Killing Wolves Actually Increases Livestock Deaths, Study Says

A gray wolf. Eric Gaillard / REUTERS

If you want to protect your herd, don't shoot wolves, a study suggests.

While gray wolves are listed as a threatened species under the Endangered Species Act (and are, therefore, protected in some areas), several states—including Montana, Idaho and Washington—have set up wolf-hunting seasons because their populations have rebounded significantly in these areas.

Wolf killing angers many because, among other reasons, the animals are intelligent and form strong family-like bonds in packs, besides being the wild predecessors of dogs (and just imagine trying to defend the slaughter of this beloved pet).

One could rationally understand the primary argument for hunting them, though: that it helps reduce predation upon rancher's cattle or sheep.

But a surprising new study suggests that killing wolves actually leads to more, not less, predation upon these domestic animals. In the paper, published in the journal PLOS ONE, the researchers found that for every wolf shot, the number of cattle killed the following year increased by 5 to 6 percent, and the number of predated sheep increased 4 percent.

The scientists, from Washington State University, came up with these numbers by looking at records of wolf hunts and livestock/sheep kills over a 25-year period.

What's the reason for this counterintuitive finding? The scientists don't know for sure, but hypothesize that it may be because killing wolves destabilizes packs and leads to the formation of more breeding pairs. These new couples, in turn, spread out and mate, perhaps moving into locations abutting ranches.

During the time that their wolf pups are nursing, the wolves are anchored to their denning spot. This leads the carnivores to hunt more animals in the immediate vicinity, perhaps including domesticated sheep and cattle, instead of their preferred prey of elks and other wild animals, according to the study.