When winters are severe, more elk die, providing needed food for the wide range of scavengers in the area, including bears, coyotes, eagles and ravens, the researchers said. Shorter, warmer winters brought on by global warming increase the survival rate of elk, causing a food shortage for the scavengers at a time when other resources are scarce.
With the help of the gray wolves, however, elk are regularly killed off regardless of the winter's severity, according to the study. And luckily for the scavengers, the wolves are willing to share their leftovers, thereby buffering the impact of climate change.
"When wolves are around, you no longer get this boom-bust cycle in carrion availability," said the study's lead author, Chris Wilmers, who conducted his work as a Ph.D. student in ecosystem sciences at UC Berkeley's College of Natural Resources. "Wolves provide a steady supply of carrion for the scavengers throughout the winter, whether it is mild or severe."
Gray wolves were once found throughout North America, but were nearly hunted to extinction by 1970. Since the U.S. Fish & Wildlife Service reintroduced wolves to Yellowstone in 1995, a growing body of research is finding that this top carnivore, which has been making a comeback, is an essential player in the region's ecosystem. There are now 31 gray wolves at Yellowstone.
The new study, which appears in the April 2005 issue of the online journal Public Library of Science Biology, builds upon earlier research led by Wilmers. The earlier studies found that wolves, unlike other predators, leave behind their kill once they've stuffed themselves, allowing scavengers to partake in the bounty.