The case of the missing Minnesota moose

  • Article by: BILL MCAULIFFE , Star Tribune
  • Updated: February 23, 2008 - 7:29 PM

Is it parasites, or climate change, or both, that's killing Minnesota's moose? Researchers are attacking the question on the ground, in the air, with radio, needle and microscope.

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Research Biologist Mark Keech (Right) and MN Zoo Veterinarian Tiffany Wolf (left) work with 800 pound cow moose #294, fitting her with a radio collar and taking samples that will help researchers study the cause of increased mortality in the Northeastern Minnesota moose population.

Photo: Brian Peterson, Star Tribune

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ISABELLA, MINN.

Moose 294 lay in deep snow in the scrubby woods, eyes half open in the bright February sun. Huffing steadily, her coat a shimmering walnut brown, she might have been enjoying a winter siesta, but for the pink-tufted tranquilizer dart lodged in her backside.

For researchers Mark Keech and Tiffany Wolf, though, this was no time to relax. From the time Keech had fired the dart from a helicopter into the fleeing 850-pound moose, Keech and Wolf had about 30 minutes for a full work-up.

Wolf, an associate veterinarian with the Minnesota Zoo, withdrew several tubes of blood. Keech, a research biologist, sliced out the barbed dart and yanked out an incisor. Wolf collected hair and fecal samples. Keech riveted an air tag through the moose's ear and screwed on a heavy leather collar equipped with a radio transmitter.

Time was running out. Wolf injected two drugs to reverse the tranquilizers and the researchers scrambled off about 20 yards. As if on cue, Moose 294 gave a little groan, stumbled, rose grandly to her feet, collected her wits and clattered off through the brush.

"Good luck!" Keech called out.

Good luck indeed. Something strange is killing the moose of northern Minnesota, and wildlife scientists hope Moose 294 and others like it can provide some clues as to why. The task is urgent: In the course of a few years, the number of moose in northwestern Minnesota has plummeted to near extinction.

What the researchers find out could shed light on broader changes in the North Woods, where the moose is an iconic part of the landscape and the web of life.

"When you think of northern Minnesota, you think of the North Shore, the Boundary Waters, wolves, loons and moose," said Mike Schrage, wildlife biologist for the Fond du Lac Band of Lake Superior Chippewa, which is partnering with the Minnesota Department of Natural Resources and the 1854 Treaty Authority in studying the northeast moose herd. "They're part of our identity. You pick up a Duluth Pack, and what's the logo? A big bull moose."

Scientists say that the moose are dying from "tipover disease," less a diagnosis than a description of how moose simply weaken and crumple to the ground, often to be finished off by wolves or other predators. Minnesota moose seem to be dying when and where they shouldn't -- in the prime of life, or in the fall, when they should be fat, and amid plenty of food. The causes are still largely unknown.

It might be due to parasites they've picked up from an exploding deer population. It might be a complication of heat stress, induced by a climate that's gotten too warm too fast. It might be combination of those and other factors.

850-pound canary?

The fate of the state's largest herbivore is about more than postcard imagery, Schrage and others say. The moose may be an outsized canary in a coal mine, representative of a struggle facing many other animals whose home ranges and climate are changing, said Dennis Murray, a professor of terrestrial ecology at Ontario's Trent University.

"We don't know those other species as well as moose," Murray said. "Therefore those changes aren't as apparent."

Researchers have been studying the northeast moose since 2002. Of the 114 they've collared and tracked since then, only 28 were still standing this year. Of the other 86, more than half died of unknown causes.

No moose were collared the past two years because there wasn't any money. Now a $200,000 federal Tribal Wildlife Grant will pay for research through the winter of 2010-11. The Minnesota Deer Hunters Association has also contributed.

Researchers aren't wasting time. Their goal this year was to put collars on 35 moose, all cows, so they can focus on pregnancy rates.

On Tuesday, months of planning turned into action. The study partners were joined at the Ely Municipal Airport by the zoo's Wolf, who handles the tranquilizers and anti- dotes, and two Alaskans in their fourth year on the job. Keech was "vacationing" from his regular job with the Alaska Department of Fish and Game, and helicopter pilot Scott Gibbens is a retired state trooper who's been tracking wildlife by air for 10 years. Ground support included a fuel truck and a pair of snowmobiles.

It was just luck that the overnight temperature hit 24 below at Ely.

"Hard on people and equipment, but good for the moose," Schrage said.

DNR pilot Al Buchert was the advance scout, flying a single-engine airplane over 30 plots of clearcut, swamp and forest. Buchert relayed moose sightings over the radio to Gibbens. The helicopter swooped down toward the moose, sometimes within 15 yards.

Keech leaned out of the craft with a rifle much like a .22 and fired a tranquilizer dart. He rarely misses.

Within five to seven minutes, the drug brought the moose to its knees. Gibbens landed the helicopter nearby, and Keech and Wolf tromped through the snow to the moose's side to begin their work.

Researchers look for many things in the moose samplings. Blood samples can yield evidence that the moose has tried to fight off a brainworm invasion, or has other diseases, or lacks key trace elements or heavy metals. The feces (extracting them by hand is "the glory part of the job," Wolf said) can reveal whether the moose is pregnant or has parasites. The hair contains DNA information, which has already been helpful in busting at least one poacher. And the tooth, like a tree, has rings that reveal the moose's age.

Cool retreats

This year, the moose collars will carry a new device -- a thermometer to record the temperature in the moose's surroundings. Schrage and DNR wildlife researcher Mark Lenarz said that may help determine whether moose are finding places in the woods -- "microclimates" -- where they can stay cool enough, winter and summer, to stay healthy. If they can prove that theory, that could lead to forestry and wildlife management efforts to protect and enhance such areas.

Lenarz pointed out that global warming, or at least the winter warming in northwestern Minnesota in the past 40 years, can be regarded as a "proximate" cause of increasing moose deaths. That means it's a context that creates the more direct causes or vulnerabilities, much like alcoholism might lead to a person's death from liver failure.

Mean midwinter temperatures in northwest Minnesota increased about 11 degrees from 1961-2001, astonishing by most climate change measures; Lenarz said researchers are still examining the trends in the northeast. Schrage said he believes mild winters and longer growing seasons are a threat to the northeast moose, but they don't explain everything.

"It's complicated in between a warm climate and a dead moose," he said. "I don't think I'm ever going to walk up to a dead moose and say, 'Oh, it died of heat stress.' There's a lot that happens in between."

A test case

Even a dead moose can help the researchers. Last December, a moose stumbling near a highway close to Side Lake was shot by a DNR warden. Two days later the moose was on a table at the Veterinary Diagnostic Lab at the University of Minnesota's St. Paul campus. A team led by pathologist Dr. Arno Wunsch-mann had scalpels in hand.

The necropsy was a rare opportunity to examine a dead moose before predators or decomposition damaged it.

The moose appeared fairly healthy, if a bit undernourished for the time of year. Wunsch-mann sliced the moose's brain, spinal cord and pituitary gland into samples that would be further processed into slides for study under a microscope. After looking at 50 slides for three hours over two days, Wunschman had a cause of death: brainworm, a parasite that has passed from deer to moose and burrows through their spinal column and brains. White-tailed deer, however, are largely immune to the damage.

End of story? Not quite. Blood sampling of collared Minnesota moose, Lenarz said, has shown that between 16 and 18 percent have been exposed to brainworm. That's less than the annual non-hunting mortality rate, and in any case it doesn't indicate anything about how successfully moose might resist the parasite and its effects.

This week's mobilization ended Friday with 34 moose collared, one short of the goal because a radio on one collar didn't work. The samples from the darted moose will take months to analyze. Now that she has a radio collar, Moose 294 will be tracked weekly by the DNR. By all appearances, she's healthy and even a little fat, Keech and Wolf noted in their encounter.

Minutes after she pushed off through the thicket of small maple and poplar, Gibbens and two passengers spotted Moose 294 in a clearing, already nearly 300 yards away. Alert to the helicopter overhead, she darted toward cover, high-stepping through the deep snow toward an uncertain future.

Bill McAuliffe • 612-673-7646

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