(The Center Square) – Environmental groups are suing the U.S. Fish & Wildlife Service for its denial of a petition to relist gray wolves in the northern Rocky Mountains as endangered or threatened.

Gray wolves are currently listed under the Endangered Species Act as endangered in 44 states, while states maintain jurisdiction in Idaho, Montana, Wyoming, as well as parts of Oregon, Washington and Utah.

The Center for Biological Diversity, the Humane Society of the United States, Humane Society Legislative Fund and Sierra Club list the USFWS and Interior Director Deb Haaland in the lawsuit filed Monday in the U.S. District Court in Montana.

The lawsuit comes after the USFWS in February denied the groups’ listing petition, but decided to develop a national recovery plan for the species.

“After an extensive peer-reviewed assessment using the best available science, the Service today announced a not warranted finding for two petitions to list gray wolves under the ESA in the Northern Rocky Mountains and the Western United States,” the USFWS said at the time. “This finding is not action-forcing; the legal status of gray wolves does not change as a result of this finding.”

The lawsuit says the USFWS’ decision was “unlawful and arbitrary,” arguing it “failed to rely on the best available science.”

“Accordingly, Plaintiffs request that this Court declare the Service’s denial of the Petition to be arbitrary and capricious and unlawful under the ESA, vacate the illegal decision, and remand the matter to the Service with direction to determine whether the best available science supports protecting wolves in the Northern Rocky Mountains as an endangered or threatened species, by a date certain,” the lawsuit said.

In Colorado, where gray wolves were reintroduced in December following a voter-approved initiative, the state got a special designation from USFWS to treat the state’s population as experimental.