After a decades-long effort to restore the gray wolf population in the United States, federal wildlife officials announced Thursday they are ready to take the animals off the endangered and threatened species list.

The U.S. Fish and Wildlife Service calls the wolf population's recovery one of the "greatest comebacks for an animal in U.S. conservation history." More than 6,000 wolves now live in nine states.

"The facts are clear and indisputable: The gray wolf no longer meets the definition of a threatened or endangered species," David Bernhardt, acting secretary of the U.S. Interior Department, said Thursday when he announced the proposal. The plan would revoke gray wolves' federal protection, which could leave them potentially subject to hunting and trapping in Minnesota and several other states.

But many environmental groups call the move premature, arguing the wolf still has not recovered a large portion of its historic range.

It's the latest move in a series of a legal tug-of-war over the past 15 years, during which federal officials have acted on several occasions to remove endangered species protection for wolves in the upper Great Lakes, only to see federal courts restore those protections.

How are wolves doing in Minnesota?

Very well. The Minnesota Department of Natural Resources released its most recent annual population estimate in September 2018. The midwinter survey put the state's population at 2,655 wolves and 465 packs.

"The wolf is recovered in Minnesota, and it has been for several decades," said Dan Stark, the DNR's large carnivore specialist. "It's really a remarkable success of the Endangered Species Act."

Once exterminated from nearly the entire lower 48 states — with only a few hundred wolves hanging on in the remote forests of northern Minnesota — the gray wolf population in Minnesota has now exceeded 2,000 for at least 20 years, making it one of the densest wolf populations in North America.

"The wolf population is secure," Stark said. And they already occupy all the habitat in Minnesota that's suitable to them, he added, which makes it unlikely they would further extend their range.

What does this federal proposal mean for Minnesota?

If it's ultimately adopted, the proposal would mean that the federal government would cede management authority over Minnesota's wolf population to state wildlife officials.

That would give Minnesota more flexibility in managing wolf conflicts with humans, while still ensuring the state maintains a healthy wolf population, said Stark.

While the gray wolf remains on the threatened and endangered species list, the animal can only be killed if it threatens a human life. When wolves were last under state management, people were allowed to kill a wolf it threatened livestock or pets.

This undated image provided by Yellowstone National Park shows a gray wolf in the wild inside the park. MacNeil Lyons | National Park Service via AP

Many opponents of removing the wolves from the endangered species list fear that removing wolves' federal protection will lead to excessive killing.

"We have not really worked on human tolerance of allowing wolves to exist," said Maureen Hackett, founder of the Minnesota-based group Howling for Wolves. "When wolves are not protected, people resort to the way wolves have been treated for centuries, which is they were annihilated."

If wolves are removed from the endangered species list, will there be a wolf-hunting season in Minnesota?

We don't know yet. The DNR's Stark said no decision has been made yet on whether a wolf season would be implemented.

The last time wolves in the Great Lakes were delisted, in 2011, Minnesota moved quickly to hold an inaugural hunting season the following fall, to coincide with the deer hunting season. Two additional seasons followed in 2013 and 2014.

That first season in 2012, hunters and trappers in Minnesota killed 413 wolves, reaching the state's target harvest of 400 in two months.

Later that year, the DNR surveyed the state's wolf population and determined that the animal's numbers had fallen from 2,931 five years earlier to 2,211, a drop of about 24 percent. But officials say the decline was likely due to a drop in the population of northern Minnesota's deer, the wolf's primary prey — not the hunt, something some conservation groups disputed.

In 2013, hunters killed 238 wolves. The following year, hunters harvested 272 wolves, prompting protests.

Stark said any decision to hold a hunt again would go through a process to determine whether that would be an appropriate step, which would include an opportunity for the public to weigh in.

Haven't there been proposals to delist the wolf before?

Yes! Several times.

Nearly 10 years ago, in March 2007, the U.S. Fish and Wildlife Service issued its first rule to remove the gray wolf from the endangered species list in the western Great Lakes states. But a year and a half later, a federal judge placed the wolf back under endangered species protection.

Endangered no more? Wolf again poised to go off federal protection

In 2009, wolves were delisted again. But another court challenge forced the federal government to reverse itself. Then in 2011, they were removed from the endangered species a third time, before a judge again returned the wolf to federal protection in December 2014.

Many of the same groups that filed those lawsuits say they will also challenge this proposal if it's approved. They argue that, while the wolf population in Minnesota has recovered well, it's too early to remove the wolf from endangered species protection because it still hasn't recovered in areas they argue contain suitable habitat for wolves, including the Dakotas and the lower peninsula of Michigan.

Why are wolves so controversial?

People have strong, often visceral feelings about wolves.

Many Minnesotans feel a strong emotional connection to wolves, an apex predator, and their iconic howl in the northwoods. Many people have a hard time stomaching what they view as a "trophy hunt."

But many hunters argue wolves have a negative impact on the state's deer population. And wolves occasionally prey on livestock and even pets.

Ojibwe people have a strong spiritual connection to wolves. The animal plays a central role in Ojibwe creation stories, and are often described as family members. When Minnesota last authorized a state wolf hunt, all of northern Minnesota's Ojibwe bands banned hunting on their reservations.

What happens next?

People have two months to comment on the Fish and Wildlife Service's proposal to remove wolves from endangered species protection.

Past moves to delist wolves have typically taken about a year.

That means that there could be another wolf hunt in Minnesota as early as the fall of 2020 — but only if state wildlife officials decide to authorize one, and if the delisting isn't once again derailed by lawsuits.