Jason E. Andersen

I learned something this week that shook the foundation of my childhood education:

Bonus Fun Fact: Bears don’t really hibernate.

No, seriously, they don’t. Sure, they take long naps during the winter, but it’s not true hibernation — it’s a state called torpor. Torpor is a low energy state that some animals can enter to survive poor environmental conditions. They enter a deep sleep where their breathing and heart slows down, allowing them to use less energy. Lots of animals use torpor as a survival method including insects, rodents, some birds, fish, and (apparently) bears.

“But Jason, what you’re describing sounds just like hibernation!” Yes, I would agree with you, they do sound quite similar. The difference between hibernation and torpor is, mostly, a) how quickly a creature can rouse from their sleep and b) their body temperature while they are in that state. Creatures that hibernate are nearly impossible to wake during their slumber and have significantly lower body temperature, due to incredibly decreased breathing and heart rates. Hibernation is basically a controlled hypothermia that keeps the creature just warm enough to not freeze to death. There are not many animals that truly hibernate.

Torpor, on the other hand, is more like sleep as we know it, but much deeper. The creature’s body temperature is maintained closer to their normal and they are much easier to rouse. If you hike in the woods and fall into a bear den, the bear might wake up and be very displeased to see you. Creatures in torpor also rouse when the conditions improve, which happens more often with climate change (and is becoming a worry for some species). 

Like most things in biology, there often isn’t a single answer and it’s generally way more complicated than you think it should be. Why would bears be any different?