A species at risk
Wolverines and global warming
Wolverines are wholly dependent on areas that maintain a deep spring snowpack throughout their denning period from February through May. Dens typically consist of relatively long snow tunnels that are thought to contribute to the offspring’s survival by providing thermal benefits, protection from predators, and proximity to high-quality rearing habitat. Therefore, elevations and habitat that maintain substantial spring snowpacks appear to be critical to successful reproduction. Global climate change increasingly threatens quality wolverine denning habitat and, by extension, successful wolverine reproduction, connectivity between subpopulations, and overall wolverine population numbers.
Locations harboring requisite wolverine breeding habitat are becoming increasingly fragmented at southern latitudes because of warming temperatures and shorter winters. These areas also are subject to timber harvesting and winter recreation (particularly snowmobiling and helicopter skiing). Wolverines are highly sensitive to disturbance, especially motorized disturbance, and they seek out areas that have minimal human intrusion. Wolverines still can be legally harvested, by trapping, in Montana, which poses an additional threat to the species and likely is further reducing already isolated populations to unsustainable levels.
Since 1994, conservation organizations and concerned citizens have been petitioning the U.S. Fish and Wildlife Service to protect the North American wolverine (Gulo gulo luscus) in the contiguous United States under the Endangered Species Act. The wolverine is the largest member of the weasel family and once ranged throughout the northern tier of the U.S., and as far south as the Southern Rockies and Southern California. Today wolverines are primarily confined to small portions of the Northern Rockies and Washington’s North Cascade Range. The population has dwindled to an estimated 500 in the Northern Rocky Mountains. The wolverine’s effective population size in the Rockies—the actual number of breeders that are believed to be contributing offspring to the population—currently is estimated to consist of fewer than 40 individuals. Not only is the existing wolverine population precariously small, it is also fragmented into isolated subpopulations. The lack of connectivity between these subpopulations is contributing to inbreeding and reduced genetic diversity, and it is increasing the chances that habitat patches that have experienced local extinctions will not be re-colonized by dispersing wolverines.
Wolverines have low population densities and range widely in high-elevation alpine and sub-alpine habitat. Because they inhabit remote and often inhospitable areas, wolverines are rarely seen. In the past decade the Fish and Wildlife Service twice decided there was insufficient information about the species’ status to warrant its Endangered Species Act listing. On March 11, 2008, the USFWS once again determined that listing of the wolverine was not warranted. This time the agency recognized the dire status of the species in the contiguous U.S., but it denied federal protection to the species, arguing that since wolverines still live in relatively large, interconnected populations in Canada and Alaska, they do not warrant protection in the lower 48 states. Had such a minimalist interpretation of the Endangered Species Act been applied to past listing decisions, contiguous U.S. populations of bald eagles, peregrine falcons, grizzly bears, and wolves would never have been designated as endangered species and recovered in this country, since healthy populations of all these species persisted outside the lower 48.
It is the Wyoming Outdoor Council’s view that the wolverine’s critically imperiled status in the contiguous U.S. and the severe and indisputable nature of the many threats the species faces (climate change, habitat fragmentation and loss, small and isolated populations, slow reproductive rate, human disturbance, excessive harvest) make this species a clear candidate for federal protection under the Endangered Species Act. As a result, in 2008, we joined other conservation organizations in a lawsuit challenging the federal government’s decision not to list the wolverine. In 2009, we reached a settlement with the Fish and Wildlife Service, in which the agency agreed to initiate yet another review to determine whether the wolverine warrants listing. The agency will publish its decision in December 2010. Meanwhile, the Outdoor Council will continue to advocate that the wolverine merits listing as an endangered species and to work with our conservation partners to ensure that our remaining wolverines persist in the Rocky Mountain region.
The Canada lynx, which inhabits boreal and subalpine forests, was designated a threatened species under the Endangered Species Act in 2000. There are remnant lynx populations in the Greater Yellowstone Ecosystem and as far south as the Overthrust Belt/Wyoming Range in southwestern Wyoming. Individual lynx that were reintroduced in southwest Colorado beginning in 1999 have ranged into southern and western Wyoming and have even bred in southeastern Wyoming’s Medicine Bow Mountains. Lynx in Wyoming are threatened by habitat fragmentation, climate change, energy development, and human disturbance. Aside from advocating the lynx’s protection in areas undergoing energy development in northwestern Wyoming, the Wyoming Outdoor Council joined other conservation partners in working to ensure that the U.S. Fish and Wildlife Service included the Greater Yellowstone Ecosystem and the adjacent Wyoming Range when it designated critical habitat for the lynx (a requirement under the Endangered Species Act). We also advocated a lynx critical habitat designation in the Medicine Bow Mountains; however, the Fish and Wildlife Service did not include this area in its 2009 critical habitat designation.