The only sea turtle that grazes like a cow, and one of the great navigators. A female crosses hundreds or thousands of kilometres of open ocean to lay her eggs on the stretch of coast where she hatched decades earlier. In 2025, after forty years of protection, it came off the endangered list.

How it finds homeSee the numbers
FamilyCheloniidae
Lives inTropical and subtropical seas
IUCN statusLeast Concern (2025)
Adult dietSeagrass and algae
GREEN TURTLES AT A GLANCE

The green sea turtle (Chelonia mydas) is the largest hard-shelled sea turtle, with a shell about a metre long. It lives in warm coastal waters around the world and nests on beaches in more than 80 countries. Young turtles eat jellyfish and other small animals in the open ocean; adults settle in shallow water and graze on seagrass and algae. It is named for the green colour of its body fat, not its shell. Females take 25 to 35 years to mature and then migrate, every few years, back to the region where they hatched. The sex of each hatchling is set by the temperature of the sand.

Figures graded and sourced in the fact sheet below.
KEY DISCOVERIES
1950sTagging beginsArchie Carr starts tagging nesting females at Tortuguero, Costa Rica, the longest-running sea turtle study.
1982EndangeredThe IUCN lists the green turtle as Endangered after centuries of hunting for meat and eggs.
2001A magnetic mapLoggerhead hatchlings are shown to steer by regional differences in Earth’s magnetic field (Lohmann et al.).
2014The lost yearsSatellite tags on young loggerheads show they swim actively in the open ocean, not just drift (Mansfield et al.).
201899% femaleOn the northern Great Barrier Reef, almost every young turtle sampled is female, because of hotter sand (Jensen et al.).
2025Least ConcernAfter a rise of about 28% since the 1970s, the IUCN moves the species from Endangered to Least Concern.
ONLY IN THE GREEN TURTLE

What makes the green sea turtle unlike any other turtle?

Short answer: It is the only sea turtle that lives mainly on plants as an adult, and its grazing shapes the seagrass meadows it feeds on.

01A grazing sea turtleAdults eat almost only seagrass and algae, cropping the same patches again and again.Bjorndal 1980
02Home by magnetismFemales return to nest in the region where they hatched, using Earth’s magnetic field as a map.Brothers & Lohmann 2015
03Sand sets the sexWarm nests produce females and cooler nests males. A degree or two changes the whole clutch.Jensen et al. 2018
04It sunbathes on landIn Hawaii and the Galápagos, green turtles haul out to bask, which other sea turtles almost never do.Whittow & Balazs 1982
05Green on the insideThe name comes from its fat, tinted green by a plant diet. The shell is brown or olive.Hirth 1997
06Off the endangered listOne of the few large marine animals to move straight from Endangered to Least Concern.IUCN 2025
FACT SHEET

How big is a green sea turtle?

Short answer: The shell is usually 0.8 to 1.2 m long and adults weigh 110 to 190 kg, which makes it the largest hard-shelled sea turtle.

MeasuredEstimatedQuoted, unverified
Shell lengthMeasured~0.8 to 1.2 mGreen turtle0.8 to 1.2 mLeatherbackup to ~1.8 mLargest hard-shelled sea turtle. Hirth 1997
WeightMeasured~110 to 190 kgTypical adult110 to 190 kgRecord395 kgSize varies by region; East Pacific turtles are smaller. Record from Hirth 1997
Age at maturityEstimated~25 to 35 yearsGreen turtle25 to 35 yrsLoggerhead~25 to 35 yrsEstimated from growth rings in bone and long-term tagging
LifespanEstimated60 to 70+ yearsEstimated60 to 70+Claimedup to ~90?No wild turtle has been followed from hatching to death
Eggs per nestMeasured~110Eggs per nest~100 to 120Nests per season~3 to 5Females nest every two to four years. Hirth 1997
IncubationMeasured~50 to 70 daysCool sand~70 daysWarm sand~50 daysWarmer sand hatches faster and produces more females
Longest diveMeasuredup to ~5 hoursResting, cool water~5 hoursFeeding dives~5 to 15 minWinter resting dives in the Mediterranean. Broderick et al. 2007
MigrationMeasuredup to ~2,600 kmLongest tracked~2,600 kmBrazil to Ascension~2,300 kmOne way, between feeding and nesting grounds
1 in 1,000 hatchlings surviveQuoted, unverified?Quoted everywhere, but it is a rule of thumb. Survival to adulthood has not been measured directly and likely varies widely between beaches.Popular figure
Lifespan Lookup →
LIFE CYCLE

What is the life cycle of a green sea turtle?

Short answer: It starts on a beach, spends years out of sight in the open ocean, settles on a coastal feeding ground for decades, and returns to its home region to breed.

NightNestingA female hauls up the beach, digs a body pit and an egg chamber with her flippers, and lays about 110 eggs.
~2 monthsIn the sandThe eggs develop without any care. Sand temperature decides how many are female.
One nightThe dashHatchlings dig out together and run for the brightest horizon, which should be the sea.
Years 1 to 5The lost yearsYoung turtles live in the open ocean, eating jellyfish and small animals at the surface.
Year 5 onwardsCoastal lifeAt about 20 to 30 cm they move to shallow water, switch to plants and may stay for decades.
BreedingMales and females migrate to mate just off the nesting beach. Females then nest several times, about two weeks apart.
Why at nightDarkness keeps eggs and adults cooler and hides hatchlings from birds and crabs.
No parental careA female never sees her young. Each clutch is on its own from the moment the sand is patted down.
A long waitA hatchling that survives will not breed for 25 to 35 years, so damage to a population shows up slowly.
Hirth 1997; Mansfield et al. 2014.
GRAZING

What do green sea turtles eat?

Short answer: Adults eat seagrass and algae. Young turtles in the open ocean eat animals, mostly jellyfish and other drifting creatures, and switch to plants when they move inshore.

Food Chain Builder →
Lawn-mowersTurtles crop seagrass short and keep returning to the same plots, where regrowth is richer in protein.
A saw-edged beakThe lower jaw is serrated for tearing leaves and scraping algae from rock.
Fermenting gutMicrobes in the hindgut break down plant fibre, as in a cow or a horse.
Young meat-eatersSmall turtles at sea eat jellyfish, salps, crustaceans and fish eggs.
Not strict vegetariansAdults in some regions, such as the East Pacific, still take jellyfish, sponges and other animals.
Meadow keepersModerate grazing keeps seagrass beds healthy. Where sharks are scarce, turtles can overgraze them.
Salt tearsGlands behind the eyes shed excess salt, which is why nesting females seem to weep.
Cleaning stationsTurtles queue at reef sites where surgeonfish and wrasse pick algae and parasites from their shells.
Bjorndal 1980; Arthur et al. 2008; Heithaus et al. 2014.
DIVING AND BASKING

How long can a green sea turtle hold its breath?

Short answer: Usually a few minutes while feeding, but resting turtles in cool water have stayed down for about five hours. An active or frightened turtle needs air far sooner.

Dive Depth tool →
Time underwaterFeeding dive5 to 15 minResting, warm water30 to 60 minResting, cool waterup to ~5 hoursLonger dives are possible in cold water because the turtle’s body runs slower. A turtle tangled in a net struggles and can drown in minutes. Hays et al. 2000; Broderick et al. 2007.
Lungs as a floatA turtle adjusts how much air it takes down so that it hangs level at the depth it wants to rest at.
Slowed heartOn long dives the heart rate falls sharply and blood is kept for the brain and heart.
BaskingHawaiian and Galápagos green turtles crawl ashore to warm up, which may speed digestion and help avoid sharks.
SpeedIt cruises at 2.5 to 3 km/h and covers about 50 km a day on a long migration.
POPULATIONS

Where do green sea turtles live?

Short answer: In warm coastal waters of the Atlantic, Pacific and Indian Oceans and the Mediterranean. They nest in more than 80 countries, but a handful of beaches hold most of the females.

Animal Map →
Raine Island, AustraliaLargest rookeryThe world’s biggest green turtle nesting site, on the northern Great Barrier Reef. Tens of thousands of females in a peak year.
Tortuguero, Costa RicaCaribbean strongholdThe largest rookery in the Atlantic, studied continuously since the 1950s.
Ascension IslandMid-AtlanticTurtles from Brazil’s coast nest here. Numbers have risen several-fold since hunting stopped.
HawaiiRecoveredOver 90% nest at one atoll, French Frigate Shoals. Numbers have climbed since protection in 1978.
Oman and the Arabian SeaMajor nestingRas al Hadd is among the largest nesting areas in the Indian Ocean.
MediterraneanSmallUnder a thousand females nest each year, mainly in Turkey, Cyprus and Syria.
The black turtleGreen turtles of the East Pacific are smaller and darker, with a more domed shell. Some researchers have treated them as a separate species, the black turtle. DNA places them within the green turtle.Seminoff et al. 2015.
EVOLUTION

What are sea turtles related to?

Short answer: Among living animals, turtles are closest to crocodiles and birds, not to lizards. Sea turtles took to the ocean over 100 million years ago, and seven species survive.

Read: sea turtles, ancient navigators →
Crocodiles and birdsThe turtles’ closest living relativesTortoises and pond turtlesLand and freshwater turtlesSnapping turtlesClose cousins of the sea turtlesLeatherbackThe only sea turtle without a hard shellHawksbill, loggerhead, ridleysThe other hard-shelled sea turtlesGreen sea turtleChelonia mydasTurtlesSea turtlesHard-shelled sea turtles
Relationships simplified, not to time scale. After Crawford et al. 2015. Snapping turtle and leatherback outlines: PhyloPic, CC0.
The shell is ribsA turtle’s shell is its ribs and backbone, widened and fused. It cannot leave it.
ArchelonA sea turtle of the dinosaur era, about 4.6 m long, the largest turtle known.
No retreatSea turtles cannot pull the head or flippers into the shell. The space went to swimming muscle.
Saltwater crocodile profile →
RECOVERY AND THREATS

Are green sea turtles endangered?

Short answer: Globally, no longer. In October 2025 the IUCN moved the species from Endangered to Least Concern after its numbers rose by about 28% since the 1970s. Several regional populations are still threatened.

Endangered register →
Red List status by regionSouth AtlanticLeast ConcernHawaii (Central Pacific)Least ConcernSouthwest Indian OceanLeast ConcernMediterraneanNear ThreatenedCentral West PacificNear ThreatenedEast PacificVulnerableNorth Indian OceanVulnerableCentral South PacificEndangeredIUCN Marine Turtle Specialist Group. Assessors note that total numbers are still far below historical levels.
Hunting and trade bansCommercial turtle fishing ended in most countries, and international trade was banned under CITES.
Protected beachesPatrols, hatcheries and lighting rules on nesting beaches from Florida to Malaysia.
Safer fishing gearEscape hatches in shrimp trawls let turtles swim out of the net.
Warming sandOn the northern Great Barrier Reef, over 99% of young turtles sampled were female. Too few males is a long-term risk.
BycatchTurtles drown in trawls, gillnets and on longlines.
Losing beachesSea-level rise, sea walls and building squeeze nesting beaches from both sides.
Tumour diseaseFibropapillomatosis causes growths on the skin and eyes, and is commonest in polluted bays.
PlasticBags and fragments are mistaken for food and can block the gut.
Egg and meat harvestStill legal or tolerated in some countries, and poaching continues in others.
Light pollutionBeachfront lighting turns hatchlings and nesting females the wrong way.
Seagrass lossCoastal run-off and dredging kill the meadows adults depend on.
IUCN 2025; Jensen et al. 2018; Chaloupka et al. 2008.
MYTH OR FACT

Six sea turtle claims, checked

3Myths2Half true1Facts
01MYTH“Green turtles are named for a green shell.”WHERE IT CAME FROMA reasonable guess.
WHAT THE EVIDENCE SAYSThe shell is brown, olive or black. The name comes from the green fat under the shell, coloured by a diet of plants, which made the species prized for soup.
WHAT IS TRUE INSTEADGreen on the inside.Sources: 01
02MYTH“Sea turtles can pull their heads into their shells.”WHERE IT CAME FROMTortoises and pond turtles can.
WHAT THE EVIDENCE SAYSSea turtles have a flattened shell and large flight muscles, with no room to retract the head or flippers.
WHAT IS TRUE INSTEADThey rely on size and speed, not hiding.Sources: 01
03HALF TRUE“A turtle returns to the exact beach where it hatched.”WHERE IT CAME FROMDecades of tagging.
WHAT THE EVIDENCE SAYSFemales return to the same region, often within tens of kilometres, and many reuse one beach. Some nest on neighbouring beaches or islands.
WHAT IS TRUE INSTEADThe same region, not always the same sand.Sources: 04
04HALF TRUE“Turtles eat plastic bags because they look like jellyfish.”WHERE IT CAME FROMPhotographs of turtles with bags.
WHAT THE EVIDENCE SAYSTurtles do swallow plastic, and young ones that eat jellyfish are most at risk. Smell matters too: plastic coated in sea growth smells like food to a turtle.
WHAT IS TRUE INSTEADLooks and smell both fool them.Sources: 14
05MYTH“Sea turtles live for hundreds of years.”WHERE IT CAME FROMConfusion with giant tortoises.
WHAT THE EVIDENCE SAYSGreen turtles probably live 60 to 70 years or somewhat more. Reliable ages beyond that do not exist for any sea turtle.
WHAT IS TRUE INSTEADLong-lived, but not for centuries.Sources: 01
06FACT“Nesting turtles cry.”WHERE IT CAME FROMSeen on every nesting beach.
WHAT THE EVIDENCE SAYSSalt glands behind the eyes release a thick, salty fluid all the time. On land it runs down the face and keeps sand out of the eyes.
WHAT IS TRUE INSTEADTrue. It is salt, not sorrow.Sources: 01
OPEN QUESTIONS

What science still doesn’t know

?Where do the young go?Tracking has begun to fill in the "lost years", but only for a few dozen turtles in a few regions.
?How do they sense magnetism?No magnetic sense organ has been found in any turtle.
?How long do they live?Sixty to seventy years is an estimate. Nobody has followed a wild turtle for a whole life.
?Can they cope with hotter sand?Females could nest earlier, or on cooler beaches. Whether they will shift fast enough is unknown.
?Why do some bask?Warming up, resting and avoiding sharks are all proposed. It is unclear why only some populations do it.
?How many survive?Survival from hatchling to adult has never been measured directly.
FAQ

Frequently asked questions

How big do green sea turtles get?+

The shell is usually 0.8 to 1.2 m long and adults weigh 110 to 190 kg.

What do green sea turtles eat?+

Adults eat seagrass and algae. Young turtles in the open ocean eat jellyfish and other small animals.

How long do green sea turtles live?+

An estimated 60 to 70 years or more. They take 25 to 35 years to reach breeding age.

Why are they called green sea turtles?+

Because their body fat is green, coloured by a plant diet. The shell is brown or olive.

How long can a green sea turtle hold its breath?+

A few minutes when active, 30 to 60 minutes when resting, and up to about five hours when resting in cool water.

Are green sea turtles endangered?+

The species was moved from Endangered to Least Concern in 2025. Some regional populations remain Vulnerable or Endangered.

COMPARE AND EXPLORE

Explore sea turtles further

TOPICSea TurtlesOpen →PROFILEBlue whale profileOpen →TOOLDive DepthOpen →TOOLAnimal MapOpen →
HOW WE KNOW

Sources and how we check

This page is written by Strange Animals and checked against primary research. Every figure carries a grade and a numbered source.

Cite this pageStrange Animals. (2026, November 15). Green sea turtle (Chelonia mydas): life cycle, navigation, grazing and recovery. https://strangeanimals.info/marine-life/sea-turtles/green-sea-turtle
  1. 01Hirth, H. F. Synopsis of the biological data on the green turtle Chelonia mydas (Linnaeus 1758). US Fish and Wildlife Service Biological Report 97(1)1997
  2. 02Bjorndal, K. A. Nutrition and grazing behavior of the green turtle Chelonia mydas. Marine Biology 56: 147-1541980
  3. 03Lohmann, K. J. et al. Regional magnetic fields as navigational markers for sea turtles. Science 294: 364-3662001
  4. 04Brothers, J. R. and Lohmann, K. J. Evidence for geomagnetic imprinting and magnetic navigation in the natal homing of sea turtles. Current Biology 25: 392-3962015
  5. 05Jensen, M. P. et al. Environmental warming and feminization of one of the largest sea turtle populations in the world. Current Biology 28: 154-1592018
  6. 06Mansfield, K. L. et al. First satellite tracks of neonate sea turtles redefine the "lost years" oceanic niche. Proceedings of the Royal Society B 281: 201330392014
  7. 07Luschi, P. et al. The navigational feats of green sea turtles migrating from Ascension Island investigated by satellite telemetry. Proceedings of the Royal Society B 265: 2279-22841998
  8. 08Papi, F. et al. Open-sea migration of magnetically disturbed sea turtles. Journal of Experimental Biology 203: 3435-34432000
  9. 09Broderick, A. C. et al. Fidelity and over-wintering of sea turtles. Proceedings of the Royal Society B 274: 1533-15392007
  10. 10Hays, G. C. et al. The diving behaviour of green turtles at Ascension Island. Animal Behaviour 59: 577-5862000
  11. 11Whittow, G. C. and Balazs, G. H. Basking behavior of the Hawaiian green turtle (Chelonia mydas). Pacific Science 36: 129-1391982
  12. 12Chaloupka, M. et al. Encouraging outlook for recovery of a once severely exploited marine megaherbivore. Global Ecology and Biogeography 17: 297-3042008
  13. 13IUCN Marine Turtle Specialist Group Chelonia mydas. IUCN Red List. Least Concern2025
  14. 14Pfaller, J. B. et al. Odors from marine plastic debris elicit foraging behavior in sea turtles. Current Biology 30: R213-R2142020
  15. 15Crawford, N. G. et al. A phylogenomic analysis of turtles. Molecular Phylogenetics and Evolution 83: 250-2572015
WATCH

Three films worth your time

ClipBBCThese Tiny Turtles Need Human Help to Reach the OceanAfter about 60 days under the sand, green turtle hatchlings emerge and make for the sea.Pairs with: Life cycle →
ClipturtletalestvGreen Turtles at cleaning station.movA green turtle is cleaned by yellow tangs and surgeonfish off the Big Island of Hawaii.Pairs with: Grazing →
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