warming cited in island's shift of wildlife numbers
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
"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
"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,"