Spring is in the air. There are many traditional signs we watch for that indicate the time has come to turn our backs on Ole Man Winter. For me, there is nothing like spotting that first turtle on a log, basking in the sunshine. As soon as the weather warms and the snow and ice recede, the first reptiles of the year begin emerging from their winter abodes. But just how do they survive the brutal winter conditions?
Like all animals that have their own adaptations for survival, reptiles have their own unique methods. Not to be confused with amphibians, reptiles include snakes, turtles and lizards. Though different regions of the country harbor a host of diverse species, all reptiles share common techniques for surviving cold temperatures.
Reptiles are ectotherms. Cold-blooded and unable to generate their own warmth, they must depend on external sources to regulate their temperature. To accomplish this, they alternate between basking in the sun or retreating to the shade in an effort to maintain a body temperature that falls within the proper range for maintaining their normal activity levels. The changing conditions regulate their metabolism, which increases with heat and decreases in the cold.
Aquatic turtles, such as painted turtles, must face the challenge of the water surface freezing over, eliminating their source of oxygen. At the onset of winter, turtles retreat into the depths of their pools, often settling on the bottom or even burrowing into the mucky substrate. As the temperatures drop and their metabolisms slow, they enter into a state of hibernation known as “brumation.” During this period, their physical activity and food intake are severely reduced. Having breathed through a set of lungs throughout the warmer months, they must now alter their respiration techniques.
Amazingly, turtles are able to absorb dissolved oxygen in the water through their skin, allowing them to “breathe” without ever reaching the surface. Their tails are extremely vascular allowing them to soak up the majority of this oxygen through the skin of their cloacas — literally breathing through their butts — a process known as cloacal respiration.
Terrestrial turtles, such as Eastern box turtles, often run the risk of being exposed to sub-freezing temperatures and other winter conditions. As autumn gives way to winter, these turtles must dig their way down beneath fallen logs or deep into the leaf litter where they create makeshift dens. As the cold creeps in, the turtles lower their metabolism considerably to conserve their energy. Some reptiles have a special antifreeze in their cells which prevents the growth of ice crystals.
Snakes, too, enter into brumation for the winter and are particularly sensitive to the cold. They seek out shelters known as hibernacula and often return to the same locations to ride out the winter year after year. These sheltered locales are often below the frost line and can include the burrows or dens of mammals. Snakes often den together in groups of over 100 individuals which may include a variety of species. By packing together and coiling around each other, snakes can actually retain some heat. Although they do not eat during this time, they are able to absorb moisture through their scaly skin which keeps them hydrated.
As the spring sun begins to warm the landscape, the soil softens and the ice recedes, releasing reptiles from their winter retreats. As the snakes bask in sunlit sites and turtles take their places side by side atop floating logs, it is easy to imagine how content they must feel to have survived another winter with a renewed interest in life.
