Tuesday, March 24, 2009

Reptile Van Winkle

I wrote this column last March, still relevant this time of year.

It’s finally starting to warm up around Auburn. On cue, red-winged blackbirds have begun to make their appearance known in area wetlands. You’ve probably heard them too, singing their distinctive, “Konk-a-ree!” About the size of a sparrow, males can be recognized by their black body and bright red shoulder patch. Small yet fiercely territorial, they’re often found perched on cattails, singing to attract mates and defend their little patch of swamp from other males.

Other animals are starting to appear and look around too. Lizards, snakes, and turtles are all beginning to emerge from the winter refuges to take advantage of the weather to warm their bodies. Most people know that these animals are reptiles and, like all reptiles, they are “cold-blooded”. This term isn’t used so much anymore in scientific circles because it implies that reptiles have no control over their body temperature. It is now known that some reptiles can keep their body temperature higher and more stable than we can, simply through their behavior. This is why you’ll see turtles lined up on a log over the water; they’re trying to raise their body temperature. You may have also seen alligators sitting on a waterbank with their mouth open, this is actually how these animals lower their body temperature. They’re letting heat escape through their mouths. Given how hot a Florida afternoon can be, I don’t blame them for trying.

But a reptile’s dependence on the weather outside brings up an interesting question, one that I hear a lot. If the temperature outside influences the internal temperature of reptiles, how do they last during the cold of winter? It’s a good question because it turns out that different animals have different adaptations for persisting in cold weather.

As you might expect, reptiles hibernate. But if you’re picturing a snake curling up in a cave like a bear might, you may be surprised. These animals don’t hibernate in the traditional sense, they are quite awake.

As cold weather approaches, lizards and snakes start seeking out shelter that will serve as their winter hibernacula (hibernation sites). Common areas include abandoned mammal burrows, gopher tortoise burrows, or the caverns surrounding burnt up tree stumps. In more northern climates, these animals will hibernate together and it’s not unusual to find timber rattlesnakes, rat snakes, and black racers all nestled together in rock outcrops. Down here in Alabama though, these animals tend to be loners.


In their refuges, snakes and lizards wait out the long, cold winter. Impressed? I get hungry just thinking about going just a few hours without food. Their secret is in their slow metabolism. Reptiles can go long periods of time without eating, particularly when it’s cold. As their body temperature decreases, so does their metabolism. Mammals like us need to use a lot of energy to maintain our body temperature, reptiles have no such obligation.

So they lay in their caverns, the cold around them making them sluggish. If these animals were truly hibernating, it would take them a long time to gradually retain their normal activity periods. But this isn’t what we see with snakes. You may have remembered that we received a warm spell over a month ago, during one of the warmer days I stepped outside and found a small red-bellied snake sunning itself on my sidewalk. This is a common, harmless snake in the Auburn area and all are less than a foot long. During warm weather, snakes and lizards may often come to the surface and enjoy the sun’s rays. The small snake that I saw likely crawled back to his shelter that night, before temperatures got too cold again.

Turtles have particularly fascinating strategies for escaping the cold. Most of the aquatic turtles you see will burrow in the mud at the bottom of their pond and swamp and wait for warmer weather there. Now, we’ve already talked about why reptiles don’t need to eat during the winter, but now there’s another problem. How do the turtles breathe?

Since their body is running at such a slow speed, turtles don’t need much oxygen. But holding their breath for months would be a feat not even they could accomplish. Although it may be hard to believe, but turtles are able to absorb oxygen from, for lack of a better term, their butt (technically referred to as a cloaca in reptiles). The chemical processes that turtles undergo during cold temperature are quite interesting and complex.

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