Deer are built with long, slender legs that allow their blood vessels to touch each other, according to AniLogics. That's just one of their clever adaptations to keep them warm. The cold blood returning from the legs to the body core is heated by warm blood that's leaving the body core. That saves the deer energy since it won't have to warm up that blood, says AniLogics.

Deer also up their insulation in preparation for winter. In the summer and fall, they start holding on to more fat and storing it around their internal organs and under their skin to provide energy reserves when they need it, according to North American Nature. They also shed their summer coats and grow a winter version with thicker, longer hairs called guard hairs, according to TuftsNow. In addition, the animals grow a thicker undercoat for the winter months, and special oil-producing glands give them a natural raincoat by making their coats water-repellent.

ncG1vNJzZmivp6x7qL7Up56eZpOkunB9j3FtbXFoZMSpsdGeZJ2nXZmypr6MrKOenaBitq9506GcZq%2BZo8Gmvo4%3D