How Long Can Sea Turtles Hold Their Breath?

 

By Sarah Milton

© Emilie Ledwidge/Ocean Image Bank

How long can you hold your breath? A minute? Maybe two? Even the current world record for underwater breath holding by a human, an astounding 24 minutes and 37 seconds, pales in comparison to sea turtles’ breath-holding abilities. Because sea turtles are ocean-dwelling air breathers, it’s clear that they must hold their breath for at least several hours in order to forage for food, avoid predators, and sleep underwater. But they may be able to go much longer—several days or even months. 

In the early 1970s, scientists learned from the Seri indigenous people and from other Mexican fishermen about green turtles that were believed to hibernate underwater in the Gulf of California during the winter, maybe for months. Shortly thereafter, turtles were pulled up when Port Canaveral (Florida, U.S.A.) was dredged, and the stained condition of the turtles’ shells suggested they had been buried in the mud for days at least. However, there was no proof of how long those animals were really submerged. 

More recent studies have sought to better understand sea turtles’ breath-holding limits in laboratory settings and in the wild using time-depth recorders. The studies have found that under most conditions, sea turtles will dive for 20 to 40 minutes while foraging and up to several hours when sleeping. Additionally, when the water gets cold, some turtles are able to remain underwater for much longer. The longest recorded submersion by a wild sea turtle was when a loggerhead turtle stayed submerged for seven hours while overwintering in Greece. But how do they do it?

How long air-breathing animals can stay underwater is a function of three factors: (1) how much oxygen they can store in their blood and muscles, (2) how fast they use the oxygen when diving, and (3) how tolerant they are to low oxygen. Sea turtles have several adaptations that help them stay underwater for long periods of time, including:

  • Oxygen storage: Sea turtles have high concentrations of hemoglobin and red cells in their blood and myoglobin in their muscles, enhancing oxygen storage during dives. The turtles can also move the oxygen into their bloodstream even when lung oxygen levels are very low.

  • Low metabolic rates: All sea turtles, except the leatherback, are cold-blooded, with metabolic rates only about 10 percent of ours. As a result, they use oxygen more slowly. Cold temperatures further slow their metabolic rates, helping them stay submerged for even longer.

  • Bradycardia: Sea turtles decrease their heart rate while diving. In a study of diving leatherbacks, heart rates decreased about 30 percent for dives of less than 10 minutes. One turtle’s heart rate declined from 27 beats per minute at the surface to 3.6 beats per minute during a 34-minute dive. Some turtles’ heart rates briefly go as low as 1 beat per minute during dives.

  • Peripheral vasoconstriction: Green turtles can shunt blood away from less important organs and tissues to conserve oxygen during dives up to half an hour long, but they appear unable to maintain the vasoconstriction for longer. Though turtles’ vasoconstriction abilities are not as developed as those of diving marine mammals, the combination of lower heart rates and altered blood flow still helps reduce turtles’ metabolic rate.

  • Hypoxia tolerance: Although most dives are relatively short and the turtles don’t use all their stored oxygen, they also have a much better ability than mammals to survive low oxygen. Their brains are adapted to prevent the damaging effects that happen when we run out of oxygen (as might happen during a stroke), so they can potentially live up to a few hours without oxygen. 

Understanding how and for how long diving sea turtles remain submerged is important for conservation efforts, because turtles face threats of drowning when caught or entangled. As a practical example, when turtle excluder devices (trap doors in shrimp nets that allow large animals such as turtles and sharks to escape but not small fish and shrimp) were first being developed, one argument against them was that shrimp net tow times were only 30 minutes and turtles could hold their breath for hours, so surely the fisheries were not responsible for the many drowned turtles along the coast each summer. But a sea turtle that is struggling and swimming frantically to escape a net will have an elevated heart rate and will use up its oxygen stores very quickly and indeed can drown. Continuing research into sea turtles’ breath-holding abilities may help further elucidate species-specific differences and provide a more definitive answer to the question of how long sea turtles can hold their breath; that research may even provide clues as to how the human brain might survive longer without oxygen. 

Author Affiliation

Sarah Milton, Department of Biological Sciences, Florida Atlantic University, Florida, U.S.A.

This article originally appeared in SWOT Report, vol. 19 (2024). Download this article as a PDF.

 
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