Take a deep breath in and hold it. Keep holding it. How long can you go without breathing?
Humans, and most other vertebrates, can survive only a few minutes without oxygen. Turtles need to breathe air just like us but, thanks to unique and remarkable physiology, they can hold their breath a really, really long time. It is this amazing adaptation that allowed freshwater turtles to spread into colder places where winter temperatures are regularly below freezing.
During the summer here in northeastern New York, turtles are likely to be spotted basking on logs or rocks under the hot sun. During the winter, they are never seen unless someone is lucky enough to spot the outline of a buried turtle through clear ice. Once the water cools in autumn, the turtles head to the bottom of lakes and ponds, dig down into the muddy bottom, and slow down.
Turtles do not hibernate. During hibernation a mammal curls up and sleeps to lower their metabolism a bit. Turtles remain conscious but depress their metabolism so much that their hearts beat only once in five minutes! Oxygen is used very slowly. As a result, turtles can, in fact, hold their breath for months, a really, really long time.
If a submerged turtle needs to breath before the ice above them melts, they employ another distinctive aspect of their physiology and absorb oxygen out of the water through their skin. The skin usually used is that of the cloaca, the opening at the rear of the turtle through which the turtle urinates, defecates, and lays eggs. Cloacal oxygen absorption has been given a fun name by turtle enthusiasts: butt breathing.
Turtles survive underwater during winters in cold climates by slowing their metabolism and, when needed, absorbing oxygen through their butts. No breathing is necessary, at least not for a long while.
Butt breathing is just one of the fascinating facts about turtle anatomy and physiology we share in our educational outreach programs.