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Minnesota's moose are dying; global warming may be to blame

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In the mid-1980s,  more than 4,000 moose roamed the forests and bogs of northwestern Minnesota. Today, there are probably fewer than 100. 

In the northeast, the population is stronger at around 7,600 moose, but researchers are learning that there, too, the numbers are declining.

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"These are animals in the prime of life that just look like they laid down and died," said Mike Schrage, a wildlife biologist with the Fond du Lac Band of Ojibwe.

The Fond du Lac band is among several agencies that have joined the Minnesota Department of Natural Resources in trying to figure out what's happening to the moose. 

Schrage and the rest of the team just wrapped up a tagging operation that placed radio collars on several dozen moose in the northeast. The collars will help researchers track the animals. They're also equipped with thermometers that will measure temperatures in the moose's surroundings.

Schrage says researchers believe a warming climate might be causing moose to get sick.  

"The vast majority of them are dying of some malady. We just have not been able to identify what that is."

"I do think global warming is having an impact on our moose," said Schrage. "I think it gets complicated between climate change and a dead moose. Because I don't think I'm ever going to walk up to a moose carcass and be able to say, oh, it died of climate change. I think there's a lot that happens in between."

The connection between rising temperatures and dying moose isn't clear. Scientists do know that in northwestern Minnesota, the average midwinter temperature has increased a startling 11 degrees in just the past 40 years. That's not good for a beast that thrives in the cold.

Scientists are now analyzing climate information in the northeastern part of the state. Data from that region shows the non-hunting mortality rate for moose has climbed to 21 percent. That's nearly three times higher than elsewhere in North America. 

Moose cows appear to be giving birth at a normal rate, but a growing number of those spring calves don't survive their first year.

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From a helicopter, shooter Mark Keech of Fairbanks, Alaska aims a dart at a cow moose in the Superior National Forest last month. The operation is part of an ongoing study of the declining moose population in northeastern Minnesota.
Photo courtesy Clint Austin/Duluth News Tribune

Mark Lenarz, a wildlife research biologist with the Minnesota DNR, says more moose appear to be dying from parasites. But Lenarz says that doesn't tell the whole story. 

"The vast majority of them are dying from some unknown malady. We just have not been able to identify what that is," said Lenarz. "Some are dying from what's called brain worm. Some are probably dying from winter ticks. Some are dying from who-knows-what disease or parasites out there, but it isn't any single smoking gun."

Lenarz says warmer temperatures mean moose have to work harder at staying cool. Heat stress makes animals more vulnerable to disease. 

At the same time, the warmer climate is helping the deer population thrive. And most deer carry parasites -- brain worm, for example -- that may be spreading more quickly to moose.   

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Lenarz says moose aren't instinctively smart enough to migrate north to cooler temperatures. He fears that if current trends continue, Minnesota's moose population could eventually be gone forever.

"I suspect what's going to happen is simply that eventually, over time, we're going to see moose disappear all together," Lenarz said, "and the southern edge of the moose distribution will simply be farther north somewhere in Manitoba."

Biologists continue to analyze data collected this year. They say they'll need more resources to figure out a plan to help the animals.

Tiffany Wolf, a veterinarian at the Minnesota Zoo, helped capture and take blood samples from moose last month. Wolf says being up close to the majestic animals was amazing. She worries about their future. 

"It's an incredible experience to be right there next to an 850-pound animal. And it's humbling, really," said Wolf. "Moose are such a hallmark symbol for Minnesota, and it would be disappointing to lose a species like that. And for Minnesota's moose population, the future doesn't look good."

Despite what's happening to Minnesota's moose, the DNR still allows people to hunt the animals. But the hunt is now limited to bulls only.

Biologists believe killing a few bulls won't affect the overall population. The DNR is taking applications now for about 250 available permits for the fall season.