Deer do not hibernate. They find a warm spot in which to sleep, often under conifer trees. Because the branches of these trees are dense and low to the ground, they shield the deer from wind and snow.
The branches of conifer trees also act as a type of roof that helps hold in heat so that deer can conserve their energy, remain as warm as possible and avoid predators. In the coldest weather, deer gather in groups in areas sheltered by evergreen trees. Deer's fur becomes longer and denser in the winter to help keep them warmer as well.