© Jack Versiani Holt

Turtle species

Turtle design

There are seven species of marine turtle existing today. They represent an extremely successful group of animals whose basic design has changed little over millennia. Their shell, known as the carapace, is smooth and streamlined. Their elegant and muscular oar-like flippers allow them to swim swiftly and gracefully through the ocean.

Marine turtles spend most of their lives at sea, but have lungs so they need to surface regularly to breathe, although they are able to sleep for several hours underwater wedged into caves or crevices. Most marine turtle species are cold-blooded and thrive in warmer climates, basking in the morning sun to raise their body temperature. The leatherback turtle is unique amongst reptiles because it can control its own body temperature, enabling it to visit temperate seas to feed on its favourite prey, jellyfish.

Turtles don’t have teeth, instead they have beak-like jaws that are specially adapted to their diet, and they drink seawater. To get rid of the excess salt they accumulate from their diet, turtles constantly cry salty tears from special glands in their eyes. These tears are particularly noticeable in female turtles when they come ashore to nest.

Turtle lifecycle

While they are well adapted to marine life, turtles must come ashore to breed usually in the tropics or in warm temperate regions such as the Mediterranean. Male turtles spend all their lives at sea, and during the nesting season they migrate to traditional nesting beaches (rookeries) where they wait offshore to mate with the females. Female turtles then crawl ashore, dig nests and lay their eggs at night under cover of darkness. After they have covered their eggs with sand they return to the sea without caring for their young.

The sex of hatchling turtles is dependent on the temperature, at which the eggs were incubated, with higher temperatures producing female turtles and lower temperatures producing males. About two months after the eggs are laid, they begin to hatch in the nest, with most eggs hatching over a couple of days. The hatchlings then dig upwards together to get to the sand surface. They emerge from the nest at night and run down to the sea as quickly as possible to avoid the many predators that await them. The hatchlings then swim for about 24 hours without stopping, until they are carried out into the open ocean by marine currents, a behaviour known as juvenile frenzy, but many are eaten by fish and sharks on the way.

Little is known of the habits of young turtles during their early “lost years” at sea, but we do know that as juveniles they feed on jellyfish and other soft bodied animals found in the open ocean. We are only beginning to understand their lives of turtles when they return to coastal waters as dinner-plate sized juveniles. At this age their main predators are sharks and man. Virtually nothing is known about juvenile leatherback or olive ridley turtles as they spend almost all their lives out in the open ocean.

Leatherback turtle

The leatherback is the largest of the marine turtles and gets its name from the black, leathery skin that covers its carapace (shell). They are unique amongst reptiles in that they have some internal control of their own body temperature, so can forage in temperatures lower than 5 degrees centigrade and dive to depths of over 1km.

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Hawksbill turtle

Hunted over the years for their beautiful shells, hawksbill turtles are considered to be critically endangered. The hawksbill turtle has a narrow head and a long, tapered beak shaped similarly to that of a bird of prey, hence the name. The scutes on their shells are misleadingly known as tortoiseshell and are sought after in some parts of the world to make jewelry and other ornaments. Trade in all wild marine turtles and their parts is currently banned under the Convention on International Trade in Endangered Species (CITES) but some illegal trade continues to endanger the species. Please don’t buy genuine tortoiseshell items at home or abroad.

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Loggerhead turtle

The loggerhead prefers to nest and forage in warm, temperate climates rather than in the tropics. The loggerhead’s name refers to its extraordinarily large head, which houses powerful jaw muscles and large beak for crushing its crustacean prey.

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Green turtle

Once hunted for the trade in turtle soup, the green turtle manages to survive with populations throughout the tropics and the Mediterranean. The name derives from the greenish fat and cartilage, known as calipee, which was the main ingredient of turtle soup. Juvenile green turtles usually have a strikingly patterned chestnut-brown coloured carapace (shell), while adult green turtles usually have a greenish-grey carapace patterned with black markings.

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Flatback turtle

The flatback turtle is unusual in that its carapace is almost completely flattened. Unlike other turtle species, the hatchlings do not swim out into the open ocean when they first enter the sea, but stay close inshore and inhabit coastal lagoons.

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Kemp's ridley turtle

Kemp’s ridleys are the rarest of all the marine turtles, and were close to extinction in the 1980’s. The carapace of adult turtles is olive-green and they have a broad, parrot-like beak.

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Olive ridley turtle

The olive ridley’s name comes from its olive-green carapace. The name ridley may come from the word “riddler” or “riddle” because this species was once thought be a hybrid of other turtle species. The olive ridley is famous for its spectacular arribadas, where thousands of females nest simultaneously on the same beach.

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