Green sea turtles are amongst the largest turtles and are so-called because their flesh is green. They swim with their paddle-like limbs. Their heads appear small in comparison with the size of their body, which is covered in brown scales with a light colored edge. Males are bigger than females and have a longer tail, sticking out well past the shell. The shell of the turtle has smooth, non-overlapping plates colored different shades of brown, with patterns that change as the turtle grows older. The underside of the shell is lighter colored. Green sea turtles are not able to pull their heads into their shells.
Green sea turtles live in the Atlantic Ocean, ranging from the eastern part of the United States along the coast of South America and over to South Africa. They are also found in the Caribbean Sea and parts of the Mediterranean, and throughout the warmer waters of the Pacific and Indian Oceans. They tend to keep to the coastline and near islands, living in bays and along protected shorelines, especially in areas that have seagrass beds. They are rarely seen in the open ocean.
Green Sea turtles spend their time alone and almost all their lives under water. They come out of the water only when nesting. Although they move quickly in the ocean, on land they are slow and also defenseless. Male green sea turtles hardly ever leave the water. Females leave the sea only to lay eggs and nest only at night. Green turtles swim underwater for approximately 4 to 5 minutes during routine activity, and come up to breathe at the surface for 1 to 3 seconds. They can sleep underwater for a few hours at a time but stay beneath the surface for a much shorter period when diving for food or escaping from predators. Although green sea turtles can’t pull their heads inside their shells, the adults have protection from predators due to their shells, their large size, and the thick scaly skin covering their heads and necks.
Green sea turtles are mostly herbivorous. Most of their time is spent eating algae in the sea or the grass growing in shallow waters. Young turtles eat plants and organisms such as crabs, jellyfish, sponges, worms, and snails.
Green sea turtles are polygynandrous, and some populations have a polyandrous mating system, with one female mating with two or more male turtles. As with many species, males compete for a female. Breeding takes place in March-October, with variation between populations. Females mate usually every 2 to 4 years. The males visit the breeding grounds every year, looking for a mate. After copulation, when ready to lay her eggs, the female crawls ashore after dark. She digs a large pit beyond the high tide line and lays 70 - 200 eggs in it before returning to the ocean. The young turtles hatch after 6 - 8 weeks, and, with the help of their flippers, come up to the surface. They hatch at night, crawl toward the ocean and stay there, solitary, until the time comes to mate. They are sexually mature between 26 and 40 years old.
The main threats to these turtles include the degradation and loss of habitat, consumption of their eggs and meat, capture as bycatch, pollution and climate change. Beach armoring, building works, and sand extraction degrade the nesting habitat, while light pollution in the nesting areas fatally attracts hatchlings so that they do not head for the sea. Increased effluent, contamination from coastal development and over harvesting of algae all threaten the habitat of the green sea turtle.
According to the Sea Turtle Conservancy resourse the total population size of nesting Green sea turtles is around 85,000-90,000 individuals. Overall, currently this species is classified as Endangered (EN) on the IUCN Red List and its numbers today are decreasing.
Green sea turtles eat seagrasses and algae, thus serving (much like mowing a lawn) to maintain the seagrass beds in a healthy state, making them more productive. Seagrass eaten by the turtles is quickly digested, becoming available as recycled nutrients for the many species of animals and plants that live in the ecosystem of seagrass. Seagrass beds also act as nurseries for a number of species of fish and invertebrates, many being of considerable value for commercial fisheries and thus important for human food security.