These Are the North American Animals Using Hibernation to Their Advantage

When an animal hibernates, it goes into a state of sleep or minimal activity. Hibernation allows many animals to survive winters, which are dark and cold, without having to migrate elsewhere or search for food under the threat of predation, injury, or death.

The most popular images that come to mind of animals that hibernate are bears, ground squirrels, and chipmunks. There are plenty of other animals that hibernate, though. Read on to learn more about the North American animals that hibernate and how they do so.

Types of Hibernation

Hibernation has become a catch-all term for any state of inactivity during certain seasons, but there are specific terms depending on the type of animal hibernating.

“Hibernation” refers mainly to warm-blooded animals. Brumation refers to cold-blooded animals becoming dormant during the winter. Estivation refers to cold-blooded animals becoming dormant during the summer.

Additionally, some animals are known to be able to survive without oxygen while hibernating. Animals that are known as “true hibernators” may wake up every few weeks to either eat or pass waste.

Winter Hibernation vs. Summer Hibernation

Hibernation is an especially popular survival tactic for animals that live in areas in North America with harsh winters, so we typically think of animals hibernating during the winter. Believe it or not, there are some animals that hibernate during the summer. Hibernation during the summer is called estivation or aestivation.

Hibernation vs. Torpor

Sometimes, there’s a difference between hibernation and torpor, although they are often used interchangeably. Hibernation involves entering a deep sleep, during which the animal does not wake up under normal conditions. Torpor, on the other hand, is a state of inactivity and deep sleep in which the animal can wake up if disturbed.

For this reason, some animals are said to be “true hibernators” to distinguish between those that seem to be dead (but still periodically awaken for basic needs) and those that do not. Let’s take a closer look at the North American animals that experience hibernation and torpor.

Mammal: Bat

Many mammals hibernate, including woodchucks and hedgehogs. But the bat is a North American mammal we don’t tend to think of as hibernating. Some bats choose to migrate to warmer areas, but most in the northernmost and mid-latitudes hibernate. Even before they hibernate, many species have to migrate to their hibernation sites in the northern United States and Canada. They can do so as early as September, hibernating with tens of thousands of other bats in caves with temperatures between 32 F-49 F.

Compared to bears and other animals, bats are one of the few true hibernators. A hibernating bat’s breathing is not noticeable, and its body is cold to the touch. Its heartbeat goes from 400 beats a minute while awake to 25 while in hibernation. Even so, bats must wake up from time to time to urinate, drink, or move to a cooler or warmer spot in the cave. They drink from the condensation on their fur or the cave walls.

Crustacean: Hermit Crab

Barnacles and hermit crabs are examples of crustaceans that hibernate. The hermit crab is a popular pet in North America. Although it lives in tropical climates with wet inland areas in the wild, it hibernates when the temperature drops to below 68 degrees F. If the temperature falls below 62°F, it will die. During this time, it hides in caves or tree roots.

As a pet, it buries itself in the cage substrate and often hibernates while molting. Hibernation can go on for several weeks or even months at a time. Hermit crabs still periodically eat and drink water while hibernating.

Amphibian: Salamander

Amphibians kept indoors as pets don’t have to hibernate, but some species need to be dormant before reproducing. They hibernate when they need to live through frost and flood, and the salamander is no exception. In order to survive the deep freeze of winter, this adaptable creature has learned to live in areas where the lower layers of the soil are permanently frozen, also known as permafrost.

Young salamanders hibernate in vegetation or rotten tree roots at temperatures no lower than 5 degrees F, and adult salamanders as low as 22 degrees F. Remarkably, the salamander can become completely frozen while hibernating. It beats even the frog, which can survive having up to 65 percent of its body water frozen.

Reptile: Crocodile

Many reptiles hibernate. However, hibernation for reptiles is called brumation. The difference is that reptiles still drink water, although they don’t eat, and they prepare by building up both fat and sugar reserves. They also don’t need as much air compared to when they are awake.

The American alligator, found in the southeastern United States, enters a state of brumation in response to cold winter temperatures, not to avoid drought in the summertime. Crocodiles in North America do not typically brumate.

Worm: Earthworm

The earthworm relies on moisture in the soil to live. It is also cold-blooded and cannot regulate its body temperature. When the soil gets too dry during the summer or winter seasons, it enters a state called diapause to survive.

It does so by wrapping its body into a tight knot to minimize the amount of body surface exposed to the dry soil, as well as secreting a layer of mucus to protect itself from drying out. It then returns to normal activity when the temperature improves.

Gastropod: Snail

The snail is another cold-blooded animal and so likewise cannot control its body temperature. When the temperature drops below 12 to 15 degrees F, which can happen anywhere from mid-October to early November, it hibernates.

It enters a state of anabiosis, or suspended animation, for four to six months. As an example of how a snail may prepare, the grape snail collects and stores limestone during the summer. When it’s ready to hibernate, it buries itself in the ground and seals its shell with a piece of limestone.

Bird: Poorwill

It’s true: almost all birds have adapted methods for surviving winter other than hibernation, such as migration. However, one species defies this rule: the Poorwill. Instead of migrating to warmer areas, it enters a state of torpor during the winter, which is when the flying insects it feeds on become scarce.

It first prepares by eating far more insects than usual before winter comes. Hibernation can last anywhere from several weeks to several months while it hides in a patch of grass or a hollow log. Its breathing decreases up to 90% or 10 beats per minute, and its body temperature decreases down to 40-65 degrees F. This is a stark contrast compared to its normal state, in which its heart rate is 130 beats per minute and its body temperature is 106 degrees F.