Green Sea Turtle (Chelonia mydas): Facts, Diet and Habitat

What does a green sea turtle look like?

The green turtle has a smooth, teardrop-shaped upper shell, or carapace, and a small, rounded head with a short snout. Unlike the hawksbill sea turtle, whose beak is hooked and pointed, the green turtle has a blunt beak with a finely serrated edge, a little like a saw, which it uses to crop seagrass.

Despite its name, the shell is not bright green. It is usually olive, brown or gray, often with radiating streaks or a marbled pattern, while the lower shell, or plastron, is pale yellow to white. In the eastern Pacific, many turtles are much darker, almost black, and are known as black turtles. The name actually refers to the turtle’s greenish body fat, as explained in why are green sea turtles called green?

Useful field marks are a single pair of large scales between the eyes (hawksbills have two pairs), four pairs of scutes along each side of the shell, and smooth scute edges that meet edge to edge rather than overlapping. Each front flipper usually has one visible claw. Adult males have a long, thick tail that sticks out well beyond the shell and a long curved claw on each front flipper, which they use to grip females during mating.

How big do green sea turtles get?

The green turtle is one of the largest sea turtles and the largest member of its family after the loggerhead in most comparisons; only the leatherback is clearly bigger. Adults usually have a shell 78–112 cm (31–44 in) long and weigh about 68–190 kg (150–420 lb). NOAA describes typical adults as about 1–1.2 m (3–4 ft) long and 135–160 kg (300–350 lb).

Size varies between populations. Green turtles nesting on Ascension Island in the South Atlantic are among the largest, often more than 1 m (3.3 ft) long, while eastern Pacific black turtles are smaller. Exceptional individuals have weighed more than 300 kg (660 lb), and the largest on record weighed about 395 kg (871 lb) with a shell about 1.5 m (5 ft) long.

Where do green sea turtles live?

Green turtles live in warm waters of the Atlantic, Pacific and Indian oceans and the Mediterranean Sea, mostly between about 30° N and 30° S. They occur in the coastal waters of more than 140 countries and nest in more than 80. Wanderers turn up much farther from the tropics, for example off northern Europe, Canada and southern Alaska, usually carried by warm currents.

In the United States, the largest numbers live around the Hawaiian Islands and Florida. Florida’s Atlantic coast is the country’s main nesting area, while the Indian River Lagoon, the Florida Keys and Florida Bay are important feeding grounds. Globally, some of the biggest nesting colonies are at Raine Island on Australia’s Great Barrier Reef, Tortuguero in Costa Rica, Ascension Island and the coast of Oman.

Life starts in the open ocean. After hatching, young turtles spend roughly their first 3–5 years drifting far from shore, often among floating mats of sargassum seaweed. They then move to shallow coastal feeding grounds such as seagrass meadows, lagoons, bays and reefs, where they spend most of their adult lives.

What do green sea turtles eat?

Adult green turtles are herbivores that graze on seagrasses and seaweeds (marine algae), which makes them unique among sea turtles. In the Caribbean, turtle grass is a favorite; in Hawaii, where seagrass is scarce, they feed mainly on algae growing on rocks and reefs. Some also eat mangrove leaves and salt-marsh plants.

Young green turtles in the open ocean are omnivores. They eat small, slow-moving animals such as jellyfish, comb jellies, small crustaceans and fish eggs, as well as floating plant matter. The switch to an almost entirely plant-based diet comes when they settle near the coast. You can compare their menu with other species in what do sea turtles eat?

A plant diet is low in energy, which helps explain why green turtles grow so slowly. Their grazing is important for the ecosystem: by cropping the tips of seagrass, much like a lawnmower, they keep meadows healthy and productive, and those meadows are nursery areas for many fish and invertebrates.

Behavior, diving and migration

Green turtles spend almost their whole lives at sea, but they breathe air and must surface regularly. During normal activity they dive for a few minutes at a time, then come up and refill their lungs in a single quick breath. When resting or sleeping, often wedged under a ledge or rock, they can stay down for several hours, especially in cooler water. Details are in can sea turtles breathe underwater?

They are known for long migrations between feeding grounds and nesting beaches. Turtles that feed off Brazil swim about 2,000–2,300 km (1,200–1,400 mi) to nest on tiny Ascension Island in the middle of the South Atlantic, and some green turtles travel more than 2,600 km (1,600 mi) to reach their beaches. They find their way partly by sensing Earth’s magnetic field.

In Hawaii and a few other places, green turtles regularly crawl onto beaches to bask in the sun, a habit rarely seen in other sea turtles. Reef fish such as yellow tangs often clean algae and parasites from their shells, and turtles visit these “cleaning stations” on purpose.

Nesting and life cycle

Green turtles show strong natal homing: females return to nest on the beach, or at least the region, where they hatched. Most females nest every 2–4 years, while males may visit the breeding areas every year. Mating takes place in shallow water near the nesting beach, and in the tropics some populations nest almost year-round, though most have a peak season, for example June to September in much of the Caribbean.

A female crawls ashore at night, digs a body pit, then excavates a nest chamber about 28–56 cm (11–22 in) deep with her back flippers. She lays about 85–200 round, white eggs, each roughly 4.5 cm (1.8 in) across, covers them and returns to the sea. She repeats this about 3–5 times in a season, around two weeks apart.

The eggs hatch after about 50–70 days. The sand temperature during incubation decides the hatchlings’ sex: warmer nests produce mostly females, cooler ones mostly males, with the switch point near 29 °C (84 °F). On the northern Great Barrier Reef, a 2018 study found that almost all young turtles were female. Read more in does temperature decide a turtle’s sex?

Hatchlings dig out together, usually at night, and head for the brightest horizon, which on a natural beach is the sea. Green turtles grow very slowly and are thought to mature at about 20–50 years, depending on the population and food supply. Only a small fraction of hatchlings, often estimated at around 1 in 1,000, survive to adulthood.

How long do green sea turtles live?

The exact lifespan of a wild green turtle is unknown, because few individuals have been tracked from hatching to old age. Given how late they mature and how many years adults keep breeding, scientists estimate they live 70 years or more, and some estimates go higher. Figures above 100 years are often repeated online but are not well documented.

Predators and threats

Eggs and hatchlings are eaten by ghost crabs, birds, raccoons, foxes, jackals, dogs, feral pigs, monitor lizards and fish. Adults have few natural predators apart from large sharks, especially the tiger shark, which takes green turtles of all sizes.

People have been the main threat for centuries. Green turtles were killed in huge numbers for meat and for calipee, the cartilage used in turtle soup, and their eggs were collected on many beaches. Today the biggest dangers are accidental capture in fishing gear such as trawls, gillnets and longlines, where turtles drown; loss of nesting beaches to coastal development; artificial lighting that disorients hatchlings; boat strikes; plastic and other pollution; and the loss of seagrass meadows.

Green turtles also suffer from fibropapillomatosis, a disease linked to a herpesvirus that causes tumors on the skin, eyes and internal organs. It is especially common in some coastal feeding grounds, including parts of Florida and Hawaii. Climate change adds new pressures: rising seas can wash away nests, and hotter sand can produce too few males or kill eggs outright.

Conservation status

The IUCN Red List now classifies the green turtle as Least Concern. It had been listed as Endangered since 1982, but in October 2025 the IUCN downgraded it after a new global assessment found that the population had grown by roughly 28% since the 1970s, thanks largely to decades of protecting nesting females, eggs and beaches. The change was widely reported as one of the biggest conservation successes for a marine species.

Least Concern does not mean the job is done. Some regional populations are still declining or very small, and the IUCN stresses that recovery depends on continued protection. The green turtle remains in Appendix I of CITES, which bans international commercial trade. In the United States, it has been protected under the Endangered Species Act since 1978, and since 2016 it has been managed as 11 distinct population segments, three listed as endangered and eight as threatened.

Florida shows what protection can achieve: green turtle nests on its beaches rose from only a few hundred a year in the 1980s to tens of thousands in recent good years. Beach patrols, lighting rules, turtle excluder devices in shrimp trawls and protected seagrass areas have all played a part.

Green sea turtles and people

Green turtles have long been important to coastal cultures. In Hawaii the green turtle, or honu, is a symbol of good luck and long life, and it appears in ancient rock carvings. The turtle is on the coat of arms and flag of the Cayman Islands, which Christopher Columbus named “Las Tortugas” after the turtles he saw there in 1503.

Today living turtles are a major attraction for snorkelers and divers, from the Red Sea to the Caribbean. Wildlife rules in many places, including Hawaii, ask people to stay a respectful distance away, never touch or feed turtles, and avoid disturbing nesting females or hatchlings on the beach.