Amphibians have very interesting behavioral adaptations to survive through winter. None of them actually hibernate; they simply go into a state of dormancy. The key difference is that dormant amphibians will very quickly start moving again when temperatures rise. Hibernating animals need much longer to wake up. Like snakes, some amphibians will burrow to avoid predators and the elements. However, many amphibians will spend the winters underwater. Adult amphibians don’t have gills, but when they are dormant, they only need a small amount of oxygen. Interestingly, most species can absorb oxygen through the skin so they can pull oxygen out of the water around them to survive. Amphibians that go dormant underwater are trapped there through most of winter. The ice freezes over so there is no way out until the ice melts.
Bumble-bees have an interesting way of getting through the winter. In the fall the colony begins to produce new queen bumblebees. Only the queen bees will go into hibernation to begin new colonies after the winter. To hibernate, the bees borrow into the ground along banks. This protects them from drowning when it rains. These bees only burrow down about 4 inches and can survive through very cold weather. When it starts to get too cold for the bee, they will produce glycerol which is a form of anti-freeze that some evergreens produce. Hibernation is the longest portion of a queen bee’s life. They may spend three quarters of their life just sleeping. After winter, the queen bees come out and start producing a new nest that will last for the year.
Bears tend to be what people think of when they hear the word hibernation. However, bears don’t truly hibernate like other mammals. Their internal body temperature only drops a minor amount from around 100°F to 87°F while true hibernating mammals can drop their internal temperature to less than 38℉. This difference has a very important effect. Bears can react very quickly to threats while they hibernate while other mammals may have no response. When someone walks near a bear den and disturbs the sleeping bear, it will likely wake up and be ready to react. In comparison, if someone picked up a hibernating squirrel, it would likely stay asleep and, if it did wake up, would need a lot more time to raise its body temperature enough to react. Despite this, bears sleep more than true hibernating mammals. Most mammals will need to wake up at some points during the winter to raise their body temperature and eat. Bears do not need to do this and will stay asleep through the winter, burning fat as needed and reusing their metabolic waste to build protein. When bears wake up in the spring, they are much leaner and have lost up to 30% of their body mass. Black bears differ from other bears in selecting a location to hibernate.
Bats have two ways of dealing with winter. One method is to migrate like birds do. Silver-Haired Bats and Hoary Bats migrate to northern Mexico for winter, but the Hoary Bats are also comfortable with Southern California and Florida. Other types of bat will stay where they are and go into hibernation like many other mammals. When bats hibernate, they reduce their energy needs by 98%. This allows them to easily survive off their fat reserves. Hibernating bats retreat to caves to stay throughout the winter where they can avoid wind and potentially predators. However, bats are at risk while they are hibernating. There is a fungus that can grow on hibernating bats that causes white-nose syndrome. This fungus has been responsible for large population declines in many species of bats. When infected, bats will be more likely to come out of their sleep to clean the fungus from themselves when they should be hibernating. Repeatedly waking uses up the bat’s energy reserves before winter is over so they cannot survive without more food. However, leaving their cave will likely result in exposure to freezing temperatures and few if any food sources available.
Snakes have their own form of hibernation called brumation. It is very similar to mammalian hibernation, but there are some important differences. For example, snakes will wake up occasionally and forage for food and water. They also may stay awake during periods of warmer weather in the winter. Snakes like to burrow into tree stumps, caves, and holes. This protects them from freezing temperatures, potential predators and from rain and wind. Snakes will also brumate with other snakes to share body heat. Snakes cannot regulate their internal temperature, so they can’t survive the cold winters. Preparing for brumation is important for snakes.