There have been some studies on predation, with mixed results. If the only thing keeping the numbers down, predators might be a place to look. The predators don't have options for food. Humans do. Humans have options on how they develop the land, how the use water, and so on.

And, has been the case with many predator/livestock issues, the operator is required to make operational changes before, as a last resort, predators are removed.