Scientists acknowledge wolves are a factor in the spiking moose mortality, but not significant enough to explain a 50 percent decline.
On the Grand Portage Indian Reservation, at the Minnesota-Canada border, Seth Moore, the Chippewa band's chief biologist, has documented similarly stark declines, including a 40 percent mortality rate among radio-collared animals. The 70-square-mile reservation's once-robust population of up to 80 moose has dwindled to fewer than two dozen. This forces Moore to plot a future without the animal that has provided subsistence to the tribe since the early 18th century.
Moose are part of the religious and cultural life of the tribe, and their disappearance would mark a "profound" change in the economic lifeblood of northern Minnesota. "I don't want to think of a world where moose don't exist here," Moore said. "I'm too much of an optimist for that."
Subzero survivor can't take the heat
It will take more than optimism, however, to help moose adapt to what meteorological data show to be one of the most pronounced warming trends in the Upper Great Lakes since the end of the last ice age, when retreating glaciers raked across the landscape creating a "Land of 10,000 Lakes."
Findings from Minnesota's Interagency Climate Adaptation Team show the state has experienced a 1.5- to 2-degree-Fahrenheit average surface temperature increase over the last 100 years, with the greatest rise in the northern reaches of the state, including primary moose habitat.
Such changes are minimally felt by humans and other native mammals such as black bear, lynx and gray wolves, but scientists note that even minor temperature shifts can affect moose, which are adapted to live in the harshest cold and deepest snow.
Although northern Minnesota is on the southernmost edge of the Northwest moose's range, which extends into Canada's vast Nunavut territory, it traditionally provided an abundance of what moose need to thrive. That includes large, contiguous forest tracts with dense stands of fir, spruce and pine trees that provide cover against harsh weather conditions, along with a healthy mix of birch and aspen trees whose bark and tender saplings are the original "moose munch."
While there were once tolerable numbers of the kinds of pests that drive wild mammals crazy -- ticks, black flies and humans -- these pests are proliferating.
Take ticks, for instance. While moose are well adapted to host some native winter ticks, their tolerance for the blood-sucking arachnids is being challenged as the tick population has surged under warming conditions.
Biologists are now documenting individual adult moose with tick burdens of 50,000 to 70,000, a ten- to twentyfold increase over what used to be a normal load. In addition to transmitting diseases, the ticks are irritating the moose, causing them to rub off large patches of hair and even skin, and leaving them greatly weakened from blood loss.
Lenarz said biologists have encountered moose in February and March, both deep winter months in northern Minnesota, with as little as 10 percent fur coverage on their bodies. "The ticks are giving them plenty of grief already," Lenarz said, "And with no hair, if you're trying to survive in a cold climate, you're basically going to die from exposure. So it's a double whammy."
Minnesota's moose are also seeing increased incidence of brain worm and liver fluke, parasites whose transmission is aided by warmer temperatures because the forest is more hospitable to deer, the primary carriers and distributors of the parasites.
Scientists and locals say deer have thrived in the North Woods over the last several decades, in part because of milder winters, but also because their primary forage food, oak and maple leaves and saplings, is migrating northward from the state's more temperate zones.