6 Animals That Hibernate During the Winter
Winter's chill makes us all want to cozy up for a big nap. Here are six animals that survive the year's more brutal months through hibernation or similar states of dormancy.
The final stretch of the year can be exhausting. This is more literal for some species than for others. For a wide swath of wildlife, the winter months translate to cold weather and a lack of readily available food, making survival a tricky business. Enter hibernation.
Hibernation is a type of dormancy, a period when an animal's system switches to a slowed bodily state. True hibernation is characterized by a slowed heart rate, a reduction in metabolic activity, and a lowered body temperature. Animals prepare for hibernation—specifically facultative hibernation, meaning determined by environmental factors like weather—by consuming a surplus of food to create a warming and energy-offering fat layer (this is why we have Fat Bear Week). Others favor obligate hibernation, which centers on internal rhythms.
Though perhaps the most commonly known of all dormancies, hibernation is not the only nap game in town. Reptiles rely on aestivation or brumation, for example, and torpor is another sleepy state. Still, the goal is always the same: slow and conserve for the sake of survival.
Here, animals that hibernate during the winter months. Aka prefer extra-long naps, just like us.
6 Animals That Hibernate
As it turns out, bears are not true hibernators. This discrepancy is due to a maintenance of body temperature, a comfier state that characterizes their dormancy as closer to a lighter sleep called a torpor.
To prepare for the extended sleep, bears do some binge eating, consuming up to 20,000 calories per day. After that, the mammals can chill in their dens for up to seven months.
2. Arctic Ground Squirrels
Arctic ground squirrels can go into hibernation for up to three weeks at a time.
The squirrels will wake between hibernation states, shivering for one to two days to return their little bodies to normal temperatures (during torpor, the rodents can decrease their body temperature from 99 to 27 degrees) before falling into another period of deep (and extremely chilly) sleep.
Many species of frogs hibernate to make it through the winter. Aquatic frogs hibernate underwater, while terrestrial frogs take their naps on dry land.
Fun fact: stores of glucose in the frog's vital organs prevents the tiny amphibians from freezing.
Bats like naps. The winged mammals enjoy hibernation or torpor states of various lengths depending on their needs, from a few hours to a month—or, in the case of the little brown bat, six months.
The caves and crevices in which bats choose to hibernate are called hibernacula (which sounds a lot like another bat-adjacent noun).
Reptiles like snakes weather winter through brumation, which is a forced state caused by the cold. Once the weather warms, snakes—and their internal systems—essentially defrost so they're free to slither freely once again.
Groundhogs—aka woodchucks, the little rodents whose shadows are said to herald spring—are among the only true hibernators!
During their months-long naps, a groundhog's temperature drops significantly, its heart rate slows from 80 beats per minute to five, and its breathing slows. Still, the well-fed animals won't lose more than a quarter of their body weight thanks to the reduction in metabolic action.
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