Green Turtle

The green turtle (Chelonia mydas) is one of the largest sea turtles in the world. Adults grow to 1.5 metres long, with an average carapace length of 78-112 cm and an average weight of 68-190 kg, though exceptional individuals can weigh 315 kg or more. The body is flattened and streamlined, covered by a large, teardrop-shaped shell that ranges in colour from olive to dark brown, sometimes spotted or marbled. Despite the name, the shell is not green - the colour comes from the greenish fat found beneath it, a result of the turtle's plant-based diet.

Green turtles live in tropical and subtropical seas across the globe, including the Atlantic, Pacific, and Indian Oceans. They favour shallow coastal waters, lagoons, and seagrass beds, and are found along the coastlines of more than 140 countries. They are protected from exploitation in most countries.

The green turtle is the only species in the genus Chelonia. The species was first formally described by Carl Linnaeus in 1758. For a time, the darker Pacific population was treated as a separate species, but DNA analysis confirmed it is the same animal, and all populations are now classified together as Chelonia mydas.

Historically, green turtles were heavily exploited by humans. Their fat, cartilage, and flesh were used to make turtle soup, a popular dish in 19th-century England and America. Their skin was tanned for leather goods, and their eggs were collected for food in various parts of the world. Commercial farms once bred them for meat, oil, shell, and leather. Over time, green turtles gained international protection, and commercial international trade in the species is now prohibited under CITES.

In Hawaiian culture, the green turtle - known as honu - is a symbol of good luck and longevity. It is also a national symbol of the Cayman Islands, appearing on the coat of arms and national flag.

Adults spend most of their time grazing on seagrasses in shallow coastal waters - they are the only aquatic turtle that is fully herbivorous when grown. Younger turtles are carnivorous, eating fish, jellyfish, invertebrates, and other small creatures, gradually shifting to a plant-based diet as they mature.

One of the most remarkable things about green turtles is their ability to migrate enormous distances. Some individuals swim more than 2,600 kilometres between feeding grounds and nesting beaches. Mature turtles often return to the exact beach where they hatched to breed - a behaviour known as natal homing. Scientists believe they navigate using the Earth's magnetic field, wave directions, sunlight, and possibly chemical cues.

Females come ashore at night to dig nests and lay between 85 and 200 eggs, repeating this three to five times in a single season. Hatchlings emerge together at night and make their way to the sea, where they spend their first few years in open ocean waters before settling into shallower coastal habitats.

Green turtles that reach maturity can live for up to 80 to 90 years in the wild. However, the journey from hatchling to adulthood is extremely perilous - it is estimated that only around 1% of hatchlings survive to sexual maturity, which itself may take 20 to 50 years to reach.

The most serious disease affecting green turtles is fibropapillomatosis, a condition caused by a herpesvirus that produces tumours on the scales, lungs, stomach, and kidneys. It is transmitted by leeches and kills a significant proportion of those it infects. Green turtles are also affected by a range of parasites including barnacles, leeches, protozoans, tapeworms, and roundworms, which can cause damage to soft tissues, blood loss, and infections of the liver and intestinal tract.

Beyond disease, green turtles face serious threats from human activity. Many drown after becoming entangled in fishing nets. Pollution, including plastic ingestion and chemical contamination, causes internal blockages and tissue damage. Boat strikes are another significant cause of injury and death. There are indications that rising temperatures linked to climate change are affecting the ability of green turtle populations in Australia to produce males, since nest temperature determines whether eggs develop as male or female.

This is general awareness only, not veterinary advice. Always consult a vet about your pet's health.

Why is it called a green turtle if it isn't green?

The name does not refer to the colour of the shell, which is typically olive, brown, or black. It comes from the greenish colour of the fat found beneath the shell, which turns green because of the turtle's diet of seagrasses and algae.

How long do green turtles live?

Green turtles can live up to 80 to 90 years in the wild if they reach adulthood. The challenge is getting there - only around 1% of hatchlings are thought to survive long enough to reproduce, and it can take 20 to 50 years for a turtle to reach sexual maturity.

Are green turtles endangered?

For many decades green turtles were listed as endangered. In 2025, the IUCN reclassified the global population as least concern, reflecting recovery in some areas. However, several subpopulations remain at serious risk - the Mediterranean population is critically endangered, and populations in Florida, Hawaii, and parts of the eastern Pacific are still listed as threatened or endangered.

Do green turtles always return to the same beach?

Often - mature turtles frequently return to the exact beach where they hatched to breed, sometimes swimming thousands of kilometres to do so. Many researchers believe hatchlings imprint on their birth beach, either by its smell or by its magnetic field, allowing them to find their way back years later.

What do green turtles eat?

Adult green turtles are herbivores, feeding mainly on seagrasses and algae. Young turtles start out carnivorous, eating fish, jellyfish, and small invertebrates, before gradually shifting to a plant-based diet as they grow. Their serrated jaws are well suited to cropping vegetation.

How far do green turtles travel?

Green turtles are remarkable long-distance migrants. Some individuals travel more than 2,600 kilometres between their feeding grounds and nesting beaches. They navigate using the Earth's magnetic field, wave directions, sunlight, and temperatures.

Green turtles can reach speeds of up to 40 miles per hour in the water, making them the fastest of all sea turtles.

Many islands around the world are known as Turtle Island because green turtles nest on their beaches - a testament to just how widespread these animals are.

Green turtles can sleep underwater for several hours at a time. At night, adults often wedge themselves under rocks or ledges on the seafloor, and many individuals return to the same sleeping spot night after night.

The sex of a green turtle is determined by the temperature of its nest. Warmer nests above 30 degrees Celsius produce females, while cooler nests produce males. Eggs in the centre of a nest, which tend to be warmer, are more likely to hatch as females.

In Hawaiian culture, the green turtle is known as honu and is considered a symbol of good luck and longevity. Some Hawaiian legends say that honu were the first to guide the Polynesian people to the Hawaiian Islands.