By Sarah Jane Keller
A new study raises questions about how to handle livestock conflicts.
In two decades of studying large carnivores, nature has never failed to surprise Rob Wielgus. For example, he and his student found in 2013 that cougar hunting does not reduce complaints about people running into cougars, or livestock attacks. Harvesting cougars actually increased complaints the following year. That research led to changes in how Washington manages the big cats; last year the state stopped using heavy cougar hunting to reduce conflicts.
Wielgus recently released his newest study with equally surprising results. “I analyzed it like 50 times, with different statisticians and layers and layers of peer review because the results are kind of astounding,” he said.
The new paper challenges assumptions about how state wildlife agencies deal with problem wolves. It turns out that killing wolves that kill livestock may backfire in the long term. According to the study, lethal removal may actually increase the odds that wolves eat more cattle or sheep the following year.
Overall, wolves are doing fine in the Northern Rockies, compared to their brush with extinction in the 1970s. Their population has dipped slightly since its peak in 2011 to roughly 1,700 wolves, but biologists say it’s secure.
People have long assumed that fewer wolves lead to fewer depredations on sheep or cattle. And wildlife managers often say that lethal removal can be a salve for vitriol toward wolves, by providing a short-term solution for the harmed livestock producers, and by showing that states are actively managing the animals.
It’s part of the reason some states allow wolf hunting, and why Washington, Montana, Idaho and Wyoming all lethally remove wolves that harm livestock. In 2013 the later three states killed 202 wolves for control purposes, or 8 percent of the population in all four states.
But when Wielgus and his coauthor looked at 25 years of data on lethal wolf control and livestock depredations from Idaho, Wyoming, and Montana, they found that killing one wolf increases the odds of sheep depredation by 4 percent the following year. For cattle, it increased the odds by 5 to 6 percent.
This pattern holds until 25 percent of the wolf population is removed. That’s because wolf populations in the states studied grow at a 25 percent rate. So once the lethal removals exceed the population’s growth rate, wolves begin to decline, and so do depredations. But that’s not a sustainable solution for the wolves, or for people who don’t want to see them on the endangered species list.
More study needed
It’s important to note that this study has found a correlation between wolf removal and livestock depredation over a large region, but it hasn’t established the exact reason for the patterns. To learn more about why lethal removal of wolves doesn’t appear to protect livestock, Wielgus now needs to drill down to individual packs.
Wielgus suspects the answer may be found in wolf social dynamics. The animals may compensate for losing part of their pack by increasing reproduction and thus, the need to hunt for those new pups. Or wolves may become less efficient hunters in smaller groups and turn to dining on livestock.
“I think the take-home point is that social behavior and social systems of these large carnivores, pack dynamics, territory, all of that is a very important element to how wolves interact with their environment,” said John Pierce, chief wildlife scientist for the Washington Department of Fish and Wildlife. “As we move forward in wolf management we should carefully be studying that and don’t assume a linear relationship [between wolf removal and depredation].”
Pierce thinks the study is too preliminary to change wolf management in the near future. But his agency is funding Wielgus to research proactive, non-lethal wolf management such as having cowboys called range riders monitoring for trouble, and using special fencing, or lights and sounds, to deter wolves. Wielgus is comparing the effectiveness of those techniques to lethal methods, and also mapping where livestock are at the greatest risk of wolf attack.
That work is still in its early stages, but Washington is starting to see good results with proactive non-lethal methods, says Pierce. Ideally, learning more about those techniques will help prevent events like what unfolded in northeastern Washington in August. The Huckleberry Pack became habituated to feeding on sheep, and after non-lethal wolf deterrents failed, a sharpshooter took out the alpha female (not the wolf they were hoping to eliminate) at the request of Washington’s wildlife department.
Wielgus hopes that his studies will help wildlife managers reevaluate practices that may be based on long-standing assumptions. “Science progresses,” he said, “and eventually we’ll get it right.”
Sarah Jane Keller is a correspondent for High Country News. She writes from Bozeman, Montana.