Before dawn on a tropical beach, a hatchling the size of a cookie bursts out of the sand and races for the waves. If it beats the odds, it will spend years drifting in the open ocean, then decades grazing underwater meadows, and one day, perhaps 30 years from now, it may return to this coast to lay eggs of its own.
The green sea turtle (Chelonia mydas) is a large sea turtle about 0.9–1.2 m (3–4 ft) long that, as an adult, eats mainly seagrass and algae. It is adapted with serrated jaws, paddle-like flippers and salt glands by the eyes. Its name comes from the greenish colour of its fat, not its shell (NOAA Fisheries).
Key takeaways
- Size: adults are about 0.9–1.2 m (3–4 ft) long and weigh roughly 113–181 kg (250–400 lb).
- 3 key adaptations: serrated jaws for cutting seagrass, salt glands that “cry” out extra salt, and flippers built for long migrations.
- Diet: young turtles eat drifting plants and animals; adults are mostly plant-eaters.
- Slow life: females first breed at about 25–35 years old and lay around 110 eggs per nest.
- Good news: in October 2025 the IUCN moved the green turtle from Endangered to Least Concern worldwide, though some populations are still in trouble.
What are the 3 key adaptations of a green sea turtle?
The green turtle’s three standout adaptations are its jaws, its salt glands and its flippers. Saw-edged jaws let it crop seagrass and algae without teeth. Glands near the eyes get rid of extra salt from seawater. Large, paddle-shaped front flippers power journeys of hundreds to thousands of kilometres between feeding grounds and nesting beaches.
- Serrated jaws (structural). Sea turtles have no teeth, only beak-like jaws, and green turtles’ jaws are serrated, a good tool for a grazer (Sea Turtle Conservancy).
- Salt glands (physiological). A turtle that lives in seawater takes in a lot of salt. Green turtles push it out as salty “tears”. In a study of salt gland function, the tears reached 1,680–2,000 mosmol/kg after salt loading (Nicolson & Lutz 1989). Seawater is roughly 1,000 mosmol/kg, so that is about twice as salty as the sea.*
- Migration (behavioural). Adults travel every 2–5 years between foraging grounds and nesting beaches, hundreds to thousands of miles each way (NOAA Fisheries).
*Our calculation: 2,000 ÷ about 1,000 ≈ 2. Seawater osmolality varies a little with saltiness.
What structural, behavioural and physiological adaptations does a green turtle have?
Green turtles combine a streamlined shell and flippers (structural), long migrations and beach nesting (behavioural), and salt control, slow resting metabolism and a plant-digesting gut (physiological). Each one solves a problem of ocean life: moving far, finding the right food, and staying healthy in salty water.
| Type | Adaptation | Why it helps |
|---|---|---|
| Structural | Serrated, toothless jaws | Crops seagrass and algae (Sea Turtle Conservancy) |
| Structural | Large flippers, streamlined body | Efficient long-distance swimming (Sea Turtle Conservancy) |
| Behavioural | Migrates every 2–5 years to nest | Lays eggs on suitable beaches (NOAA) |
| Behavioural | Nests about every 2 weeks during the season | Spreads eggs across several nests (NOAA) |
| Physiological | Salt glands by the eyes | Removes extra salt (Nicolson & Lutz 1989) |
| Physiological | Can rest underwater for hours | A resting turtle can stay under 4–7 hours (Sea Turtle Conservancy) |
| Physiological | Temperature-dependent sex | Sand temperature sets whether hatchlings are male or female (NOAA) |
How big is a green sea turtle?
Adult green turtles are about 0.9–1.2 m (3–4 ft) long. NOAA Fisheries gives a weight of 250–400 lb (about 113–181 kg) in its quick facts, and 300–350 lb (136–159 kg) for typical adults elsewhere on the same page. That makes the green turtle one of the larger hard-shelled sea turtles (NOAA Fisheries).
Picture it
An adult green turtle is about as long as a small child is tall, and can weigh as much as two or three grown adults put together. The giant of the sea turtle family, the leatherback, averages about 2 m (6 ft) long (Sea Turtle Conservancy). Read why the leatherback is in trouble.
Green turtle shell length: 0.9–1.2 m
Leatherback average: about 2 m
What does a green sea turtle eat?
Adult green turtles are mainly herbivores that eat seagrasses and algae in shallow coastal waters. Young turtles are different: after hatching they spend several years in the open ocean eating plants and small animals from drifting communities such as Sargassum seaweed. The East Pacific population eats more animal food than others (NOAA Fisheries).
Our full guide to what sea turtles eat compares the green turtle’s menu with jellyfish-eating leatherbacks and crab-crunching loggerheads. For freshwater turtles that hunt, see what animals turtles eat.
What is the life cycle of a green sea turtle?
A green turtle’s life runs from egg to hatchling, open-ocean juvenile, coastal grazer and finally breeding adult. Eggs hatch after about two months. Females take 25–35 years to mature, then return every few years to nest, laying about 110 eggs per nest and nesting roughly every two weeks during the season (NOAA Fisheries).
- Egg: about 110 per nest; incubation about 2 months. Warmer sand produces more females, and very hot sand can kill eggs (NOAA).
- Hatchling: races to the sea. Only about 1 in 1,000 hatchlings is estimated to reach adulthood (Sea Turtle Conservancy); that is a widely used rough estimate rather than a precise count.
- Juvenile: several years drifting in the open ocean, then a move to coastal feeding grounds (NOAA).
- Adult: maturity at 25–35 years for females; lifespan unknown but estimated at 70 years or more (NOAA).
What role does the green sea turtle play in its ecosystem?
Green turtles are grazers of seagrass meadows. Like lawnmowers, they keep the grass short, which can support healthy growth. Seagrass beds are nurseries for many fish, shellfish and crustaceans, so turtles help shape habitats that many other animals use (Sea Turtle Conservancy). The Conservancy suggests that fewer grazing turtles may be linked to seagrass decline, though it presents this as a possible connection, not a proven one.
Green turtles share these meadows with manatees. Their eggs and hatchlings also feed beach and ocean predators, moving energy from the sea onto land and back again.
Is the green sea turtle endangered?
Not globally any more. On 10 October 2025, the IUCN moved the green turtle from Endangered to Least Concern on the Red List. It had been listed as Endangered since 1982. Protecting nesting females and eggs, cutting harvest and trade, and using Turtle Excluder Devices on fishing nets all helped (Oceanic Society).
The recovery is uneven. In the United States, the species is split into 11 populations under the Endangered Species Act: 3 are Endangered and 8 are Threatened (NOAA Fisheries). Threats include bycatch, harvest of turtles and eggs, lost nesting beaches, boat strikes, marine debris, climate change and a tumour disease called fibropapillomatosis.
Three things you can do: on nesting beaches, keep lights off and stay well back from nesting turtles and hatchlings; pick up plastic and fishing line on beaches; and never buy tortoiseshell or turtle products on holiday.
Myths about green sea turtles
Myth: Green turtles are named after their green shells.
Fact: The name comes from the greenish colour of their fat. Other sea turtles have greenish fat too (NOAA Fisheries).
Myth: Sea turtles cry because they are sad when laying eggs.
Fact: The “tears” come from salt glands that remove extra salt (Nicolson & Lutz 1989). Why people believe it: the tears are easiest to see when a female is on the beach.
Myth: Green turtles are now safe, so protection can stop.
Fact: The global recovery came from decades of protection, and some populations are still declining, such as the Southwest Pacific group that nests at Raine Island, Australia (Oceanic Society).
Test yourself
1. What colour gives the green turtle its name?
The colour of its fat.
2. What do adult green turtles mainly eat?
Seagrass and algae.
3. What decides whether a hatchling is male or female?
The temperature of the sand around the eggs.
Where to next?
➡️ Go wider: what all sea turtles eat⬆️ Go deeper: why the leatherback is endangered🔀 Go sideways: how big sulcata tortoises get
Frequently asked questions
How long do green sea turtles live?
Nobody knows for sure. NOAA Fisheries estimates a lifespan of 70 years or more. Females do not breed until about 25 to 35 years old, which is one reason populations take so long to recover after losses.
How long can a green turtle hold its breath?
A resting or sleeping sea turtle can stay underwater for about 4 to 7 hours, according to the Sea Turtle Conservancy. An active or stressed turtle needs air far sooner, and one trapped in a fishing net can drown within minutes.
Are green sea turtles still endangered?
Globally, no. In October 2025 the IUCN Red List moved them from Endangered to Least Concern. Some regional populations are still at risk, and in US law 3 of 11 populations remain Endangered and 8 are Threatened.
Why do green turtles eat seagrass when they are young?
They mostly do not. Young green turtles spend several years in the open ocean eating plant and animal life from drifting communities such as Sargassum. They switch to mainly seagrass and algae after moving to coastal waters.
Sources
- NOAA Fisheries. Green turtle.
- Sea Turtle Conservancy. Information about sea turtles: green sea turtle.
- Nicolson, S.W. and Lutz, P.L. (1989). Salt gland function in the green sea turtle Chelonia mydas. Journal of Experimental Biology 144: 171-184.
- IUCN (10 October 2025). Arctic seals threatened by climate change, birds decline globally: IUCN Red List.
- Oceanic Society (2025). Green sea turtle status improvement.
Sources checked 12 October 2026.
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