Twelve conservation groups say they’ll file a lawsuit Monday in an effort to reverse a U.S. Fish and Wildlife decision to remove the gray wolf from federal Endangered Species Act protection.

Along with the lawsuit, the groups will seek an injunction from a U.S. District Court judge in Missoula, Montana to prevent people from killing wolves in Wyoming’s predator management area. As of April 25, hunters have reported 13 wolves killed in Sublette County, according to the Wyoming Game and Fish Department.

Earthjustice is litigating the case for the Jackson Hole Conservation Alliance, the Natural Resources Defense Council, Sierra Club, and the Center for Biological Diversity, among others.

According to Craig Noble, spokesman for the Natural Resources Defense Coun-cil, the “rash of wolf killings” in Wyoming has conservationists worried about the wolf’s future. Wyoming allows people to kill wolves at any time without a permit in all but the northwest corner of the state.

In the northwest corner, they will be trophy game, with the exception of Grand Teton and Yellowstone national parks and the National Elk Refuge. Trophy game classification means wolves can only be killed with a hunting license or other permit, such as one issued in the case of livestock depredations.

“This may be the first time that an animal has faced slaughter upon being removed from the Endangered Species List,” Noble said, explaining that Wyoming’s state plan encourages wolf killing. “People are able to essentially shoot wolves any time, anywhere, for any reason. There’s clearly a lot of hostility on the ground to the wolves.”

The states of Wyoming, Idaho and Montana have pledged to maintain a minimum population of roughly 450 animals in the Rocky Mountain region, 150 in Wyoming, including those in Yellowstone. But Noble says that minimum estimate for a viable population relies on 20-year-old science. More recent research suggests that a population of 2,000 to 5,000 wolves is necessary to maintain enough diversity to sustain the species, he said.

Further, Noble said wolf watchers contribute about $35 million to the local economy.

“Thousands of visitors are flocking to Yellowstone every year to see and hear wolves in the wild,” he said. “They’re good for people too.”

There are 359 wolves in Wyoming today. Yellowstone accounts for 188 while the remaining 171 are outside the worlds first national park.

Wyoming Game and Fish spokesman Eric Keszler said Wyoming’s plan is adequate to maintain a recovered population of wolves in northwest Wyoming.

“The department’s position is that delisting is justified right now,” he said. “We don’t feel like a challenge to delisting or an injunction that would change the status of wolves are needed.”

Keszler said the current population can withstand the recent wolf shootings in Sublette County. He pointed out that roughly 90 percent of Wyoming’s wolves live in the trophy game area, and that Wyoming’s wolf population has continued to grow despite losing between 60 and 80 wolves per year due in control actions resulting from livestock depredations. “That’s something that we’ll continue to monitor,” he said.