How Do Turtles Breathe Under Water?

There are around 350 species of turtles worldwide. Some species live their entire life on land, others live only in the water, and still others go between both environments. Just how do turtles breathe under water? These animals breathe air and need to surface for oxygen, but they have some interesting adaptations that allow them to remain under water for long periods of time.

Do turtles have gills or lungs? Turtles do not have the ability to breathe under water. They have lungs, but their hard shells don't allow their ribs to expand or contract, so specialized muscles lining their shell help push air in and out.

Turtles have nares (openings similar to nostrils) above their mouth that they use to take in air. These nares allow turtles to breathe with their mouth closed, and air travels into the inner nares and down the trachea into the lungs, where alveoli (tiny air sacs) help to maximize oxygen exchange.

Some species of turtles are able to breathe through their butt in a process called cloacal respiration. The cloaca is an opening in a turtle's rear end through which their urine and feces empty. This opening contains many blood vessels, and turtles are able to absorb oxygen from the water when it moves over these blood vessels. Though this process is technically called respiration, it doesn't actually involve the lungs.

Turtles are ectotherms, meaning their body temperatures are dependent on the environment, and in cold water, their body temperature will be low. So, what happens to turtles in the winter when the water gets cold and ponds freeze over?

Turtles don't hibernate in the winter but instead go through a process called brumation. Brumation is a period of very low activity, similar to a deep sleep, during which bodily processes slow way down. Brumating turtles do not eat but are able to live off fat stored in their body. This process keeps the turtles alive during brumation but causes lactic acid to build up in their body. To combat this, a turtle's shell releases carbonates into its system, which neutralizes the acid and keeps it from becoming dangerous.

Turtles spend the winter under water or tucked into mud. Water temperatures are more stable than air, and turtles need a source of water to absorb oxygen. This is where cloacal respiration comes in handy. Since turtles are in a deep sleep and aren't surfacing to breathe, cloacal respiration ensures that they are able to absorb the oxygen they need from the water.

All turtles need to breathe air, even sea turtles who live most of their life in the ocean. During warmer seasons, a turtle's metabolism is faster, and it requires more oxygen than during brumation. Sea turtles can hold their breath for up to about seven hours, while other semiaquatic species can stay under water for about an hour before needing to come up for air.

Turtles can drown if they become trapped under water and cannot reach the surface to breathe. This may happen if a turtle comes out of brumation in a pond with a surface that is still frozen over. Once a turtle's metabolism kicks back in, she needs more oxygen than the limited amounts she gets from cloacal respiration, and she must breathe air. Even sea turtles can drown if they become caught under water in a fishing net or trap and cannot get out. A trapped turtle will thrash around to try to escape, and this stress depletes oxygen more quickly and can result in the turtle drowning.