Mamma bear and cub, all cozy and cuddling, while snowflakes float gently and everything is quiet. In the wintertime bears enter something called "torpor", not hibernation. "The main difference between hibernation and torpor is during torpor, the animal is able to wake up quickly to avoid danger, or if the opportunity exists exit the den to feed. Waking expends energy and involves violent shaking and muscle contractions, much like shivering. The energy lost is offset by how much energy is saved in the torpid state. Females bears awaken from torpor to give birth."