Derek Kellenberg

A study from the University of Montana shows that when wolves attack cattle, it can cause calves to gain less weight.

Report co-author Derek Kellenberg says his team found that when wolves were simply in the area, there was no change in cattle weight, but that on ranches where there was a kill, the cows weighed less.

Kellenberg says skinnier cows are worth less, so ranchers can lose thousands of dollars.

But he says wolf predation was not the biggest factor affecting weight.