By Meg Deak
When the weather turns cold for winter, food can become scarce for animals that depend on insects and plants. To solve this problem, some animals hibernate. From skunks to bats to bears, there are many animals that spend some part of the winter in some form of hibernation. But what exactly does that mean?
What Is Hibernation?
When one thinks of hibernation, many consider bears. However, bears aren’t true hibernators. True hibernation is characterized by three things, low body temperature, slow breathing, low heart rate, and a low metabolic rate.
Contrary to popular belief, hibernation is not a form of sleep. Hibernation is considered an extended state of torpor, where metabolism, the chemical processes that maintain life, is depressed to less than five percent of normal.
Hibernating animals get ready for hibernation by eating extra food and storing it as body fat which they use when hibernating. There are two types of fat, white fat and brown fat. The brown fat surrounds the animal’s organs, such as the brain, heart, and lungs. The brown fat produces heat in a process called nonshivering thermogenesis.
Little brown bats are an example of a true hibernator. They hibernate from October or November to March or April, most often in caves that remain above freezing. One of Canada’s largest hibernators are groundhogs.
To stay warm, they hide in rock crevices and burrows safely below the frost line. On warm winter days, some animals in brumation will move to find water, unlike animals in hibernation. There are also some species of frog, such as the wood frog and spring peeper that do not dig a burrow to survive.
Instead, they survive the winter freezing with the rest of the land. These frogs can survive because a high concentration of glucose in the frog’s vital organs prevents freezing, despite ice crystals elsewhere in the body cavity.
Blanding’s Turtles and Northern Leopard Frogs are both other Canadian species that enter brumation.
Torpor is considered light hibernation. Unlike hibernation, torpor is involuntary and lasts a short period of time. This allows animals to wake up on warmer winter days for food and water.
Grizzly bears are an example of a species that enters torpor. During torpor they enter a period of dormancy where their heart rate is extremely low, but their body temperatures are high.
Striped skunks, and eastern chipmunks are other examples of species that enter torpor dormancy.