Through the spring, summer and even early fall we can find turtles out swimming or basking on logs, soaking up the sun. But now that temperatures have gotten colder, what do turtles do? Do they migrate somewhere warmer or stay right here? Do they hibernate or stay active? Do they have any special adaptations that help them survive the winter?
Freshwater turtles live in and around ponds, lakes and rivers. When temperatures start to drop as fall turns to winter, most freshwater turtles swim down to the bottom of the body of water where they are living. There they will spend the winter on top of or nestled into the mud.
Words to know
Basking: To lie exposed to warmth and light.
Metabolism: The chemical processes that occur within an organism to maintain its life.
Neutralize: To render something harmless by applying an opposite force or effect.
Nourishment: The food or other substances necessary for growth, health and good condition.
Turtles are cold-blooded, which means their body temperature depends on the temperature of their environment. When the temperature gets colder, turtles’ bodies also start to slow down, and it gets harder for them to move. But wait! Since they are cold-blooded, don’t they freeze under the water? Believe it or not, water temperatures are more stable than air temperatures through the winter. That means water temperatures are more likely to stay the same, but air temperatures can change from cold to colder to warmer and then cold again over and over throughout the season.
Also, water temperature can be warmer than air temperature. Water temperature will not go below freezing. Once ice freezes over, the water cannot get any colder. Water freezes at 32 degrees Fahrenheit and stays that way as long as the air temperature stays that cold or colder. Air temperature can drop below freezing, though. Brrrr!
Do turtles hibernate?
Turtles do not hibernate, but they do go through a similar process called brumation. Brumation is a period of very low activity. It’s like a deep sleep, but they may still move a little bit. Their metabolism slows down to the point that they can survive without food or even oxygen! They don’t breathe, and their hearts hardly even beat.
How can turtles survive winter without food and oxygen?
Turtles are able to survive the winter without eating. During the rest of the year, they are able to eat their fill of plants and insects. When winter comes, they live off the extra fat and sugars their bodies stored up the rest of the year. Because their metabolism is so slow during brumation, they don’t need much nourishment.
Although turtles aren’t breathing, they are able to take in oxygen through blood vessels at the surface of their skin. But there is a side effect to not breathing. Waste starts to build up as lactic acid. This can happen to humans too. Have you ever exercised really hard and had your muscles start to cramp? That’s the feeling of the lactic acid building up. Turtles have a cool adaptation that helps them absorb the lactic acid safely — their shells! The calcium and carbonates in their shells absorb and neutralize the acid.
How do turtles know when it’s spring?
Turtles have several ways of knowing that the warmer temperatures of spring have arrived and it’s safe to come out of brumation and emerge to the surface of the water. As the ice begins to melt, more sunlight is able to make it through the water. Turtles’ eyes are adapted to sense changes in light, even when they are closed during brumation!
Turtles are able to sense movement in the water through their nervous system as other creatures start to become more active. They are also able to feel changes in water temperature as the sun heats it up. Because turtles are cold-blooded, as the water temperature rises, so does their body temperature. And as their body temperature rises, they are able to move more easily. They will swim to the surface and bask in the sunlight to regain full movement — and a full appetite too!
Do all turtles spend winter underwater?
In a word, no. Land turtles, like species of box turtles, follow the same pattern of brumation, but underground instead of underwater. They will dig a burrow under dirt and leaves to protect themselves from the cold winter temperatures. Sometimes the tops of their shells can still be seen, but often they are completely covered. Sometimes they continue to dig deeper as the winter stretches on and temperatures continue to drop.
____________
Follow Willy's Wilderness on Facebook for more kid-friendly nature stories and activities.