During the winter, temperatures drop, and the food supply decreases. To survive, certain animals will hibernate – meaning to enter a period of inactivity through deep sleep/unconsciousness. This allows animals to store food, suppress their metabolism, and reserve energy.
Sometimes, animals will not go into a deep sleep but decrease their activity. This is another form of hibernation.
During hibernation, an animal’s temperature will drop significantly, and its heart rate will slow. Although this allows them to survive, it also carries great risk if they haven’t stored enough fat during the summer/autumn months. Animals are also at risk of death during hibernation if found by predators and exposed to extreme weather. This makes the location where animals hibernate important.
What is Torpor?
Torpor is a form of hibernation. It is a shorter, temporary period of inactivity to reserve energy in harsher conditions. Torpor usually lasts less than a day and allows certain animals to survive through shorter periods of extreme conditions.
Animals that Hibernate
A variety of different animals hibernate. Many animals need to hibernate to survive, from mammals to insects and reptiles.
Bears in colder climates will hibernate during winter when finding food is more difficult. Bears will eat twice as much food towards the end of summer and then hibernate in their dens. These can be in caves, under tree roots, and hollow trees. Bears will enter a deep sleep until the spring when they awaken.
There’s a reason you won’t see bumblebees in winter; during the autumn months, most of them die, leaving the queen bumblebee to hibernate. The queen bumblebee will hibernate in the soil until spring when she begins her new colony of bumblebees.
Most hedgehogs hibernate through the winter months until spring. However, hedgehogs can remain active in the winter if the conditions are milder. During hibernation, hedgehogs will sleep in their nests built in thick undergrowth.
Bats in colder climates during the winter will hibernate in caves and other dark, enclosed areas. Bats can hibernate for up to six months.
The box turtle hibernates within its shell. This turtle will usually hibernate, depending on the temperature, around autumn/winter.
The skunk is an example of an animal that doesn’t enter complete inactivity during hibernation. Instead, they’ll enter small, enclosed spaces close to food and water during the winter, where they’ll become less active.
Animals that hibernate – why do they do it?
Hibernation isn’t the same as sleeping. During hibernation, animals reduce their metabolism and conserve energy, sometimes to an incredible degree. For example, during periods of hibernation, dwarf lemurs reduce their heart rates from over 300 BPM to fewer than 6. As a result, they can go up to 10 minutes without taking a single breath, and their brain activity becomes undetectable.
So why do they do it? While some animals, like bears and bees, hibernate during the winter months to avoid the cold, hibernation can also help animals endure other difficult conditions.
Some animals that hibernate do so to survive food shortages. For example, in Australia, echidnas will hibernate after fires, conserving their energy until food becomes plentiful again. Unfortunately, lots of smaller mammals are also harder to detect when hibernating. As a result, they’re five times more likely to die each month when they’re active compared to hibernation periods.
How do animals know when it’s time to hibernate?
It’s thought that there’s a compound in animals’ blood that, when triggered, alerts them to the fact that it’s time to hibernate. A combination of shorter days, dropping temperatures, and food shortages are all factors that contribute to the triggering of this compound.