How Deep Can Leatherback Turtles Dive? Record Dives

What the tag records show

Scientists study leatherback diving by fitting turtles with time-depth recorders and satellite tags, usually attached to nesting females on the beach. These devices log depth every few seconds and send summaries via satellite, revealing how deep and how long the turtles dive across entire ocean crossings.

The results show a huge range. Typical dives reach a few tens of meters to a few hundred meters, and in many studies most dives are shallower than about 250 m (820 ft). Dives below 1,000 m (3,300 ft) are uncommon but have been recorded in several ocean basins. The deepest widely cited records sit at around 1,200 to 1,300 m (about 4,000 to 4,200 ft), deep enough that the water is near-freezing and completely dark.

Why leatherbacks dive so deep

The main reason is food. Leatherback sea turtles eat almost only jellyfish and other gelatinous animals such as salps and siphonophores. Many of these animals sink to deeper water by day and rise toward the surface at night. Leatherbacks track them, so in many areas they make deeper dives during daylight and shallower dives at night.

Jellyfish are mostly water and low in energy, so leatherbacks need to eat a lot of them, and following prey into deep water allows them to keep feeding around the clock. Not every deep dive is clearly about food. Some researchers think a few very deep dives may help turtles explore for prey layers, avoid predators such as large sharks, or cool down when they are in warm tropical water between nesting trips.

How leatherbacks cope with pressure

At 1,000 m (3,300 ft) the water pressure is about 100 times that at the surface. A rigid, air-filled body would be crushed. The leatherback’s solution starts with its shell. Unlike the hard shells of other turtles, its carapace is a flexible mosaic of small bones under thick skin, and its underside has very little bone. The whole body can compress slightly as the turtle descends.

Leatherbacks dive with air in their lungs. As they go deeper, the lungs are squeezed and collapse, which pushes air out of the parts where gas exchange takes place. Scientists think this limits how much nitrogen dissolves into the blood, which helps the turtle avoid the decompression sickness, or “bends,” that affects human divers. How leatherbacks manage repeated deep dives without harm is still an active research question.

How they hold their breath

Leatherbacks carry a large share of their oxygen in their blood and muscles rather than only in the lungs. Compared with other sea turtles, they have a high volume of blood and high levels of hemoglobin, and their muscles are rich in myoglobin, an oxygen-storing protein. During dives the heart rate slows, which helps save oxygen.

Most dives last a few minutes to around 15 minutes, followed by a short spell at the surface to breathe. Longer dives of 30 minutes to over an hour have been recorded, but they are rare for an active leatherback. Resting sea turtles of other species can stay under for much longer, because sleeping uses far less oxygen; see can sea turtles breathe underwater.

Diving into cold water

The deep ocean is cold, often around 4 °C (39 °F) at 1,000 m, and leatherbacks also feed in cold surface waters off Canada and northern Europe. They stay active thanks to a combination of large size, a thick layer of oily fat, muscle heat produced by almost constant swimming, and countercurrent heat exchangers in the flippers that keep warm blood in the body core. Adult leatherbacks have been measured with core temperatures up to about 18 °C (32 °F) higher than the surrounding water. Other sea turtles can become stunned by cold water, but leatherbacks can feed where few reptiles could survive.

How leatherbacks compare with other deep divers

Among air-breathing animals, the leatherback is one of the deepest divers, but not the champion. Emperor penguins reach a little over 500 m (1,640 ft). Southern elephant seals and sperm whales can exceed 2,000 m (6,600 ft), and Cuvier’s beaked whale holds the record at close to 3,000 m (9,800 ft).

That still puts the leatherback far ahead of every other reptile. For more extreme divers, see how deep can whales dive and our guide to deep-sea animals.