BOISE - A coalition of conservation groups and a U.S. congressman from Oregon have sent separate letters asking the U.S. Forest Service to require a pro-hunting group get a permit before being allowed to hold a wolf- and coyote-shooting contest in Idaho.

The letter sent Tuesday by Democratic Rep. Peter DeFazio and another sent Monday by environmental groups cite a recent U.S. Bureau of Land Management decision revoking a special use permit for the predator derby.

The BLM on Nov. 25 canceled a permit less than two weeks after issuing it to Idaho for Wildlife to hold the January event in east-central Idaho near Salmon. The BLM cited late changes in derby rules.

Amy Atwood, an attorney at the Center for Biological Diversity, said the letter from conservation groups is intended to give the Forest Service an opportunity to reassess its position that a permit for the derby isn't needed.

"I would say that litigation is highly likely if they don't take a new look at this," she said.

If a lawsuit is filed, it would follow an earlier lawsuit filed by another group also seeking to force the Forest Service to require Idaho for Wildlife to obtain a permit. Such a permit typically requires an environmental analysis before being issued.

"Despite the fact that much of the hunting was to occur within the National Forest System (NFS), the Forest Service determined that the contest was not a commercial event occurring on NFS land, and, therefore, no special use permit was required," DeFazio, the ranking member of the House Committee on Natural Resource, wrote in the letter addressed to Forest Service Chief Tom Tidwell. "This determination was questionable at the time, and I ask that you revisit it in light of recent events."

The recent events refer to the BLM decision revoking the permit it issued.

However, a federal judge ruled in 2013 that Idaho for Wildlife didn't need a Forest Service permit for the event because promoters were encouraging use of the forest for a lawful activity.

"I don't understand why the urbanites and radical anti-hunters don't understand our lifestyle," said Steve Alder, who plans to seek a BLM permit again next year. "They've elevated the status of the wolf above us and it's just insane."

Losing the 3.1 million acres of BLM land cuts the area for the derby in half. Alder said hunters would likely hunt on BLM land anyway, but any wolves or coyotes killed wouldn't be eligible for prize money. The event is planned for Jan. 2-4, and includes a $1,000 prize each for whoever kills the most wolves and coyotes. The event last year drew 230 people, about 100 of them hunters, who killed 21 coyotes but no wolves.

Travis Bruner of Western Watersheds Project, one of the environmental groups that signed the letter, said wolves tend to disperse so any wolves killed in the derby could limit wolves ultimately spreading out to other states.

"We'd like to see wolves reclaim their range all over the West," Bruner said. "If hundreds of people are going to (hunt) places where wolves live, that's certainly going to reduce their ability to travel."

Charles Mark, supervisor of the Salmon-Challis National Forest didn't return a call from The Associated Press on Tuesday.