Long ago, Polish peasants tied old rags onto ropes, creating corrals that funneled wolves into areas where they could be killed easily.

Wary of the unfamiliar objects, the wolves refused to duck under the flapping rags – even with hunters in pursuit.

In recent years, the idea has been reinvented as a way to keep wolves away from livestock. Researchers use fladry – cord with plastic flags attached – to create a barrier. It’s the same stuff that used-car dealers drape around their lots, said Stewart Breck, a research biologist for Wildlife Services.

Researchers aren’t entirely sure why wolves avoid the plastic flags, but they think that encountering an unnatural object raises the pack’s guard.

“Wolves are neophobic,” Breck said. “They’re scared of new things.”

In an experiment near Salmon, Idaho, fladry was used to protect cattle from a wolf pack. Fladry was also used successfully at a hatchery, where wolves had been conducting nightly raids on a pond stocked with salmon smolts.

Eventually, wolves do test the fladry by biting it, usually after about 60 days. To make the fladry more effective, electric fencing is sometimes added.

The idea for the electric enhancement came from Carol Williams, the wife of a retired Wildlife Services agent in Idaho. She was watching remote camera images of wolves in Canada biting fladry, and suggested that a shock would provide negative reinforcement.

Williams now sells electrified fladry to customers in the United States, Canada and Europe. She’s starting to experiment with lights on the fencing as an added deterrent.

–Becky Kramer