Bears are the only mammals that don’t pee or poo during their winter hibernation.

The U.S. National Park Service confirms that bears do not urinate or defecate during their winter hibernation.

The U.S. National Park Service confirms that bears do not urinate or defecate during their winter hibernation.Grizzly bears and black bears hibernate in winter during which they generally do not eat, drink, urinate or defecate. Their body fat is metabolized to produce water and food, but instead of defecating or urinating to eliminate waste, they recycle it. Other mammals awaken every few days to raise their body temperature, move around, urinate, and eat.

Black bears in Sierra usually den from mid-December through March or early April. If sufficient food is available, bears don't den and remain active throughout winters while others would hibernate and leave the den at various points throughout the winter.