Make it nine straight years. According to the Minnesota Department of Natural Resources (DNR) northeastern Minnesota moose survey, the moose population has remained relatively unchanged.
However, the report notes that reproductive success, a key factor for moose survival over time, remains low.
The 2020 winter aerial moose survey estimated 3,150 animals (between a range of 2,400 and 4,320 animals). Although the 2019 estimate was 4,180, because of the statistical variance in the moose population, the estimate “does not suggest a decline from last year’s estimate.”
Conducted from January 6 to January 17, 2020, the survey involved flying in 52 survey plots (out of 436 survey plots on the grid) distributed across northeastern Minnesota’s moose range over an area of 5,985 miles (almost 4 million acres). While the count is statistically sound, there is inherent uncertainty associated with it, because researchers will never see and account for all of the animals across the 6,000-square-mile survey area.
Of the 308 moose observed, there were 131 bulls, 138 cows, 37 calves and two unclassified adults.
The calf to cow ratio of .036 is similar to the 15-year average since 2005. Calves were 12 percent of the 308 total moose observed and represented 18 percent of the population.
The survey suggests that calf survival from birth in spring to January continues to be relatively stable but consistently low. Field studies have shown survival rates are even lower by spring, translating to small numbers of moose calves living through their first year.
One finding of the DNR’s field research shows that wolves have consistently accounted for two-thirds of the calf mortality and one-third of adult mortality. Moose injured in attacks by wolves also died because of their injuries, and moose that were sick or suffering from disease were more susceptible to attacks by wolves.
The annual population survey is the most critical aspect of DNR moose management. Tracking moose numbers and determining the gender and age makeup of the population allows the DNR to closely monitor the health and well-being of moose.
In 2012, the DNR made nine forested areas a permanent part of the moose survey. These areas include different types of forest, including forests disturbed by events such as wildfires, blow-downs, and timber harvests.
Higher population counts within specific regions may indicate that moose prefer certain types of habitat. The DNR and its partners can use this information to better target current and future habitat enhancement projects to provide better conditions for long-term moose survival in Minnesota.
While the survey is statistically sound, there is inherent uncertainty associated with such studies, because researchers will never see and count all of the animals across the 6,000 square mile survey area.
Each year the population estimate is compared to 2006 because the state’s highest moose population estimate of 8,840 occurred that year.
Reproductive success and adult survival have the most significant impact on the annual aerial count. The 2020 study noted “although we know from recent field studies that fertility (pregnancy rates) of the population’s adult females has been robust, overall, survey results indicate calf survival to January 2020 remains low, typical compared to most years since the population decline began following the 2006 survey.”
Over the years, predation has been consistently the leading cause of calf mortality. During the 2013-14 and 2014-15, wolf and black bear accounted for 66 and 16 percent of the calf mortality.
In 2015-2016 and 2016-17, wolves and black bears caused 69 percent and 15 percent of the calf mortality.
The study went on to say, “But it is also important to note that adult moose survival has the greatest long-term impact on the changes in the moose population.”
DNR wildlife research is in its eighth year of an extensive study to determine how winter nutrition affects moose survival and reproductive success. One method for collecting information about a moose’s winter diet is to take urine samples. It’s a good way to find out what they are eating without interfering with the animals, the study notes.
Since 1960 the DNR has conducted annual aerial moose surveys each year in northeastern Minnesota. Adjustments made to the survey in 2005 made it more accurate and its yearly results more comparable from 2005 to the present.
The Fond du Lac Band of Lake Superior Chippewa and 1854 Treaty Authority again contributed funding and provided personnel for the annual moose survey.
More information about moose is available on the DNR website at mndnr.gov/moose
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