Wolverines in the lower 48 states warrant protection under the Endangered Species Act, but they are “precluded” from a listing because other species have a higher priority, the U.S. Fish and Wildlife Service announced Monday.
However, the federal agency’s “warranted but precluded” decision effectively reverses a 2008 determination made under the Bush Administration that wolverines do not warrant ESA protection because adjacent wolverine populations in Canada are healthy.
A coalition of environmental groups challenged that conclusion, noting that strong populations of grizzly bears and wolves in Canada have not influenced ESA protection for those species in the United States.
“This decision finally reverses years of official denials that the wolverine faces a significant threat of extinction in the lower 48 states,” said Tim Preso, an attorney with Missoula-based Earthjustice. “Unfortunately, the decision still fails to give the wolverine the legal protections that it needs. We will continue to work to make sure that the wolverine remains a living, breathing part of our nation’s wildest landscapes.”
The U.S. Fish and Wildlife Service rated the wolverine as a 6 on a scale of one to 12 for species priority, with 1 being the highest priority species.
“The threats to the wolverine are long-term due to the impacts of climate change on their denning habitat, especially important to assist the species in successfully reproducing,” said Steve Guertin, director of the Service’s Mountain-Prairie Region. “If we work with state and other partners to help the wolverine now, we may be able to counter the long-term impacts of climate change on their habitat and keep them from becoming endangered.”
Shawn Sartorious, a listing-recovery biologist with the agency’s Montana field office, explained that wolverine occupy the region’s coldest areas in alpine or subalpine habitat, and they particularly require persistent spring snow cover.
“The need for that snow relates to wolverine denning, which involves elaborate snow tunnels,” Sartorius said during a Monday conference call.
Tunnels are used to protect against predators, shield their young from extreme cold. Wolverines have very low reproductive rates, another factor in the determination they warrant ESA protection, Sartorius said.
The main threat identified to their habitat has been identified as climate change. Research carried out over the last few years in Glacier National Park’s Many Glacier Valley played into the decision for wolverines to become a candidate species for ESA protection. Disappearing and retreating glaciers have been well documented in the park over the last century.
Sartorius said it is believed that there are only about 200 wolverines remaining in the Northern Rockies, and only 10 in the Cascade Mountain Range. One is known to inhabit Colorado, and one in California.
But Sartorious acknowledged that wolverine population estimates are based on “the best professional judgments” of biologists who are familiar with the species and the habitat they use.
“It’s a very difficult thing to determine populations for wolverines,” he said.
The wolverine is a resilient species which was likely extirpated from the lower 48 states during the early 20th century and has re-established populations by moving down from Canada into the north Cascades Range of Washington and the northern Rocky Mountains of Montana, Idaho and Wyoming.
Deep snow is required for successful wolverine reproduction because female wolverines dig elaborate dens in the snow for their offspring. These den structures are thought to protect wolverine kits from predators as well as harsh alpine winters. Data and analysis requested from the University of Washington Climate Impacts Group and the U.S. Forest Service Rocky Mountain Research Station predict a reduction of wolverines' cold and snowy habitat of 63 percent by 2099.
As wolverine habitat is reduced, the USFWS expects the remaining habitat will become more fragmented, with distances growing between habitat "islands." Evidence suggests this diminished and fragmented habitat will support fewer wolverines with reduced connectivity between populations. The impact of climate warming may exacerbate the impact of other threats, such as recreational use of habitat, infrastructure development, and transportation corridors.
The agency will add the wolverine to its list of candidate species and review its status annually. Candidate species do not receive protection under the ESA, although the USFWS works to conserve them. The annual review and identification of candidate species provides landowners and resource managers with notice of species in need of conservation, allowing them to address threats and work to preclude the need to list the species. The USFWS is currently working with landowners and partners to implement voluntary conservation agreements covering 5 million acres of habitat for more than 130 candidate species.
A copy of the finding and other information about the wolverine is available online at http://www.fws.gov/mountain-prairie/species/mammals/wolverine