Ever wonder where animals go when winter blows in? Many birds migrate to warmer locales, some species adapt to the cold weather, and some thrive in it. But what happens if a species can’t tolerate the cold and isn’t migratory? Those animals may enter into hibernation, torpor, or brumation.

Hibernation

Treehugger.com explains that “hibernation is a voluntary state that an animal enters into in order to conserve energy, survive when food is scarce and minimize its need to face the elements in the cold winter months.” Think of hibernation as a truly deep sleep, a state noted by low body temperature, slow breathing, lowered heart rate, and low metabolic rate. Hibernation is triggered by decreasing exposure to daylight and hormonal changes that indicate the need to conserve energy.

Animals that hibernate must first build up their fat reserves to survive their long winter naps. Animals may wake up briefly during hibernation to eat, drink, or defecate, but for the most part, their bodies maintain a low-energy state for as long as possible. Arousal from hibernation takes several hours and uses up much of an animal's conserved energy reserve.

The true hibernators in our neck of the woods are bats and groundhogs. That’s right, not bears! Bears are not true hibernators because their body temperatures don’t significantly drop. Instead, they enter into torpor. 

Torpor 

Torpor is usually shorter term than hibernation, and the animal is able to wake easily if hurt or threatened by predators. Think of torpor as a state of decreased activity over shorter periods of time. By contrast, hibernation lasts longer and requires a lot of energy to wake from. Torpid animals may move around, get a drink, or even move into the sun to passively rewarm.

Torpor is the most effective means of energy conservation for mammals and birds. Bears, raccoons, skunks, and some hummingbirds and other birds all use torpor to survive the winter.

Brumation

Animals that relly primarily on the external environment to regulate body temperature are called an ectotherms - think reptiles and amphibians. So what do ectotherms do in the winter? They brumate! Brumation is loosely referred to as the reptile form of hibernation.

Brumation is a survival tactic. Since ectotherms rely on the environment to regulate their body temperatures and must be warm to hunt, eat, and digest food, they must adapt to survive when it’s cold outside. These animals typically find burrows, rock crevices, caves, and leaf litter within their environment, where they can be somewhat insulated during their the brumation periods. 

When a reptile or amphibian brumates, it becomes lethargic, sometimes not moving at all for the duration of the cold season. Some will move on warmer winter days to find water, and most don’t eat during brumation.

In broad terms, reptiles enter brumation in the late fall, when temperatures drop and daylight decreases. They come out of brumation in spring, triggered by increased temperatures, longer days, and changes in barometric pressure.

Read about Tiger, our tiger salamander, as an example of an animal that goes into brumation.

How we can help animals in winter

Put our black oil sunflower seed and suet for our bird friends to help them stay powered up. Install nest boxes, and leave parts of your yard wild for our animal friends that need winter cover to sleep in. Think of your yard and woods as a blanket for our animal neighbors. They will thank you in the spring!