The US Fish & Wildlife Service has come to the inescapable conclusion that global warming is fragmenting the high altitude habitat of the wolverine. The largest member of the weasel family (Mustelidae) is dependent upon snow and cold temperatures near tree line for birthing dens. A persistent, stable snowpack greater than five feet in depth appears to be required by the fierce, solitary hunter. Although able to kill prey many times its size, it is not adapted to warm climates, but is well adapted to cold weather year round with a thick, double layer of fur, wide padded paws, and small extremities. It prefers to disperse only across suitable high altitude (4500-8500 ft) habitat and avoids hot summer weather by inhabiting environments with persistent spring snowpack. They almost never reproduce in lower altitude forests. The
Service said, "extensive modeling indicates that the wolverine's snowpack habitat will be greatly reduced and fragmented in the coming years due to climate warming" and is thus threatened as defined in the Endangered Species Act. 78 FR 7886. The agency was under a court imposed deadline to reach a decision on listing this fiscal year. Wolverines were nearly killed off at the turn of the 20th century, but have increased their numbers with the end of widespread predator poisoning and trapping. The
agency proposal covers the discrete wolverine population of the contiguous Untied States.
The polar bear is in a similar situation as the wolverine. It needs ice pack to cover the Arctic Ocean so it can hunt seals effectively. However, the agency and the current administration have so far side-stepped the issue of declaring the polar bear endangered by global warming because of the consequences for potential resource development in a melting Arctic. The same considerations played a role in the wolverine listing decision. The Service went so far as to propose a special exception for human use of backcountry areas such as timber harvesting and recreational activities which it does not consider "significant threats" to the survival of the wolverine. Intentional killing or harming of wolverines would still be prohibited. The surviving 250-300 wolverines are now restricted to remote mountain tops in the Cascades and Northern Rockies of the lower 48 states and Alaska. Ninety-four percent of wolverine habitat is on federal land. It once ranged over the entire Rocky Mountain and the Sierra Nevada ranges. A reintroduction proposal is also made to re-establish the wolverine to its historic range in Colorado, New Mexico and Wyoming. A ninety day comment period on the proposed listing has begun. The public may submit comments at http://www.regulations.gov by entering the docket number FWS-R6-ES-2012-0107 A final decision on listing the wolverine is expected in a year.
