Moose population decline continues in northeastern Minnesota
According to results of an aerial survey released by the Minnesota Department of Natural Resources (DNR), the moose population in northeastern Minnesota continues to decline.
Survey results revealed lower moose numbers and the proportion of cows accompanied by calves continued a 13-year decline and dropping to a record low of 28 calves per 100 cows.
“These indices along with results from research using radio-collared moose all indicate that the population has been declining in recent years,” said Dr. Mark Lenarz, DNR forest wildlife group leader.
Moose populations are estimated using an aerial survey of the northeast Minnesota moose range. Based on the survey, wildlife researchers estimate that there were 5,500 moose in northeastern Minnesota. The estimate, while not statistically different from last year’s 7,600, reinforces the inference that the moose population is declining. In addition to the decline in the calf to cow ratio, the bull to cow also continued to decline with an estimated 83 bulls per 100 cows. Aerial surveys have been conducted each year since 1960 in the northeast and are based on flying transects in 40 randomly selected plots spread across the Arrowhead.
A study of radio-collared moose in northeastern Minnesota between 2002 and 2008 determined that non-hunting mortality was substantially higher than in moose populations outside of Minnesota. Lenarz indicated that, “combined with the reduced number of calves, the high mortality results in a population with a downward trend.”
The causes of moose mortality are not well understood. Of 150 adult moose radio-collared since 2002 in Minnesota, 103 have subsequently died, most from unknown causes thought to be diseases or parasites. Nine moose died as a result of highway vehicle accidents. Two were killed by trains. Only six deaths were clearly the result of wolf predation.
Analyses by Lenarz and other scientists have indicated a significant relationship between warmer temperatures and non-hunting mortality. “Moose are superbly adapted to the cold but intolerant of heat,” said Lenarz, “and scientists believe that summer temperatures will likely determine the southern limit of this species.”
As recently as the 1980’s as many as 4,000 moose inhabited northwestern Minnesota, an area of agricultural land interspersed with woodlots. The population declined dramatically during the 1990s and currently numbers fewer than 100 animals. In contrast, the northeastern population occurs in wetland-rich forested habitat which presumably provides thermal cover in a warming environment.
In August, a Moose Advisory Committee convened by the DNR released their findings which will be used in the development of a legislatively-mandated research and management plan. They indicated that while climate change is a long-term threat to the moose in Minnesota, moose will likely persist in the state for the foreseeable future. The plan should be ready later this spring and will be open to the public for comment.
The Fond du Lac band of Lake Superior Chippewa and 1854 Treaty Authority contributed funding and provided personnel for the annual survey.
A copy of the aerial survey report is available online.