Moose Disappearing

Minnesota Department of Natural Resources voices concern over declining moose population; Michigan’s Isle Royale declining population linked to increasingly hotter summer temperatures

As recently as 2003, the Minnesota Department of Natural Resources reported that, “Wildlife managers have concerns over both of Minnesota’s moose populations” in the northwest and northeast portions of the state.

According to the DNR: “In the northwest, where about 250 moose live in scrubby bogs and aspen parklands, only about 55 percent of the cows are pregnant in any given year, an abnormally low rate. The reason for such poor reproduction? Still unknown, despite a long study,” said Mark Lenarz, DNR Forest Wildlife Populations and Research Group leader. Clearly, however, the northwestern population is much smaller than it was a decade ago.

“In the northeast, site of the current study, research indicated more than 90 percent of the adult cows were pregnant last year-a healthy, normal rate. By rights, the moose population ’should have been going through the roof,’ Lenarz said. Instead, the DNR estimated 4,200 moose lived in northeastern Minnesota last winter, down from 5,200 the year before. Did the drop suggest a real problem? Or simply an undercount because cows and calves were tough to spot from the air with last winter’s patchy snow….”

On August 22 2007, Science Daily reported on the moose populations of Michigan’s Isle Royale.

“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.”

According to the science source, “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.”

There’s a lot of suggestive evidence showing the impact of global warming on moose populations. Does it mean moose populations are bound for extinction? Certainly, some regions will see this kind of loss.

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