HOW DO TURTLES COPE WITH WINTER?

by Whit Gibbons

December 4, 2016

With the coming of winter, temperature is the most obvious environmental factor influencing the lives of plants and animals. Many mammals add a layer of body fat when Jack Frost arrives. Migratory birds fly south as cold weather approaches. Deciduous trees lose their leaves. Following are questions I have received about how turtles survive the cold.

Q: I live in central Alabama and realize that many reptiles hibernate underground during cold weather. But where do the turtles go that I saw on logs in the river a few weeks ago? Can they live all winter beneath the water or do they hibernate on land?

A: For most reptiles, including turtles, when their body temperatures reach 40 to 50 degrees F, they become sluggish, stop eating and seek hiding places to get safely through the winter. Many aquatic turtles go into the bottom mud or under the bank where the water is cold but does not freeze. An advantage reptiles have over most birds and mammals is that their metabolism drops with their body temperature, which means they require less oxygen. Some turtles can stay below the water for days at a time, as long as the water stays cold.

Some aquatic turtles are capable of underwater respiration through special capillaries that allow them to release carbon dioxide while acquiring oxygen from the water itself. Others sit quietly on the bottom, rising to the surface periodically to take a breath. I once caught a large snapping turtle in Michigan that poked its head up through a hole in the ice of a lake, took a breath and then proceeded to head back to the bottom. It was moving so slowly that I reached out of the boat and picked it up with no problem.

Q: Last week I found six newly hatched slider turtles that I have kept inside in a small aquarium. I read that baby sliders and painted turtles usually stay in their nest until spring but sometimes hatch out in the fall like these did. My question is this: Should we return the hatchlings to the pond to live out the winter or do they have a better chance of survival in the aquarium until spring? I assume they would survive just fine in our large pond but thought I’d check with an expert.

A: As far as winter weather goes, the hatchling turtles will be OK if you put them in the pond. They will find places to hibernate when the water begins to turn cold and will emerge in springtime to start feeding. The threat of predators, however, exists whether you release them now or wait till spring. Placing them in an area with heavy aquatic vegetation would confer a slight advantage as it would provide cover that might allow them to avoid some predators.

Q: I read that turtles lay eggs in spring, but, even though the babies may hatch during summer, they might not leave their underground nest for a year or more. Is this true?

A: Yes. Most turtles lay their eggs on land in spring or early summer, and most eggs hatch in late summer or autumn. In many species the hatchlings do not leave the nest until the following spring, often a year or more after the eggs are laid. This phenomenon, known as overwintering in the nest, occurs worldwide among many different kinds of turtles.

Hibernating underwater is not particularly unusual for a reptile. That some hatchlings spend the winter on land in the nest, however, demonstrates, once again, the versatility and intricacy of our native wildlife. This winter, if you take a walk around a lake or pond, adult turtles will be lying dormant in the water whereas baby turtles will be hidden away on land. Although scientists learn more each year about how plants and animals survive in the natural world, many questions remain to be answered about even the most common species.

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