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Wolf hunting has prevented livestock loss in a measurable way, but it is by no means a silver bullet, according to an international research team led by the University of Michigan.

"Hunting, on the whole, is not removing negative impacts associated with wolves. It does have some effect on rates of livestock loss, but the effect is not particularly consistent, widespread or strong," said Neil Carter, associate professor at the U-M School for Environment and Sustainability and senior author of the new study in the journal Science Advances.

As governmental protections have helped rebuild once-dwindling wolf populations, it's become increasingly likely that the predators encounter domesticated animals to prey on. Hunting is often presented as a remedy, but it's a contentious and polarizing proposal. Advocates on both sides of the issue have active lawsuits across the U.S. aiming to relax or redouble regulations.

But several northwestern states already allow hunting in some capacity, which has given researchers an opportunity to bring new information to the issue. The new study showed that, on average, each wolf that was killed by a hunter was associated with a 2% reduction in predation.

The team also analyzed how hunting affected "lethal removals." These are expensive operations led by government agencies, targeting specific wolves, typically after multiple or severe predation events, said lead author Leandra Merz, assistant professor at San Diego State University.

Based on the team's study, hunting led to no reduction in lethal removals.

"We're not necessarily saying that we shouldn't be hunting and I want to be clear about that, because there are other motivations for hunting," said Merz, who worked on the project as a postdoctoral scholar at U-M's School for Environment and Sustainability.

"But if the goal is to reduce livestock predation and we're using hunting for that, it's not as effective as we would like."

The research team also included collaborators from the University of Idaho, Washington State University, Ohio State University and the GESIS Leibniz Institute for the Social Sciences in Germany. The researchers said this is an important part of a small but growing body of research that brings relevant information to a charged debate about wolf management strategies.

"A lot of uncertainty exists about the utility of public wolf hunting in reducing negative impacts from these animals as their populations recover," Carter said.

"In an issue that's divisive and contentious, that uncertainty is something that we should try to minimize, because we could be making decisions that are just not as efficacious as they should be nor in the public's best interest."

And out come the wolves

The Endangered Species Act, or ESA, has protected gray wolves across the contiguous U.S. for decades and, in the 1990s, the U.S. launched a successful wolf reintroduction campaign in the Northern Rocky Mountains. Within about 20 years, the Northern Rocky wolf population grew to where some states rolled out legalized hunting programs.

Since then, wolf hunting has been characterized by starts and stops driven by litigation brought by parties on both sides. In fact, in 2020, the U.S. Fish and Wildlife Service determined that gray wolf populations had recovered significantly enough to remove federal protections under the ESA before a court order reversed that decision in 2022. And the debate is far from over.

"There are timely things happening related to wolf management, both domestically and internationally," Carter said, pointing to Michigan and Europe as regions where the issue is especially being pressed.

"Stakeholders involved in wolf management are bringing up the topic of hunting wolves and it's an imminent conversation we'll be having."

Yet the actual impact of wolf hunting on protecting livestock was unknown, meaning there have been a lot of assumptions involved in the discourse, Carter said.

So he, Merz and their colleagues saw an opportunity to shed light on that using information from areas where wolf hunting was legal—Idaho and Montana—and from areas where wolf hunting was not legal, specifically Oregon and Washington.

The research analyzed data available for those areas from 2005 and 2021 using an array of mathematical models to connect hunting to its influence on depredation and lethal removal events. No hunting was permitted prior to 2009, helping researchers establish a control scenario.

Again, hunting showed no impact on the number of lethal removal operations, but predation was more nuanced. The average county in the analysis lost roughly three to four livestock animals per year to wolves. With the 2% reduction mentioned earlier, that translates to about 0.07 animals protected per wolf hunted, Carter said.

But the team also emphasized there can be huge variations from that average. For instance, Merz knows of an Idaho rancher that lost 65 sheep in one night to wolves. And a loss need not be that severe to have devastating economic consequences and steep psychological tolls.

"The cost can be really high to an individual rancher, even over very short time periods," Merz said. "We don't want to minimize that."

From a policy perspective, though, it's helpful to ask what are the best management methods to spread that cost effectively and equitably, Merz said. Hunting, as the study shows, relieves a minimal burden from ranchers, but at no direct cost to them.

Then there are nonlethal methods that are proving to be effective, Merz said, including fladry, a combination of flags and barriers that can be electrified. Even increasing the presence of humans or human activities helps (drones blasting AC/DC and arguments from the movie "Marriage Story" recently made news). But the cost of implementing and maintaining these measures almost exclusively falls on ranchers.

"There's not going to be an easy solution either way. If there were, we would have figured it out by now and we'd be using it," Merz said.

"But the upside is that people are really creative. We just need to be a little bit more creative in how we redistribute some of the costs and benefits. I think outside of managing wildlife, we do that a lot in society."