Winter Study 2009
Each winter since 1959, researchers have been tracking and observing the wolves and the moose that are virtually their only prey. During this year's Winter Study, Vucetich and Peterson found two dead wolves with misshapen vertebrae, one killed by other wolves and the other, which also had severe arthritis, frozen under the ice of a lake.
This was a particularly cold, hard year on the wolves and moose of Isle Royale. The researchers counted 24 wolves, close to the long-term average population size, but two of the four wolf packs did not have any pups that survived, Vucetich reported. East Pack's numbers declined to a sole surviving female who has taken a new mate from one of the other packs.
The researchers estimated the moose population at 530 this winter, a decrease from last year and not even half the average long-term population size.
Not only are fewer moose surviving, making food harder for the wolves to find, but the wolves are having to hunt older, more arthritic moose, Vucetich and Peterson found. Three years ago, the average age of a moose killed by a wolf on Isle Royale during the winter was 12 years old. Two years ago, it was 13, and now it is 14.
Atypically, the wolves didn't kill any moose calves this winter, although calf numbers were low, "so the wolves probably didn't save any for the winter," said Vucetich. In fact, a pair of moose calf twins both survived, a rare occurrence.
"What we learned raises the question of whether the wolves of Isle Royale should be genetically rescued," Vucetich said.
Up to now, wildlife management agencies in the US and Scandinavia have cited the Isle Royale wolves as proof that small wolf populations can avoid genetic deterioration and remain viable.
"Our study removes
|Contact: Jennifer Donovan|
Michigan Technological University