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How Do Ectotherms Survive the Winter?

Arkansas Natural Heritage Commission - Friday, November 20, 2015

Ectotherms, or cold-blooded animals, must find a way to stay warm or cool as temperatures outside fluctuate. Most mammals and birds are endothermic, or warm-blooded, and can regulate their body temperature by seeking shelter, increasing activity, increasing calorie consumption, or in some cases, hibernating. But what do ectotherms do?

Survival Strategies

In order to survive the winter, ectotherms have developed specific strategies to help them survive the cooler months. Many regulate their body temperatures by moving to a different place (which they also do in warmer months to cool down). Most people have witnessed a snake, lizard, or turtle lying in the sun or “basking”, which is one strategy that animals use to increase their body temperature.

As temperatures become cooler, ectotherms move around less to conserve energy. This is especially true for insects which can be observed moving sluggishly at night or in the early hours of the morning. Once the temperature increases and their body temperature regulates, you’ll notice the insects flying, hopping, and moving around in their normal ways.

Other ectotherms engage in another behavior that helps them to survive colder temperatures – they burrow deep into the ground. By doing so, they are protected from the colder air and blanketed by the layer of earth above and around them. Generally, fish are protected from the temperature by the water and by remaining active, with only a few species burrowing into the mud. Many frog species bury themselves in the bottom of lakes and rivers. In winter, many aquatic turtles stay underwater, by obtaining oxygen from their highly vascular cloaca (posterior opening).

There are some ectotherms, called poikilotherms, that have actually developed chemical processes to survive the cold. These animals, such as spring peepers, chorus frogs, and gray tree frogs endure the cold by undergoing chemical changes to prevent their tissues from freezing. Others, such as the wood frog, can tolerate and regulate a frozen state by changing the chemical composition of their blood to a sugary concoction (a cryoprotectant) that helps them avoid freezing to death.

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