Article: No proof that shooting predators saves livestock
Science - September 7, 2016
On 5 August, biologists from the Washington Department of Fish and Wildlife ascended in a helicopter to shoot two members of the Profanity Peak wolf pack, which had been preying on cattle in the state’s northeast corner. After the cull failed to end predation, the state removed four more members of the 11-wolf pack. Some conservationists were outraged, but the logic behind such lethal control seems airtight: Remove livestock-killing wolves, coyotes, bears, and other predators, and you’ll protect farmers and ranchers from future losses.
A new study, however, claims that much of the research underpinning that common sense notion is flawed—and that the science of predator control needs a methodological overhaul. Adrian Treves, a conservation biologist at the University of Wisconsin, Madison, and his colleagues examined more than 100 peer-reviewed studies, searching for ones that randomized some by removing or deterring predators while leaving others untouched. Not a single experiment in which predators were killed has ever successfully applied this randomized controlled design, they reported 1 September in Frontiers in Ecology and the Environment. “Lethal control methods need to be subjected to the same gold standard of science as anything else,” Treves says. He argues that policymakers should suspend predator management programs that aren’t backed by rigorous evidence.
David Mech, a wolf expert at the University of Minnesota (UM), Twin Cities, isn’t persuaded. He notes that many of the studies Treves scrutinized “met some pretty good scientific standards, but just weren’t quite perfect. … Drawing the conclusion that therefore all these depredation management programs should stop until gold standard studies are done—that’s a very big leap.”
Lethal control has long been a staple of wildlife management. Eurasian lynx have been culled by hunters in Norway, wolves killed in Spain and Sweden, jackals and caracals eliminated in South Africa. In the United States, predator control often falls to the federal APHIS Wildlife Services, a branch of the U.S. Department of Agriculture. In 2015, the agency killed 385 gray wolves, 284 mountain lions, and more than 68,000 coyotes. Unlike the Profanity Peak wolf pack, which wasn’t targeted until it began killing livestock, coyote populations in many states are subject to preemptive thinning.
Treves says he was inspired to look at the science behind predator control by a book unrelated to wild carnivores: The Emperor of All Maladies: A Biography of Cancer, Siddhartha Mukherjee’s epic history of cancer. As Treves paged through it, he says, “a light bulb went off in my head.” He suspected that predator management was plagued by the same methodological problems that had once led cancer researchers to promote ineffective cures—particularly a dearth of randomized controlled trials. Although removing carnivores to ease livestock loss makes intuitive sense, Treves and other scientists were skeptical: For instance, some research suggests that coyote populations subject to culling have higher pup survival rates, and that male cougars expand their ranges in response to hunting.
What Treves found when he and his co-authors—Miha Krofel, a wildlife researcher at Slovenia’s University of Ljubljana, and Jeannine McManus, a researcher at the Landmark Foundation in Riversdale, South Africa—delved into the literature confirmed his suspicions. Only 12 studies came close to Treves’s gold standard or even a lesser “silver” standard, in which livestock losses before and after predator management were monitored, or analyzed in retrospect. Many other studies had flaws that he says make it impossible to draw reliable inferences. A 1999 experiment purporting to show the effectiveness of shooting coyotes from helicopters, for instance, had a higher density of sheep in its control pastures, which could have made them more attractive to hungry coyotes. Others failed to properly randomize intervention and control sites or described their methods inadequately, making replication impossible.
“There are so many ways that these studies could have been improved,” says Robert Crabtree, a carnivore ecologist and founder of the Yellowstone Ecological Research Center in Bozeman, Montana. “Not by spending more money, but by paying careful attention to standardization protocols, transparency, and replication.”
Some of the authors whose studies Treves critiques object to his analysis. Wildlife Services representative Gail Keirn said via email that Treves's calculation of sheep densities in the 1999 aerial gunning study was "based on incomplete information." Treves also discounted a 2008 study suggesting that trapping male wolves reduces livestock loss, for instance, in part because it excluded certain data points. But lead author Elizabeth Harper, then at UM, says that the paper thoroughly explains why each data point was excluded, and that the omissions kept misleading data from contaminating the results. Harper adds that she isn’t convinced Treves’s own study lives up to his standards: The authors assessed the validity of studies themselves, rather than asking independent experts. “That could create their own bias,” Harper says.
Others say that Treves is setting an impractically high bar. The complexity of field biology precludes most gold standard experiments, argues Adrian Wydeven, Timber Wolf Alliance coordinator at Northland College in Ashland, Wisconsin. Scientists face countless variables, including subtle differences in habitat, weather, and the unpredictable movements of animals themselves. “I just don’t see that it’s an attainable standard—it’s not like being in the lab,” Wydeven says. Such research also relies on the cooperation of farmers and ranchers, who may not be eager to take part in a randomized, controlled study. When wolves are at the door, who wants their flock to be one that doesn’t get help?
Treves counters that two of the studies he and his colleagues analyzed did meet the standard. Both evaluated nonlethal predator deterrence techniques: guard dogs and strings of flapping red flags that scare off wolves and coyotes. Performed by Tom Gehring, a biologist at Central Michigan University in Mount Pleasant, they showed that wolves and coyotes both steered clear of cattle farms patrolled by Great Pyrenees dogs, and that the flags deterred wolves, but not coyotes.
To prepare for the studies, done on Michigan’s Upper Peninsula, Gehring combed through data on the ranges of local wolf packs to identify vulnerable farms, then visited each operation to secure its commitment. He paired farms based on attributes like size and location and randomly assigned one to the treatment group and one to the control group. “It was an ordeal,” Gehring acknowledges. “It took months.”
In the end, he claims, the rigorous design was well worth the trouble. Before his experiments, he says, many ranchers and biologists were skeptical that guard dogs could protect stock against wolves. By the end, though, the ranchers who had been assigned to the control group were clamoring for dogs of their own. “You don’t hear anybody question that guard dogs work in Michigan anymore,” Gehring says.
This article was published by Science
Article: The Case for Mass Slaughter of Predators Just Got Weaker
By Jani Actman
National Geographic September 1, 2016
Wildlife officials in Washington State recently green-lit a controversial plan to kill a pack of wolves fingered as the culprits behind a spate of attacks on cows there. The way the state sees it, taking out the carnivores could help prevent more livestock losses.
The United States used this justification to kill thousands of coyotes, wolves, bears, and other predators last year. Other nations, including Canada and Finland, have also authorized predator hunts for this reason.
But these killings might not solve any problems after all. A new study published Thursday in the journal Frontiers in Ecology and the Environment found that there's little scientific evidence that killing predators actually accomplishes the goal of protecting livestock.
"We know anecdotes and perceptions don’t get us very far when we’re dealing with a problem like livestock predation," says Adrian Treves, a conservation biologist from the University of Wisconsin who co-authored the paper. "The science of predator control has been slow and not very advanced."
Hunting for Evidence
Treves and his colleagues reviewed previous research attempting to measure the effectiveness of various predator-control methods in North America and Europe. Some studies looked at whether killing predators meant fewer livestock deaths, while others examined the success of nonlethal deterrents, such as the use of guard dogs and flag-lined ropes or wires.
The scientists found that most of the research doesn’t hold up scientifically. Only two of the studies were deemed top notch because they took into consideration the possible effects of things like disease, weather and other elements that could influence livestock deaths. But neither study focused on the effectiveness of killing predators. Instead the papers concluded that certain nonlethal predator-control methods helped ward off future attacks on livestock.
As for the studies that did evaluate the effectiveness of lethal predator control, seven used shoddier science but were reliable enough to “draw an inference about,” Treves says.
But only two showed that the killings prevented livestock loss, while the majority found that killing predators either doesn’t help eliminate attacks on farm animals or actually makes things worse by increasing predation (meanwhile most of the papers falling into this category that examined nonlethal predator control methods found them successful).
For instance, one study, published in 2013 that focused on Washington State, concluded that hunting cougars only increased their attacks on livestock. That’s because research has shown that hunting older males—be they cougars, wolves, or black bears—tends to lead to more predation because those males keep out the youngsters, which are more aggressive.
"Lethal methods tend to be more risky for livestock and therefore for livestock owners than nonlethal methods," Treves says.
A Way Forward
Treves wants the findings to prompt governments and hunters to stop shooting, trapping, and using other methods to kill “problem” predators until better science becomes available. The way he sees it, this will aid ranchers as well as the public, whose tax dollars help fund the wildlife agencies making decisions about how to deal with predation. (Also see “This Government Program's Job Is to Kill Wildlife.”)
“People deserve to hear the options and understand the evidence, especially if our government claims to be science-based in our policies,” Treves says.
In the United States, employees with a government program called Wildlife Services kill thousands of predators a year as part of its mission to solve conflicts between humans and wildlife. Despite growing criticism in recent years, the program has always said the methods they use are legitimate.
“Wildlife Services’ policies and decisions are based on the best available science,” Pamela Boehland, a spokeswoman for the program, wrote in an email. “Not all wildlife damage problems can be resolved using nonlethal techniques alone. Even with the use of single or combined nonlethal methods, livestock losses to predators often continue.”
But according to Treves, the new study shows there’s not enough science to support the killing of these animals. “Any government action that destroys wildlife should be scrutinized to a higher level,” he says.
Doug Smith, a senior wildlife biologist with Yellowstone National Park, who wasn’t involved in the study, says that the new data fill a gap in the research into the effectiveness of predator-control methods. “It’s about time that lethal and nonlethal control had a critical evaluation,” he says.
Smith points out that a move away from killing predators would require a culture shift among ranchers, who often jump to lethal predator control because they think it offers a quick and easy fix with short-term results. “People are instant gratification creatures,” he explains. “A lot of ranchers are very comfortable with that model.”
Report: Killing Wolves and Coyotes May Not Protect Livestock
New Mexico Tribune - September 6, 2016
ALBUQUERQUE, N.M. – The practice of killing predators such as wolves, coyotes and bears to protect livestock has little scientific validity, according to a new study. The article, called Predator Control Should Not Be a Shot in the Dark just came out in a journal called Frontiers of Ecology and the Environment.
Researchers from the University of Wisconsin and two other schools evaluated two dozen prior studies to determine whether they followed the scientific method and found half the studies weren’t sufficiently rigorous.
Michael Robinson, conservation advocate with the center for Biological Diversity in Silver City, said the results of the remaining studies are somewhat counter-intuitive.
“There’s either no effect on protecting livestock because there’s other predators that can move in, and if livestock protection practices don’t change, that makes sense,” he explained. “Or it actually would increase the number of livestock that would be killed.”
The study found that when the leader of a predator group is killed, it sows chaos in the pack and multiple, less-experienced members may end up targeting the livestock. Robinson said this study undercuts the reasoning behind the actions of a federal program, Wildlife Services, and many state game agencies, that kill tens of thousands of coyotes, bears, bobcats, cougars, even the highly endangered Mexican gray wolf every year.
He added that there are now only 97 known Mexican gray wolves left in Arizona and New Mexico.
“The Fish and Wildlife Service, this year, still trapped and removed the alpha male, the papa of a litter of pups in the Luna pack in New Mexico because of conflicts with livestock,” he said.
Robinson is calling on Wildlife Services to stop using aerial snipers, poisons and steel leg-hold traps to eliminate members of predator species.
A preview of the study can be found here.