Wolf kills increase livestock deaths, WSU study says
Thu., Dec. 4, 2014
Rob Wielgus noticed something interesting when he studied reports of wolf attacks on sheep and cattle in the Northern Rockies.
Killing wolves to reduce livestock predation actually led to more dead sheep and cows the following year. The trend held true until more than 25 percent of a state’s wolf population was removed.
“It’s counterintuitive,” Wielgus, director of Washington State University’s Large Carnivore Conservation Lab, said of the study’s results. “People think, let’s kill the wolves and get rid of the problem. But it doesn’t work that way with carnivores. Sometimes, the punitive solution is causing the problem.”
Wielgus tied the increased livestock deaths to disruptions in the pack’s social structure.
“If you kill the alpha male and female, the pack fractures,” he said. “Instead of one breeding pair, you may have two or three.”
That results in more pups the next spring, increasing the potential for livestock attacks, Wielgus said.
His research, published Wednesday in the journal PLOS ONE, questions the accepted practice of killing wolves that prey on livestock. It analyzed 25 years of data from Idaho, Montana and Wyoming.
More dead wolves correlated with higher numbers of dead livestock, Wielgus and data analyst Kaylie Peebles found. The correlation lasted until the numbers of wolves killed exceeded the species’ reproductive growth rate of about 25 percent per year. Then, overall wolf populations fell and the number of livestock attacks dropped the following year.
But Wielgus said killing more than 25 percent of the wolf population isn’t a solution in Washington, which is trying to recover wolves.
His research was partly funded by the Washington Department of Fish and Wildlife. The work is the first phase of an $80,000, two-year research project paid for by WSU and the agency. The study’s second phase will focus on preventing wolf attacks on livestock.
Publication of the study follows a tense summer between ranchers and wolves in northeast Washington.
In a highly publicized incident, the breeding female from the Huckleberry pack was killed by a wildlife agent after the pack killed or injured 33 sheep in Stevens County.
In 2012, the Department of Fish and Wildlife killed seven members of the Wedge pack after the wolves repeatedly attacked cattle owned by another Stevens County rancher.
The northeast corner of the state is home to 12 of Washington’s 15 wolf packs and also has an active livestock industry.
John Pierce, the department’s chief wildlife scientist, said the research hasn’t caused the agency to rethink its actions.
“If his findings are true – and I think of them more as hypotheses – our typical understanding of how animals react to lethal control is not intuitive for wolves,” he said. “By removing the resident animals, you might exacerbate the situation” in the long term.
But that doesn’t reduce the short-term value of killing wolves to halt ongoing livestock attacks, Pierce said.
Both of Washington’s lethal control actions were limited in scope, designed to address continued attacks by specific packs, he said.
“I think it’s too early in wolf recovery to say that killing wolves backfires,” Jack Field, executive vice president of the 1,350-member Washington Cattlemen’s Association, said in response to the study. Among ranchers, prompt removal of problem wolves helps build acceptance for wolf recovery in the state, Field said.
Mitch Friedman is the executive director of Conservation Northwest, which helps pay for range riders and other nonlethal deterrents to protect livestock from wolves. The research “should cause us to double down on conflict avoidance,” Friedman said. “Wolves are complicated; nature is complicated. With each thing we learn, we recognize mistakes that we’ve made.”
Department officials are eager to see the second phase of Wielgus’ research, Pierce said. That work includes mapping northeast Washington to determine where wolf-livestock conflicts are likely to occur, based on pack size, livestock location and the abundance of deer and elk.
“We’re hoping to get into a proactive mode,” Pierce said. “We’re interested in identifying which nonlethal measures are most effective for preventing future conflicts.”
Wielgus is working on parallel research paid for by the state Legislature, where both wolves and livestock are being collared to study the animals’ interactions on grazing lands in northeast Washington, the Cascades and the Colville Reservation. For those herds, the use of range riders, noise-makers and flashing lights at night was successful in preventing wolf attacks over the summer, he said.
Meanwhile, Wielgus said the results from the research’s first phase show similarities to past studies on grizzlies and cougars. When large, older males were killed, younger males moved in. The young males were more likely to hang around ranches and kill livestock, he said.
But whether the wolf research will influence policy remains to be seen, Wielgus said.
“Often, policy is not based on facts,” he said. “People want predators to be killed, so that will happen, even if it generates more trouble in the future.”
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