Peterson, a professor of wildlife ecology at Michigan Tech, said the 2002 survey counted 17 wolves on the island, as opposed to 19 last year. 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. 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 and that last year's seven pups kept the population near steady. The Isle Royale wolves have formed three packs: the east pack with six members, the Chippewa Harbor pack with five, and the middle pack with four. There are also two single wolves unattached to a pack.
Researchers confirmed a confrontation between the east pack and the Chippewa Harbor pack, with the east pack's alpha male killed. Peterson's team found that particular wolf, one of four on the island wearing a radio collar, just offshore in Lake Superior.
"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.
"We watched about 15 encounters between wolves and moose this winter," he said. "The moose were almost always intimidating, so the wolves didn't bother to attack."