Over the federal government’s 30-year effort to revive endangered red wolves in North Carolina, there have been many attempts by opponents to get rid of them. But to argue that the wolves engaged in so much sex with coyotes that the two species somehow became one? That was a novel approach.

It is a good argument if you can prove it. Red wolves are a rare and dying breed that actually went extinct in the wild before a few were set free again after being bred in zoos. Coyotes are plentiful, and unlike the larger wolves, they are ineligible for protection under the Endangered Species Act.

Last year, North Carolina officials and landowners opposed to a U.S. Fish and Wildlife Service reintroduction program helped convince Congress to commission a nearly $400,000 study to determine if the wolves are more coyote than wolf. Opponents greeted it as a victory for those who want to run the animals out of the state.

On Thursday, the National Academies of Sciences, Engineering and Medicine released their findings nearly a year to the day after the study was ordered, settling a seesaw battle over the red wolf’s taxonomy that had dragged on for decades.

Leading up to the study’s release, the red wolf recovery program in and around the Alligator River National Wildlife Refuge was in a steep decline. The number of wolves has fallen from a high of 50 to about 35.

The U.S. Fish and Wildlife Service’s southeast division, which manages the recovery, announced a plan to reduce the population by more than half, saying the program could only accommodate about a dozen animals.

The announcement was another indication of Fish and Wildlife’s growing hostility to its own mission to save federally protected wolves, conservationists said. In a major reversal three years back, Fish and Wildlife issued permits allowing landowners to kill any red wolf that strayed onto their property. Within weeks, a female red wolf seeking food for her pups was shot dead.

A federal judge blasted Fish and Wildlife’s decision to issue the permits in a ruling handed down seven months after the agency announced its effort to reduce the population. “Wildlife are not the property of landowners but belong to the public and are managed by state and federal governments for the public good,” wrote the judge, Terrence Boyle.

“Notably . . . the red wolf population saw a drastic decrease from 2013 to 2015,” with only 50 wolves remaining, Boyle wrote. The population’s plummet coincides with Fish and Wildlife “making internal revisions to its guidelines and management policies in response at least in part to mounting public pressure against red wolf recovery efforts.”

The state approved night hunts to reduce coyotes, but a judge shut it down after conservationists argued that hunters were mistakenly shooting red wolves to death — in broad daylight.

The irony is that there would probably be no coyotes in North Carolina if more red wolves were around. Red wolves once roamed the entire southeast and a portion of the southwest, assuring that coyotes, which they killed for encroaching on their territory, were pinned in the West.

But a century of state-sanctioned hunting all but wiped out red and gray wolves, as well as cougars, allowing coyotes to move in. Coyotes are amazing canids in one respect, wildlife biologists say. When confronted with stress such as hunting, they respond by producing more coyotes.

Before 1990, coyotes had not been established in North Carolina.

Red wolves and coyotes enjoy the same meals: an occasional deer, raccoons, rabbits and other small game. Those just happen to be the animals that some people in North Carolina like to hunt, and the money that hunters pay farmers to track animals on their land helps farmers get by between harvests.

Having lost most of their battles to relieve themselves of red wolves, the state and its allies turned to unsettled scientific theorizing that coyotes are the new red wolves.

When red wolves were going extinct in the late 1970s, they could no longer be choosy about mates. They were breeding with coyotes so often that Fish and Wildlife officials rushed in to Texas and Louisiana to grab the last pure red wolves, place them in zoos and attempt to resurrect the species through breeding.

It was a smash hit, scientifically. Two pairs of wolves were set free at the Alligator River National Wildlife Refuge in 1987 and, by all accounts, flourished. Fish and Wildlife struck bargains with some supportive landowners whose property bordered the refuge and set more wolves free.

But after Republicans took control of the state government, North Carolina turned against the program, and landowners opposed to wolves started lobbying residents against them. They were upset that some of the wolves outside the refuge were meandering onto their land.

On the rare occasions that they spotted a stealthy wolf or came across one in a trap, some farmers thought they looked a lot like coyotes or a hybrid maybe.

Opponents of the program met with Fish and Wildlife regional officials in Atlanta and members of the state congressional delegation in Washington to push the idea that as a genetic hybrid, the wolves are not eligible for federal protection.

It fell to the academies to determine if red wolves are a distinct species worthy of a strong program to rescue them. And last week, the decision came down:

“The evidence . . . supports the classification of the contemporary red wolf as a distinct species,” the 94-page report said.

Not only are they distinct from gray wolves and coyotes, current red wolves trace back to ancestors that lived more than 10,000 years ago, scientists who participated in the study said.

In other words, red wolves did not have so much sex with coyotes that they mated themselves out of existence.

After studying reams of the best available historic data and the genomes of numerous canids, the academies declared that, contrary to arguments that critics have made, red wolves are exactly what they are called.

They do note that “North American canid species are genetically very similar to each other and have substantial amounts of shared genetic variation.” There’s a bit of gray wolf and coyote in the DNA of red wolves.

Then again, they say, “the contemporary population of red wolves in North Carolina is morphologically distinguishable from coyotes and red wolf-coyote hybrids."

While red wolves are more genetically related to coyotes than gray wolves, “the red wolf has some degree of genetic ancestry not found in reference populations of western gray wolves or coyotes,” the study said.

It goes on to challenge a key argument for not protecting red wolves. Red wolves “have a social organization and reproductive behavior that are more similar to those of gray wolves than to coyotes, and when mates are available red wolves exhibit assortative mating.”

That is another way of saying when a red wolf has a choice between another red wolf and a coyote, the coyote does not cut it. The admixture premise can be rejected for three reasons, the study said: the “deep divergent DNA” in red wolves; there was not enough time for coyotes and red wolves to mix their way to a new subspecies of coyote; and red wolves have a gene linked to gray wolves on Galveston Island that coyotes lack.

Both the Fish and Wildlife Service and North Carolina Wildlife Resources Commission said they are reviewing the study.

“We have the utmost respect for the Academy, and we appreciate their efforts to better illuminate red wolf taxonomy,” said Gordon Myers, director of the state wildlife commission.

“The findings of the . . . report validate everything we’ve been doing to try to goad FWS into taking better care of the remaining wild red wolves in North Carolina,” said Ron Sutherland, chief scientist for the Wildlands Network in Durham, N.C. “Now that the National Academy of Science experts have deemed the red wolf to be a valid species, it is time for FWS to stop looking for excuses and start revamping and revitalizing their stalled recovery efforts for the red wolf in the wild.”

With about 35 red wolves left, “the onus is now on the U.S. Fish and Wildlife Service to protect the red wolf before it is driven to extinction,” Jamie Rappaport Clark, president and chief executive of Defenders of Wildlife, said in a statement. “The Service has faltered in that duty for years.”