Some Turtles Survive Winter by Breathing Through Their Butts

Every winter, painted turtles sink to the bottom of ponds and streams, lock themselves under several feet of ice, and stay there for months without coming up for air. If you or I tried that, things would go poorly very quickly. Turtles, however, have a rather unconventional backup plan.

The trick lies in a process called cloacal bursae respiration — or, as biologists who enjoy a good chuckle prefer to say, "butt breathing." The cloaca is a multi-purpose opening near a turtle's tail, and it happens to be lined with tissue rich in blood vessels. By pumping water in and out, turtles can extract just enough dissolved oxygen to keep their slowed-down winter metabolism ticking over.

It's not exactly efficient — turtles still have to drop their body temperature near freezing and basically hibernate at minimal life-support mode. But it is enough. They'll sit motionless in the cold mud, absorbing oxygen through their hindquarters, until temperatures rise and ice melts.

The best part? Painted turtles aren't alone. Several other freshwater turtle species use the same trick. So the next time someone asks you how turtles survive a frozen winter, you now have a completely accurate answer that will ruin dinner for at least three people.