The first year of a landmark study found higher mortality rates than normal and listed several causes. Researchers say more work is needed.
A bull moose, sprouting the bumps of new antler growth on its head, grazed in a swamp off the Gunflint Trail in northeastern Minnesota — possibly one of the lucky ones in a declining population. One season of a high-tech study showed that the adult death rate was 18 percent; for calves, it was 71 percent.
It’s tough to be a moose in Minnesota.
The deaths of 54 that were tracked as part of the biggest and most high-tech research study ever conducted on moose provide a rare glimpse into the harsh life they face in the wild and help explain why they are rapidly disappearing from Minnesota’s North Woods.
By far the greatest number, primarily calves, were killed by bears and wolves. A number were abandoned by their mothers; one drowned. Three adults died from massive infestations of winter ticks, and others succumbed to deer-related parasites and infections.
Researchers said one season’s worth of data from about 150 collared moose is not enough to illuminate trends or to provide solutions in how to help them rebound. But it’s clear, they said, that more are dying than is normal.
Calves suffered a 71 percent mortality rate after only one summer, said Glenn DelGiudice, the wildlife researcher for the Minnesota Department of Natural Resources who is running the calf research portion of the study.
And the ones that made it so far still have to survive their first winter.
Moose need a mortality rate of 50 or 55 percent in the first year of life to maintain their population, DelGiudice said.
The adult death rate was 18 percent, said Michelle Carstensen, who is running the adult research for DNR. If that rises to 30 percent in the winter, as expected, “that’s not sustainable,” she said.
The number of moose in Minnesota plummeted by one-third last year, double the rate of previous years.
Results of the annual aerial moose survey conducted in January indicated that 2,760 moose were left, down from 4,230 in 2012.
In 2006, the population in the northeastern corner of the state peaked at 8,840, but by then moose had already largely disappeared from the northwestern corner of Minnesota, where they had long been part of the landscape.
The sharp decline adds new urgency to the effort to understand why moose are dying in such numbers. So far, the project has been funded for two years with $1.2 million from the state, tribes and the University of Minnesota Duluth.
Now researchers are hoping for another $750,000 from the state in part to determine how much of an impact global warming may have on the moose population.
Researchers want to attach devices on 30 moose that measure ambient and body temperatures to determine whether heat stress from higher average summer temperatures is playing a role in their demise.
A number of other studies have shown a connection, but none actually have provided the biological evidence, DelGiudice said.
103 adult moose collared
In the first year of the study, wildlife crews found and collared 103 adult moose with GPS devices that track their every movement.
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