Winter Below the Surface: The Surprising Survival Skills of Painted Turtles
A nature blog by Calista Foisy, BSc
Have you ever seen a painted turtle laying on a rock in the sunshine? They are basking – using the heat from the sun to warm their bodies and keep their metabolism running. So, how do turtles survive our winters in BC when our ponds freeze and it is too cold for them to bask? The answer depends on if they are a hatchling (younger than a year old) or older.
That first year of life is extremely important to painted turtles. It is the most dangerous time for these turtles. When they survive their first year, they will likely live a happy, long life. Painted turtle hatchlings will stay in their nest all winter, which their mother has carefully dug away from the water. The nest will be insulated by snow and keep the hatchlings warmer than if they were in the pond. Hatchlings are naturally freeze tolerant. This means that if the temperature of their nest is -4°C or warmer, they are not going to freeze and are perfectly comfortable. If it is colder than -4°C, hatchlings will use “supercooling”. Supercooling means that the water inside the hatchling (and its cells) is colder than the freezing point. Naturally, this should mean that the hatchling freezes. However, they are able to keep ice crystals from forming. It is when ice crystals form (when the water goes from a liquid to a solid) that would be harmful to the hatchling. Using supercooling, hatchlings are able to survive in their nest all winter, and are perfectly healthy when the temperature begins to warm in the spring. This is when they will emerge from their nests for the first time.
After their first winter, painted turtles will spend their winter in the shallow waters of a pond or lake. They will dig themselves into the mud at the bottom of the lake, where the water does not freeze. This is where they will brumate (sleep). This way, they can conserve their energy. They do not eat or move much, only relying on their stored fats and nutrients to do the most necessary functions to survive. They will even limit their “breathing”. There is not much oxygen under the water where they are staying, and they absorb a small amount of oxygen through their skin. Have your muscles ever burned after a run? This is because when we do not get enough oxygen, lactic acid builds up in our muscles which causes them to be sore. Too much lactic acid build up is bad for your body. Since painted turtles are not getting a lot of oxygen during the winter, they will get a buildup of lactic acid. They will borrow calcium and magnesium from their shell, and use it to buffer (fight off) the lactic acid. This keeps the lactic acid in their body safe for them all winter, and they will get rid of it once the spring comes and they have fresh air to breathe.
This blog was written for Nature Kids BC, a wonderful nature discovery and environmental action organization that helps children form meaningful and enduring connections with nature alongside their families. Check them out at the link below!
https://naturekidsbc.ca/
