Animals that hibernate: 10 representatives of the fauna that enter winter slumber.

The classic image of hibernating animals is bears. However, many other members of the animal kingdom also escape the cold, food shortages, and lack of water.

What is hibernation? The animal website The Dodo refers to this state as torpor (hibernation), during which life processes slow down to minimize energy expenditure for survival. The publication Tree Hugger considers this an excellent adaptation that enables survival.

Publications like The Dodo, Tree Hugger, the educational site Better Planet Education, and the wildlife magazine Knowable Magazine regard bears as the most famous hibernators. However, in Southeast Asia, where it is always warm and food is available year-round, bears remain active throughout the year and do not hibernate.

During hibernation, bears' breathing and metabolism slow down by 75%. Females can sustain a couple of cubs during this time using their own reserves.

Bats have been included in the list of hibernating animals by The Dodo, Tree Hugger, and Better Planet Education. These animals inhabit almost all continents and many climate zones, resulting in significant variability in their hibernation patterns. In colder temperatures, some can sleep for a month, but most enter a prolonged seasonal hibernation lasting up to 8 months.

In this state, metabolism and breathing rate decrease. Heartbeats slow from 200–300 beats per minute during active life to 10 beats per minute during hibernation. Bats conserve energy by resting in a hanging position, clinging upside down with their claws. As temperatures warm, bats sunbathe to warm up.

On the island of Madagascar, among endemic lemurs, three species hibernate, including the fat-tailed dwarf lemur, noted by The Dodo and Tree Hugger. National Geographic magazine describes the lemur as the only primate with this characteristic.

This warm-loving animal enters torpor in the tropics, where there are no harsh winters. Their reason for this is the onset of the dry season, which leads to water shortages. The small lemur stores fat in its tail, which is why it is called the fat-tailed lemur. In autumn, it burrows into the foliage and sleeps for 3 to 7 months, surviving on its own reserves. However, during this time, the sleeping animal periodically experiences elevated body temperature and increased heart rate.

Ground squirrels are considered hibernating animals by The Dodo and Tree Hugger. They begin hibernation early, in August–September. They gather in winter burrows with 2 to 24 individuals. The entrances are blocked with plugs made of soil, stones, and branches, ensuring that the temperature inside the burrow does not drop below 0 °C.

During hibernation, the body temperature of ground squirrels decreases, their breathing rate drops from 16 to 2 breaths per minute, and their heart rate slows from 80–100 to 5–10 beats per minute. They wake up every two weeks to accelerate their heart rate and relieve themselves in a separate tunnel. During their winter hibernation, these animals survive on stored fat and water, but they can lose up to a quarter of their body weight. Hibernation lasts from 5 to 6–8 months. If the winter is mild, they awaken in February.

Who hibernates in the winter in the forest? In addition to bears, this also includes hedgehogs, raccoons, snakes, and forest frogs. Hedgehogs are noted as hibernating during winter by The Dodo and Tree Hugger.

Before winter, some hedgehogs gain over 1 kg in weight, allowing them to start hibernation as early as August. Those that weigh less enter hibernation in October. In burrows, bushes, under porches, or in old buildings, hedgehogs create nests from hay and leaves, curling up to sleep. However, they wake up every 2–4 days or once a month, often moving to another nest.

The body temperature of a hedgehog can drop to 1.8 °C, but during brief periods of waking, it can rise to 30 °C. They can lose up to 38% of their body weight during the winter. They awaken when temperatures rise to 15 °C.

Turtles enter a special type of winter hibernation known as brumation, which is characteristic of cold-blooded animals. This is noted by The Dodo and Tree Hugger. Like all reptiles, turtles do not generate their own heat but instead absorb it from their environment. However, when it gets cold, they cannot even digest food, so although they are not asleep, they enter a state of torpor.

Better Planet Education states that Central Asian turtles enter brumation for 1–2 months in the summer to survive the heat. Their winter inactivity begins in the fall. They burrow into the mud at the bottom of bodies of water that do not freeze.

As noted by The Dodo and Tree Hugger, tree frogs, forest frogs, and grass frogs also go into hibernation. Some hibernate in forest litter or soil, while others stay in mud at the bottom of bodies of water. The hibernation period typically lasts from September to March. Some species also enter summer hibernation to survive very dry conditions.

During hibernation, frogs' hearts may stop beating, and up to 45% of their body can freeze. At this time, water in their bodies is partially replaced with glycerin, which lowers the freezing temperature. Throughout the winter, cycles of freezing and thawing can occur multiple times. In Alaska, instances have been observed where frogs survived freezing at temperatures as low as minus 16 °C.

Skunks, as noted by The Dodo and Tree Hugger, do not hibernate in winter but can enter a state of special torpor. In colder climates, this lasts for several months, while in the south, it is much shorter.

Before the cold weather, skunks accumulate a significant layer of fat to survive the winter in their dens. Like all hibernators, their life processes slow down: body temperature decreases, breathing slows, and heartbeats decrease. Female skunks do not leave their dens during hibernation, keeping their young warm, while males venture out during warm spells to search for food.

Raccoons are included in the lists of hibernating animals by The Dodo and Tree Hugger. The duration of their hibernation depends on their habitat:

Starting in the summer, raccoons accumulate subcutaneous fat in preparation for hibernation. They hide for the winter in tree hollows, old burrows of other animals, crevices among rocks, or in old buildings.

In winter, snakes enter a state of inactivity without sleep—brumation, as noted by The Dodo and Tree Hugger. The duration of this state depends on their habitat. In northern latitudes, it lasts several months, while in the south, it lasts several weeks. However, snakes can emerge from this state to drink. If the winter is mild and openings appear in the snow, reptiles come out to bask in the sun.

A drop in air temperature below 10 °C signals the onset of winter hibernation. Snakes hibernate in soil cracks, rodent burrows, or under tree roots. They often coil together in a single mass of hundreds of individuals of different species.

Winter hibernation helps many animals survive the time when food or warmth is scarce. Nature has equipped them with the ability to slow down their life processes to a minimum for this purpose.