Can Sea Turtles Breathe Underwater? How Long They Can Dive

How do sea turtles breathe?

Sea turtles breathe through two nostrils at the tip of the snout, using a pair of large lungs that sit just under the upper shell. When a turtle surfaces, it lifts only its head out of the water and takes a single explosive breath out, followed by a quick, deep breath in. The whole exchange can take just a second or two, and the turtle can then dive again almost at once.

Unlike mammals, turtles cannot expand their ribs, because the ribs are fused to the shell. Instead, they move air in and out using muscles that work on the lungs and other organs, along with movements of the limbs. Sea turtle lungs are large and can be refilled quickly, which is ideal for an animal that spends almost its whole life below the surface.

Like other reptiles, sea turtles are cold-blooded, meaning their body temperature follows that of the water (see are reptiles cold-blooded?). That is a big part of the secret: a cold-blooded animal uses far less oxygen than a warm-blooded one of the same size, so the same breath lasts much longer.

How long can sea turtles stay underwater?

How long a sea turtle stays down depends mostly on what it is doing, plus the water temperature and the species.

Active turtles breathe often because swimming and chasing food burn oxygen quickly. A green turtle or loggerhead going about its normal business typically surfaces every few minutes. When resting, a turtle lowers its heart rate and uses very little energy, so it can stay on the sea floor for hours. In cool Mediterranean waters, loggerheads have been recorded staying submerged for more than 10 hours during winter, among the longest voluntary dives recorded for any air-breathing vertebrate.

How sea turtles save oxygen

Sea turtles store oxygen in three places: in the air in their lungs, in their blood (bound to hemoglobin) and in their muscles (bound to myoglobin). Different species rely on these stores in different ways. Hard-shelled species such as the green sea turtle carry much of their oxygen in their lungs, which also help control their buoyancy, like a diver’s buoyancy vest.

During a dive, a turtle can slow its heart rate, a response called bradycardia, and send more blood to the organs that need it most, such as the heart and brain. Remarkably, sea turtles stay aerobic, meaning they keep using oxygen rather than switching to oxygen-free metabolism, for nearly all of their normal dives. That lets them surface without needing a long recovery.

Leatherbacks: the deepest-diving turtles

The leatherback sea turtle is the deepest diver of all reptiles. Leatherbacks have been recorded diving deeper than 1,200 m (3,900 ft), among the deepest dives known for any air-breathing animal apart from some whales. Most of their dives are much shallower and shorter, typically lasting about 3–8 minutes, with occasional dives of 30–70 minutes.

Leatherbacks are adapted for this in several ways. Their flexible, leathery shell can compress under pressure, and their lungs are designed to collapse during deep dives, which helps prevent decompression problems. Instead of relying mainly on lung air, they store a large share of their oxygen in their blood and muscles. Read more in how deep can leatherback turtles dive?

Do sea turtles sleep underwater?

Yes. Many sea turtles sleep on the bottom, often wedged under a rock or coral ledge where currents and predators are less of a problem. Green turtles in Hawaii and elsewhere often return to the same sleeping spot night after night. While asleep, their metabolism slows and a single breath can last for hours.

Turtles in deeper water, or those far out at sea, may instead sleep floating at the surface. Young turtles living in the open ocean often rest among floating mats of sargassum seaweed.

Why sea turtles drown in fishing nets

A turtle that chooses to dive can stay down for hours, but a turtle that is forced underwater is in serious trouble. When a turtle is caught in a trawl net, gillnet or longline, it struggles, becomes stressed and uses up its oxygen far faster than normal. Its body switches to oxygen-free metabolism, lactic acid builds up and the turtle can drown in a short time.

Accidental capture in fishing gear, called bycatch, kills large numbers of sea turtles every year and is one of the main threats to all species. In the United States, shrimp trawlers must use turtle excluder devices (TEDs), grids with an escape hatch that let turtles slip out of the net. NOAA reports that properly installed TEDs let about 97% of turtles escape.

Myths and facts

Myth: turtles can breathe through their bottoms. A few freshwater turtles, notably the Fitzroy River turtle of Australia, can absorb a significant amount of oxygen from water through sacs in the cloaca, the opening under the tail. Sea turtles cannot do this in any useful way and depend entirely on their lungs.

Myth: sea turtles drink only fresh water. Sea turtles live in salt water and swallow it with their food. They get rid of the extra salt through large glands near the eyes, which is why they sometimes appear to cry when out of the water.

Fact: turtles can be stunned by cold. When water temperatures drop suddenly below about 10 °C (50 °F), sea turtles can become sluggish, float and be unable to dive or swim properly. These cold-stunning events happen in places such as Florida and Cape Cod in Massachusetts, where rescue teams collect stranded turtles each winter.