From The Spokesman-Review:
After hours of watching Yellowstone elk herds through a spotting scope, Scott Creel noticed a few interesting things.

When wolves appeared, the elk… spent more time on alert… and less time eating. They also left prime winter range to take cover in forested areas, where less food was available….

Creel and fellow researchers linked the altered elk behavior to lower calf production. As their body fat drops, cow elk have difficulty staying pregnant through winter. They grow emaciated and abort, the research concluded…. [All of which] indicates that wolves affect elk populations in subtle but important ways beyond direct kills, he said.

“If you look at the observed rate that wolves are killing elk calves, there are too many calves missing,” Creel said. “We can’t account for them all through direct predation….”

“Those things elk are doing to avoid being killed may carry high costs,” he added.

Check out the full article.