Turtles; Leatherback

I am intrigued by the magical appearance of turtles. I try to learn more about their biology, the different types of turtles and the threats they face. On Nurtured by Nature I will share 7 posts about turtles, each post containing general and turtle-specific insights. This time the Leatherback turtle!

See my previous posts on the Kemp’s Ridley turtle here and the Loggerhead turtle here

General – Distribution and habitat

Sea turtles tend to live in warm coastal waters. This includes the tropics, sub-tropics and warm regions like the Mediterranean. While nesting, they hug more closely to the coast, where normally they swim anywhere across the continental shelf. Waters are relatively shallow here and therefore warm up quickly. Also, most of their food is found in the lush green seagrass beds (max 2 m deep) and the somewhat deeper coral reefs.

All turtles nest on the beach. They enter the beach (at night) and move all the way up to above the flood line. The eggs ought not to be flooded and this way they can remain nice and warm during the 60 day incubation time. I’ll talk more about reproduction another time. A hatchling will typically crawl towards the ocean right away. When entering the open water some turtles may find shelter in the root system of mangrove forests. In lack of mangrove, or despite, other turtles move out to the seagrass beds and past towards the coral reefs beyond. Like mangrove, coral reef structures provide shelter and abundant (size appropriate) food resources – both perfect nurseries. Mature turtles don’t have too many predators left and can now move more freely on offshore seagrass meadows and inshore lagoons.

As sea turtles migrate vast distances across open ocean to find new feeding grounds, most turtle species can be found throughout the entire marine tropics and subtropics. Relatively little is know about migration patterns, but all the more data is available on landing sites. See below four maps on the abundance of turtle species nesting along “warm” coastlines.

Biogeography of sea turtle nesting sites – Miami University Shark research center

Dermochelys coriacea

The Leatherback! Such an exciting turtle, because it is from a different family than the other six. The leatherback turtle belongs to and is the only extant species within the family of Dermochelyidae. And it looks so different too. It has an almost leathery back (hence the name), but this is not real leather. Instead of a hard carapace, it has a though rubbery skin, overlayered with thousands of tiny bone plates, called osteoderms. These also can be found in armadillos, crocodiles, and some dinosaurs. ‘Its carapace is large, elongated and flexible with seven distinct ridges running the length of the animal’ [Sea turtle conservancy]. Also, it is the largest of all living turtles. Mature leatherbacks can grow 1.5 to 2 m long and weigh 200 to 700 kg.

Leatherback sea turtle – seaworld.org

IUCN classifies these turtles as vulnerable. ‘Fisheries bycatch was classified as the highest threat to Leatherbacks globally, followed by human consumption of Leatherback eggs, meat, or other products, and coastal development.’ [IUCN report] They are more widely distributed than other turtles, partly because of their tolerance for colder conditions. They seem to maintain a high body temperature at any time by increased metabolic rate and increased physical activity (speculated, not proven). Leatherback diet consists of predominantly jellyfish and some tunicates like salps. With their delicate, scissor-like jaws they have to feed continuously to get enough energy from these low-nutrient soft-bodied prey.

An animal like the Dermochelys coriacea needs a whole book to do its complex and interesting nature justice. I cannot wait to meet one in real life. What a dream!

Sources

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