Science

That was my first thought.

A bear hunkered down in its winter den is in a different state of energy conservation than hibernation. Instead, bears enter a state called torpor (the adjective for which is torpid).

Unlike hibernation, torpor is involuntary, and primarily triggered by lack of food. This state is also found in other groups of mammals like marsupials, and even in some birds that depend on summer insects.

Another difference between torpor and hibernation is that torpor is a continuous low-energy state, without arousal periods when the animal’s activity spikes.

Torpor is primarily found in black and brown bears. That’s largely because these bears are omnivores with a preference for plants.

You might think that polar bears, living in harsh Arctic conditions, would enter torpor for longer than other bears, but most remain active all winter. Once again, it all comes down to diet.