Too many species, too little staff. That's the roadblock preventing the U.S. Fish and Wildlife Service from immediately adding the wolverine population in the contiguous 48 states to the list of species with protection under the Endangered Species Act.

On Monday, more than a year after the agency sat down with conservation groups concerned about the future of gulo gulo, it issued a statement saying that wolverines do indeed merit ESA protection, largely because of habitat loss to climate change, but that it will be withheld indefinitely due to a backlog of other species awaiting an official ESA listing.

“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, who heads 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.”

Currently, FWS officials say wolverine populations are restricted to the North Cascades Range in Washington and the Northern Rockies of Montana, Idaho, and Wyoming. Populations once existed in the Sierra Nevada of California and the southern Rocky Mountains in the states of Colorado and Utah. Currently, at least one individual wolverine is known to inhabit the Sierra Nevada and one in the southern Rocky Mountains, the service said, adding that "both are thought to be recent migrants to these areas."

Climate change threatens the wolverine because females den in snowfields, which are shrinking under warmer temperatures. Also, while wolverines have been known to hunt deer, elk, and even moose that founder in deep snows, they also are expert scavengers; in winter and spring they often make meals of wildlife killed by avalanches. Less snow is also reducing the opportunity for easy meals.

According to FWS officials, "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 Service 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."

At Earthjustice, which had argued for the listing, attorney Tim Preso said that while the decision "reverses years of official denials that the wolverine faces a significant threat of extinction in the lower 48 states,” 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.”

Fewer than 500 wolverines are thought to survive in the lower 48, and a recent study found that just 35 individuals are breeding successfully in the western United States, a release from Earthjustice said.

The Fish and Wildlife Service’s “warranted but precluded” finding means that the status of wolverines will be reviewed annually until a final determination is made to officially list the species as threatened or endangered. On a scale of 1 to 12, where 1 is the highest priority level, the wolverine received a listing priority number of 6 due to “threats that are of high magnitude but that are not imminent.”

That ranking frustrated conservationists.

“The wolverine is in desperate need of protection, but rather than provide that protection the Obama administration is shuffling papers,” said Noah Greenwald, endangered species director at the Center for Biological Diversity. “The wolverine has been put in line along with hundreds of other species, many of which have been waiting decades for protection.”

The wolverine is the 14th species declared to be “warranted, but precluded” for an ESA listing under the Obama administration. In addition to the wolverine, there are currently 251 species that are waiting for protection under the government’s candidate list, the Earthjustice release said.