What happens when animals hibernate during the winter?

Lots of arctic animals, including bears, woodchucks and chipmunks, hibernate through the cold winter months.

During hibernation, these animals aren't sleeping. Instead, their heart rate, body temperature and breathing rate slow way down. This helps them conserve energy, which means they can stay inside instead of going out in the cold to look for food.

North American black bears have heart rates as slow as 14 beats per minute in the winter, according to a study from the University of Alaska in Fairbanks, a huge drop from their normal BPM of 55.

Woodchucks' heart rates fall from around 80 BPM to just 5 BPM during hibernation. Chipmunks usually have a heart rate of 350 BPM, but in hibernation their hearts beat only 4 times per minute - just once every 15 seconds. They seem hardly alive, but they are.

To understand just how slowly a hibernating animal's heart beats, compare it to your own. With your finger, find your own pulse - you can find it on the back of your wrist or at the base of your throat.

Once you find your own steady beat, set a timer for 15 seconds, then count the pulses. Multiply that number by 4 and you have your own BPM rate. (For most kids, it's between 60 and 110.)

Imagine if your own heart beat only 14 times a minute instead of more than 60, and you can understand why hibernating animals are so sluggish through the winter. But this process allows them to survive until spring, when it's safer and easier to find food to fuel their bodies.

Comments: molly.duffy@thegazette.com