Green sea turtles are most noticeable due to their large shell or carapace which is shaped like a teardrop. This is coloured greenish brown to black on the upper surface often with streaks that are brown or yellow. On the underside the shell is white. A variant exists in the eastern Pacific ocean which have much darker shells and are called black turtles.
They have a small head relative to the size of their body. Unlike other turtles this cannot be drawn back in to the shell. Their legs have modified to become flippers to push them through the water. Each flipper has a single claw.
An adult green sea turtle will measure 83-114cm (3-4ft) and they weigh 110-190kg (240-420lbs). The largest green sea turtle on record measured 152cm (5ft) and weighed 395kg (871lbs).
Green sea turtles are unique among sea turtles in that adults are mostly herbivorous. As adults they will eat sea grass, algae, mangrove roots and leaves. This is assisted by their toothless beak which has a sharp edge and serrations on the lower jaw.
Juveniles are omnivorous and will feed upon a range of jellyfish, crabs, molluscs and sponges in addition to the foods eaten by adults.
— AD —
They live in the ocean and can be found in a band around the globe through the tropical, subtropical and temperate waters. They can be found along the coastline of at least 140 countries.
Their habitat is the warm waters near the equator. Typically they are found near seagrass and coral reefs. They are able to live in almost any area provided the water temperature does not drop below 20oC (68oF) at any time.
Green sea turtles regularly undertake migrations between their feeding grounds and the beaches where they hatched.
Green sea turtles return to the same beach to breed each season. Egg laying is the only time that the green sea turtles ever leave the water.
Mating takes place at the shallow shore line. Males will come to the breeding grounds every year to try and mate with as many females as possible. Females typically breed once every two to three years.
They will return to the same nest where they were born to lay their eggs potentially travelling up to 1,000km (620miles) to achieve this. Females crawl high up the shore to ensure the nest does not become waterlogged. The nest is dug in the sand using their strong front flippers.
In to the nest the female will deposit as many as 100 eggs. The eggs take 6-8 weeks to hatch with the variation in hatching times dependent on the temperature.
After they hatch the young will dig themselves out of the nest and then need to run down the beach to the water. On the way many of these hatchlings will be eaten by crabs, lizards, snakes and seabirds. Once in the water young are still not safe with many being eaten by sharks, kingfish and dolphins.
Eggs are also preyed upon by invasive species such as dogs and foxes.
At the start of their life they spend time in oceanic areas floating on ocean currents. They then move to the feeding grounds where they begin to transition on to plant matter and reach maturity.
Age at sexual maturity may be as much as 30 or 50 years old.
As a reptile the green sea turtle has lungs and must come to the surface to breathe. When at rest they may stay underwater and hold their breath for 5 hours. When active such as feeding or travelling they will surface every 3-4 minutes.
They rest on ledges or the sea floor.
Predators and Threats
Adult sea turtles face very few predators though sharks may prey on them.
Humans have affected their population through entanglement in fishing nets and pollution. One of their main threats is plastic pollution. As the plastic resembles a jellyfish they will eat them and then this can make them ill.
They also suffer though degradation of the nesting sites. Where lights are set-up on their nesting beaches hatchling turtles often go towards the lights or the water. This increases the time they are exposed to predators.
They are also hunted by humans for food.
The green sea turtle is named for the colour of fat under their shell not the shell itself.
Used under license
Burnie, D., 2011. Animal. 3rd ed. London: DK
Ambrose, J., 2015. Wildlife Of The World. 1st ed. London: Dorling Kindersley,
Conserveturtles.org. 2020. Information About Sea Turtles: Green Sea Turtle – Sea Turtle Conservancy. [online]
Available at: <https://conserveturtles.org/information-sea-turtles-green-sea-turtle/> [Accessed 26 June 2020].
World Wildlife Fund. 2020. Green Turtle | Sea Turtles | Species | WWF. [online] Available at: <https://www.worldwildlife.org/species/green-turtle> [Accessed 26 June 2020].
The Nature Conservancy. 2020. Green Sea Turtle. [online] Available at: <https://www.nature.org/en-us/get-involved/how-to-help/animals-we-protect/green-sea-turtle/> [Accessed 26 June 2020].
Seminoff, J.A. (Southwest Fisheries Science Center, U.S.). 2004. Chelonia mydas. The IUCN Red
List of Threatened Species 2004: e.T4615A11037468. https://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T4615A11037468.en. Downloaded on 26 June 2020.
Genomics.senescence.info. 2020. Green Sea Turtle (Chelonia Mydas) Longevity, Ageing, And Life
History. [online] Available at: <https://genomics.senescence.info/species/entry.php?species=Chelonia_mydas>
[Accessed 26 June 2020].
The Australian Museum. 2020. Green Turtle. [online] Available at:
<https://australian.museum/learn/animals/reptiles/green-turtle/> [Accessed 26 June 2020].