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Is The Arrowhead Moose Herd In Trouble?

Moose are among the most popular denizens of the Northern Wilds, but biologists are puzzled why some of the monstrous animals are dying for no readily apparent reason.

In recent years, folks have been commenting that there seem to be fewer moose in northeastern Minnesota. The big black critters haven’t disappeared entirely or even become uncommon, but you see fewer of them along the roadside and back in the brush. This concerns many folks, because moose are not only popular with hunters, they are enjoyed by nonhunting residents and visitors alike.

The concern about what may be a dwindling moose herd is shared by state and tribal wildlife biologists. Although recently improved aerial survey techniques have allowed biologists to make more accurate (and somewhat higher) annual population estimates, they are quick to point out that better counts don’t necessarily mean there are more moose in the woods. In fact, a growing body of scientific evidence suggests that north country moose may be in trouble.

"The moose population is barely sustaining itself," says Mike Schrage, wildlife biologist for the Fond du Lac Ojibwe Band.

"The moose population is barely sustaining itself," says Mike Schrage, wildlife biologist for the Fond du Lac Ojibwe Band.

Schrage is participating in a cooperative study between northeastern Minnesota tribes and the DNR to determine moose mortality rates. Biologists are tracking radio-collared moose to determine where they live and, more importantly, how they die. Prior to this study, biologists had good harvest data from state and tribal moose hunts, but knew little about how many moose died from nonhunting causes such as predation, disease, parasites, and accidents.

The study data shows unusually high mortality rates for adult cows and low calf survival. Combined, these two factors create a situation where there are hardly enough calves entering the population to replace dying adult moose. More troubling is the fact that biologists are uncertain why so many cows are dying. Although a few radio-collared animals have died from predation or various accidents, the cause of death for many more is unknown.

"Even after a necropsy, we don’t have answer," says Minnesota DNR research biologist Mark Lenarz.

Moose are dying throughout the year. Many are emaciated and appear to be starving, even though their intestinal tracts are full of food and fecal pellets. For an undetermined reason, they seem to be wasting away. In fact, Swedish scientists use the term Moose Wasting Disease (unrelated to Chronic Wasting Disease) to describe a similar condition among moose in that Scandinavian country. There, too, the cause remains uncertain.

Minnesota biologists say some likely causes do not appear to be killing large numbers of Arrowhead moose. Although the whitetail deer population has blossomed in the wake of the 1999 BWCAW blowdown storm and a series of mild winters, only a few moose are dying from brain worm—a parasite associated with deer. Blood samples from moose captured during the study show that about one quarter of the animals have been exposed to the parasite, yet only one of the "positive" moose has actually died from brain worm. As for diseases, Arrowhead moose test positive only for Lyme’s Disease. Lenarz says veterinarians have told researchers that the symptoms they are seeing in dying moose are not consistent with Lyme’s Disease.

The Arrowhead situation appears to be similar to what occurred in northwestern Minnesota, where once-abundant moose crashed during the 1990s, but again the cause of mortality differs. Lenarz says the authors of a several-year study in the northwest believed moose were dying from liver flukes and other parasites. In the northeast, liver flukes are uncommon.

One possibility that remains untested is that Minnesota is becoming too warm to support moose. A Twin Cities television recently proclaimed moose to be the state’s poster child for global warming, but Lenarz says researchers do not have data to support that assertion. Nevertheless, Minnesota lies on the southern extremity of the moose range.

Researchers do know that the northwestern moose decline correlates with a longer growing season and higher summer temperatures. They also know that moose begin to pant when the air temperature rises above 67 degrees, which means they may feed less in warm weather. The heat of summer dog days is more stressful to moose than winter’s cold temperatures.

"You can’t help but wonder if climate change is affecting moose in Minnesota," says Lenarz.

For now, the trouble in the moose herd is unlikely to be reflected in harvest quotas for the state or tribal moose hunts. Since most hunters choose to shoot bulls, hunting isn’t believed to affect the moose herd’s capacity to sustain itself. For now, researchers say the population appears stable. However, Schrage warns that if moose numbers start to plummet, hunting may be restricted.

At this point, researchers are uncertain if moose might benefit from more intensive habitat management. Moose are what as known as an "early successional species," which means they flourish in forest areas where there was a recent disturbance such as a fire or timber harvest. For moose, the larger the disturbed area, the better. Schrage says some wildlife managers are concerned that the new U.S. Forest Service plan for the Superior National Forest highlights deer rather than moose. Tribal wildlife managers and members of hunting groups, including the Minnesota Deer Hunters Association, met with Forest Service officials last fall to express their concerns regarding national forest habitat management for northern game species.

To some extent, habitat changes may explain why folks are seeing fewer moose. DNR wildlife technician Dan Litchfield of Ely, who has participated in the aerial moose surveys for three decades, says he’s noticed how local moose populations reflect habitat conditions. For instance, after the Little Indian Sioux Fire in 1971, the moose became very abundant in the burned over area and then slowly declined as the forest grew up. Presently, moose are abundant in locales devastated by the 1999 blowdown. Litchfield thinks that some roadside cut-over areas where folks once regularly viewed moose are less attractive to moose as the saplings grow into trees.

"I’m still seeing good numbers of moose back in away from the roads," he says. "However, I am seeing fewer moose along the roads near Ely."

Litchfield says he isn’t comfortable making predictions for northeastern Minnesota moose based on possible consequences of climate change. And he points out, as did wildlife biologist Lenarz, that the purpose of the radio-collar study is to determine why the northeastern moose population hasn’t increased to fill existing habitat. But it is fair to say that what researchers are learning from the study is leading them to ask new questions about moose survival. Although researchers presently plan to follow the radio-collared moose for another one or two years, Schrage says they are considering seeking funding to capture and collar more moose, and continue the study.

Tags: Moose


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