Governments often take on the job of killing problem wolves that attack livestock in order to increase public tolerance for the predators and, in theory, to reduce poaching by frustrated citizens.

Turns out, it could be having the opposite effect.

In what is likely to be a controversial finding, researchers from Wisconsin and Sweden have found that poaching appears to increase when governments are allowed to kill wolves.

The most likely explanation, they said in a paper published Tuesday, is that when the government kills wolves it sends an unintentional signal that it’s also OK for others to “shoot, shovel and shut up.”

If they hold up, the findings are important for Minnesota, which has far more wolves than any state but Alaska and is now the only Midwestern state where government culling is allowed.

After years of legal wrangling, a federal court last fall put Great Lakes wolves back under federal protection. But in contrast to Wisconsin and Michigan, where wolves are listed as endangered, wolves in Minnesota are listed as threatened. That means that, for now, state and federal wildlife officers in Minnesota can trap and kill wolves that kill livestock or pets, while they cannot in states where wolves are endangered.

Researchers found wolf populations were about one-third lower than they should have been each time government culling programs were in place.

On average, wildlife officers in Minnesota kill 100 to 200 wolves per year out of a current population of about 2,400. The number of poached wolves is unknown, but the state Department of Natural Resources (DNR) investigates several cases a year.

Wildlife officials for the DNR declined to comment on the research paper because they had not seen it.

‘Invisible signal’

Government culling has long been used in wildlife conservation to manage wolves and other predators on the assumption that it would prevent people “from taking the law into their own hands,” said Jason Fisher, a wildlife research scientist at the University of Victoria, British Columbia, who reviewed the paper before it was published. But culling has never been scientifically studied to see if it produces the desired side effects, he said, in part because it’s so hard to accurately measure an illegal activity like poaching.

This research, led by Adrian Treves of the University of Wisconsin-Madison and published in the Proceedings of the Royal Society journal, “challenges prevailing viewpoints and is bound to be controversial,” he said.

The researchers examined about a dozen different years of wolf counts in Michigan and Wisconsin. They compared periods when wolves were on the endangered species list to those when they were off and government-sanctioned culling was allowed.

Overall, wolf populations were about one-third lower than they should have been each time government culling programs were in place. After excluding other possibilities, such as deaths tied to overpopulation or migration to other states, the researchers concluded that the most likely explanation for the lower numbers was poaching.

“Culling has this invisible effect,” said Treves, a wolf biologist. “The government seemed to be sending a signal, unintentional, that poaching was OK.”

Their data analysis, conducted by Guillaume Chapron at the Swedish University of Agricultural Sciences, relies on mathematical modeling, not actual wolf counts. Fisher said they used the most sophisticated techniques possible, but other scientists cited that as a weakness.

“It’s an inference,” said Dave Mech, a Minnesota-based wolf researcher with the U.S. Geological Survey. “It’s only as strong as that.”

Other surveys of public attitudes indicate that culling programs can increase tolerance for wolves, he said.

“We have evidence on both sides of the equation,” Mech said. “But in both cases it’s soft evidence.”