From Science journal in the USA:
Killing wolves to save livestock may backfire
By Virginia Morell
3 December 2014 2:00 pm
When gray wolves from Washington state’s Huckleberry pack killed more than 30 sheep this summer, state wildlife officials responded by shooting four wolves, including the pack’s alpha female. Many people think that such “remedial control,” as this predator management method is called, solves the problem.
But a new study examining 25 years of wolf predations on cattle and sheep in three states (Idaho, Wyoming, and Montana) and wildlife agencies’ subsequent retaliatory measures shows that the technique actually backfires. It leads to more dead sheep and cattle the following year, not fewer, the scientists report today in PLOS ONE.
Indeed, the study reveals that in wolf-occupied areas, killing one of the wild canids increases the odds that the predators will attack sheep the following year by 4% and cattle by 5% to 6%. Shooting (including sport hunting) and trapping wolves is counterproductive, because the killing disrupts their societies, the scientists say.
The researchers previously showed that lethal control of cougars also fails because it causes social turmoil for the cats. Wolf packs that lose their breeding pair—or even one member of the pair—break apart. The younger, sexually mature wolves then form their own packs, increasing the number of breeding pairs, the scientists say.
Often, these younger wolves have lost their elders’ knowledge of where and how to hunt. And when they have pups, they’re tied to a den, making it harder for them to hunt deer and elk, so they may turn to sheep and cattle. The only way to eliminate the problem entirely is to kill all the wolves, the scientists conclude. Because that is not desirable, they suggest that ranchers and farmers increase their use of nonlethal interventions such as using guard dogs, horseback riders to patrol the range, flags, and spotlights.