Web address: http://www.sciencedaily.com/releases/2007/08/070817210729.htm

Source:        Michigan Technological University
Date:        August 17, 2007

Global Warming Threatens Moose, Wolves

Science Daily – Global warming is impacting more
than the water levels in the Great Lakes. It
could be the beginning of the end for the moose
and wolves of Isle Royale. And if it is, a
Michigan Technological University scientist
places the blame squarely on the human race.

“Humans have made summers increasingly hot, which
likely exacerbates moose ticks,” says John
Vucetich, a population biologist in Michigan
Tech’s School of Forest Resources and
Environmental Science. “Both the heat and the
ticks are detrimental to moose. If wolves go
extinct for a lack of moose, humans will be to
blame.”

Isle Royale is an isolated wilderness island near
the northwestern shores of Lake Superior, close
to the Canadian border. A U.S. National Park, it
is home to a variety of rarely seen wildlife,
including moose and wolves.

But the moose and wolf populations on Isle Royale
are shrinking, and Michigan Tech researchers, who
have been them for nearly 50 years, blame it on
climate change. Five of the last six summers have
been the hottest in half a century.

“Hot summers are hard on moose,” said Vucetich.
Hot weather causes moose to rest more and forage
less, he explained, and summer foraging is how
moose prepare to survive the long, bitter winters.

Warm springs and falls may also promote breeding
of winter ticks, a species of tick that feeds on
moose. The past five warm years have brought
devastating tick infestations to Isle Royale.
“The ticks weaken the moose and make them
vulnerable to wolves,” Vucetich explained. “The
loss of blood caused by the ticks can even kill
the moose outright.”

In 2000, there were 1,100 moose on the 210 square
mile island. Now there are fewer than 400.

As the numbers of moose dropped, the wolf
population initially grew, probably in response
to the additional food supply provided by
weakened moose. But now the wolves-the moose’s
only predator on Isle Royale-are themselves
falling prey to the changing climate. Between
2006 and 2007, the number of wolves on the island
decreased from 30 to 21.

Again, Vucetich blames the weather. “There are
too few moose for the wolves to eat, and the
reason there are too few moose is very likely
that hot summers and ticks made them too easy for
the wolves to kill,” he said.

During the ongoing 50-year study of the wolves
and moose on Isle Royale, the populations have
never dropped this low. The wolves on the
isolated island are the only predator of moose,
and moose are virtually the only prey for the
wolves. It’s a model ecosystem that may be
slipping into a new balance-one that may not
include wolves.

“Ecosystems change; that’s normal,” said
Vucetich. “When they change quickly in dramatic
ways, that creates a new balance,” he explained.
“Nature is still in balance. It may just be a
balance that doesn’t favor humans and
disenfranchises certain kinds of wildlife.”

Scientists believe that wolves first walked to
Isle Royale in the mid-20th century, across the
15-mile channel between the island and Canada.
That channel used to freeze regularly. It freezes
much less frequently now-another sign of climate
change. Wildlife experts think that the moose
swam across, although it is possible that they
were brought on a boat.

“Continued hot summers could mean more trouble
for moose, and as a consequence, for wolves on
Isle Royale,” Vucetich added.

If the moose or wolves vanish from Isle Royale,
“we will have lost one of the best opportunities
to study the relationship of predators and prey,”
the population biologist said. “And we must study
it in order to understand and preserve it.”

Note: This story has been adapted from a news
release issued by Michigan Technological
University.

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