Many different animals hibernate or enter dormancy as a survival strategy to endure the challenges posed by seasonal changes in temperature, food availability, and other environmental factors. Hibernation allows them to conserve energy, lower their metabolic rate, and avoid the need to hunt for food during times when it is scarce or difficult to find. When spring arrives, they typically emerge from hibernation with renewed energy and can continue their life cycles.
- 1 Strategies for surviving the winter
- 2 What is hibernation
- 3 Types of hibernation
- 4 Which animals go into total hibernation?
- 5 Which animals go into partial hibernation?
- 6 Which forest animals don’t hibernate?
- 7 Animals that thicken their fur
- 8 Animals that migrate
- 9 What are the seasons of hibernation?
- 10 Which animals hibernate in autumn?
- 11 Which animals hibernate in winter?
- 12 How do they survive hibernation?
- 13 Animals that hibernate longer
- 14 More on this topic
Strategies for surviving the winter
In temperate climate regions, winters are long and cold, snow cover makes food scarce, so this season is a critical time for many species. To ensure their survival, different species have successfully developed different mechanisms.
Some animals migrate, such as birds, while others remain, but have developed strategies to resist the cold. Some mammals, generally ungulates and predators, can thicken their fur and increase the layer of subcutaneous fat to face the harshness of winter. Others take refuge in burrows with food reserves, such as squirrels, and others even allow themselves to freeze (amphibians, reptiles, insects).
What is hibernation
Animals have developed various techniques to survive the rigors of winter, but without a doubt hibernation is one of the most advanced strategies. In fact, it involves a behavioral adaptation that also involves significant physiological changes, aimed at reducing energy expenditure through a controlled and reversible lowering of body temperature and metabolism level.
The animal thus lives in slow motion for several months, consuming its fat reserves while waiting for the return of the hotter seasons. This strategy is found in many orders of mammals, including monotremes (echidnas), marsupials (Australian kultarr), insectivores (hedgehogs), chiroptera (bats), but it is the most common way to survive the rigors of winter in rodents (dormice, lemurs, herons, egrets, hamsters, squirrels and marmots).
Hibernation is not to be confused with dormancy, a state of quiescence, even very long, adopted by insects, reptiles and invertebrates, which go into a condition that resembles death more than deep sleep. The body temperature can approach zero and all metabolic activity is almost blocked. Thanks to the high concentration of substances present in the blood, the water present in the blood does not crystallize and the body’s cells are preserved.
In practice, during hibernation the body temperature of these animals lowers, in some species by up to 10° C / 50° F, and the heartbeat decelerates, even by 80%. During this time, digestion and breathing slow down, as do other physiological needs.
It is with the arrival of spring, the mating season, that animals that hibernate awaken, and also resume their metabolic activity.
In this long ‘sleep’ they lose a lot of weight and their energy will be low. In fact, once they emerge from the vegetative state, they will return to feeding vigorously, as before hibernation.
Types of hibernation
Hibernation is not a one-size-fits-all phenomenon: it can be total or partial, and there is a spectrum of dormancy states observed in animals. Let’s delve into these distinctions:
- Total Hibernation (True Hibernation): This is what many mammals are known for. During total hibernation, animals experience a profound reduction in metabolic activity, body temperature, and physical activity. Their heart rate, breathing rate, and overall energy expenditure drop significantly. Some examples of animals that undergo total hibernation include ground squirrels, hedgehogs, and some species of bats. In this state, these animals are essentially “asleep” for extended periods of time, typically through the winter months.
- Partial Hibernation (Torpor): Some animals enter a state of partial hibernation known as torpor. Torpor is characterized by a reduction in metabolic activity and a lowered body temperature, but it is not as deep or prolonged as true hibernation. Animals in torpor can periodically rouse themselves to eat, drink, and even move around, especially on warmer winter days. Black bears, for instance, undergo a form of torpor, not true hibernation. This state allows them to conserve energy but still remain somewhat responsive to their environment.
- Daily Torpor: Some animals, particularly small mammals and birds, may enter a daily torpor, where they go into a temporary, short-term state of reduced metabolic activity and lower body temperature each day or night. This is often observed during cold nights, enabling them to conserve energy.
- Seasonal Dormancy: Insects and other invertebrates often enter a form of seasonal dormancy in response to changes in environmental conditions. This dormancy can range from a temporary slowdown in activity to more extended states of reduced metabolic activity and inactivity, depending on the species and the severity of the environmental conditions.
Which animals go into total hibernation?
It’s generally warm-blooded animals, with some exceptions, as we will see that go into total hibernation, also known as true hibernation. True hibernation is characterized by a significant reduction in metabolic activity, a lowered body temperature, and a state of prolonged dormancy, during which the animal is essentially “asleep” for an extended period. Some examples of animals that undergo true hibernation include:
- Ground Squirrels: Ground squirrels, such as the Arctic ground squirrel, groundhog, and thirteen-lined ground squirrel, are well-known hibernators. They enter a deep hibernation state during the winter, with body temperatures dropping close to freezing, and they do not eat or drink during this period.
- Bats: Some species of bats hibernate during the winter months. They enter caves, mines, or other sheltered locations, where they experience a significant reduction in metabolic activity and body temperature to conserve energy.
- Hedgehogs: European hedgehogs are known hibernators. They find sheltered locations and enter a state of hibernation to survive the winter when food is scarce.
- Hamsters: Some species of hamsters, like the European hamster, hibernate during the winter months. They reduce their metabolic rate and spend long periods in burrows.
- Turtles: Certain species of freshwater turtles, like the box turtle and the painted turtle, hibernate. They find shelter in bodies of water, allowing them to survive in an environment that would be lethal for other reptiles during the winter.
- Amphibians: Certain species of frogs and salamanders hibernate. They may bury themselves in mud or find sheltered locations in ponds and streams to endure the cold months.