Green Sea Turtle — facts, diet, habitat & conservation

The green sea turtle is the large, gentle grazer of the reef — the only sea turtle that gives up hunting as it grows and settles into a life of cropping underwater meadows. It also performs one of the animal kingdom’s great feats of navigation, finding its way back across open ocean to the exact beach where it hatched.

Overview

Green turtles are found in warm seas around the world, but their life is spent in a few specific places connected by long migrations: the open ocean where they drift as juveniles, shallow seagrass meadows and reefs where adults feed, and a small number of sandy nesting beaches where females return to lay eggs. An individual turtle may commute hundreds or thousands of kilometres between its feeding grounds and its nesting beach.

Physical characteristics

An adult green turtle has a smooth, heart-shaped shell up to 1.5 m long, a small rounded head, and paddle-like front flippers that “fly” it through the water. It cannot pull its head or limbs into its shell like a land tortoise. Special glands beside the eyes excrete excess salt as thick tears, which is why nesting turtles often look like they are crying.

Green turtles are reptiles and must surface to breathe, but they can slow their heart rate and rest submerged for hours; a foraging dive typically lasts four to five minutes.

Diet

Hatchling and juvenile green turtles are omnivores, eating jellyfish, small crustaceans, and floating plants in the open ocean. As they mature and move to coastal feeding grounds, they switch almost entirely to seagrass and algae — one of very few large marine herbivores. By repeatedly cropping the same patches of seagrass, green turtles keep the meadows healthy and productive, much as grazing herds maintain a grassland.

Reproduction and life cycle

Every two to five years, a female green turtle migrates to her natal beach. Over a nesting season she comes ashore several times at night, digs a chamber with her hind flippers, lays around 100–115 soft-shelled eggs, covers them, and returns to the sea — investing no further care.

The sand temperature during the roughly two-month incubation sets the hatchlings’ sex: warmer nests produce females, cooler nests males. Hatchlings dig out together, usually at night, and scramble toward the brightest horizon — historically the open sea. They then spend a “lost years” phase drifting in ocean currents before recruiting to coastal habitats. Green turtles grow slowly and may not breed until they are 20 to 40 years old.

Threats and conservation

The green turtle is listed as Endangered, though many individual populations are now increasing thanks to sustained protection:

Bycatch in trawls, longlines, and gillnets — reduced where turtle excluder devices and gear rules are enforced.
Direct take of eggs and adults for food, now illegal in most countries but still a pressure in some.
Coastal development and light pollution, which destroy nesting beaches and disorient hatchlings away from the sea.
Climate change, which warms nesting sands (skewing sex ratios), raises seas over nesting beaches, and damages the seagrass and reef habitats adults depend on.
Fibropapillomatosis, a tumour-causing disease linked to degraded coastal water quality.

The recovery of nesting beaches in places like Tortuguero in Costa Rica, Hawaii, and the Great Barrier Reef shows that, given decades of consistent protection, green turtle numbers can climb back.

Green Sea Turtle: common questions

Why is it called a green sea turtle if its shell is brown?

The name comes from the colour of its body fat, not its shell. Adult green turtles graze on seagrass and algae, and the pigments in that plant diet turn their fat greenish. The shell itself is usually olive to brown, sometimes with dark streaks.

How do sea turtles find their way back to their birth beach?

Green turtles imprint on the unique magnetic signature of their natal beach as hatchlings and use the Earth's magnetic field like a map and compass to navigate back — often thousands of kilometres — decades later to nest on that same stretch of coast. It is one of the most precise long-distance homing abilities known.

Does temperature decide a turtle's sex?

Yes. Sea turtles have temperature-dependent sex determination — warmer sand during incubation produces females, cooler sand produces males, with a pivot around 29 °C. Rising sand temperatures from climate change are already skewing some populations heavily female.

Are green sea turtles endangered?

The species is listed as Endangered, but the story is more hopeful than that sounds. Decades of beach protection, bans on egg and meat harvesting, and turtle-safe fishing gear have allowed many nesting populations — in Hawaii, Florida, Australia, and elsewhere — to grow steadily, some by several percent a year.