How many of Colorado’s wolves can die before experts raise the alarm?
Seven of Colorado’s 25 reintroduced wolves have died, a number which Colorado Parks and Wildlife and other experts say is within expectations
Colorado Parks and Wildlife/Courtesy photo
In the 18 months since Colorado Parks and Wildlife began the voter-mandated reintroduction of gray wolves, seven of the 25 wolves it has relocated from Oregon and British Columbia have died. Four of these deaths occurred this year between March 16 to May 15.
The deaths have been caused by conflicts with other animals, illegal poaching in one instance, and two legal, human-caused deaths in Wyoming. Two of the deaths this year are still under investigation.
Colorado’s wildlife agency has maintained throughout the reintroduction efforts that some level of mortality was planned for and expected.
Most recently, at the May Parks and Wildlife Commission meeting, Eric Odell, the agency’s wolf conservation program manager, said the deaths up until that point were not a cause for concern. At the time, the agency had confirmed the death of six wolves, with a seventh dying eight days later in northwest Colorado.
“These mortalities are unfortunate in our sense of trying to establish a self-sustaining population of wolves, but it does not in any way indicate a failure of the program,” Odell said.
What Colorado’s wolf plan says about mortality and survival
How many wolves does Colorado expect to survive? When does this mortality exceed what is expected or considered “normal” for a wildlife species? And what role do humans play in whether this restoration succeeds?
Colorado Parks and Wildlife’s guiding management plan, finalized in 2023, for the wolf restoration grants some insight into what it expected around wolf mortality.
The plan’s primary goal is for Colorado to establish a “self-sustaining population of wolves,” defined not necessarily by a number but as a population that “maintains viability over time without continuous human intervention and conservation actions.”
Getting to this point will depend on a number of environmental, population and conflict factors, including the overall survival and recruitment rates of wolves. To be successful, restoration should see “low mortality rates over the initial 2-3 years post-release,” according to the plan.
“The reasonable scientific assumption is, all other things being equal, it’s the nature of wolf packs in suitable habitat with adequate prey base that what’s called recruitment — birth and survival of new pups — will outweigh natural mortality,” said Michael Saul, Rockies and plains program director for Defenders of Wildlife. “Then you’ll get sub-adults striking out on their own to start new packs and essentially filling in the available habitat.”
Defenders of Wildlife is a national environmental and wildlife advocacy nonprofit that has been engaged in wolf reintroduction efforts in Colorado and other Western states.
As a wild animal, natural mortality of wolves — including deaths related to weather, injuries, disease, conflict with other species — is expected, Saul added.
“If we let wolves be, they will recover,” he said.
The plan offers a few insights into how much mortality wolf populations could survive. One place it looks to set expectations is the wolf reintroduction efforts in Idaho and Yellowstone National Park, both of which had “relatively high survival rates,” according to the plan.
After two years, 30 of the 35 wolves survived in Idaho (an 85% survival rate). In Yellowstone, 22 of 31 animals survived that two-year mark (a 70% survival rate). While Colorado has not yet hit the two-year mark, the state has seen 72% survival of its reintroduced wolves, with 18 of the 25 animals introduced still alive. (This does not include the five wolves born last year, nor wolves that have entered Colorado from other states.)
If the survival of reintroduced wolves dips below 70% in a six-month period, what the plan calls a “translocation protocol review” would be initiated. Colorado has not hit this threshold in any six-month period.
Citing research from general population studies and some of Canada, Alaska and Minnesota populations, the plan indicates that annual mortality rates from 22% to over 50% “may suppress wolf population growth.”
In the Technical Working Group recommendations, it reports that “wolf populations can sustain 25-30% annual mortality while maintaining a stable or increasing population.”
Travis Duncan, a public information officer for Parks and Wildlife, said that as each wolf population and study is unique, “these percentages should be viewed as ranges in which the Colorado wolf population may fall somewhere in the range.”
“(Parks and Wildlife) will continue to monitor the overall mortality rate of wolves in Colorado, as well as the cause of each mortality from the (U.S. Fish and Wildlife Service) necropsy, to determine how this founding population aligns with previous studies,” Duncan added.
In Colorado’s first year, while three wolves died, five were also born, making the mortality rate 20%. In 2025, following the January release of 15 wolves from British Columbia, Colorado’s wolf population was estimated around 30, making the mortality rate with four deaths around 13%.
A ‘dangerous phase’ for Colorado’s wolves
To build its self-sustaining population, the plan recommends Parks and Wildlife release 10 to 15 wolves annually over three to five years, targeting the transfer of 30 to 50 animals.
So far, the agency has completed two years of releases, transferring a total of 25 wolves from Oregon and British Columbia. The agency has also confirmed the presence of several additional wolves — including one in Moffat County and another in Jackson County early this year — that have entered Colorado naturally.
In May, Odell confirmed the agency will do at least one more year of releases in accordance with the plan. No decisions have been made about the next release, he added.
With mortality falling within what is “expected” based on data from other efforts and the wolf plan, Saul said Colorado is “on track” to “getting that initial founding population of 30 to 50 animals.”
The majority of the wolves released thus far have been young — the plan requires they be between 1 and 5 years old when captured — and have been primarily traveling alone or in pairs. Both of which can make it difficult for the animals, he said.
“They’re in kind of the most dangerous phase of life, which is they are 1- to 2-year old animals trying to stake out their own territories and packs,” Saul said. “Colorado is a good place for wolves because we got a lot of wild country, but it’s got a lot of big, challenging prey and predators. Elk and even moose can be prey for a pack of wolves, but they are dangerous and challenging animals for a single wolf.”
One of the male wolves that died last year was reportedly due to a mountain lion attack, with a second attributed to a fight with another wolf.
As Colorado’s wolf population grows, they are expected to form packs, which will help bolster their success. So far, Parks and Wildlife has only confirmed one pack: the Copper Creek pack, with the mother and four of the pups released back into the wild this January. In May, Odell reported that the agency is reportedly tracking up to four potential dens, which could increase the population further.
The Technical Working Group included wolf experts and biologists from federal and state agencies, Colorado State University and county commissioners who provided recommendations toward the final wolf plan.
So far, of the seven wolf deaths, five have been males, which Saul said isn’t entirely unexpected.
“(Males) are the ones who are going to be taking greater risks generally in setting off to find territory, and hopefully a pack, so certainly it’s conceivable,” he said.
Duncan said that the current sex ratio of Colorado’s wolves is “not a concern at this point in time,” but confirmed it’s something the agency is tracking.
“Both sexes are important to pack formation, reproduction, and the overall population,” he added.
The human threat
While disease, starvation, and conflict with other species are reportedly the highest natural forms of mortality, human-caused deaths could also pose a significant threat to Colorado’s burgeoning wolf population.
The working group’s recommendations warn that “the vulnerability of recently reintroduced wolves to illegal human-caused mortality may be an additional impediment to reaching critical mass.”
“I think the real danger we’re facing, where we’re still at these very low starting numbers, is that if humans put too heavy a film on the scale by legally or illegally killing off wolves in Colorado, that’s potentially going to lead to too small a founder population with potential implications for lack of genetic diversity,” Saul said.
He added that it’s critical that the founding population of wolves have a “chance at building robust, well-distributed, genetically diverse packs in multiple areas of the state and that we don’t give in to hysteria and propaganda and start killing off our wolves before we can you know get to that initial founder population threshold.”
So far, humans have been connected to the deaths of three of Colorado’s reintroduced wolves.
One, the Copper Creek pack’s adult male, reportedly died following a gunshot wound in the fall. The U.S. Fish and Wildlife Service is investigating this as illegal poaching.
Additionally, this year two of Colorado’s wolves have been legally killed by humans in Wyoming. One was killed by federal officials after being tied to livestock deaths, and another died within the state’s management area, where state law allows anyone to kill a wolf without a license.
“This is not a surprise to anybody,” Saul said of the Wyoming deaths. “Colorado Parks and Wildlife, the stakeholder working group and the technical advisory group went into this with their eyes open, realizing that until the management regime changes in Wyoming, Wyoming is going to be what biologists call ‘population sink.'”
Still, the overall population should be able to survive this sink, he added.
“If we get a robust and well-distributed breeding population of wolves established in Colorado, these animals are adaptable enough and breed fast enough that they can still thrive knowing that there is inevitably going to be some degree of loss over the northern border,” Saul said.
