Have you ever wondered what happens to cold-blooded animals in the winter? Where do the turtles, frogs, and snakes go? They can’t migrate far south like birds, and they can’t keep warm like deer and foxes. So, how do they cope?
First off, let me explain what I mean by cold-blooded. A cold-blooded animal is known as an ectotherm. These animals are dependent on the temperature of the environment to regulate their body temperature. This is in contrast to endotherms which use their metabolism and their own body’s mechanisms to maintain a constant internal temperature. Mammals are endotherms. So, how do ectotherms survive when it drops below freezing? Let’s start with turtles.
When winter comes around, a turtle’s body temperature will drop. Once it reaches about 40-50°F, the turtle will stop eating and start seeking out a place to ride out the coldest part of the year. Most turtles are going to want to find a place under a bank or in the mud where it is cold, but the water doesn’t freeze solid (Figure 1). You might be asking, “How do they breathe if they are under water?” One of the advantages to being cold-blooded is that as the temperature cools, your metabolism decreases. When their metabolism slows down, they don’t require as much oxygen. In this state, they can go days without breathing and some absorb enough oxygen through tissues in their throat and under their tail.
Some frogs spend their winters underwater, preferably under vegetation or mud (Figure 2). They need to leave some skin exposed to the water so that they can get enough oxygen through their permeable skin. There are other frogs that like the land and will hibernate out of the water under rocks or leaves or in a fallen log. There is even a frog that can freeze itself solid! This amazing creature is the Wood Frog (Figure 3). How does it do it you ask? Well, urea and glucose accumulate in the frog’s body. These two compounds combined act as protection against tissue damage from freezing. It keeps the frog’s cells from being damaged by ice formation. Once the weather warms up, they thaw and hop away unscathed. They are the Mr. Freeze of the frog world.
Snakes also hibernate, and like frogs and turtles, different species have slightly different tactics for survival. Garter snakes will often hibernate in dens with other snakes (Figure 4). Others like to hibernate in animal burrows. The Eastern Ribbon snake will hibernate in areas where it can be partially submerged during its hibernation. If a snake is living in an area where temperatures do not get bitter cold, they might not reach the deep state of hibernation but enter into a state called brumation. Brumation is a time when their body temperature drops and their metabolism slows, but it’s not as drastic as hibernation. If there is a bright, warm, sunny day in winter, brumating snakes may emerge. If you see snake out in winter, leave it alone. Chances are, it is enjoying the slight warming period as much as you are. As the temperature cools again, it’ll move back to its den.
So while you are bundled up and scraping ice off of your car, think about all the amazing reptiles that are toughing out the long, cold winter days. It is really amazing the adaptations animals have to surviving the extremes of nature. This is the last post of 2015. There will be a whole new batch of posts coming out starting January 8 and 15 due to closure of the Lewis and Clark Community College campus. Be sure to come back and start your year off right with more info about the amazing natural wonders around you.