Thirty-four years after wolves first went on the endangered species list and 13 years after reintroduced wolves took their first steps in Yellowstone National Park, the northern Rockies gray wolf is recovered, federal officials say.

Federal officials announced Thursday that gray wolves in the Northern Rockies will be removed from the endangered species list.

“Gray wolves in the northern Rockies are thriving and no longer require the protection of the Endangered Species Act,” Interior Deputy Secretary Lynn Scarlett said in a teleconference Thursday.

A number of conservation groups, including the Sierra Club, Defenders of Wildlife, Natural Resources Defense Council and the Jackson Hole Conservation Alliance, have vowed to challenge the decision in court. Defenders of Wildlife and the Natural Resources Defense Council have also formally petitioned the U.S. Fish and Wildlife Service to prepare a comprehensive recovery plan for wolves in the lower 48 states.

The delisting will go into effect 30 days after a notice is published in the Federal Register. Officials hope to publish the delisting by Feb. 29.

Wolves in the lower 48 states were mostly extinct by 1930, following a policy of eradication by federal and state governments. The U.S. Fish and Wildlife Service put wolves on the endangered species list in 1974. The agency set 66 Canadian wolves free in Yellowstone National Park and central Idaho starting in 1995. The total northern Rockies population is now more than 1,500 animals.

“The population has exceeded its recovery goal every year since 2002,” Scarlett said. “Wolves are back.”

Idaho, Montana and Wyoming have committed to maintaining a minimum of 15 breeding pairs and 150 wolves in each state, for a total of 450 wolves. But according to U.S. Fish and Wildlife Service wolf recovery coordinator Ed Bangs, the individual state plans suggest the states will maintain a total of between 900 and 1,250 wolves in the region.

“It’s a pretty good feeling to know that this final part of this recovery project is happening ... that the future of the wolf population is secure in state hands,” Bangs said.

Bangs said hunting and state control efforts likely wouldn’t hurt the wolf population because the animals are such prolific breeders. About 26 percent of the adult wolf population dies each year, and most of the deaths are caused by people. Federal wildlife managers have killed more than 700 wolves for preying on livestock since the reintroduction program began.

“The wolf population has been expanding 24 percent per year,” Bangs said. “Their social structure is resilient. The population of wolves that the states are going to manage for has no threats to it by increasing human-caused mortality a little bit.”

Natural Resources Defense Council spokeswoman Louisa Willcox said the states and the federal government haven’t figured out how to pay for wolf management after delisting. According to Bangs, while some federal funds will be available, most of the burden will fall on Montana, Idaho and Wyoming. The U.S. Fish and Wildlife Service has spent about $3 million a year on wolf management in recent years.

Bob Wharff, Wyoming executive director of Sportsmen for Fish and Wildlife, called the delisting “a huge victory” and denounced the conservation groups that plan a lawsuit.

“I’m frustrated that the environmental groups want to continue to litigate everything,” he said. “It’s up to the environmental groups; they can either show that the Endangered Species Act works or they can continue to show that they have another agenda besides species restoration. It marginalizes the environmental movement.”

Franz Camenzind, executive director of the Jackson Hole Conservation Alliance, said his group didn’t take the decision to litigate lightly.

“A lawsuit is not the way to resolve issues, but we felt there is too much at stake here,” he said. “We fear the rhetoric that we’ve heard ... we fear the Wyoming plan could push wolves back toward extirpation.”

Outside the northwest corner of the state, wolves could be killed by any means without a license under Wyoming’s wolf management plan.

“Two miles [southwest] from the Town Square,” Camenzind said, “if wolves showed up, under the Wyoming plan, they could be shot by anyone at any time — right in the heart of Jackson Hole.”