Most everyone knows that bears hibernate in the winter. But polar bears spend the winter hunting for food. So, do polar bears hibernate?
The short answer is: not really. Hibernation usually entails a dramatic reduction in metabolism and heart rate, and this state is not found in the polar bear.
In the late spring and throughout the summer, after the bears have come off the ice, they will become lethargic as air temperatures rise. This serves two purposes – to prevent overheating (remember, they have usually put on a large amount of fat which serves to insulate them), and to prevent burning of precious calories that they will need to see them through the rest of the summer and fall until they can begin seal hunting again when the sea ice forms. They will often dig into a bank along the shore to stay cool. Since this lethargic state does entail some drop in metabolic rate (again, to preserve calories), it has been called walking hibernation. But to be clear, it is not true hibernation.
However, pregnant females come closest to the concept of hibernation when they enter the den in late fall to give birth. During the time the fetus is developing in her womb, she will not eat, drink or defecate and she becomes very quiet. But again, like walking hibernation, discussed above, her reduced activity doesn’t meet the true criteria of hibernation.
Do polar bears hibernate? To sum up, no, but they are able to slow some of their biological processes in order to conserve stored calories between hunting seasons.
For one of the best works on polar bear adaptations and evolution, read Canadian polar bear researcher Dr. Ian Stirling’s book Polar Bears. You can find the book on Amazon – clicking on the link below will open in a new window.