These Non-Lethal Methods Encouraged by Science Can Keep Wolves From Killing Livestock

Science
جمعه 21 آذر 1399 ساعت 14:41
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Smith sonian mag
Nestled amid butterscotch-scented Ponderosa pines in Idaho’s backcountry one sunny, summer day in 1991, Suzanne Stone scooped her hands around her chin and let out an “Ahwooooo.” Stone, now an expert in wolf restoration heading the International Wildlife Coexistence Network, was then an intern at the United States Fish and Wildlife Service (USFWS). After she sent two boisterous wolf howls rippling through nearby meadows, she listened curiously for a reply. Instead, a bullet from a distant rifle whistled just above her and her supervisor’s heads. Steve Fritts, a leading wolf scientist at USFWS, hurried Stone back to their car before reporting what happened. Hunting was legal in the area, but firing at federal employees—even unknowingly—was not. Federal investigators later traced the shot to a hunting outfitter hundreds of yards away.
“I knew then what wolves were facing in the backcountry,” she says. For nearly three decades, wolf populations in Idaho have been on the rise, pitting local communities and powerful interest groups against each other, a situation that plays out in many areas across the country where wolves exist. Hunters contend that wolves have fully recovered and now deplete elk and deer populations while some ranchers argue wolves need to be killed to keep livestock alive. Conservationists, on the other hand, say that the apex predators contribute vitally to a healthy ecosystem and are still functionally extinct in about 85 percent of their historic range.
In October, the Trump administration delisted gray wolves from the endangered species list, a move celebrated by the National Cattlemen’s Beef Association and Safari Club International, a hunter advocacy group, in a joint statement . The conservationist group Defenders of Wildlife, meanwhile, issued a statement of their own calling the delisting “premature and reckless.” They have joined other conservation groups to file a formal intent to sue the USFWS soon after the law takes effect in January.
With gray wolves set to lose their federal protection when delisting takes effect in January, individual states have resorted to patching together their own terms for management, making it easier for people to hunt them in some states. But hunting will likely stunt wolf recovery and destabilize ecosystems already hobbled by their scarcity. Wolves regulate coyote populations, preventing the latter group from hunting pronghorn sheep; wolves pick off weak, rather than healthy, prey, leading to stronger deer and elk herds; and they keep wild herbivores from overgrazing, rippling benefits down to the soil. For these reasons, biologists have been trying to convince ranchers and policymakers that nonlethal methods, both old and new, should be used to reduce livestock conflicts and keep wolf populations stable or growing.
Wolves were nearly wiped out from the lower 48 by 1960, but numbers rebounded after Congress passed the Endangered Species Act in 1973 and scientists reintroduced the predators to Yellowstone National Park and Idaho in 1995. Hunting ramped up between 2008 and 2012 when the USFWS delisted gray wolves in Idaho, Montana, and Wyoming, in part to protect livestock from attack. But that tactic may have been counterproductive. Research from the Carnivore Coexistence Lab at the University of Wisconsin Madison has shown that killing gray wolves actually leads to three times more livestock attacks , a finding supported by behavioral studies elsewhere. “The wolf pack is a family,” says Adrian Treves, who runs the lab. They cooperate to defend territory and raise pups. When one is killed, the destabilizing effect ripples through the pack. Reproductive age goes down, and naive juvenile attacks on livestock go up, according to Colleen St. Clair, a biologist at the University of Alberta.
Ranchers’ fears also run deeper than just slain cows. Even if livestock don’t die, wolves may chase or stress cattle enough that many lose weight, get trampled or injured. “I have major concerns about [wolves],” says Megan Brown, a cattle rancher in northern California who has encountered bears and wolves on her property. “I’ve noticed this happening slightly more now that the wolves are back.” (In 2011, California confirmed its first wild wolf sighting in 87 years.)
One newly proven tactic to discourage wolf-cattle conflicts is to keep an abundant population of the predators’ natural prey. Wolves prefer eating native wild animals , and depleted deer or elk populations nudge them toward abundant sheep and cattle. “Predators are always facing this cost benefit ratio,” St. Clair says. “When they choose to try to prey on livestock, it's because they are in a situation where that's their best option.” She suggests planting deer or elk carcasses in wolf habitats or imposing stricter hunting limits that could increase prey populations. Since doing so could also grow predator numbers, both approaches are contentious.
A tried-and-true change some ranchers have made is to keep their herds disease-free and haul dead livestock far from the rest. Wolves are exceptionally sensitive to weakened prey. “It's like ringing the dinner bell and saying, ‘Come on in there's a feast here’,” says Stone. Once the scent of a carcass lures them near a herd, healthy livestock become more vulnerable. Moving bone piles and carcasses far from the herd “may be the single best action” to prevent wolf predation on livestock from happening in the first place, according to the Oregon Department of Fish and Wildlife . This approach, while effective, adds costs to ranching and requires some to manage land differently than they have for generations.
It’s also not going to be a cure-all; ranchers can’t bury or haul thousand-pound carcasses from some remote pastures in the dead of winter, and healthy herds need protection too. Since wolves have evolved to be shy around unfamiliar things, a common strategy is to scare them away with devices called nonlethal deterrents. A centuries’ old example comes from Polish hunting practices: fladry is a perimeter of tightly spaced colorful flags. The configuration is not a physical barrier, but the narrow spacing between flags still throws wolves off. Hunters previously used fladry to funnel wolves into an ambush area, but scientists now champion the tool to spare them. In one instance , a biologist used fladry around a carcass visited by wolves. A hungry carnivore leapt over a nearby barbed wire fence “like it wasn’t even there,” but didn’t cross the fladry.
Since wolf reintroduction in 1995, scientists have gathered much evidence showing that random blasts of colorful light, noise or motion can also protect livestock enclosures by keeping wolves on edge. Stone recalls one wolf getting blasted with Van Halen. “It was one of our Wildlife Services guys’ favorite albums, and it was very hard rock,” she says. The frightened wolf fled further than any other in her experience. Ranchers also scare away wolves using strobe lights and starter pistols . Stone, who has used countless deterrents in her 30 years of experience, even reported success with inflatable tubemen—those giant grinning effigies that dance unpredictably, often around used car lots. She assembled a pair on an Oregon hobby farm in 2018 where wolves had eaten llamas, and wolves have still not returned, she says.
Nonlethal deterrent devices have limitations, though. Some require electricity and all only protect enclosed areas—two deal-breakers for herds grazing open pastures. Even in ideal scenarios, wolves eventually tease out empty threats. “Animals are incredibly smart,” says St. Clair. “Their lives depend on figuring out which of these dangers are real dangers.” Targeting multiple senses with a rotating library of deterrents staves off their pattern recognition, but habituation remains a major consideration.
St. Clair is currently researching how tricking wolves into thinking livestock is disgusting food, can condition, rather than scare them. Her approach includes developing microcapsules with nauseating chemicals that she plants in carcasses as bait for curious carnivores. Making an animal vomit triggers an association with what they just ate, ironing a crease into a primitive subsection deep in the brain. So if a wolf eats a carcass laced with this flavorless capsule, it would start to steer clear of dead steer. This “conditioned disgust” aversion showed promising results in a 2009 study on captive wolves, but the method hasn’t been tested widely in wild wolves.
Recognizing animal cognition inevitably leads to appreciating individual differences between wolves. “We know that individuals vary in their ingenuity—their determination to get through our defenses, their tendency to repeat and cause multiple problems,” Treves says.
The environmental nonprofit Resolve and AI company CVEDIA recently announced WildEyes , a field camera that reportedly recognizes different individuals. “It's a perfect example of how technology is catching up with the new paradigm of coexistence-type work,” says Stone. WildEyes can automatically alert ranchers of worrisome individuals in the area, or set off deterrents to scare the wolves away. The new technology has been tested on Tibetan wolves, but has not been used in the United States.
According to Stone, one rancher in Montana is testing a tool that monitors livestock heart rates to detect distress—a sort of Fitbit for ungulates. When the device senses stressed livestock, it alerts the rancher that a predator may be close. And other ranchers are also supercharging classic deterrents. Turbofladry combines fladry with electric fences, and works well for smaller enclosed herds.
While some ranchers try new methods, others have stuck with a couple of old standbys that scientists still encourage. Range riders , people paid to travel alongside free-grazing herds on horseback or ATV, can cover more area than electric fences usually surround. In addition to just supervising cattle, range riders encourage wolf-resistant behaviors: grazing as a dense cluster, keeping newborns with moms and moving injured cattle to safety. And guardian dogs, such as Great Pyrenees, can also travel with livestock beyond fence lines. A 2010 study from Central Michigan University proved their ability to dramatic reduce wolf activity , protecting sheep, goats and cattle. At several cattle farms randomly assigned guardian dogs, wolf visits dropped from about once per month to zero visits in three years. Brown says, however, that ranchers with many acres need many dogs—each costing thousands to feed and maintain.
“Every part of this is about having the right tool and using it the right way,” says Stone, pointing out that some ranches require multiple tactics at once. In 2017, Stone published findings from a seven-year case study comparing sheep killings in a lethally controlled area to one protected by range riders, turbofladry, guardian dogs and other nonlethal deterrents. The nonlethal controls led to 3.5 times fewer dead sheep—just .02 percent of the total population.
Switching from lethal to nonlethal measures widely, however, is tough without more buy-in from government and ranchers. More than half of ranchers surveyed in one study wanted to learn more about nonlethal techniques, but funding to foster that desire is lagging. Some states, such as Oregon , do provide grants to help cover costs for nonlethal controls though. When Colorado welcomes wolves back after passing a reintroduction bill in November, Stone hopes policymakers will learn from that evidence, and encourage the suite of nonlethal solutions for protecting livestock and wolves, rather than the lethal measures which endanger both.
For now, the best approach to deter gray wolves’ from attacking livestock is to combine multiple nonlethal methods, and encourage biologists and ranchers to keep innovating. “People often want a silver bullet: they buy this technique, they install it, it works forever,” says St. Clair. “It'll never be like that. Animals will always be testing, especially animals as smart as wolves.”
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