Green turtles are the largest of all the hard-shelled sea turtles, but have a comparatively smaller head. They are occasionally referred to as black sea turtles. They are large in size, attaining about 120 cm in length and weighing about 136-159 kg.
The green turtle has a smooth carapace, which varies in shape between sub-circular and heart-shaped and in colouration between black, grey, green, brown and yellow. The plastron (bottom shell) is yellowish-white in colour. Hatchlings are just 2 inches (50 mm) in length. Track marks are 100-130 cm wide, are deep, with symmetrical diagonal marks made by forelimbs and tail drags are a solid or broken line.
Species: C. mydas
Sexual maturity in green turtles is reached anytime between 20 and 50 years of age. Females return to their natal beaches once every 2-4 years. Eggs measure about 4.5 cm in diameter.
Until very recently, it was held that adult green turtles are unique among sea turtles in that they are herbivorous, feeding primarily on sea grasses and algae. This diet was thought to have given them greenish coloured fat. Recent reports however, suggest that during the mysterious “missing years” (from the time hatchlings leave their nesting beaches to when adults return to lay eggs), they have been seen to feed on small crustaceans and jellyfish. But as they move towards the shores there is a dramatic change in their diet and they feed only on sea grasses and algae.
Green turtles are found on large, open beaches to small coves covered with sea grasses, or in areas where seaweeds are found. The species (like the hawksbill turtle) is also known to prefer nesting on island beaches mainly, the beaches of tropical and subtropical areas near continental coasts and around islands, for instance the Lakshadweep Islands in India. They use scattered rocks, bars and coral heads as night-time sleeping sites. They are primarily seen in the Atlantic Ocean, Gulf of Mexico, Argentina, in the Mediterranean Sea and Indo-Pacific.
The systematic harvest of eggs and adults on nesting beaches and juveniles and adults on feeding grounds over the years has taken a heavy toll on the species. With changing fishing patterns, incidental capture in fishing gear, especially gillnets, trawls, traps and pots, longlines and dredges is a serious threat, which prevents species’ recovery. In India, a large number of green turtles used to be captured in the waters of the Gulf of Mannar and off the coast of Tamil Nadu until the Wildlife Protection Act was enforced in 1972. Illegal take of turtles however still occurs. In some parts of the world, green turtles are also threatened by a disease known as (sea turtle) fibropapillomatosis, the symptoms of which are tumours that grow on all the soft tissue areas of a sea turtle, including the eyes and mouth and can also grow through the carapace and plastron.
Indian Wildlife (Protection) Act: Schedule I
IUCN Red list: Endangered (http://www.iucnredlist.org/apps/redlist/details/4615/0)