Last winter broke records for its relatively warm and dry weather, with many potential impacts on the balance of nature in northern ecosystems. Dr. Rolf Peterson, principal investigator of Earthwatch's Moose and Wolves project, says the mild winter explains recent changes in the wolf population at Isle Royale National Park, Michigan.
Peterson, a professor of wildlife ecology at Michigan Technical University, said the 2002 winter survey counted 17 wolves on the island, as opposed to 19 last year. Meanwhile, the island's moose population increased from about 900 last year to 1,100 in 2002.
"The significant factor was a lack of winter," Peterson said, referring to the very light snowfall this year. "Moose were in places where we don't normally see them in the winter-on hillsides and out of the conifer swamps."
The Isle Royale wolf-moose survey is the longest running predator-prey study in the world, now in its 44th year. Peterson has conducted the study for the last 32 years, 14 years with the help of Earthwatch volunteers. As an island in the middle of Lake Superior, Isle Royale presents a unique opportunity for such research.
Peterson said the wolves suffered a mortality rate of almost 50 percent this winter, but that last year's seven pups kept the population near steady. Researchers found evidence of a confrontation between two of the three wolf packs on the island, resulting in the death of the alpha male from one of the packs.
"The Chippewa Harbor pack has been pushing the East pack aside and enlarging their territory," Peterson said. "A mild winter is always tough on the wolves, and this probably contributed to the confrontation."
The moose population on Isle Royale fared much better, thanks to the mild winter. Typically the wolves prey on old moose and young calves. But with little snow cover, the moose could move more freely and avoid the wolves.
"We watched about 15 encounters between wolves and moose this winter," said Peterson. "The moose were almost always intimidating, so the wolves didn't bother to attack. Last year, two-thirds of the kills were moose calves. This year, it was about 20 percent. The wolves had to work hard to find a moose to kill."
Earthwatch teams will continue to explore predator-prey relationships on Moose and Wolves this summer. Peterson expects three litters of wolf pups to be born in late April, as all three packs had breeding activity, so the cycle of death and survival will continue on Isle Royale.
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