In the animal kingdom, hibernation is a common occurrence as it helps an animal survive harsh climatic conditions in the winter by inducing a comatose state.
Hibernation is an important part of some animals' lives as it keeps them alive and well during food shortages in the winter season. During this time, body temperature and metabolic changes are induced in the body to keep it functioning.
Hibernation in animals is a source of great curiosity in humans, the process is fascinating as during the process, the brain function of the hibernating animal slows down, and the body goes through several changes. Even in this state, animals do not die, they live through the changes in their cells and tissues. Muscle deterioration is also avoided even though the hibernating animal may or may not feed itself for long periods. No bone deterioration is another interesting factor as a lack of movement is supposed to have some effect on the body, but in hibernating animals, it plays no part throughout the sedentary period.
If you like this article about how do animals hibernate? Then you will surely love these how do amphibians breathe and how do gills work too!
What is hibernation?
Hibernation in animals is the process of deep sleep to conserve energy as animals prepare to survive the cold winter weather. Hibernation helps animals stay warm during the winter months without the need of migrating to another part of the world or forage for food.
The process of hibernation involves entering a state of deep sleep where the breathing rate is lowered and heat is generated through metabolism to stay warm. In doing so, mammals, reptiles, and amphibians, among larger animals, consume less energy compared to when they are active, and in turn mimic cold-blooded animals. This low energy usage allows animals to induce a coma-like state, which is the simple definition of hibernation. During these hibernation periods, animals hibernate without food. Hibernation can be stress-inducing as well since the hibernating animals have to maintain proper body temperature as they might die if the body temperature drops too low.
When animals hibernate, they remain immobile and can go for weeks and months without having to consume food since they do not have access to any food or water sources during their comatose state. Many animals prefer to store an ample amount of food before hibernation but many animals do not bother to store food as they depend on their slow metabolism and hence do not forage for food when they prepare for hibernation. In the cases of many small and large animals like ground squirrels and bears (true hibernators), a den is the preferred sleeping location as they are safe from other larger carnivorous birds and mammals that might feast upon the unresponsive bodies of hibernators.
During the hibernation process, the metabolism, breathing rate, and heart rate are slowed down by the hibernating animals' bodies. The body temperature of the hibernating animals is also lowered, in extreme cases, it can be as low as freezing temperatures. The dormant animals produce all the necessary nutrients by burning excess stored fat. As the temperatures get lower, the body burns more of the fat to keep the animal's body temperature at a stable rate to avoid death by freezing. Hibernation resembles sleeping. However, some differences separate hibernating from sleeping. The main difference is that the brain wave of the animal hibernating is similar to that of their waking brain patterns.
There is a common misconception that animals that hibernate do not wake up during the hibernation process and lay in a dormant state until the animal's hibernation is finished with the arrival of warmer seasons. However, reflecting on this misconception, hibernating animals do wake up, but for how long of a period depends on whether they are true hibernators, like bears, or light hibernators.
In the case of bears, it is difficult to say whether they wake up or not as they have to store lots of body fat when they get ready to hibernate and in case of emergency. This could include a risk to their survival or attack by another species, which wakes them up from their warm slumber. Groundhogs are another example of true hibernators. The bodies of these groundhogs drop the heart rate from 80 beats per minute to only five beats and the rate of breathing from 16 breaths a minute to two breaths a minute.
Light hibernators in mammals like raccoons, skunks, and squirrels wake up throughout the hibernation period during the winter season and return to normal by regulating their body temperature, heart rate, and breathing rate.
What animals hibernate?
There are a lot of warm-blooded animals in the wild that hibernate through the winter season to avoid extremely cold weather conditions. Reptiles, mammals, amphibians, and even a type of bird, hibernate during the winter season as they use up the body heat to provide energy to their dormant bodies.
Chipmunk species prepare for hibernation by digging burrows as deep as 3 ft underground, and aptly cover the holes to keep themselves warmer and avoid predators. When these animals sleep, their body temperature and breathing rate are drastically decreased so that they can sleep for periods without the need of waking up. Unlike true hibernators, they wake up for food and go back to sleep until they are ready to wake up in the spring.
Bears are one of the true hibernators and are well-known to hibernate for months to avoid the cold winter weather in their dens and survive throughout the hibernation process using the body fat they stored all summer long. Female bears give birth during hibernation and nurse their babies throughout spring without needing to eat.
The bat is another mammal that hibernates. However, not all bat species hibernate as some inhabit warmer climates or choose to migrate to warmer climates instead of hibernating. These warm-blooded animals do not need to stock up on food for the winter seasons and go into hibernation that can last for up to six months. This animal's body temperature takes a significant dip and the slow metabolism process helps their heart rate stay at a shallow rate. Bats start hibernating during late fall.
Among the species of reptilian animals that hibernate, box turtles and snakes are known for hibernating. Box turtles do not need to move to warmer areas during the fall and they just revert into their hard shells to survive through the cold winter seasons. The garter snake, another reptile species, hibernates through the winter season to save energy. They can be found in dens in the ground. Since garter snakes are found in colder climates, they travel to better living conditions in search of dens where they curl up in large numbers to keep each other warm. Reports of as many as 8,000 garter snakes hibernating together have been found.
When you think of hibernating animals, the first thing that comes to mind is a bear, but, some insects hibernate too! The bumblebee is of the few insect species that can be found hibernating. During the fall, all the worker bees begin to die, leaving the queen alone. The queen hibernates and prepares for the birth of a new colony during the spring season. The queen is often found digging into the soil as she avoids the winter sun. She will stay buried in the ground and survive off the pollen that she has acquired before going into hibernation. Queen bumblebees emerge from the ground later, after the cold weather has passed by.
The common hedgehog is another animal that hibernates to survive the harsh winter conditions. These animals slow their metabolism to slowly burn through the fat stored in their bodies to survive. The animals' body temperatures drop to match the temperature around them during the winter. The minimum threshold for these animals to survive without the need to consume is to be at least 1.3 lb (600 gm) in weight.
In gastropods and cold-blooded animals, some snails are known to hibernate. They move to locations with no frost and revert into their shells under leaves or rocks, and in some cases, hibernate in groups to keep each other warm. The opening of the shell is covered with their slime as they attach themselves to their nearby habitats.
Many amphibians are also hibernators and the wood frog is one such example. These frogs are not picky and bury themselves in the ground. After burying itself, the frog stops breathing, and its heart stops pumping blood to the rest of the body. The body, as a result, becomes frozen, and 65% of the water within its body turns to ice, but the frog does not die. With spring approaching, the ice on the body melts and the breathing process starts functioning again.
Hibernation in birds is also possible, as it is showcased in the common poorwill, the first known hibernating bird. They hide inside hollow logs or grass patches to conserve energy. Before hibernation, they feed on insects and use that as their source of body fat to survive during the hibernation process. These birds can stay in a deep sleep for months!
How do animals prepare for hibernation?
Hibernating animals stock up on food supplies in preparation before they hibernate.
When the climate is still mild, hibernating animals start stocking up for the winters. Mammals like ground squirrels and groundhogs collect nuts and plants to store them in their nest or den. During or after hibernation, when these animals wake up from their deep sleep, they need to have an ample amount of food to eat as their bodies have used the nutrients from these food supplies to keep warm and circulate their body heat.
Honeybees use the honey they collect over the summer to feed themselves and their colonies. In mammals, it is common to eat as much as they can to store an excess amount of fat to burn through the hibernation process. The fat provides insulation as well as warmth, which helps the animal ease its way through hibernating.
How long does hibernation last?
In a general sense, hibernation can last for weeks or months depending on how much energy the hibernating animal has consumed to keep itself warm.
True hibernators, like groundhogs, bears, squirrels, and bats can hibernate for a long period that can be over weeks and even several months! There is no approximate amount of days in the hibernation process as an animal's hibernating period can not be predicted precisely.
Waste Management During Hibernation
One of the most common questions asked about hibernating animals is whether they poop or not. The answer to that is simple. Some animals do produce waste, while others do not.
Light hibernators wake up amid hibernation to stretch around and eat. They also urinate and defecate during this period. The amount of waste is minimal as these animals do not eat too much and the animals that go through the entire hibernation process may not require excreting waste as the food they eat is converted into fat.
In general, bears can go through an entire hibernating period without the need to excrete waste. The animal converts all the urea into muscles, which makes it look muscular even though it has lost weight by not eating. Their entire energy is used up in going through hibernation which, in turn, leads to the absence of the need to produce any form of excretion.
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