Minnesota moose herd stable but still down
Mike Schrage / Special to Forum News Service
A large bull moose runs through the snow near Swamp River in Cook County in northeast Minnesota during January's aerial moose survey of northeastern Minnesota. Moose numbers have remained relatively stable in recent years but are still far below numbers of a decade ago and show no signs of improving.
ST. PAUL — Minnesota's troubled moose population remains in the dumps, with only about 3,710 animals according to the annual winter survey by the Minnesota Department of Natural Resources and tribal resource agencies.
The DNR on Monday released the results from the helicopter survey of random sects of the moose range in the state — namely St. Louis, Lake and Cook counties — showing the population has remained relatively stable since 2012.
That stability, a statistically insignificant drop from the 4,020 estimate in 2016, is the good news.
But the bad news it that the population is still down 58 percent from the 8,840 moose estimated in 2006.
While the big, annual declines of a few years ago seem to have slowed, there's no sign the population can rebuild itself to traditional levels, DNR scientists said.
"At this point, results do not indicate that moose are recovering in northeastern Minnesota," said Glenn DelGiudice, DNR moose project leader. "While it is encouraging to see that the decline in the population since 2012 has not been as steep, the apparent stability does not allow us to forecast the direction of the population's trajectory into the future."
Trying to count moose from helicopters is hard enough, and extrapolating a few selected survey areas to the entire moose region is even more difficult. But the DNR says it is 90 percent certain that the population estimate is somewhere between 3,010 and 4,710 moose.
Scientists for the past decade have been trying to find out why moose declined so rapidly in the northeast. That decline followed a complete collapse of the state's northwestern moose herd 15 years ago. They have focused on several key factors, including the impact of warmer temperatures on moose nutrition and moose parasites. Other issues include disease, a fatal brain worm spread by deer (which have thrived farther north in moose territory thanks to lesser snowfall) and predation by wolves and bears, especially on moose calves.
Other scientists have looked at moose habitat, especially what food is available, noting moose numbers have actually gone up significantly in a few areas where big forest fires occurred in recent years. The highest moose numbers in the Boundary Waters Canoe Area Wilderness now are found where the Pagami Creek, Ham Lake and Cavity Lake forest fires occurred in the past decade. Those fires regenerated the forest and that new growth makes for perfect moose food.
Meanwhile, research also suggests the recent signs of stability could have resulted from higher calf survival in recent years. But the DNR says it's clear that infections, parasites and other health issues are making adult moose sick, leaving them vulnerable to wolves.
Studies have shown that adult moose survival has the greatest long-term impact on changes in the size of moose populations. In Minnesota, survival of adult moose remained between 85 and 88 percent from 2014 to 2016, up from 81 percent from 2002 to 2008 and 81 percent in 2013.
"The research shows the adult mortality, or survival, is what drives the population. That said, having more calves to later become adults certainly wouldn't hurt our situation," said Mike Schrage, wildlife biologist for the Fond du lac Band of Lake Superior Chippewa and a leading moose researcher in the state.
Schrage said the lack of more big fires inside the Boundary Waters Canoe Area Wilderness and a decline in large-scale logging outside the wilderness, have helped keep moose numbers low.
"Even if we solved climate change, even if we didn't have deer causing problems for moose, or wolves taking calves, I think we have a serious problem with a decline in overall moose habitat," Schrage said. Outside the Boundary Waters Canoe Area Wilderness "we need more logging that resembles fire — big areas with lots of trees removed, but also with lots of trees and patches (of standing trees) remaining."
Annual aerial moose surveys have been conducted each year since 1960 in northeastern Minnesota. Adjustments were made in 2005 to make the survey more accurate and annual results more comparable.
From Jan. 5 to 14 this year, researchers flew over 52 survey plots, each 13 square miles, across northeastern Minnesota. The Fond du Lac Band of Lake Superior Chippewa and 1854 Treaty Authority contributed funding and provided personnel for the survey.