July 11, 2024, 5:25 am | Read time: 4 minutes
A human diver runs out of air after just a few meters underwater, will need fins at a depth of 40 meters (about 131 feet), and will require oxygen tanks and pressure-equalizing diving suits after that. But even then, a diver will still stop breathing after 450 meters (about 1,476 feet). For the leatherback sea turtle, however, this is just one third of its potential diving depth, as researchers have observed.
The leatherback turtle is a truly incredible animal. Not only is it the largest turtle in the world, with a shell length of up to 2.5 meters (about eight feet), but it is also the best diver. And not just among turtles, but among all reptiles. According to a new study, a leatherback turtle has been able to dive even deeper than the previous diving record.
Leatherback turtles regularly set diving records
The most recent global diving record for a leatherback turtle dates back to 2006 and is documented on the Guinness World Records website. On December 16, 2006, a leatherback turtle was seen diving to a depth of 1,280 meters (almost 4,200 feet) southwest of Cape Verde. The previous record in this category was also from a leatherback turtle. According to “Guinness World Records”, this was 1,200 meters (3,937 feet) and was recorded in May 1987 off the Virgin Islands.
However, this record may soon be surpassed. A blog post from the Nature Conservancy shares the details of the new sighting. The leatherback turtle, Uke Sasakolo, was named after the Sasakolo beach where it laid its eggs. Uke was tagged as part of an ongoing research project. As soon as the research is published and reviewed by other scientists, there could very likely be a new entry in the Book of Records.
What the leatherback turtle is looking for in the depths
With the help of the transmitter, Uke Sasakolo’s journey through the South Pacific could be traced exactly. First it laid its eggs, then it swam from the Solomon Islands through the South Pacific to New Zealand, where its hunting grounds are located. For leatherback turtles, however, these are not on the surface of the sea but several hundred meters below.
They have a preference for feeding on deep-sea jellyfish, consuming several kilograms a day. Consumption reports range from 10 (22) to 100 kilograms (ca. 220 pounds) of jellyfish per day. Uke Sasakolo dove a record-breaking 1,344 meters (ca. 4,409 feet) deep for its daily supply of cnidarian snacks. To avoid poisoning themselves while feeding, leatherback turtles have developed esophageal papillae. These allow the slippery animals to slide safely into their stomachs and transport salt water back out again.
295 pounds of pressure per square inch is no problem for the leatherback turtle
It is also remarkable how the world’s largest turtle manages to dive to such depths. After all, the leatherback turtle doesn’t get its name from nowhere. Its soft, flexible shell is not made of its skin. Instead, it contains bone keels that allow the tough, leathery skin to move freely.
This adaptable shell compensates for changing pressure conditions. In fact, it is so effective that leatherback turtles can survive water pressure at depths of over 1,000 meters (around 3,260 feet). During Uke Sasakolo’s deepest dive, the pressure was so great that every single square centimeter (inch) of the turtle was exposed to 134 kilograms (about 295 pounds) of pressure.
The temperature differences that the leatherback turtle experiences when diving are also enormous. From the up-to-28-degree (82 Fahrenheit) warm sea of the tropical South Pacific, it goes into ice-cold, eternally dark water. This can even reach below zero degrees (32 Fahrenheit). This is possible because salt water has a lower freezing point than fresh water. Nevertheless, the leatherback turtle does not get cold. It maintains an internal body temperature that is 18 degrees (64.4 Fahrenheit) higher than the outside temperature during its dives, which can last up to 90 minutes. This is because, unlike many other reptiles, they are not cold-blooded.
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Why the leatherback turtle does not get decompression sickness
Instead, they use something that scientists call gigantothermy, a small ratio between the surface area and volume of the animal. This means that the animal’s core temperature changes very slowly. The leatherback turtle is also wrapped in a layer of fat that stores 90 percent of its body heat inside. They also use the countercurrent principle for heat exchange, which prevents cold blood from mixing with warm blood. This same principle explains why penguins’ feet do not freeze to the ice, as reported by PETBOOK.
In a 2010 study, researchers were also able to demonstrate how leatherback turtles manage to sink and resurface without much effort or signs of decompression sickness. This is because they do not have to use a lot of energy to reach unimaginable depths. They simply allow their lungs to collapse and then draw on the large oxygen reserves in their muscles and blood. On the ascent, CO2 gradually builds up in their lungs, providing buoyancy1.