Very occasionally passing through Bermuda as adults, these dark and prehistoric turtles are a wonder to behold. Leatherbacks (Dermochelys coriacea) are the largest of the turtle species by far. The largest specimen ever observed was 2,015 pounds and almost 3 metres long. Sleek and black on top, and white or pink speckled on the bottom, they spend their lives roaming the pelagic seas.
1. Extreme living: The leatherback can complete long-distance migrations and deep dives, up to 1,280 metres, to forage for food. Its body is designed to be hydrodynamic, and is tear-drop shaped with 7 grooves running laterally across it. It also has the largest fins compared to its body size of any turtle.
2. Thermoregulation: Leatherbacks are found in the coldest waters that any turtle species can stand, visiting places as northern as Iceland. They are able to maintain their body temperature as much as 10 degrees higher than the surrounding water. Recent studies have revealed that the turtles spend very little time resting, and their heat regulation is generated by their own muscle movement.
3. Soft shell: Their shells are not like typical turtle shells – instead the bony part of the carapace is made of thousands of small interlocking bones, and this is grown over by leathery tissue covered in skin. The leatherback is the only modern turtle derived from prehistoric turtles with soft shells, the six other current species all belong to a sister family of this group, Cheloniidae.
4. Iron maiden gullet: Leatherbacks have special adaptations to enable it to most efficiently eat its diet of jellyfish. It has backwards facing spines lining its oesophagus that enmesh jellyfish and prevent their gelatinous bodies from escaping the turtle’s jaws. Unfortunately, this also means that if they accidentally ingest a plastic bag, there is no way for them to spit it out.
5. Jellyfish diet: Jellyfish are about 95% water, so leatherbacks must feed constantly in order to sustain themselves. There is some evidence that the turtles follow jellyfish blooms in order to feed most efficiently. Though jellyfish are not very nutritious, leatherbacks hunt with an 100% success rate, and nothing goes to waste.
Jellyfish are even more abundant in the deep ocean, which explains their diving habits. It’s estimated that leatherbacks eat 73% of their weight in jellyfish every day, that’s about 850 pounds of jellyfish!
6. Conservation: It’s essential to determine critical areas for the leatherbacks in order to target conservation measures, since they are a highly pelagic species and we cannot hope to protect the entire ocean. However, their lifestyle makes them hard to study, and we are not sure where young leatherbacks grow up, or exactly what patterns the adults might follow.
Leatherbacks are threatened on the nesting beach and as adults. Turtle eggs are harvested for consumption, and full-grown turtles are often by-catch in long-line fishing operations. In addition, pollution of the ocean by plastic, and habitat loss on nesting beaches threatens these giants.