Tortue Luth
Tortue Luth

Nom commun: tortue luth
Nom scientifique: Dermochelys coriacea
Taille: 1,40 à 1,60 m
Poids: 300 à 900 kg (660 à 2000 lb)
Population: estimée à environ 25 000
Distribution: mondiale, des océans tropicaux aux mers subpolaires. Sites de ponte sur les plages tropicales.
Enjeu: surexploitation des œufs, perturbation des sites de ponte, équipement de pêche, pollution de plastique, surpêche
Statut Liste Rouge UICN: en danger critique d’extinction

The leatherback turtle is the largest of all the world’s turtles. By weight, it is the third-largest reptile, after the saltwater and Nile crocodiles.

Its name comes from the character of its shell, which is leather-like, rather than boney like other turtles (the French name, tortue de luth, refers to the shape of its shell, which resembles the musical instrument called the lute). It is easily recognized by the seven ridges that run along its back from head to tail.

Sea turtles are mysterious animals in many respects. They have crisscrossed the oceans for over 100 million years, but what we know about them comes mostly from their egg-laying sites on tropical beaches. Six to 10 times per year, female leatherback turtles will climb up one of the world’s many beaches, dig a nest, and lay her eggs. She will lay fewer than 100, 20 percent of which will be small and infertile. Of the rest, 50 to 60 percent will hatch after approximately 70 days. The sex of the baby turtles is determined by the temperature: above 29.5º C, females will hatch. Below this temperature, males will hatch.

The smooth, dark-blue skin of the leatherback is irregularly dotted with small pink or whitish spots. Perfectly adapted to the marine environment, it is an excellent swimmer, able to dive to 1,300 metres, deeper than any other reptile, and can hold its breath for up to 80 minutes. It feeds on soft-bodied organisms, and, as it is particularly fond of jellyfish, helps control the numbers of these animals.

Critically endangered, the Pacific Ocean population of leatherback turtles has declined by nearly 80 percent over the last 15 years. We know this thanks to observations of the number of females coming to lay eggs at their numerous nesting sites. This decline appears to be due to two significant threats: over-collection of their eggs (in certain cases up to 95 percent of clutches) and their entanglement in fishing equipment such as nets an lines.

Because leatherback turtles cannot swim backwards, they are not able to reverse course when they encounter a fishing net. Some trawlers are starting to equip their nets with turtle excluder devices to allow turtles to escape from the nets when they get caught in them.

Beachfront development and tourism also disturbs egg-laying and hatching. In addition, ocean warming is contributing to the hatching of increasing numbers of female turtles, causing a significant imbalance in the ratio of males to females. In short, leatherback turtles are under siege from several sides. Worldwide measures to protect and conserve them will be required if these peaceful inhabitants of the seas are to survive to see better times.

Did you know?
The leatherback turtle is the only living member of the family Dermochelyidae. These turtles are characterized by shells that lack scales or bone, instead being covered with a thick leather. Other Dermochelyidae species are known from the fossil record. Like other sea turtles, the leatherback turtle cannot withdraw into its shell.

RÉFÉRENCES: Liste rouge des espèces menacées de l’Union internationale pour la conservation de la nature (UICN) et Encyclopedia of Life.

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