The green sea turtle is a fascinating turtle that can be found throughout the world in various oceans. An ancient species, it is thought that they came to be 110 million years ago when the dinosaurs were still roaming the earth. If you want to learn more about these turtles, like why they are actually called green sea turtles, then keep reading!
If you’re interested in learning what other sea turtles there are, check out our list of “The 7 Gorgeous Sea Turtles Of The World.“
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Scientific Name: Chelonia mydas
Common Names: Green Sea Turtle, Green Turtle, Black Sea Turtle, Pacific Green Turtle
Geographic Range: Atlantic, Pacific, and Indian Oceans
Life Span: 75 Years
Conservation Status: Endangered
Green sea turtles are the second largest sea turtle species, with only the leatherback sea turtle being larger. The average carapace (shell) length for these turtles ranges from 100 – 120cm (3.3 – 3.9 feet), however, a specimen with a shell length of 152cm (5 feet) has been found. The average weight for them ranges between 150 – 200kg (330 – 440 pounds), and the large specimen mentioned before had a weight of 395kg (871 pounds).
Green sea turtles have a round and smooth head and jaw shape. Their beaks are strong, short, and serrated which helps them rip and tear plants apart. Large upper eyelids help to protect their eyes. Their eye lenses are also spherical in order to help them see clearly underwater. However, this does make them nearsighted on land, making it harder for them to see while out of water. They have long paddle-like front legs that help them easily swim through the water. While they do have an inner ear, they don’t have any external ear holes on their heads.
Green sea turtles have large, hard round shells with rather smooth edges. Their shell is usually a mix of dark brown, brown, tan, grey, black, or olive on top. While some green sea turtles may appear to have a green shell, it is actually just a covering of algae. Underneath, their plastron (bottom of the shell) is a light cream or yellow color. They are not able to retract their heads into their shells as other turtle species can.
Green sea turtles are found in the saltwater of most of the world’s oceans. The only oceans they are not found in are the Arctic and Antarctic oceans, as these are far too cold for them. These turtles prefer warm, shallow tropical and subtropical waters and coastline beaches. They prefer areas that have lots of algae and seagrass for them to forage for food. Occasionally, they will bask on sandy beaches, which is also where females will go for nesting. Young turtles will venture out into much deeper open waters than adults will.
The breeding season for green sea turtles is from June through September. Every 2 to 4 years female turtles will revisit their natal beach, which is the beach they hatched at. If necessary she may go to a beach with the same sand texture and color. Males tend to show up for breeding season every year. Green sea turtles are polygynandrous, which means that males and females have multiple mates. If a female accepts the male’s advances the pair will mate in shallow waters. If the female rejects the male she will either swim away with her back legs closed, or she will try to bite the male.
An average of 15 days later the female turtle will travel to her natal beach, and make her way up the sand until she finds a suitable nesting site. She will then clear the area of any debris and dig a hole. Once the nest is ready, she will lay a clutch of anywhere from 75 – 200 eggs at a time. After this, she will bury the eggs to conceal them from predators, and then return to the water. Females can lay anywhere from 1 – 9 clutches during the breeding season, however, 3 is more common.
When they are laid, the eggs are around 3.5 – 5.8cm (1.4 – 2.3 inches) in diameter. The eggs can take anywhere from 30 – 90 days to hatch depending on if it is the wet or dry season, with the wet season usually taking longer. The sex of the babies can be influenced by the temperature of the eggs while they incubate. Eggs that are kept at temperatures under 28.5°C (83.3°F) tend to produce more males. Eggs incubated at temperatures over 30.3°C (86.5°F) tend to produce more females.
When green sea turtles are ready to hatch, they will break out of their egg with what is called an egg tooth. Once they are out of the egg they are on their own, and must instantly fend for themselves. After emerging from their egg they will dig their way out of their nest, crawl down the beach, and head into the water. These hatchlings will then swim out into the open sea, and go through their pelagic (open water) phase. Not much is known about this stage, and many scientists refer to it as the “lost years”. This phase can last up to 10 years, and they usually don’t return until they have grown to around the size of a dinner plate. Once they have finished this stage they will return to shallower coastal waters to keep growing and maturing. Hatchlings are omnivores, eating both plant and animal matter.
When they hatch, hatchlings only weigh around 25g and have a shell length of only 5cm (2 inches). Their shell is a blue-black color, and their plastron (underneath their shell) is white. Juveniles are around 40cm (15.7 inches) in shell length, and subadults range between 70 – 100cm (27.6 – 39.4 inches) in length. It can take anywhere from 27 – 50 years for a green sea turtle to reach full maturity.
When green sea turtles are first born, they start out as omnivores, which means they eat both plants and animals. In the open waters, young turtles will prey upon fish eggs, jellyfish, sea sponges, crustaceans, mollusks, worms, small invertebrates, and various sea grass and algae.
As they age these turtles slowly transition into being herbivores, which means they eat plants. This makes adult green sea turtles the only herbivorous sea turtle. They have a serrated jaw instead of teeth, and this helps them chew various plants easily. The main part of their diet is made up of various sea grasses and red and green algae, like red moss, sea lettuce, green seaweed, and more. What type of plant makes up the biggest parts of their diet depends on where the turtle is and what is available around them.
Green sea turtles spend a large amount of time swimming. They can swim anywhere from 20 – 90km (12.4 – 55.9 miles) a day. Over short distances, they are able to swim at speeds of up to 3.6km/h (2.2mph). When they aren’t sleeping, green sea turtles are most likely eating, resting, or basking on warm beaches in the sun. They are primarily diurnal, meaning that they spend most of the day awake, and sleep at night. During the nighttime, they may wedge themselves under rocks and ledges while they sleep, in order to keep themselves protected against predators.
Green sea turtles spend the majority of their life submerged underwater. However, they do still need to come up to the surface in order to breathe air. The length of time that they can hold their breath depends on what they are doing, and their stress level. For example, when they are resting or sleeping they are able to hold their breaths for hours. But, if they are looking for food, trapped, or escaping from predators they are not able to hold their breaths for as long.
Green sea turtles can migrate long distances, especially during the breeding season. They have a couple of different adaptations that help them navigate through the ocean and find specific areas. In the open ocean, they are able to navigate by paying attention to the wave directions, sunlight, and temperatures. Their inner ear specifically is able to detect acceleration and the direction of the waves. Interestingly, green sea turtles contain an internal magnetic compass. This allows them to detect the earth’s magnetic field and helps them navigate to various areas like breeding grounds or nesting areas. It is thought that hatchling green sea turtles will imprint on the magnetic field of their beach, allowing them to find their way back years later.
Hatchlings are at a higher risk of predation due to their smaller size. They are often preyed upon by crabs and saltwater crocodiles. In open oceans both juveniles and adults are attacked by sharks, such as the whitetip and tiger sharks. Turtle eggs are often preyed upon by land mammals like feral dogs and jaguars, reptiles, and crustaceans.
An adult green sea turtle’s best protection against predators is its hard shell. Nesting females on land are also vulnerable with their heads and limbs being exposed to predators. These turtles are also hunted by humans, and their eggs collected.
Green sea turtles have an important role in the ecosystem that they live in. They will graze on the seagrass and algae, which helps maintain the health and growth of the seagrass beds. Without the turtles eating the grass, it would grow upwards and not outwards, growing too tall. When it gets too long the seagrass will start to obstruct currents, as well as block light. It is important for these seagrass beds to stay healthy for various reasons. Seagrass is called the “lungs of the sea” and produces large amounts of oxygen for the water. They also provide areas for fish, crustaceans, etc to breed and develop, helping keep those species stable.
Green sea turtles are also in a mutualistic relationship with various fish. Mutualistic relationships are when both sides of the relationship benefit. In this instance, the fish will peck at the turtle’s shell, cleaning it, and in return, the fish get a meal.
According to the IUCN Redlist, green sea turtles are endangered. They are also listed in Appendix I of CITES, which is for the species that are the most endangered, and are at risk of extinction. This also prohibits the trade of green sea turtles, unless it is for research purposes.
There are many different things that are contributing/have contributed to the decline of the green sea turtle’s population. Fishing that uses shrimp trawl nets, longline hooks, and fishing gillnets is responsible for trapping and drowning huge amounts of turtles, as they are unable to get to the surface to breathe. Some have been injured or killed by being hit by boats. Habitat loss and degradation is another huge issue for the stability of the green sea turtle. Beaches being developed and having large amounts of people can ruin nesting areas. Pollution can cause there to be less food, as well as illness and diseases in turtles. Garbage and other pollutants may be eaten and cause death or serious sickness.
Finally, despite them being a protected species, 10s of thousands are hunted each year for food, medicine, traditional ceremonies, or are made into products like bags or jewelry. Eggs are also harvested to be eaten.
When Christopher Columbus first visited the Cayman Islands in 1503, he called the islands “Las Tortugas” because of the abundance of green sea turtles in n the water around the islands. Many early visitors to the island went to capture the turtles as a fresh source of meat on their long voyages. The green sea turtle is a national symbol and is displayed as part of the coat of arms. Their currency also uses the turtle as a watermark in their banknotes. A stylized version of a green sea turtle called “Sir Turtle” is the mascot of the national airline Cayman Airways.
In Hawaii, green sea turtles are called honu. A Ki’i Pōhaku (carving on a stone) of a green sea turtle was found on the big island of Hawaii, in the Pu’u Loa lava fields. This carving may date back to when the islands first became populated and hint at the importance of the green sea turtle to the Hawaiians. Ancient Hawaiians used to eat the meat of the turtle, used their bones for fish hooks, and used the shells as containers. The turtle symbolizes a navigator that can find their way home time after time.
There are quite a few legends that include the honu (green sea turtle). One legend describes a female sea turtle named Honupo’okea who came out of the ocean onto the Big Island to lay a special egg. She laid and buried the egg in the sand to hatch. Before she made her way back to the sea, she and her mate Honuea dug a freshwater pond next to the egg. When the egg hatched, a turtle named Kauila emerged from the egg and lived at the bottom of the freshwater pond, blessing people with fresh drinking water. She was also able to take the form of a human woman, and she would often watch over and play with the children while they played on the shoreline of Punalu’u beach.
A population of green sea turtles in the Eastern Pacific ocean is often referred to as black sea turtles. This population of turtles tends to be much darker in color (hence the name) and seems to be a bit smaller than the rest of the green sea turtles. Some people think they should be their own subspecies of the green sea turtle (Chelonia mydas agassizi), however, they are currently still considered the same species.
Green sea turtles did not get their names because they are green in color (however, algae can make their shell appear green when it is not). They actually got their name because their cartilage and a layer of fat between their inner organs and shell have a green color to them. It is thought that these are green because of the turtle’s herbivorous diet.
In the scientific name, the genus “Chelonia” was named after the Greek word “chelone”, which means turtle or tortoise. The species name “mydas” was named after the Greek word “mydos” which means dampness and refers to the turtle’s aquatic habitat.
Green sea turtles and hawksbill sea turtles are often confused with each other. However, if you know what you are looking for it can get easier to tell them apart!
Hawksbills have a more hooked beak, hence the name, and a longer neck while green turtles have a more rounded beak and shorter neck. If you are able to look at the face of the turtle, another difference you’ll be able to notice is the nostril placement. On Hawksbills the nostrils are more on top of their beak, angled upwards. Greens have nostrils that are forward-facing and on the front of their beak. Another difference is that on their heads, hawksbills have 2 pairs of scales in between their eyes (called prefrontal scales), while greens have only one pair. If you look at the edges of their shells you’ll be able to see that green sea turtles have a smoother edge, while the edge of a hawksbills shell is much more serrated.
Finally, the last way to tell is by size. Green sea turtles tend to be larger than hawksbills. However, if you’re trying to identify a sea turtle this shouldn’t be the only thing you go by. While green sea turtles may be larger overall, not every green sea turtle will be the max length. Their age also has an effect on their size, as juveniles will be smaller than adults.
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