Environmental groups claiming the government put politics over science in refusing to protect wolverines under the Endangered Species Act filed a lawsuit Tuesday, seeking federal protection for the elusive member of the weasel family.

The suit that Defenders of Wildlife and eight other groups filed in U.S. District Court in Missoula challenges the Interior Department and one of its agencies, the U.S. Fish and Wildlife Service, on the status of wolverines outside Alaska.

Not counting Alaska, the U.S. wolverine population consists of about 500 animals, the Fish and Wildlife Service estimates, a figure the plaintiffs say may be high by 20 percent or more. Wolverines inhabit Montana, Idaho, Wyoming and Washington.

In denying Endangered Species Act protection, the service said in March that even if wolverines disappeared from the 48 contiguous states, the species would survive because wolverines in the United States are connected to larger populations in Canada. There, the population has been pegged at 15,000 to 19,000 animals.

"Americans want these animals protected on our own soil," David Gaillard, Northern Rockies representative for Defenders of Wildlife, said Tuesday.

The suit naming Interior Secretary Dirk Kempthorne and Fish and Wildlife Service Director Dale Hall asks the court to order the wildlife agency to reconsider its decision against declaring wolverines an endangered or threatened species. A call to the Interior Department was returned by Fish and Wildlife Service spokeswoman Diane Katzenberger, who said the agency does not comment on pending litigation.

Gaillard said documents obtained under the Freedom of Information Act revealed that science-based Fish and Wildlife Service conclusions that wolverines need protected status were rejected in the upper reaches of the Interior Department, and other officials then "fell into rank."

Climate change is among wolverines' perils, but the Interior Department did not want another case of climate-driven concern about wildlife to have prominence around the time of a status decision on polar bears, Gaillard said.

In May, the government declared polar bears a threatened species in need of increased protection. The Interior Department found the bear at risk of extinction as Arctic sea ice, on which the animal depends, decreases. Scientists have tied the melting of sea ice to global warming.

In the wolverine debate, warming is an issue because wolverines need alpine snow in the spring so they can rear their young successfully, Gaillard said.

He said documents were sought under the Freedom of Information Act because it was strange that the Fish and Wildlife Service had acknowledged wolverines were in jeopardy, yet would not protect them.

"This was pretty strong, saying we know a fair amount and everything we know shows they're threatened and yet we're not going to do anything," Gaillard said.

Supporters of the Fish and Wildlife Service decision against Endangered Species Act protection include the Montana Furbearer Conservation Alliance, which has spoken in favor of wolverine trapping in Montana. It is the only state, other than Alaska, that allows the trapping. The service was correct in evaluating the U.S. population in the context of Canada's, alliance spokesman Don Bothwell said Tuesday.

"The wolverine range crosses international and state boundaries," Bothwell said. "Wolverines have no concept of our political divisions. They travel where they will. It's nothing for a wolverine from Alberta to find its way into Montana and then Wyoming."

The environmental groups question claims about migration and contend that wolverines in the United States and Canada are genetically separate, a point on which some scientists disagree.