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Great Lakes Article:

Global warming cited in island's shift of wildlife numbers
Associated Press
03/08/04

TRAVERSE CITY -The moose population on a remote Lake Superior island chain is down sharply while gray wolf numbers have jumped - a population shift likely caused by global warming, a scientist says.

Rolf Peterson, a wildlife biologist with Michigan Tech University in Houghton, has studied predator-prey interaction between the two species at Isle Royale National Park every winter for 34 years.

His recently completed survey turned up about 750 moose, down from 900 last year and 1,100 in 2002. Meanwhile, the number of gray wolves jumped from 19 last year to 29, matching the highest total recorded on the island since 1980.

"What we think is happening is that wolves are cashing in on moose vulnerability thatís been induced by a warmer climate," Peterson said.

Their numbers fluctuate nearly every year and the reasons arenít always clear, he said. But the extent of the moose decline appears linked to stress and a winter tick infestation brought on by milder temperatures.

Isle Royaleís warmup began with the onset of El Nino in 1998 and has not abated, Peterson said.

"Moose canít feed in the summertime if itís too hot" he said.

That makes them weaker, more disease-prone and less able to fight off wolf attacks, he said.

Unusual warmth in spring and fall brings an out-of-control tick problem in winter. Tens of thousands of ticks can attach themselves to a single moose, each sucking a cubic centimeter of blood.

Warmer weather isnít all bad for moose; thereís less snow and more growth of the trees on which they browse. But the negatives outweigh the positives, Peterson said.

Wolves are taking full advantage of the moose misery. While two died in the last year, 12 newborn pups survived and the islandís three packs are thriving.

But if moose numbers eventually drop too low, it could spell trouble for the wolves - especially if the resulting food shortage came on top of a disease epidemic or some other problem.

"When the wolf population is reduced periodically, thatís when they come close to the potential threshold of extinction, when just random bad luck can do them in," Peterson said.

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