Minnesota's iconic moose are dying off
It wasn't long ago that thousands of moose roamed the gentle terrain of northwestern Minnesota, affirming the iconic status of the antlered, bony-kneed beast from the North Woods. In just two decades, though, their numbers have plummeted, from 4,000 to fewer than a hundred.
They didn't move away. They just died.
The primary culprit in what is known as the moose mystery, scientists say, is climate change, which has systematically reduced the Midwest's already dwindling moose population and provoked alarm in Minnesota, where wildlife specialists gathered for a "moose summit" this month in Duluth.
"There's not a lot of opportunity to turn this around," said Mark Lenarz, a wildlife research specialist at the Minnesota Department of Natural Resources. "Here in Minnesota, they [moose] have been weakened by climate change."
Temperatures tell much of the story. Over the last 40 years in northwest Minnesota, the average winter temperature has risen significantly — 12 degrees — while summers are 4 degrees warmer. Solitary and temperamentally grumpy, moose have made it clear in their estimated 13,000 years in North America that they hate warm weather.
The mounting concern about the fate of the moose comes as the Bush administration in its last weeks is revising endangered species regulations in ways that prohibit federal agencies from evaluating the effects of increased global warming on endangered species.
Officially, the moose is not endangered in the United States. But it is in danger of disappearing from the Midwest, which is the far southern fringe of its range. Roughly 7,700 moose reside in Minnesota, nearly all in the northeast section of the state. That's a drop of almost 50 percent in the last 20 years.
Isle Royale National Park, a 45-mile-long island in western Lake Superior, has about 650 moose, down from 2,500 in 1995. Michigan's sparsely populated Upper Peninsula has about 450, and that population has remained steady, according to a wildlife biologist at the Michigan Department of Natural Resources.
"The trends for the past 20 years are pretty clear, and if they keep up there won't be any moose in 50 years," said John Vucetich, a population biologist at Michigan Technological University in Houghton.
One of the many questions raised by the demise of the moose is, "What does it mean if the moose go away?"
It's not as if the moose leaving Minnesota and Michigan would upset a delicate ecological balance that would occur with, say, a dramatic falloff of the bird population that would allow insects to proliferate.
"That's the $64,000 question," Vucetich said. "As the climate warms, some creatures will do better, some worse. For moose it's fairly straightforward that we'll lose them ... and there are a lot of people who identify with moose."
That identity, from wooden carvings to giant polystyrene moose next to roadside restaurants, helps define the region's image.
"They're a symbol of the great north, of wilderness, and a lot of people would not want to see that go away," Vucetich said.
All romantic symbolism aside, the beasts are in big trouble.
Minnesota and Michigan offer separate living laboratories that help explain why the moose are dying. Heat, water and parasites play important roles, but temperatures are the trigger. While deer, wolves and bears have adapted to warmer temperatures, wildlife biologists say, the moose have suffered. Moose require shade, water and cool weather, each of which is dwindling in northwest Minnesota.
Lenarz said the moose population in the northwestern part of Minnesota struggles among small patches of aspen woods and farmland.
When temperatures rise, the moose have to work harder to obtain food and find places to stay cool. Lenarz said that affects their immune systems, prevents them from putting on more fat in the summertime (which they need to get through the winter) and makes them vulnerable to infestations from parasites.
Although northeastern Minnesota is comparatively more moose-friendly—greater shade, more opportunities to cool off—the population is declining, albeit more gradually, by 10 percent to 13 percent per year. Lenarz said the pregnancy rate is a little more than half the norm for moose, and mortality rates are 2 to 3 times higher than the average.
Hunting is not a significant factor. It is banned in northwest Minnesota and limited to 150—bulls only—in the northeast.
Heading north to cooler climes is not an option.
"When moose are in trouble, they don't move. They die," said Rolf Peterson, a research professor at Michigan Tech and the chairman of the Minnesota Moose Advisory Committee. Peterson has spent decades studying the interrelationship between moose and wolves, the only big animals on Isle Royale.
Moose on the isolated island are not exposed to many of the threats from Minnesota—cars, hunters and multiple parasites usually carried by deer. Wolves are the predators. Yet a decade-long trend of hotter-than-normal summers, according to a report issued in March, has negatively affected moose. Along with a drop of nearly 2,000 moose since 1995, temperatures are rising, leaving moose more vulnerable to disease.
The summer of 2007 was the driest of the last 45 years, the report said.
"I don't see the temperature change we're seeing as cyclical. The trend is definitely in one direction," Peterson said.
Moose can be moved, as a herd was transferred from Ontario to the Upper Peninsula in the mid-1980s. But the options and the chances for success, in the face of climate change, are formidable, he said.
"I'm not terribly hopeful that the trend can be reversed by something we can do," Peterson said. "There aren't too many things we can do."
Copyright © 2008, Chicago Tribune
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