Don’t call it a comeback. These animals have been here for years
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This article is part of ongoing production for an episode of Colorado Experience about the history and reintroduction of gray wolves in the state. Follow along for behind the scenes content and updates on the episode.
DENVER — What do rainbow trout, mountain goats and your neighbor with the Texas plates have in common? None of them are native to Colorado.
Coloradans’ frustration with “Texpats” is well-documented — even Governor Polis has jokingly poked fun at transplants — but less-discussed is the fact that many animal species are only in Colorado because human beings put them here.
For more than half a century, Colorado wildlife officials have worked to increase certain animal populations in the state, including moose and lynx, for ecological and recreational benefits.
Sometimes, these efforts were considered reintroductions — in other words, the wildlife officials restored animal populations to the animals’ native lands.
Introductions, conversely, occur when a non-native species is integrated into our ecosystem. Historically, introductions happen for recreational reasons such as fishing and hunting. This is why Colorado now has pheasants, rainbow trout and mountain goats.
Eric Odell with Colorado Parks and Wildlife is hoping that lessons from these past animal introductions and reintroductions prove useful in his current project: bringing wolves back to Colorado.
“The wolf reintroduction has been the most challenging and the most difficult from all aspects,” said Odell, CPW’s species conservation program manager and the technical lead on the wolf reintroduction plan.
“From the logistical aspect to the social and the political aspect — all of that has been tremendously challenging,” he said.
One of the ways the ongoing wolf reintroduction in Colorado is distinct from previous animal reintroductions is that this plan was kickstarted by a citizen-led ballot initiative. After voters narrowly approved the reintroduction, CPW became responsible for making it happen.
CPW is the first state agency in history to reintroduce wolves. Previous wolf reintroductions, including those in Yellowstone National Park and Idaho, resulted from efforts by federal agencies or Native American tribes.
“So the wolf scenario is very different on a whole bunch of different aspects [compared] to other reintroductions that Colorado Parks and Wildlife, and other state wildlife agencies, have taken on in the past,” Odell said.
Around the time Coloradans voted to approve the reintroduction, CPW recorded instances of wolf migration in northern Colorado near the Wyoming border. However, Odell said the agency would not have pursued full reintroduction of wolves — at least not right now — had it not been for the ballot initiative.
“We [CPW] had other priorities that we probably would have taken on prior to that” he said.
Odell, who has worked for CPW for about 24 years, said the reintroductions of black-footed ferrets and Canada lynx are most similar to the current wolf situation, but that all reintroductions provide useful insights for future efforts.
Below, you can read more about Colorado’s animal introductions — the successes, challenges and what animal is next.
MOOSE
Despite their notable presence in places like State Forest State Park, moose are not native to Colorado. Coloradans recorded sightings of moose herds traveling into northern Colorado from Wyoming dating back to at least 1850. However, the herds were never big enough to establish a full Colorado population of moose.Wildlife officials expressed interest in bringing moose to Colorado in the 1950s, but public meetings on the issue included concerns over moose competing with cattle and sheep on grazing lands, an issue that is playing out today with wolf reintroduction.
Years later, after coordinating with local ranchers and federal officials, wildlife officials in 1978 transported 24 male and female moose from Wyoming and Utah to the North Park region of Colorado.
“Since then, moose have distributed themselves much, much more broadly throughout the state,” Odell said. He explained that because moose used to travel into Colorado from Wyoming, establishing a Colorado population was considered a reintroduction.
Today, there are approximately 3,000 moose in Colorado, enough that CPW issues moose-hunting permits.
RIVER OTTER
Like moose, river otter sightings in Colorado date back to the 1800s. But these cute, torpedo-shaped mammals were much more abundant in our state than moose.“Historically, we had them throughout all of the major drainages of the state,” Odell said. “And then, for a whole variety of reasons — trapping, the unregulated fur trading, water quality issues, habitat degradation — they eventually were extirpated from the state.”
Extirpated means an animal is no longer present in its former habitat. It is different from extinction, Odell explained, because river otters were thriving in other parts of the country while their population dwindled in Colorado.
Between 1976 and 1991, CPW — then-called the Colorado Division of Wildlife — released 122 otters “across the Gunnison River, Upper Colorado River, Dolores and San Miguel Rivers, Piedra-San Juan-Navajo-Pine Rivers and their tributaries, as well as the Yampa and Green Rivers.”
The reintroduction was a success, and the otter population now serves as a measurement of river health, according to CPW. If the population grows, that suggests the river ecosystems are healthy. The inverse is also true.
“We have river otters in three quarters of the state,” Odell said. “We don't have them down in the southeast part of the state, in the Arkansas drainage. And there's some interest. We haven't really explored it too much, but, you know, that's a species that has been very prolific. They've done a really good job of spreading themselves out.”
While otters are useful in that they hunt invasive fish species, there are some challenges. Odell said the otters can be “pretty destructive” for people with privately stocked ponds (i.e., they eat the fish). But because of the otters’ status as “state threatened,” CPW is limited in what they can do to manage the populations that target private ponds.
“It's probably time for us to reevaluate the status of river otters,” Odell said. “They've got a really good distribution … the threats are largely diminished. The water quality issues, the habitat issues aren't there. There is no regulated trapping, hunting of river otters.”
LYNX
In 1973, Colorado officially listed lynx — solitary, large felines similar to bobcats — as an endangered species. The last known lynx was illegally trapped in Vail one year later.
Colorado Parks and Wildlife started working on a lynx reintroduction plan in the mid 1990s. In 1999 — one year before the U.S. Fish and Wildlife Service declared lynx a protected species — CPW released more than 40 lynx from Canada and Alaska into the San Juan Mountains. The project was not an immediate success.
“We had really, really poor success initially,” Odell said. “We brought animals in and did what's called a hard release, meaning that there was not any preconditioning. The animals were flown in, those crates were brought to a place and then essentially opened up the next day. And the lynx were set on their own. And we had very high mortality rates.”
Odell said the plane travel and elevation change likely made it difficult for the lynx to establish themselves in Colorado.
After witnessing the high mortality rates, CPW changed course. The agency stopped the hard releases and instead moved the cats into a pen, fed them and trained them to hunt on their own. By 2003, the lynx had successfully reproduced. CPW deemed the project an official success in 2010.
Today, there are an estimated 150-250 lynx in Colorado.
Because they are a solitary species, Odell explained that lynx provide no measurable ecological impact — positive or negative — but he added that there is an “intrinsic value” of returning a species to its native land.
“They were and they remain a federally threatened species. And so there is some value to trying to restore that population, that species, throughout its historic range,” Odell said. “So that's what the primary motivation for reintroducing lynx was.”
BLACK-FOOTED FERRET
Meet your new BFF. According to the Colorado Wildlife Council, black-footed ferrets (BFF, for short) are the only ferret species native to North America, and they’ve roamed this continent’s plains — including those of Colorado — for thousands of years.Their population dramatically declined in the early 20th century. BFFs were one of the first species listed under the Endangered Species Act of 1973. But by 1979, they were declared extinct.
Two years later, though, ranchers in Wyoming discovered a small population of BFFs on their land, leading to reproduction and reintroduction efforts across multiple states, including Colorado.
Odell described the reintroduction work around BFFs as “fairly straightforward.” He said the animals are fairly easy to capture and release. The challenge, Odell explained, is that they are entirely dependent on prairie dogs for food and shelter. If the prairie dog population is affected by disease, as Rocky Mountain PBS’ Carly Rose previously reported, then the BFFs suffer as a result.
“So ferret conservation requires prairie dog conservation,” Odell said.
In October of 2023, Rocky Mountain Arsenal National Wildlife Refuge released 19 BFFs onto the land.
Nick Kaczor, the deputy refuge supervisor in the U.S. Fish and Wildlife Service’s Mountain Prairie Region, previously worked as assistant manager at the refuge. He helped organize the reintroduction of BFFs to the refuge.
“As a wildlife biologist, it’s one of the best feelings you can have to reintroduce a native species,” Kaczor said in October. “Watching others experience that same thing, it's remarkable and always something that will stick in my career.”
Today, there are about 30 BFFs at the Rocky Mountain Arsenal National Wildlife Refuge. The World Wildlife Council estimates that there are more than 300 BFFs in North America, but the ferrets remain one of the continent’s most endangered mammals.
WOLVERINE
If Odell could wave a magic wand and immediately bring one animal back to Colorado, that would be the wolverine, he said.
Soon, his wish will come true (albeit not as fast). In May of this year, Colorado Governor Jared Polis signed a bill to reintroduce wolverines to Colorado, a plan that will start in the “relatively near future,” Odell said.
“I’m anticipating [wolverine reintroduction] to be the most challenging logistically, to capture. Because they are very, very low-density animals [with] home ranges of hundreds of square miles,” he said.
The remote, snowy areas where wolverines thrive are also difficult to reach, Odell said.
According to a Colorado Sun report, the last-known sighting of a wolverine in Colorado occurred in 2009, when one of the animals — the largest of the Mustelidae family, which includes badgers — migrated south from Wyoming.
According to the National Wildlife Federation, the number of wolverines in the lower 48 states ranges anywhere from 25 to 300. They are listed as “state endangered” by CPW.
“This is a species that was once historically very prevalent in the high country of Colorado,” Odell said, “and so we're looking forward to reestablishing Wolverine into the state.”