Green Sea Turtle

The green sea turtle (Chelonia mydas) is one of the largest and most iconic sea turtles in the world, with a wide distribution spanning tropical and subtropical oceans across the globe. Adults can weigh between 68 and 190 kilograms and measure up to 1.5 meters in length, making them the largest hard-shelled sea turtle. Despite their name, green sea turtles are not typically green on the outside — their smooth, heart-shaped carapace ranges from olive to brown or black. The name 'green turtle' comes from the distinctive greenish color of the fat stored beneath their skin, a hue derived from their herbivorous diet of seagrasses and algae. These ancient mariners have roamed the oceans for more than 100 million years, surviving the mass extinction that wiped out the dinosaurs. Today, however, they face a very different kind of threat — one driven by human activity.

The green sea turtle has a streamlined, oval-shaped carapace (shell) that is smooth and lacks a ridge — unlike the leatherback turtle. The shell is typically olive-brown or dark brown, often with mottled or streaked patterns. The plastron (underside) is pale yellow to white. Adults have two large, non-retractable flippers that function as powerful paddles, giving them impressive swimming speed and agility underwater. Their small, rounded head has a single pair of prefrontal scales between the eyes, a feature that distinguishes them from other sea turtle species. Males can be identified by their longer, thicker tails and slightly curved claws on the front flippers, which they use to grip the female during mating. Their eyes are adapted for underwater vision, and they can hold their breath for up to seven hours when resting.

Green sea turtles are generally solitary animals, coming together mainly during the mating season. They are strong swimmers capable of traveling thousands of kilometers between their feeding grounds and breeding beaches in an extraordinary phenomenon known as natal homing — returning to the very beach where they were born to reproduce. During non-nesting periods, they are often found resting on the seafloor or on rocky ledges. Unlike most reptiles, green sea turtles have been observed in social-like behaviors near feeding areas, where multiple individuals may gather at the same seagrass beds. They are also known to bask on beaches in Hawaii and the Galápagos — one of the very few sea turtle species known to do so regularly. Hatchlings emerge from the sand at night and instinctively head toward the ocean, guided by the brightness of the sea horizon.

Juvenile green sea turtles are omnivorous, feeding on jellyfish, sponges, mollusks, small crustaceans, and worms alongside algae and seagrasses. However, as they mature into adults, their diet shifts dramatically to become almost exclusively herbivorous. Adult green sea turtles graze on seagrass meadows and algae growing on reefs and rocky substrates. This dietary shift is ecologically significant — by grazing, they function like 'underwater lawnmowers,' keeping seagrass beds healthy and stimulating new growth. Seagrass digested and then excreted by green turtles also plays a role in recycling nutrients back into marine ecosystems. Without sufficient populations of green turtles, seagrass ecosystems can become overgrown and die off, affecting the many species that depend on them.

Green sea turtles reach sexual maturity at 20 to 50 years of age — a remarkably long time. Mating occurs offshore near nesting beaches, with males competing for access to females. Females can store sperm from multiple males and use it to fertilize successive clutches of eggs. A single female may nest up to nine times in one season, laying an average of 100 to 115 eggs per clutch. She hauls herself ashore at night, digs a deep flask-shaped nest with her rear flippers, deposits her eggs, covers the nest, and returns to the sea — all within a couple of hours. The eggs incubate for approximately 60 days. The sex of hatchlings is determined by nest temperature: cooler temperatures produce more males, warmer temperatures more females. Hatchlings emerge together, typically at night, and race toward the ocean. Only an estimated one in 1,000 hatchlings survives to adulthood.

Throughout history, green sea turtles have had a complex and often tragic relationship with humans. For centuries, they were a crucial food source for coastal communities and sailors on long voyages — so much so that some historians credit them with enabling European exploration of the tropics. Their eggs were harvested en masse, and their shells were prized for jewelry and decorative items. Despite now being legally protected in most countries, illegal poaching still occurs in parts of Asia, Africa, and Latin America. Modern threats are more insidious: plastic pollution, fishing bycatch, climate change, and beach development. Conservation programs involving nest protection, satellite tracking, and community education have helped some populations rebound. Green turtles are also important to ecotourism — turtle-watching programs generate significant income for coastal communities, creating economic incentives to protect them.