Sea Turtle Facts

A mature green turtle is 2.5 to 4 feet in carapace length and 150 to 350 pounds, its smooth, heart-shaped upper shell (carapace) mottled brown, olive, and gray over a pale plastron, fused to the rib cage and spine. Unlike land tortoises it can't pull its head or limbs into the shell; its legs are elongated paddle-like flippers, the foreflippers driving it to burst speeds near 20 mph while the hind flippers steer. The name is a misnomer for its outside — it comes from the greenish color of the fat beneath the shell, a product of its chlorophyll-rich diet. To live in salt water it has large "salt glands" behind the eyes that pump out excess sodium and chloride as salty tears, and by slowing its heart it can rest submerged for hours. It belongs to the hard-shelled sea-turtle family Cheloniidae; marine turtles evolved from land ancestors in the early Cretaceous and return to land only to breed.

Green sea turtles range around the globe through the tropical and subtropical Atlantic, Pacific, and Indian Oceans, along the coasts of over 140 countries. Their habitat use changes as they grow: hatchlings enter the open ocean for a years-long pelagic phase drifting in convergence zones among floating sargassum, then, at around 20 to 25 centimeters of shell, they shift dramatically to shallow coastal foraging grounds — lush seagrass meadows, coral reefs, and bays that serve as their developmental and adult habitat.

The green turtle is unique among the seven sea-turtle species for its dietary shift with age. As pelagic hatchlings and small juveniles it is omnivorous, taking macroplankton, jellyfish, comb jellies, and small crustaceans. On reaching coastal foraging grounds it turns to strict herbivory, feeding almost entirely on seagrass and marine algae, and its lower jaw is finely serrated like a saw to crop fibrous seagrass blades cleanly without uprooting them. That grazing works like a lawnmower, keeping seagrass from overgrowing and shading itself out and raising the meadow's health and productivity — a classic keystone role.

Green turtles are generally solitary but often gather in numbers at rich foraging grounds, and in some places, notably Hawaii and the Galápagos, they even bask on land, hauling onto quiet beaches by day to warm up. Their most spectacular behavior is reproductive migration with precise natal homing: females travel thousands of miles across ocean basins to return to the region — often the very beach — where they hatched decades earlier, navigating by an innate magnetic sense that reads both the intensity and inclination angle of the Earth's field.

The green turtle's life cycle is slow and perilous early on: individuals take 25 to 35 years to reach sexual maturity. Mating happens offshore near the nesting beach, then the female hauls out at night, digs a flask-shaped chamber with her hind flippers, and lays roughly 100 to 200 leathery eggs before covering them and returning to the sea — nesting 3 to 5 times a season. Incubation runs 45 to 70 days, with sand temperature setting sex (warmer sand yields females, cooler males). Hatchlings wait for night, dig out together, and scramble to the sea guided by moonlight on the water, running a gauntlet of crabs, birds, and raccoons. Green turtles are long-lived, often reaching 60 to 70 years or more.

The green sea turtle is Endangered with a decreasing global trend. Historically it was decimated for its meat, fat (turtle soup), and eggs, and human threats remain severe: incidental bycatch in longlines, gillnets, and trawls drowns huge numbers, floating plastic mistaken for jellyfish causes fatal gut blockages, and the tumor disease fibropapillomatosis — linked to agricultural runoff and coastal pollution — is debilitating. Coastal development hits reproduction hard: beachfront lighting disorients emerging hatchlings toward roads, and seawalls and lost seagrass grounds erode both nesting and foraging habitat.

• IUCN Red List: Green Turtle
• WWF: Marine Turtles
• NOAA Fisheries: Green Turtle