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