The Green Sea Turtle (Chelonia mydas) is one of the largest sea turtles and the only herbivore among the different species. Adults typically measure 83–114 cm in carapace length and weigh between 110–190 kg. The largest green turtle ever recorded was an impressive 152 cm long and weighed 395 kg! They are definitely among our favorite marine animals, and we absolutely love watching them glide gracefully while scuba diving around Koh Tao.
Distinguishing Features
Green sea turtles are named for the greenish color of their fat, not their shells. They have a blend of green, brown, or black on their shells and skin, and the color of their shell changes as they grow older. Young green sea turtles have dark shells, while older ones have lighter colors. The carapace of green sea turtles is rounded and features overlapping scutes, which may support algal growth that provides camouflage in some habitats. They are easily distinguished from other sea turtles because they have a single pair of prefrontal scales (scales in front of its eyes), rather than two pairs as found on other sea turtles and all flippers have 1 visible claw. These turtles are known for hosting remoras during their journeys, which attach to them and feed on parasites and leftover food particles. They have a rounded beak with serrated jaws, which are essential for slicing through seagrass and other vegetation.
Behavior and Diet
Green sea turtles are mostly solitary, often found alone except during mating or when feeding in areas with plentiful resources. They are known for their long migrations, traveling vast distances between feeding grounds and nesting sites. They also spend time basking on beaches or floating on the surface to regulate their body temperature.
They are primarily herbivores, feeding mainly on seagrasses and algae. Their serrated jaws are well-suited for slicing through these plants. Occasionally, they may consume jellyfish or sponges, but their diet is largely plant-based. The algae on their shells can help with camouflage and might provide some additional nutrients.
Reproduction
Green sea turtles return to their birthplace to lay eggs, usually nesting at night to avoid predators and extreme temperatures. The female digs a hole in the sand with her flippers, deposits 100 to 200 eggs, covers them, and then heads back to the ocean.
Mating occurs in the water and can be quite a sight. The male approaches the female from behind and grips her shell with his front flippers. He then aligns himself to transfer sperm into her cloaca. This process can take several hours and often involves multiple mating sessions.
After about 60 days of incubation, influenced by temperature, the eggs hatch, and the tiny turtles make their way to the sea. The journey from nest to ocean is risky, with many hatchlings falling prey to predators or environmental hazards.
Green sea turtles reach sexual maturity between 20 and 50 years and return to their nesting grounds to lay eggs, continuing the cycle of life.
Predators
Green sea turtles face various predators throughout their life stages. As hatchlings, they are especially vulnerable to seabirds, crabs, and fish during their perilous journey from the nest to the ocean. This early stage is fraught with danger, and many hatchlings do not survive.
In their juvenile and adult stages, green sea turtles have fewer natural predators due to their size and tough shells. However, they are still at risk from large marine animals such as sharks. Despite their formidable defenses, green sea turtles face the most significant threats from human activities. Their shells are highly prized for decoration, and they are hunted for their meat and eggs. Additionally, green sea turtles are often affected by entanglement in fishing gear, ingestion of plastic waste, and other marine debris.
Where to find The Green Sea Turtle on Koh Tao
Koh Tao offers several dive sites where you can have memorable encounters with Green turtles. Here are some of the top spots:
