This Week In Zoology: Bears Don’t Hibernate


When our Animal Physiology Professor started one of our lectures with this revelation, the entire class was floored. Bullshit! Of course bears hibernate! An entire childhood full of cartoons and kids books couldn’t possibly be wrong, could they?

Well, the reason for this misconception is that bears sort of hibernate. What they actually do is go into torpor. Like hibernation, going into torpor also involves reduced body temperature and metabolic rate. Like hibernation, torpor is used to survive a period of suboptimal conditions, generally due to a scarcity of food and low temperatures. Some small animals even go into daily torpor, allowing them to survive certain parts of the day without the need to constantly search for food or maintain an optimal body temperature.

Well, this all sounds an awful lot like hibernation, doesn’t it? So what is the real difference between torpor and hibernation?

According to the old school Zoologists who taught us, the difference between the two is the ability to wake up under certain conditions.

Normally, animals will come out of their hibernating state due to temperature and/or light cues, which indicates to them that the harsh conditions are over. However, animals who go into torpor can also wake up for other reasons. If you go poking around a cave with “hibernating” bears, and disturb them sufficiently, they will wake up, despite the weather conditions not being favorable to them. True hibernators, like hedgehogs, won’t wake up if you just poke them in the face, but rather require cues that indicate that the season has changed.

This is unfortunate for the poor hedgehog, as it seems to be one of the causes of their demise in Britain. When people rake the leaves off their lawns in the Fall, many hedgehogs seem to feel that a nice big pile of leaves is the perfect place to hibernate for the winter. Once that pile then gets destroyed, or set on fire, the poor dears cannot wake up and run for it, and so are killed in the process.

So, if you live in an area inhabited by hedgehogs and have a lawn, check it before you get rid of it your leaves! Of course, there are also excellent reasons to just let the leaves be, but I’ll let you be the judge of that.

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