An ongoing DNR research project looking into the adaptations of deer to winter verifies that these animals are indeed well suited to surviving Minnesota's cold months. These evolutionary adaptations help them to survive the challenging conditions of winter. As long as they maintain ample energy levels, says Del Giudice, the whitetails can survive. The combination of scarce food, deep snow, and cold temperatures requires deer to change their physical makeup and behavior to slow the loss of fat and protein energy reserves. The primary physical change is the long, thick winter coat, which deer begin to grow in late fall.
Late fall is also when deer attain peak body weight.
These reserves of fat and protein help deer through the lean months when food is scarce. Because highly nutritious food is so scarce in winter, deer can't take in much energy. As a result, they maintain the balance of energy needed to survive by decreasing the amount they expend. One method is migrating to dense conifer stands, where thick groves of pine, cedar, fir, and spruce act as gigantic down comforters that block cold winds and retain infrared radiation between the ground and tree canopy. In addition, snow is shallower within the conifer stands, requiring less energy for deer to move about.