Study: Noise Machine Keeps Predators Off Property

John Pickrell
for National Geographic News

January 13, 2004

Conservation scientists may have hit upon the 21st century's answer to
the good old-fashioned scarecrow. A motion-activated device which blasts
out a cacophonous chorus of gunshots, helicopters, and other sounds,
together with blinding flashes of strobe lighting, may be a highly
effective tool in repelling wolves, bears, and other large carnivores.

The fright device could be a valuable new tool in fighting the escalating problem of human-carnivore conflict, suggest conservationists behind a new study confirming its effectiveness. Currently when coyotes, mountain lions, and other predators threaten livestock, U.S. federal wildlife managers are forced to kill them.

"To promote the existence and expansion of large carnivores, conservation biologists should assist with the real world problems predators cause," wrote the conservationists in the current issue of the science journal Conservation Biology.

New Tool

Shooting predators is an often used—and not always effective—solution to stopping the predation of livestock and pets in rural regions of the United States, but this practice damages efforts to restore rare carnivore populations.

"We're hoping to give communities, landowners, and wildlife managers another tool in their kit other than traditional lethal control," said study co-author Adrian Treves at the Wildlife Conservation Society in New York City.

Established non-lethal deterrents include electric fences, trenches, and walls, and guarding sheep and cattle with dogs and people. Few landowners supervise their flocks as shepherds once did, but now many farmers in the western U.S. have completely dispensed with barriers. "The elimination of many large predators made it possible to reduce reliance on these methods," said Treves.

However, as wolf conservation efforts and others pay off in terms of rising numbers of reintroduced animals, farmers may need to consider protecting their livestock again, and no longer rely on removal of predators.

With this in mind, study author John Shivik of the Wildlife Services' National Wildlife Research Center in Fort Collins, Colorado has developed the infra-red activated device for deterring predation of livestock.

Other devices, which randomly activate lights and sirens, have been effective as deterrents, but carnivores (especially bears) may quickly learn they pose no real threat. Shivik's fright device not only activates as an animal approaches, but also produces a random selection of 30 people-related sounds, including gunshots, yelling, vehicles, glass breaking, helicopters, and dogs barking. Because the device is only set off when animals approach human property boundaries, they become used to it more slowly.

Acid Test

To test the effectiveness of the device at dissuading predators from feeding, Treves, Shivik and colleagues set up three study plots in each of six Wisconsin wolf (Canis lupus) pack territories. They placed road-killed deer carcasses in roped-off plots that were either unguarded, rigged with yellow flagging, or linked up to a motion-activated fright device.

Though scientists cannot yet explain it, evenly spaced flags appear to deter wolves (an old Polish hunting technique, known as fladry, makes use of the behavior to encircle and trap the animals).

Images from night-vision video cameras identified bears, foxes (Vulpes vulpes), turkey vultures (Cathartes aura), wolves, bald eagles (Haliaeetus leucocephalus), and others at the plots. The researchers found that consumption of meat on fright-device guarded plots was 68 percent less than at unguarded plots. There was no significant difference in meat consumption between flagged plots and those unguarded, though the majority of meat in these cases may have been consumed by black bears (Ursus americanus), which were not expected to avoid the flagging, said Treves.

Further tests on captive wolves in Minnesota also indicated that the fright device was effective at preventing feeding on meat in experimental plots.

A commercial version—the Model 9,000 Frightening Device, manufactured on a small scale by Avian Systems in Louisville Kentucky—is currently available, but it is activated instead through radio collars attached to wolves by local wildlife managers.

The U.S. Fish and Wildlife Service and wildlife services departments are already using some in the northwest, according to conservationist Shivik, who is now based at Utah State University in Logan.

Treves suggests that the device would, alongside other guarding methods, be most useful for protecting small plots of land due to the limited range of motion detectors (only a few yards). Protecting the nation's many commercial beekeeping operations and private homes from bears might be one useful application, said Treves. Protecting endangered species, such as rare ferrets (Mustela nigripes) from birds of prey is another, wrote the researchers. However, the prohibitive cost of the device, at several thousand dollars or more, means its use will be limited to wealthy countries such as the U.S.

Predators Lend a Helping Hand

"We're always looking for more tools … and would certainly be interested and willing to try these devices," commented Adrian Wydeven, head of the wolf recovery team at the Wisconsin Department of Natural Resources in Park Falls. "We've had some situations where wolves have become bold and attacked pets … [these devices] might be used to alter their behavior so they become fearful of people once again," he suggested, though trapping and euthanasing would still be required in many cases.

Though the fright device has not yet been tested on mountain lions (Puma concolor), it could have applications for this species too, said Christopher Papuochis, conservation biologist with the Mountain Lion Foundation in Sacramento, California.

"If you can teach a predator that certain areas are off-limits, they can assist you in keeping others out," he said. When bears or mountain lions are killed, others come to take their territory, perpetuating the problem. Papouchis pointed to one example were a landowner had acquired permits to kill 18 mountain lions over a 30-year period, but the problem wasn't solved until non-lethal methods including guard dogs were employed. Even taking simple actions such as leaving a radio or lights on overnight can have some effect, he said.

"In the U.S. for a long time the de facto solution to dealing with carnivores was to kill them," said Papouchis. "As humans continue to spread [and some carnivore populations rebound], it's all the more important we develop non-lethal techniques for dealing with the problem."