When the temperature drops and the days grow shorter, many of us feel like climbing into bed and waiting it out. Well, for a lot of animals in New York State, this is exactly what they do. To conserve energy during the season when food sources become scarce, some animals go into an inactive or sleep-like state called hibernation. How and where the animal hibernates, as well as the amount of time it hibernates usually varies by species, but all end hibernation when the warmer spring weather returns.
Most mammals will prepare for hibernation by spending the months leading to winter gorging themselves and building up their fat stores. To these animals, every day is Thanksgiving when they are getting ready to hibernate. Once the animals sense shorter days, colder temperatures, and less food, it knows that hibernation should soon begin.
When most people think of an animal hibernating, they think of a bear curled up asleep in its den all winter long. While bears do hibernate, they are not the only animals that spend their winter this way. Many other mammals, including reptiles, amphibians and even insects hibernate the winter months away.
Let’s take a closer look at these hibernation strategies. While bears hibernate in their pre-made dens, groundhogs will build special burrows just for hibernation. Deer mice don’t completely hibernate but instead enter a light hibernation often conserving warmth by snuggling together. The little brown bat enters into such a heavy state of hibernation that they appear to be dead with their breathing slowing so much it could take an hour for them to take one breath. The meadow jumping mouse is one of the longest hibernators; they sleep from early October until early May
Cold-blooded amphibians and reptiles hibernate differently than warm-blooded animals. Instead of sleeping the months away, they will enter a state of suspended animation sometimes called brumation. Animals that are in brumation are actually semi-conscious and have no control over their body temperature. Snakes, turtles, and frogs will undergo brumation in burrows, mud or underwater anywhere the temperature might be above freezing for them to survive. Often times they will borrow themselves so far they are below the frost line. Some frogs cannot hide from winter’s cold; they hibernate under rocks and logs and may freeze during the cold winter days. Natural chemicals and processes in the animal’s blood prevent them from freezing. The animal’s body produces an “anti-freeze” (a cryoprotectant) as the temperature begins to drop; the animal’s body concentrates sugars and other compounds that prevent the animal’s organs from freezing. The antifreeze prevents the animal’s organs from freezing. A frozen animal will stop breathing and the heart will stop beating. Most of the fluid in the blood pools in the animal’s body cavity. Learn more about freezing frogs in a previous blog.
Some insects known for hibernating are the Mourning cloak butterflies and Woolly bear caterpillars. One of the first species you see when spring is on its way, the Mourning cloak butterfly, spends the winter months frozen but alive usually under loose tree bark. One of the most recognizable insects, the woolly bear caterpillar can spend its winters frozen as well. These insects also survive freezing by producing a cryoprotectant that shields their tissues from being damaged by the freezing temperatures.
One mammal that does not hibernate is humans, so make sure to get out and enjoy all the beauty New York State Parks has to offer this winter!
Wooly Bear Video:
Cold-blooded in the cold: hibernation Conservationist for Kids, NYS Dept. Conservationist
Post by Kristin King, State Parks
featured image from Wikicommons