arctic squirrel
Photo by Alla/

10 incredible facts about animals who hibernate

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As the cold sets in, we’re beginning to bundle up, cook, and freeze massive casseroles, and spend long periods of inactivity marathon-watching television series online. Not surprisingly, our animal counterparts are doing the same. Okay, so the television-watching might be a stretch, but for some mammals and rodents in our Canadian forests it’s time to bunker down for winter hibernation.

Here are 10 incredible hibernation facts of what it takes for some creatures to survive winter in the wild.

1. Animals can survive without oxygen while hibernating. During hibernation, an animal’s body temperature drops, their heart rate lowers, and their breathing rates are reduced by 50 to 100 percent. (Yes, you read that right—100 percent.

2. Animals that are true hibernators wake up every few weeks to pass waste and eat. However, it’s estimated that up to 90 percent of store energy reserves are used for these brief periods of alertness.

3. Arctic Squirrels can lower their body temperature to below freezing during hibernation. In one study, the rodents’ body temperatures were recorded at minus 2.9 degrees Celsius, which may be the lowest core body temperature ever recorded in a mammal.

4. Hibernation can occur during the summer months. Known as “aestivation,” this is a period of animal dormancy, usually by insects, reptiles, and amphibians, which occurs during dry months to retain water and conserve energy.

5. Animals don’t dream during hibernation. During their long winter sleep, an animal’s body is too cold to produce the electric currents related to dreaming. The exception to this rule is the fat-tailed dwarf lemur, the only primate known to hibernate. Unlike their rodent counterparts, they enter long periods of REM sleep.

6. You might have owned a hibernating animal at one point in your life. Both domesticated goldfish and hedgehogs hibernate.

7. Bears don’t hibernate. Unlike “true” hibernators, bears can be easily awoken from their winter lethargy and their body temperature doesn’t drop substantially. However their heart rate does drop from 55 to 9 beats per minute and their metabolism is reduced by 53 percent. They also don’t defecate or urinate all winter long, instead turning urine into protein.

8. Bears give birth and nurse their young while “hibernating.” Wouldn’t it be great to wake up from a deep sleep and to realize that the hard part was already over with?

9. Groundhog Day is actually a fairly accurate predictor of spring. Groundhogs wake up early from hibernation to get a head start on reproduction.

10. Hibernaculum is Latin for “winter quarters” and refers to where an animal hibernates, such as a den or cave. So the next time you’re getting ready to spend your cold Friday night at home watching Netflix, just tell your friends that you’re “hanging out in your hibernacula.”