Laurent Louis Jean
The different species
A sponge eater: the hawksbill turtle
Also known in the West Indies as the karet, Eretmochelys imbricata can be recognized by its slender head, its beak, which evokes that of a falcon (hawk-billed turtle, in English), the serration of the posterior part of its shell and the arrangement of its scales like the tiles of a roof. It lives near coral reefs and seaweed beds. It is the only one that consumes sponges, for which it has a particular taste, even if it does not disdain other invertebrates such as crustaceans, jellyfish, squid and sea urchins, as well as algae. Its hooked beak allows it to search for food in crevices. Of medium size, it measures 60 cm to 1 m for 43 to 75 kg in adulthood. It is the most tropical of all species. It evolves preferably on shallow coastal bottoms, but it is able to dive more than 50 m deep for half an hour on average. Its top speed was measured at nearly 25 km/h. The populations of hawksbill turtles in the French West Indies have exchanges in particular between Martinique, Barbados and Saint Lucia, or between Guadeloupe, Cuba, the Virgin Islands and Antigua. Their main nesting site is in Mexico.
A grass-colored turtle: the green turtle
green turtle, Chelonia mydas, owes its name to its color, which comes from the pigments contained in the plants it consumes. Indeed, if juveniles are omnivores, and eat jellyfish and crustaceans among other things, adults are exclusively herbivores. They live not far from coral reefs and areas of seagrass beds and deep-sea algae that are their food. It is the largest of the Cheloniidae, and the liveliest of the sea turtles: it can reach nearly 35 km/h at a peak. The average height and weight of adults varies depending on the geographical area. The size of the carapace averages 1.10 m, and the animal weighs between 80 and 130 kg. Some specimens can reach 300 kg for 1.50 m. It is mainly found around the continental coasts and oceanic islands of nearly 140 countries, up to 45° latitude on either side of the equator. It is there that it feeds, but most of the time, it is in the tropical seas that it comes to lay eggs. From one site to another, it can migrate more than 2,000 km. For example, the populations of the French West Indies have exchanges with the islands of Aves (Venezuela). Their largest nesting site is located in Tortuguero, Costa Rica.
The most traveler of sea turtles: the leatherback turtle
Its carapace, black to midnight blue, spotted with white dots, has 7 whitish longitudinal keels and its huge head has a pink frontal spot, called muzzle. Dermochelys coriacea is the largest of all sea turtles, hence its nickname the sea giant. The height of adults can reach 2 meters, and their weight is almost a ton, but on average it weighs 400-500 kg. She can swim up to 36 km/h. Carnivorous, it feeds mainly on jellyfish, but also on hydrozoans and plankton. Of all the reptiles, it is the one with the widest distribution: it is found in all the oceans up to the Arctic Circle. It is pelagic at all phases of its cycle: it lives in open water, far from the coast, dives to nearly 1,300 meters with apneas lasting more than 80 minutes. It can travel 15,000 km per year, which makes it one of the most migratory species in the world. The beaches of French Guiana and Gabon are its most important nesting sites. Leatherback turtles laying eggs in the French West Indies have been observed in the central Atlantic, in Colombia, Dominica, Grenada, Guyana, Saint Lucia, Trinidad and with exchanges between Guadeloupe and Martinique.
A “big head” among turtles: the loggerhead turtle
Caretta caretta is one of the most studied species in the world. It is present in the French West Indies, but never in large quantities. It lives offshore, on bottoms around 50 m, and chooses to nest the higher latitudes of temperate zones. It is found a lot in Florida and the Mediterranean. It is also a large species: the carapace of adults, orange-brown in color, can measure up to 1.50 m, for a weight of a hundred kilos. It is particularly recognizable by its large head, equipped with a large and powerful jaw. It is omnivorous, but above all carnivorous, and not very faithful to its egg-laying sites.
The smallest sea turtle: the olive ridley turtle
Lepidochelys olivacea is one of the smallest. Its carapace, flat and brown, is cordiform (heart-shaped) and very indented at the level of the front legs. It measures between 50 and 70 cm, for about forty kilos. Omnivorous, it feeds readily on what it finds: preferably jellyfish, large invertebrates (crabs and other crustaceans) and fish, but does not disdain, if necessary, algae and aquatic plants. It is very rare in the West Indies, its main spawning sites are located on the Guyana plateau.
Both American and Caribbean: Kemp's Tortoise
It is absent from the West Indies, Lepidochelys kempii but it is found near the coasts of Mexico, Florida and the North Atlantic. It evolves mainly on the flats and around the mangroves. It is the smallest of the sea turtles and the most narrowly distributed species. Its heart-shaped carapace, wider than long and relatively domed, barely reaches 75 cm, and, like the olive ridley turtle, the adult weighs about 45 kg. It is mainly carnivorous.
sea turtle habitats
sea grass beds
Seagrasses, which should not be confused with algae, are flowering aquatic plants with long, narrow leaves. They constitute underwater meadows which play an important role in the ecosystems of coastal areas. They can host hundreds of species, such as starfish, conch or even sea urchins, and serve as a refuge for juvenile and adult fish. They stabilize the substrates and promote the sedimentation of the seabed, mechanical protection against waves and the limitation of coastal erosion. Thalassa testudinum , known as "turtle grass", is particularly appreciated by green turtles.
Coral reefs are natural structures formed by microorganisms. They form complex marine ecosystems rich in biodiversity, as sources of food, refuge and protection for many aquatic organisms. They cohabit with sponges, generally attached to the marine substrate. Both contribute to the enrichment of fishing areas, their ecological, economic and tourist role is essential.