A 40-pound bundle of fur, teeth and tenacity has returned to its home range in Colorado.
Now the U.S. Fish and Wildlife Service is proposing to list the seldom-seen North American wolverine under the Endangered Species Act because of the threat of climate change on its snowy mountainous habitat.
In 2009, a male wolverine equipped with a tracking device from Grand Teton National Park in Wyoming made its way 500 miles to Rocky Mountain National Park in Colorado. M56 is the first documented wolverine in the state since 1919. He has been photographed and is roaming a 100-square-mile area.
"He's looking for a female to start a family," said Shawn Sartorius, a USFW biologist and lead researcher on the wolverine listing proposal.
M56 is protected in Colorado from trapping, and will find plenty of ideal territory, he said.
"Colorado has good wolverine habitat, including in the San Juans, and has had them in the past," Sartorius said. "They are adapted to cold, snowy conditions above 8,000 feet that is generally avoided by their competitors."
The population of wolverines in the Rocky Mountains is thought to be low, with an estimated 250 in the northern ranges of the Lower 48.
A key justification for listing the species is the general warming trend of the climate, and the impacts that has on snowpack relied on by the wolverine, the largest member of the weasel family.
"Their high elevation, arctic habitat is fairly limited and we determined that climate change will shrink that habitat significantly, reducing the wolverine's ability to persist," Sartorius said.
But disagreement over the impacts of climate change on wolverine habitat prompted the USFW to recently extended the deadline and comment period for a final decision by 6 months on whether the animal warrants additional protections under the ESA.
"Within the peer review process, there was significant scientific disagreement on how we characterize wolverine habitat, so we need to go back and see if we are doing a reasonable job evaluating the likely impacts of climate change on the species."
Wolverines thrive in snowy conditions and don't hibernate. Females rely on dens dug deep into the snow to raise their young. The carnivores are adept at scavenging animals buried beneath the snowpack, and mostly hunt smaller mammals.
Due to their high-altitude habitat, wolverines are not seen as a threat to livestock, and would not likely have much impact on ski areas because of their wide-ranging ways.
"They are not much of a nuisance," Sartorius said. "They have huge home ranges, and move an incredible amount over extreme terrain."
To alleviate concerns over conflicts with livestock, the listing proposal recommends establishing an experimental, non-essential population for the southern Rockies. The specialized designation allows for more flexible management of the species if it's re-introduced.
Reintroduction is being discussed by Colorado Parks and Wildlife, but they have not made a decision to move forward with that option.
Eric Odell, a species conservation project manager with CPW, reported to Public News Service that the wolverine population in Colorado declined because of poisons used in the early 1900s to control mountain lions, coyotes and wolves.
"This is an animal that is native to the state and might be able to do well here," he said.
To comment electronically on the proposed listing go to http://www.regulations.gov. In the keyword box, enter Docket No. FWS-R6-ES-2012-107. Then in the search panel check on the proposed rules link, then click on Comment Now.
jmimiaga@cortezjournal.com