Minnesota Moose: Researchers Reveal What's Causing Population Declines

Wildlife researchers are on the brink of discovering what is killing Minnesota's moose and causing drastic population declines. A new report from the state's Department of Natural Resources (DNR) suggests it is a combination of health issues and increased predation. 

After three years of monitoring live adult moose via satellite, retrieving them as soon after death as possible and carefully examining their remains, wildlife biologists have been able to narrow down specific causes of death. The department captured and fitted a total of 173 moose with GPS radio collars. Of the 47 moose that died, their preliminary analysis shows two-thirds succumbed to various health issues, while the other third were likely killed by wolves - 25 percent of which had illnesses that made them easy prey.

Some of the various illness found among the dead moose include brainworms, winter ticks, bacterial infections, liver flukes and severe malnutrition.

"I think the DNR has come a long way in three years and done a good job of answering a lot of the unknowns we had from some earlier moose studies and what the causes of mortality are," Mike Schrage, wildlife biologist for the Fond du Lac Band of Lake Superior Chippewa, which has been involved in much of Minnesota's moose research, said in a statement. "I think they've done a good job of getting at some of the interplay between health issues and wolf predation."

However, project leader Glenn DelGiudice notes their results are preliminary and it'll be about six years before the department has enough data to determine long-term mortality trends and causes.

The DNR originally launched the project following reports of a long-term decline, from an estimated 8,840 in 2006 to 3,450 last winter. Results of the 2016 winter survey are expected to be released in late February. 

Considering that wolves killed a relatively small percentage of the tagged moose, researchers are most concerned about the illnesses, and particularly how winter nutrition affects a moose's health. For example, urine samples collected from snow packs indicate the animals experience heat stress during the winter, meaning moose aren't getting enough food and eventually succumb to health problems, weakness or wolves. Therefore, winter nutrition could be the key to the state's moose decline. 

"In summer, moose can go to ponds or streams to cool down when they get too warm. In winter, moose can only lie in the snow and shade, which offers less cooling," DelGiudice said. "When air temperatures reach 23 degrees in winter, moose can begin to experience heat stress, increasing their metabolism, heart rates and respiration."

Researchers will continue tracking the remaining 74 adult moose with working collars and hope to recover data from another 20 collars that stopped working. 

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