Depending on the wolf pack’s structure, killing a wolf one year can increase livestock conflicts the next, a Washington State University researcher says.
But ranchers and wildlife managers question the study’s findings, saying that killing wolves needs to be one of the tools they need to stop attacks on livestock.
Robert Wielgus, associate professor and director of WSU’s Large Carnivore Conservation Laboratory, recently published his findings in the international online journal PLOS ONE.
“For each wolf you kill, the livestock depredations appear to go up 5 percent the next year,” Wielgus said. He examined 25 years of wolf-livestock interaction data from Montana and 17 years of data from Idaho and Wyoming.
For wolves, breeding pairs are responsible for most livestock attacks. Breeding pairs stay near their dens and don’t follow natural prey. When natural prey move out of the pair’s area, the wolves may turn to eating livestock, he says.
He found that killing wolves leads to a 5 percent increase in breeding pairs, he said. A breeding pair, — the dominant male and female in a pack — suppress reproduction in the other wolves in the pack. If they’re killed, the pack’s structure fractures and some of the remaining wolves become breeding pairs, which can be more inclined to attack livestock if natural prey is not available.
The number of livestock depredations increases until 25 percent of the wolves in the pack have been killed, Wielgus said. The number of breeding pairs also declines after 25 percent of the wolves in a pack have been killed.
Wielgus recommends nonlethal means of preventing depredation such as fladry, moving the wolves and Foxlights. Fladry are small flags or ribbons attached to fences. Foxlights have a series of lights that give the impression of movement at night, keeping predators away from livestock.
He’s studied seven wolf packs’ interactions with 14 livestock herds. Few or no livestock depredations occurred when fladry, shepherds and range riders were used during one year, he said.
“My sample sizes are low, but so far so good,” he said. “Ranchers who are working with me using preventative and remedial measures have suffered zero or very little livestock losses, and ranchers who have refused to cooperate with me, some of them have experienced very severe livestock losses.”
State wildlife managers and ranchers say killing problem wolves quickly eliminates the depredation problem, but Wielgus said he hasn’t seen a peer-reviewed, published paper to that effect.
Jack Field, executive vice president of the Washington Cattlemen’s Association, doesn’t see any value for ranchers in Wielgus’ report. He believes it’s too early to draw any conclusions, and called for more wolf-collar data on packs that roam the state.
“Lethal control is an absolute necessity in wolf recovery,” Field said. “There’s great value in nonlethal deterrents, but we can’t fool ourselves to think you can use nonlethal deterrents and never have conflict.”
Field said ranchers believe the state’s current cougar management strategy, based on Wielgus’ previous study, is not working.
Wielgus previously reported a similar social disruption in cougar populations, in which older cougars that were killed were replaced by younger cougars that were more likely to attack livestock.
“I don’t know of any livestock producer out there who’s going to embrace the concept of considering the idea of killing fewer wolves and that allowing wolves to depredate on livestock is anything tolerable,” he said.
John Pierce, chief wildlife scientist for the Washington Department of Fish and Wildlife, said Wielgus’ study is not definitive, because it’s a “retrospective look at a hodgepodge” of information. It’s not surprising that the social structure of large carnivores is an important part of how they interact with their environment, he said.
It’s premature to expect Wielgus’ study to influence the state’s wolf recovery efforts, Pierce said. Wielgus’ results might be more relevant when wolves have recovered and are more established on the landscape, he said.
“We don’t do a lot of lethal removal. We’re very strategic in the lethal removal that we do,” he said, calling it an effective tool and a stopgap relief for ranchers whose repeatedly lose livestock to wolves.
“We would have lethal removal in our tool box, and use it judiciously when we needed to,” Pierce said.
WDFW is most interested in the effectiveness of nonlethal measures, he said.
Wielgus advises ranchers to report conflicts quickly and use preventive measures, if they can.
“If preventative doesn’t work and remedial doesn’t work, you’re left with lethal measures,” he said. “All we’re saying is, instead of jumping to lethal right off the bat, maybe we should look at nonlethal, because down the road, lethal measures give you this increased predation. I see no reason why the nonlethal (measures) would do the same thing.”