"Warranted, but precluded"

Polar bears.  Walrus. Ringed and bearded seals. And now wolverines have joined the list of northern animals threatened by warming winters and shrinking snow and ice packs.

The U.S. Fish and Wildlife Service listed the bear in 2008 and is considering adding the walrus and the seals. This week, the agency announced that while listing the wolverine is justified, mostly because of the projected effects of climate change, budget restrictions and the needs of more urgently-threatened species will prevent it from actually adding Gulo gulo to the endangered species roster. It now joins roughly 250 other species on the "candidate" list, and even there its priority isn't high -- on a scale of 1 to 12, where 1 is highest priority, the agency assigned the wolverine a 6. Gunnison sage grouse rate a 2 on that list.

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The "warranted but precluded" finding is a step forward, though, say conservationists: FWS has previously declined even wait-listing wolverines three times since 1994.

The Northern Rockies are home to perhaps 200 wolverines, said FWS biologist Shawn Sartorius during a Dec. 13 press conference. Another 10 or so roam the North Cascades. And there's one in the Sierra Nevada, and one in western Colorado (as of two weeks ago, his radio collar signal indicated the lone male was still kicking). Canada and Alaska have robust wolverine populations, though -- and that's what prevented the carnivores from being listed previously. However, wolves and grizzlies also have healthy Canadian and Alaskan populations but are on the endangered species list in the lower 48; now, the FWS has finally applied the same reasoning to wolverines, considering those in the contiguous U.S. as a (PDF) distinct population segment deserving of protection.

Wolverines depend on cold conditions and deep spring snow cover to successfully den and raise young, said Sartorius. But climate change, as it warms winters and decreases snowpack, will shrink the wolverine's suitable habitat into smaller, more scattered pockets. Secondary threats to the animals include Montana's  wolverine trapping season and winter recreation such as snowmobiling and cross-country skiing, which disturbs them.

The efforts of the Great Northern Landscape Conservation Cooperative (PDF), an alliance of federal, state, tribal and NGO partners, may help those isolated wolverine populations remain in contact, said Steve Gurtin, regional director of the FWS's Mountain-Prairie Region. The alliance, announced last spring, will work on habitat connectivity and corridors in the northern Rockies and Columbia Basin.

Startlingly little is known about wolverines, said Sartorius, and the agency plans to support additional research. "We'll use science to help us move forward and guide our long-term strategies," he said, "and we'll evaluate the wolverine's status each year to see if it should move up or down (on the priority list)." He noted that "there is no adequate regulatory mechanism to address the main threat to wolverines: climate change."

For more of HCN's wolverine coverage, see these stories and blog posts:

Would listing the wolverine even help?

Wolverine: Chasing the phantom

The perils of secrecy

Secret life of wolverines