Federal wildlife officials say they've dropped plans to create protections for snow-loving wolverines, saying it was impossible to be sure how climate change might affect the animals.

The move comes amid an ongoing debate over what kinds of impacts global warming might have on temperature-sensitive species such as wolverines, which need habitats with late-season, deep snow in which to create their dens.

"Climate change is a reality," U.S. Fish and Wildlife Service Director Dan Ashe acknowledged, but he said predictions about such impacts are still "ambiguous," making it difficult to determine if climate change might present wolverines with a risk of extinction.

In deciding not to pursue protections for the wolverines, Ashe was going against the recommendation of outside experts and even some scientists within his own agency.

In discussing his decision, he noted evidence of expanding populations of the animals that suggests, "it's possible wolverines are adapting and continuing to adapt."

That's an argument that didn't fly with wolverine expert Jeff Copeland.

"What's happened today is nothing less than a travesty of science," said Copeland, a research biologist and director of The Wolverine Foundation in Idaho. "This was not a scientific process. It was a political process."

Some federal wildlife officers, citing evidence that future warming temperatures might melt snowfields that are habitats of wolverines in mountain ranges in the lower 48 states, had called last year for more protections to prevent wolverines from becoming extinct in those areas.

Officials in a number of western states opposed any increased federal protections, suggesting wolverine populations have in fact increased in some areas over the last few decades.

Wildlife advocates, blaming the USFWS backtracking on pressure applied by state wildlife agencies, said they planned to sue to force the federal agency to adopt the increased protections.

Wolverines, sometimes known as "mountain devils," were once common in the Rocky Mountains and the Sierra Nevada mounting range in California, but were wiped out in most of their habitat ranges in the lower 48 states by unregulated hunting and trapping.

It is estimated fewer than 300 wolverines remain in small, isolated groups, mostly in the northern Rocky Mountain regions of Wyoming, Montana, Idaho and Washington.

Larger populations are still found in Canada and Alaska.

Climate change is a valid consideration when it comes to gauging risks to species like wolverines, experts say, noting the in the past 5 decades snow melt around the northern Rockies has moved  earlier into spring by two weeks.

"If you take 50 more years and think of it as two more weeks earlier, wolverines are probably one of the classic poster children of a highly temperature-sensitive animal," says Steve Running, a University of Montana ecology professor who's also a member of the Intergovernmental Panel on Climate Change.