Environmental groups sued the federal government Tuesday to protect wolverines under the Endangered Species Act, saying the Interior Department disregarded scientific conclusions that the species was in jeopardy.

The U.S. Fish and Wildlife Service denied the species Endangered Species Act protection in March by saying that even if wolverines disappeared from the Lower 48, the species would survive because there are larger populations in Canada.

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

The nine environmental groups sued the Interior Department and one of its agencies, the U.S. Fish and Wildlife Service, asking the U.S. District Court in Missoula to order the wildlife agency to reconsider its decision to deny the wolverine protection.

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 Canada, the population has been pegged at 15,000 to 19,000 animals.

Fish and Wildlife Service spokeswoman Diane Katzenberger said the agency does not comment on pending litigation.

Gaillard said documents obtained under the Freedom of Information Act show the upper reaches of the Interior Department rejected the Fish and Wildlife Service's conclusion that wolverines need protected status, and Fish and Wildlife Service staff then "fell into rank."

One threat to wolverines is climate change, and Gaillard said 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.

In May, the government declared polar bears a threatened species because Arctic sea ice is decreasing. Scientists have tied the melting of sea ice to global warming.

Wolverines need alpine snow in the spring so they can rear their young successfully, Gaillard said.

The Montana Furbearer Conservation Alliance, which favors wolverine trapping in Montana, supports the agency's decision against Endangered Species Act protection. Montana is the only state besides Alaska to allow wolverine trapping.

The agency 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."

Environmental groups say wolverines in the United States and Canada are genetically separate. Some scientists disagree.