Warming Alters Predator-Prey Balance

"There were bare-naked moose running around," he said.

No one thinks the moose, which arrived on Isle Royale about 100 years ago by swimming from the mainland, will disappear. But with fewer moose, the wolves could be doomed. Desperate wolves have been seen chomping on old moose bones and even eating green apples from trees.

Peterson, who lives with his wife in a fishing cabin on Isle Royale surrounded by hundreds of antlered moose skulls, said the wolves are still suffering from the moose crash of 1996.

"Now wolves are living on moose born in the early 1990s, before the collapse," he said. "It's like they're feeding on a baby boom generation that's not backed up."

Vucetich noted that climate change can have contradictory effects. Milder winters and earlier springs mean more food for moose, while winters with deep, crusty snow benefit the predators, which can walk atop the snow while the moose crash through. Less snow gives the moose an advantage.

But ultimately, Vucetich said, "moose are creatures of the north country who like it cold. If it gets warmer, they won't fare well."

It's worse for the wolves. "Wolves will go extinct before moose do, and their extinction could definitely be caused by climate change," Vucetich said.

In 1978, gray wolves of the type found on Isle Royale were listed as an endangered species in all the Lower 48 states except Minnesota, where they were labeled threatened. Wolf-recovery programs around the country had solid success over the next few decades, and in 2007, the western Great Lakes wolves were delisted, although legal wrangling over their status continues. There has also been debate over the years about the fate of the wolf-moose study, which is financed by the National Park Service, the National Science Foundation and others.

Vucetich conceded that the survival of about 20 wolves on an isolated island visited by relatively few people may seem like a less-than-urgent issue. But he sees larger symbolism to the project, since it illustrates the intricate interdependence of species.

"It is an opportunity to appreciate how complicated this is, to generate a sense of wonder about nature," he said. "That's why we should care."