Increased daily temperatures and climate change are one idea of why the moose are leaving Minnesota or dying off. Although the direct relation is still unknown, according to an article by the Minnesota Department of Natural Resources, humidity levels have a direct correlation with moose survival. Moose can become heat stressed in both summer and winter, which in turn puts stress on their immune systems. Moose populations where there are ocean currents, including Scandinavia, and less humid air have a higher survival rate.
An increase in the number of wolves may also play a role in why the moose population is dwindling. Wolves prey on moose, especially in areas where white-tail dear aren't abundant. While the wolf population is increasing, the deer population is declining due to hunting and other factors. Wolves are turning to moose to supplement their diets.
Moose are dying from multiple causes from accidents with vehicles to a combination of factors from malnutrition to parasites. Deer can carry diseases and may be a factor in spreading brainworm and other parasites that may contributing to mortality of the moose. The term "Tipover Disease" has become a common way of referring to moose mortality due to the moose just tipping over and dying.
According to the Minnesota Department of Natural Resources, cow/calf ratios need to be above 20 percent to maintain the population level of moose. In northwestern Minnesota, where the moose are disappearing at the highest rate, pregnancy rates are almost 40 percent lower than heavily populated areas of moose, including Alaska. A combination of infections and malnutrition may be to blame. Calf life expectancy is also lower as climate changes, malnutrition and disease are more detrimental to young calf than older moose.
