(Inside Science) -- This past winter, hunters in Finland killed 46 wolves, nearly 20 percent of the country's estimated population of only 250. The hunt was entirely legal, with the purpose of reducing poaching in rural areas, where landowners had been shooting and killing wolves they considered a threat to livestock.
It's a rationale that officials have used to justify such culls throughout Europe and North America, including the U.S.
"There's this perception that if the government is aggressive in reducing populations of predators, then individual citizens will be less likely to take the law into their own hands," said wildlife research scientist Jason Fisher of Alberta Innovates, a research agency for the government of Alberta in Canada.
But now a new study in the journal Proceedings of the Royal Society B suggests that culling doesn't reduce poaching after all. Instead, culling increases it.
The analysis adds to a highly contentious issue that's culturally, legally, and politically complex, involving ranchers, hunters, politicians, government agencies, conservationists and scientists.
"The implications are pretty profound, which is why I suspect this paper is going to be hugely controversial," said Fisher, who wasn't part of the study.
Culling has been used to curb poaching and as a way to protect livestock from wolves. "However, there's no scientific evidence for any of these claims," said conservation biologist Adrian Treves of the University of Wisconsin, Madison. The new study, which he conducted with ecologist Guillaume Chapron of the Swedish University of Agricultural Science, is part of a growing body of evidence that questions the reasons for culling, he said.
For instance, a 2014 study suggested that killing a wolf to protect livestock actually increases the chances that wolves will attack in the future.
"It's no longer tenable to make the argument that killing wolves is a conservation strategy like the government once said," Treves said. "I find no scientific justification for culling wolves, period."
Today, the gray wolf is listed as an endangered species in most states, but the regulations vary widely.
"It's a mosaic," Treves said. In general, however, culling is allowed in most of the country, he said. In the new analysis, culling refers to any government-approved killing of a wolf that was deemed a threat to livestock, pets, or human safety (although killing a wolf in self-defense was always legal under the Endangered Species Act).
Treves and Chapron studied the gray wolf populations in Michigan and Wisconsin between 1995 and 2012. During this period, shifting policies meant culling was intermittently permitted. By comparing how wolf populations changed when culling was allowed with when it wasn't, the researchers could determine how culling affects the population.
They found that simply establishing a policy that allowed culling was enough to slow the population growth rate -- regardless of how many wolves were actually killed.
In their analysis, the researchers incorporated the population numbers with the number of culled wolves to calculate a potential growth rate, which measures how much the population would've grown if no wolves were actually culled. It turns out that when culling was allowed, the potential growth rate was lower than when culling wasn't allowed.
A slower growth rate could be due to many causes. For example, wolves might not breed as readily as their population becomes denser. But the researchers couldn't find evidence that this was the case, nor for any other possible causes. The most likely reason for the population slowdown, the researchers concluded, is illegal killing happening side-by-side with government culling.
The researchers speculate the reason culling causes poaching to rise lies in attitudes and psychology. A policy that allows culling may send a signal that killing wolves isn't a big deal, Treves said. Government-sanctioned killing may also diminish the perceived value of wolves. Or, people might decide that they might be better at killing wolves than government agents, and take their own initiative.
The results are disappointing, said Doug Smith, a wildlife biologist at Yellowstone National Park who's been in charge of wolf management research since 1995. "It's disappointing because this is a fundamental philosophy for wolf management across North America and Europe." If it turns out culling doesn't reduce poaching, then it makes managing wolves even harder.
"However, I'm not necessarily convinced," Smith said. The study was limited to two states, and culling might have other effects on poaching in different regions, where attitudes may be different. In Canada and Alaska, for example, where humans have always lived with wolves, there's less animosity, he said.
The study might also be limited because it measures poaching indirectly, Smith said. Because the evidence is limited, it's inherently difficult to track poaching. But a previous study in 2014 that measured illegal killings of wolves wearing radio-collars found the opposite conclusion: relaxing restrictions decreased poaching. "To say that culling itself is increasing illegal kills, that's a bit more difficult to make that comparison," said Adrian Wydeven, a retired wildlife biologist formerly with the Wisconsin Department of Natural Resources and an author on the earlier study.
Even if the new study's conclusions are preliminary, the statistical analysis is rigorous, and Smith trusts the results. The challenge, though, is coming up with a realistic solution because humans will always clash with wolves. "Wolf harvesting is not going away," he said. "There's no getting rid of it, and they sound like they want it to go away."
Relying on science is the best way forward, Fisher said. "What we need to do is implement science, and rigorous and robust science every time we undertake a decision like this."
But that may be unrealistic as the issue is inherently a human one.
"This stuff is all dealing with human values -- not biology," Smith said. "The poaching of wolves is more a clash of values and cultural norms than it is game regulations."