in the Southern Rocky Mountains" before electing 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 wolverine plan was back on the table, however it remained on hold while the state waited for a ruling on the animals' status.

Could the wolverine be next on Colorado's reintroduction list?

That came in late November 2023, when the USFWS 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."

“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.

A rare sighting of a wolverine in Yellowstone National Park.

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.

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