Hibernation is an amazing physiological feat that is necessary for animal survival. Bears are the animals most known for hibernating, but they aren’t the only ones. Turtles, snakes, wood frogs, and groundhogs are other animals that engage in some form of hibernation, torpor, or estivation.
Take a look at some of the animals that like to hide until spring arrives.
Fat-Tailed Dwarf Lemur
The fat-tailed dwarf lemur is the only primate known to engage in a combined hibernation and torpor state for an extended period of time. Endemic to Madagascar, the nocturnal lemur hibernates during the dry season when water is scarce. During this hibernation, fat-tailed dwarf lemurs also engage in periods of warming and increased heart rate.
Box Turtles
As reptiles, turtles are ectothermic, meaning that they can’t produce their own body heat and instead receive heat from the environment. To save energy, it’s important for turtles to brumate when temperatures start dropping.
Like hibernation, brumation is a period of inactivity during winter. Unlike hibernation, however, brumation does not involve sleep. It varies from one turtle species to another, but box turtles generally dig a nice hole and brumate during winter for a few months.
Groundhogs
Traditionally relied upon to predict the weather, groundhogs (or woodchucks as they are also known) are true hibernators. The hibernation period can last up to five months, and during that time, a groundhog will lose as much as a fourth of its body weight. During hibernation, their heart rates go from 80 to 100 beats per minute to only five or 10, their body temperature decreases from 99 to 37 degrees, and their breathing slows dramatically from 16 breaths per minute to just two.
Common Poorwill
The common poorwill has the distinction of being the first documented hibernating bird. Reduced food supply and harsh temperatures cause the common poorwill to hibernate. While other birds migrate or enter brief states of torpor like the hummingbird, the poorwill can be in a torpid state for several months. During torpor, the bird has a reduced breathing rate, lower body temperature, and a reduced heart rate.
Hedgehogs
Toward the end of autumn, hedgehogs enter a state of torpor. In preparation, they look for the best places to build their nests, usually in a big pile of leaves or underneath old buildings or sheds. Hedgehogs tend to awaken during hibernation, as often as every two to four days, or as infrequently as once per month. When hedgehogs wake up during torpor, they may relocate to a new nest.
Wood Frogs
If it’s late winter or early spring and you find a frog that’s not moving, it might be a hibernating wood frog. During hibernation, the wood frog’s heart actually stops beating and 35 to 45 percent of its body becomes frozen. Wood frogs actually go through a freeze and thaw pattern several times during the winter. In the spring, the frogs thaw and begin the feeding and mating process all over again.
Snails
Not all snails hibernate, but when they do, it’s an interesting process. Snails hibernate any time the weather is extreme: in hot weather, when the process is known as estivation, and in cold temperatures. Since they come equipped with a built-in hibernation spot, they are ready for all weather conditions. During hibernation and estivation snails can use mucus to seal their shells and protect themselves from the elements. Depending on the species, snails can hibernate for as long as several months.
Skunks
Skunks are not true hibernators, but like hedgehogs, they may enter a state of torpor. For those in northern areas, skunks have longer periods of torpor, lasting a few months; in more southern regions, the period of dormancy is much shorter. During a torpid period, skunks will spend more time in their dens, waking occasionally to search for food. They will also breathe more slowly and have a lower temperature and heart rate.
Snakes
Nearly all snakes will experience some form of brumation (hibernation for cold-blooded animals), though the length of dormancy depends on location. For instance, a snake in Minnesota might hibernate for months, while one in southern Texas might only go a few weeks. Snakes take their cues from their surroundings; when the daylight hours become shorter, they are aware that winter is coming. During brumation, snakes experience periods of wakefulness when they’ll travel outside of their resting spot to hydrate.
Bumblebees
Not all bees hibernate, but bumblebees do. The bumblebee life cycle begins in the spring, when the queen bumblebee emerges from her winter underground hibernation. The queen lays broods of worker bees first, followed by new queens and male bees. At the end of the cycle, the old queen and worker bees die. The new queens feed heavily, dig underground hibernation spots, and the cycle begins again.
Bats
Bats go into a state of torpor when temperatures get cold and they need to conserve energy. Torpor in bats can last from a couple of hours to a month. During this time, the bat’s heartbeat can go from 200 to 300 beats per minute down to as few as 10. In order to rewarm themselves from torpor passively, bats sometimes use energy from the sun.
What Happens During Hibernation?
Animals hibernate to survive winter months, mostly to keep warm and conserve energy during periods of water and food scarcity. During this “deep sleep”—not exactly a sleep—most of an animal’s bodily functions will slow down significantly, by about 98%, or stop entirely. This includes its heartbeat, breathing rate, and metabolic activities. Its body temperature will also drop to reduce the animal’s need for calories.
