Latin name: Chelonia mydas
Location: Tropical and subtropical coastal waters worldwide
Size: 80 cm – 1.5 m (carapace length)
Fun fact: There are seven species of sea turtle found around the world.
Appearance
Green turtles are among the most beautiful turtles to encounter in the ocean. They have a smooth, shiny carapace (shell) that often contains subtle shades of green, brown and gold. These colours form unique patterns across the shell.
Their name does not actually come from the colour of the shell, but from the greenish fat beneath their skin, which is influenced by their seagrass-based diet. Sometimes green turtles have algae growing on their shells, which can make them appear even greener.
Green turtles have a relatively small, rounded head with light brown or beige scutes on their face. Some individuals may also display brighter or more varied colouration depending on their habitat and age. The bigger the turtle, the older it is. Green turtles can typically live between 60-80 years, sometimes more.
Scutes and Identification
There are several global databases that track the migration and movements of sea turtles. If you are lucky enough to see a turtle while diving or snorkelling, taking a photograph or short video of its face can be extremely valuable.
Sea turtles have distinctive black-and-white scale patterns on their faces called scutes. These patterns are unique to each individual turtle, similar to human fingerprints.
Researchers use these patterns to identify and track individual turtles. If you happen to photograph a turtle that has not yet been recorded in the database, you might even have the opportunity to help scientists identify a new individual and even name it!
What Do They Eat?
When green turtles are young, they are omnivorous and will feed on small invertebrates such as worms, jellyfish and crustaceans.
As they grow older, their diet completely changes. Adult green turtles become almost entirely herbivorous, feeding mainly on sea grass and marine algae.
By grazing on seagrass beds, green turtles play an important role in maintaining healthy marine ecosystems. Their feeding keeps seagrass short and productive, which benefits many other marine species. When turtles feed, they trim the tops of the plants without damaging the roots. This encourages new growth and prevents the seagrass from becoming overgrown or covered in algae, which is important because seagrass is one of the most effective natural carbon sinks in the ocean. By maintaining healthy seagrass beds, green turtles indirectly help store large amounts of carbon in the seabed, which plays a role in reducing the impacts of climate change.
The Lost Years
After hatching on the beach, tiny black hatchlings scramble towards the sea, beginning a mysterious stage of life known as the “Lost Years.”
During this time, young turtles drift and swim in the open ocean for five to ten years, often hiding among floating seaweed such as sargassum. This habitat provides both food and protection from predators.
Despite this, young turtles remain highly vulnerable to predators such as birds and large fish, particularly when they are close to shore.
Male green turtles will spend their entire lives at sea. Females will return to land only when it is time to lay eggs.
Nesting and Reproduction
Female green turtles usually return to the same beach where they were born to lay their eggs. How they manage to navigate back to the same location after decades at sea is still not fully understood, although scientists believe they use the Earth’s magnetic field to guide them.
Once on land, the female faces a difficult challenge. Having evolved for life in the water, her body becomes heavy on the beach. As she drags herself up the sand, she leaves distinctive tracks behind.
After choosing a suitable nesting site, she digs a body pit using her flippers before creating a deep chamber for the eggs. A single clutch usually contains 100–150 eggs.
Once the eggs are laid, she carefully covers them with sand and returns to the ocean, leaving the eggs to incubate.
After about two months, the hatchlings emerge from the sand and make their dangerous journey to the sea.
Interestingly, the temperature of the sand determines the sex of the hatchlings:
Cooler sand → more males
Warmer sand → more females
A common phrase used to remember this is: “Cool dudes, hot chicks.”
However, rising global temperatures are causing sand temperatures to increase, leading to the production of far more females than males. Over time, this imbalance could threaten the future stability of green turtle populations.
Threats to Sea Turtles
Despite being protected in many parts of the world, green sea turtles still face numerous threats.
Illegal hunting: In some countries, turtles are hunted for their meat, shells and eggs, which are sometimes considered delicacies or sold on the black market.
Bycatch: Turtles are frequently caught accidentally in fishing nets or on longlines intended for other species. As turtles must surface to breathe, being trapped underwater can lead to drowning.
Plastic pollution: Plastic pollution poses a growing danger to sea turtles. Floating plastic bags can resemble jellyfish and may be accidentally eaten. When swallowed, plastic can block the digestive system and prevent turtles from eating real food.
Boat strikes: When turtles surface to breathe, they can be struck by boats. As the turtle’s spine is fused to its shell, injuries from propellers or hull collisions can be severe and often fatal.
Fortunately, many conservation efforts are underway around the world. Organisations work to reduce plastic pollution, protect nesting beaches and encourage sustainable fishing practices that minimise bycatch.
Turtle vs Tortoise
Both turtles and tortoises belong to the order Testudines, but they have evolved to live in very different environments.
Turtles (Sea Turtles)
- Cannot retract their heads fully into their shells
- Have flippers adapted for swimming
- Possess streamlined, flatter shells
- Spend almost their entire lives in the ocean
Tortoises
- Can retract their heads into their shells
- Have sturdy legs adapted for walking on land
- Have rounder, dome-shaped shells
- Are strictly land-dwelling and herbivorous
- Often have very long lifespans