Predators and prey affected by warming.

• Position: Ecology - Decline in numbers of North American moose, increase in number of wolves - Brief Article

Wolves were up and moose were down in the spring of 2004 at Isle Royale National Park, the home of a 46-year study of predators and their prey. Researchers suspect that a global warming trend may be behind the shift. The moose population slid to 750 on this Lake Superior wilderness island park, down from 900 in 2003 and 1,100 in 2002. In the meantime, the number of wolves has seesawed upward over the past decade, and now stands at 29, as many as the park has seen since 1980 and 11 more than in 2003.

What is bad for moose has been good for wolves, and moose thoughout North America have been hit hard by warmer temperatures that began in 1998 with El Nino and never let up, according to professor Rolf Peterson of Michigan Technological University, Houghton, who has led this study for 34 years.

"What we think is happening is that wolves are cashing in on moose vulnerability that's been induced by a warmer climate," Peterson says. The moose population has been stressed by higher temperatures, particularly the drought of 1998 and then the...