SLE ROYALE (AP) - At least three rare wolves drowned in an abandoned mine shaft on Isle Royale, which explains a worrying drop in their population in the Lake Superior wilderness area, Michigan Technological University officials said Thursday.
The university said its experts wondered why the annual winter count only found nine wolves and one confirmed female. It was the lowest since scientists began observing the predator-prey relationship between the remote national park's wolves and moose more than 50 years ago.
"We found there had been a real catastrophe in early winter, before we arrived on the island in January," said population biologist John Vucetich.
At the time of the count, Vucetich and wildlife ecologist Rolf Peterson said that it might be a sign that the wolves were becoming extinct in the remote national park, where they live in balance with the moose population.
In late May, a National Park Service biologist reported animal carcasses floating in water at the bottom of a deep, 19th-century mineshaft. An examination found at least three wolves drowned, and one was a young female that would have helped maintain the wolf population.
"There were three dead wolves from the Chippewa Harbor Pack in the shaft: a collared male that we had been unable to locate this winter, an older male - maybe the alpha male - and a female born in 2011," Vucetich said. "We believe the incident occurred between mid-October and mid-January.
"There is no way to know how the three wolves ended up falling into the pit, but very likely, accumulating snow and ice played a role in the accident."