BILLINGS, Mont. — Thirteen years after the government listed Canada lynx as a threatened species, wildlife advocates on Thursday asked a federal judge to force the U.S. Fish and Wildlife Service to finish its long-awaited recovery plan for the snow-loving wild cats.

Four groups represented by the Western Environmental Law Center allege the long delay on the part of the U.S. Fish and Wildlife Service violates federal law.

In a lawsuit filed in U.S. District Court in Montana, they asked the court to set a date for the government to adopt a “road map” that would detail what’s needed for lynx to recover.

While the government has taken steps to protect lynx since their 2000 listing – including a 2009 designation of habitat considered critical to the species’ survival – the recovery plan has been on hold.

That’s in part because of lawsuits over the 39,000 square miles of lynx habitat identified in Washington, Idaho, Montana, Wyoming, Minnesota and Maine, federal officials said. It’s also due to the higher priority that’s been given to other species that face more acute threats, they said.

But the plaintiffs in the case say the government should be pushing ahead on both the habitat and recovery issues simultaneously to keep the lynx from edging closer to extinction.

“Thirteen years is a long time to wait for something that’s really an essential part of recovering a species,” said Arlene Montgomery with Friends of the Wild Swan in Big Fork, Mont.

The other plaintiffs in the case are Rocky Mountain Wild, San Juan Citizens Alliance and the Biodiversity Conservation Alliance.

Canada lynx aren’t listed as threatened in Alaska, and it’s believed that they number only in the hundreds in the Lower 48 states. Federal wildlife officials say the cats’ elusive nature makes it hard to know for certain.

Its large, furry paws help the predator stay on top of the deep snows that are typical through its range — and also make it easier to capture the snowshoe hares that are its primary prey.

Weighing about 20 to 30 pounds and roughly the size of a bobcat, the animals are rarely seen across a range that once covered 14 states. They’re still found in portions of the Northeast, the Rocky Mountains, the western Great Lakes and the Cascade Range of Washington state.

They were reintroduced to Colorado in 1999, under a program that state officials in 2010 declared as a success. Whether Colorado should be included as part of the species’ designated habitat is under review as the result of a separate lawsuit.

In a March 6 letter to the Western Environmental Law Center, the Fish and Wildlife Service said the agency will start work on the recovery plan only after it submits a new critical habitat rule by Sept. 30, 2014.

The agency also said additional litigation could prevent that work from going forward.

Federal law “does not specify a time line for completion of recovery plans,” the letter said.

Matthew Bishop, a Montana attorney who filed Thursday’s lawsuit, said habitat loss due to logging, climate change and other factors remains a threat that needs to be dealt with across the lynx’s range.

“A recovery plan would identify specific management actions that need to occur to achieve recovery. Not just survival, but recovery,” he said.