What's the difference between hibernation and torpor?

While we’re in the middle of winter, many animals are spending their time sleeping through it. Most of us think about animals hibernating during the winter, however, that’s not what all animals do. Some animals enter a state called torpor instead of hibernation. What’s the difference?

Torpor is similar to hibernation, but it doesn’t last as long. It’s a shorter term, daily sleep in which their body temperature, heart rate, and metabolism drops. It’s influenced by food availability and the climate.¹ While in torpor, animals can wake up fairly easily if they need to, like if there’s a threat or they need to give birth.²

Hibernation on the other hand, is a much longer period of time. In fact, when torpor lasts longer than 24 hours, it’s considered hibernation.³ It’s influenced by daylength and hormonal changes.¹ Their body temperature, heart rate and breathing drop very low to help them survive the winter.² Hibernation isn’t for the entire winter though. Animals will wake up every few weeks in order to drink water and release waste.¹

Animals enter these states to help them survive the winters where the weather is harsh and their food sources are scarce. Normally, they have very high metabolism rates to maintain their body temperatures. This uses a lot of energy. In order to conserve energy and survive the winter, they’ll eat more leading up to this time of year and become less active. 

Sources & Further Reading:

1. https://scottishwildlifetrust.org.uk/2013/01/torpor-or-hibernation/

2. https://www.scienceworld.ca/stories/do-bears-actually-hibernate/

3. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/torpor