Outforia Quicktake: Key Takeaways
- Green sea turtles (Chelionia mydas) are the largest hard-shelled sea turtles and are only slightly smaller than leatherback turtles. They can grow up to 4 ft (1.2 m) long and weigh over 400 lbs (181.4 kg).
- They are primarily herbivores, feeding on large amounts of seaweed and algae, which gives their subcutaneous fat a green hue, hence their name.
- These turtles live in tropical and coastal waters worldwide, with the largest population found around the Great Barrier Reef in Australia. However, they are now endangered due to poaching, fishing, and habitat degradation.
- Green sea turtles play a critical role in maintaining healthy seagrass beds and coral reefs. They are now protected under numerous international agreements and conservation efforts.
- Despite their long lifespans (60 to 70 years), they face many threats, including poaching, plastic and chemical pollution, decreasing nesting sites, and climate change.
Green sea turtles are the largest hard-shelled sea turtles in the world. They are only slightly smaller than the leatherback turtle.
Altogether, there are seven types of sea turtles worldwide. Six of those species live off the coast of the United States.
Interestingly, green sea turtles don’t get their name from the color of their shell. While their shells are green, they get their name from the color of their subcutaneous fat.
Green sea turtles are herbivores that eat so much algae that it changes the color of their insides.
These beautiful animals live in waters and on beaches worldwide. They are becoming less common and are now endangered. Poaching, fishing, and habitat degradation have caused their populations to plummet.
Fortunately, there are many protections in place for these majestic animals. Plus, there are ways that we can help as individuals.
What Are Green Sea Turtles?
The green sea turtle (Chelonia mydas) doesn’t get its name from the skin or shell; it gets it from its insides! Green sea turtles eat so much algae that their internal fats have a green hue.
There is a subspecies of the green sea turtle called the black sea turtle (Chelonia mydas agassizii). Black sea turtles live in the eastern Pacific Ocean.
While green sea turtles aren’t named for the color of their shells, they are still green. Their teardrop-shaped, domed carapaces may combine green, black, yellow, gray, and brown colors. Their plastrons, or lower shells, are a light yellowish-white.
These sea turtles are also recognizable for their small, rounded heads. At the tip of each flipper is a single claw.
Green sea turtles are the largest sea turtle species with a hard shell. The largest individuals can grow up to 4 ft (1.2 m) long and weigh over 400 lbs (181.4 kg).
Compared to the rest of their bodies, green sea turtles have small heads. They have serrated lower jaws that make shredding their food easy.
There are five scutes running down the center of the shells and four scutes on either side. Green sea turtles also have two large scales between their eyes.
Green Sea Turtle Range and Habitat
These turtles live in tropical and coastal waters worldwide. They live in the waters surrounding more than 140 countries and nest in over 80 countries.
Some green turtles live in subtropical waters, though they’re less common.
They usually stay close to shore in coastal waters, estuaries, and bays. The areas they choose to live in have a lot of algae and seagrass for the turtles to feast on.
The Endangered Species Act says there are 11 distinct populations of green turtles.
The largest population exists around the Great Barrier Reef on Raine Island, Australia.
During the height of the nesting season, over 60,000 females gather simultaneously. They nest on the island and live around the reef.
The second-largest population occurs in Tortuguero National Park. The park exists on the Caribbean coast of Costa Rica. During the height of the nesting season, over 30,000 female green sea turtles gather together.
Diet and Hunting
Green sea turtles are omnivores as juveniles but are mostly herbivorous as adults.
They eat large amounts of seagrass, mangrove leaves, and algae. They consume a wide variety of vegetation besides those listed above. The exact type usually depends more on availability than preference.
Adults mostly stick to plants. They sometimes eat invertebrates, sponges, and dead fish while foraging.
The East Pacific population eats more meat than other populations. They remain mostly herbivorous.
Juvenile green sea turtles eat small invertebrates, hydrozoa, bryozoa, and sea hare eggs.
These turtles have serrated beaks that are perfect for shredding and eating seagrass.
Green sea turtles are the only sea turtle species that are herbivorous. All others are carnivorous.
Green Sea Turtle Behavior
Green sea turtles spend most of their time swimming, traveling 12.4-55.9 miles per day (20–90 km per day).
These turtles are unique in that they like to drag themselves onto protected beaches to bask. Most sea turtle species avoid leaving the water except during breeding.
Holding Their Breath
Green sea turtles are great at holding their breath. Their bodies store lots of oxygen, which allows them to stay submerged longer. They can dive underwater for up to 30 minutes without surfacing.
During sleep, they can remain submerged for even longer. Sleeping green sea turtles can stay underwater for up to two hours without breathing.
Traveling In Groups
These sea turtles travel in big groups. The groups usually comprise individuals from the same natal beach.
Green Sea Turtle Communication
Green sea turtles have good vision and locate their food through sight.
While swimming, green sea turtles can sense wave movement and magnetic channels. These help the turtles navigate the waters and orient themselves at greater depths.
One study shows that turtles use their inner ears. The inner ears can sense the speed and direction of waves to help with direction.
Green sea turtles have long lifespans, often living for 60 to 70 years. Despite these estimates, researchers are unsure how long green sea turtles can live.
Reproduction and Mating
These sea turtles may live for 70 years, but they don’t reach sexual maturity until 20 to 50 years of age. Females most often reach sexual maturity between 25 and 35 years of age.
It’s difficult to tell male and female green sea turtles apart without looking closely.
Males have longer tails than females but have shorter carapaces and longer claws.
The female’s cloacal opening sits between the anus and the tip of the tail. The male’s cloacal opening sits further back, closer to the base of the tail, but at the end of their carapace.
Traveling To The Nesting Site
Once they are old enough to reproduce, adult sea turtles migrate to their nesting sites. Most females reproduce every two to five years.
Green sea turtles almost always return to the beach where they hatched to mate and lay their eggs. If they don’t return to their natal nesting site, they choose a beach that is similar.
Green sea turtles nest in over 80 countries worldwide.
Their foraging grounds are far from their nesting grounds. They travel thousands of kilometers from their foraging grounds to their nesting sites.
Choosing A Mate
Green sea turtles are polygyndandrous—both males and females have several mates.
The female determines whether a male is good enough for her. A male approaches a female after first looking her over. She then has the chance to accept or reject him.
If she approves of her suitor, the female will become submissive and allow him to mount her. If she rejects him, she usually swims away with her hind legs closed.
Other times, the female may orient herself so she is facing upward. Her plastron, or bottom shell, faces the male, and she spreads her limbs. Taking this position shows the male that he is not wanted.
A male who is too persistent after rejection is likely to get bitten.
Once they pair up, the male and female mate off the coast of their nesting site in shallow water. The male mounts the female and holds onto the “mating notches” at her shoulders to help him stay on.
Mating can take several hours; the longest observed copulation lasted 119 hours.
Males are jealous of other males. They will not accept “defeat,” even when another pair is in the act of mating.
A male that wasn’t chosen may mount another male that is currently copulating. He tries to separate the male from the female so that he can have a chance with her.
The mating male may temporarily dismount the female to scare off the other males. Other times, he may simply ignore the intruders and keep going.
It usually takes about 15 days after mating for a female to begin nesting. Green sea turtles wait to lay their eggs until nighttime, when it’s dark and safest.
They choose a suitable site and dig a hole with their front legs. They also cleared debris from the area during this time.
After digging the hole, the mother turns around and lays the eggs inside the hole. Then she fills the hole with sand to hide the eggs from predators.
After laying her eggs, the mother returns to the ocean.
A female green sea turtle may lay one to nine clutches per breeding season, though most lay three. She will lay between 70 and 200 soft, white eggs with each clutch. Each egg is about 1.4–2.3 in (3.5–5 cm) in diameter.
The mother will produce a nest once every two weeks for several months.
Once finished, she will leave the nesting site. She migrates thousands of kilometers back to her foraging grounds.
The incubation period of the eggs is 45 to 75 days long. Incubation usually lasts longer during the wet season.
Eggs lying in cooler temperatures—below 83.3°F (28.5°C)—become predominantly male hatchlings. Those lying in warmer temperatures—above 86.5°F (30.3°C)—become mostly female hatchlings.
In-between temperatures usually produce an equal mix of males and females.
Hatchling Green Sea Turtles
At hatching, green sea turtles have black shells. They slowly change to shades of green and brown as they age.
These babies are only about 2 in (5 cm) long and weigh about 0.9 oz (25 g).
The Journey To Sea
As they emerge from their eggs, hatchlings immediately make their way to the water.
They know to head toward the water by looking at the bright horizon above the ocean. The darkness of the dunes and vegetation points them in the opposite direction.
Surviving The Journey
Unfortunately, many hatchlings never make it to the water. Predators snatch them up during their short journey.
Hatchlings can only defend themselves by moving quickly and hiding among the masses. The hatchlings all move together in a large group to make themselves harder to eat.
The increasing presence of artificial lights along beaches is also proving fatal. The hatchlings mistake the artificial lighting for the light of the horizon.
Rather than heading toward the ocean, they head back toward land. Trekking in the wrong direction gives predators more time to catch them.
Entering The Water
Hatchling green sea turtles take to the open ocean or stay near the continental shelf.
During this crucial time of survival, they are mostly carnivorous. Hatchlings seek out tiny invertebrates to eat.
As the turtles grow into adults, their diets turn more herbivorous. They also journey closer to the coastline.
Juvenile Green Sea Turtles
Juveniles are turtles with carapaces of about 15.7 in (40 cm) in length.
Subadult Green Sea Turtles
Subadult green sea turtles have carapaces about 27.6-47.2 in (70–100 cm) long.
Green Sea Turtle Predators
Sea turtle eggs and hatchlings are most in danger from predators.
Raccoons, jaguars, red foxes, feral dogs, golden jackals, and other land mammals will dig up the eggs. Reptiles and crustaceans will also dig them up.
Most newly hatched juveniles become food, too. Gulls, crabs, and saltwater crocodiles pick them off on their way to the ocean.
Those that survive the journey are still not safe. They are often eaten by gulls, crabs, saltwater crocodiles, sharks, or large fish. Very few sea turtles make it to adulthood.
As adults, green sea turtles are large and have few predators. Still, larger, more aggressive shark species sometimes attack adults.
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Conservation Of Green Sea Turtles
Green sea turtles and other sea turtle species are in serious danger.
The International Union for the Conservation of Nature (IUCN) lists them as “endangered.” The species was most recently assessed in 2004. Research shows that their populations are “decreasing.”
Poaching is one of the biggest concerns. People hunt sea turtles for their meat and their nests for their eggs.
Poaching is illegal in many countries, though it still happens. In some countries, the practice remains legal despite the declining population.
Nest poaching has decreased over the years. There are now groups that watch and protect the nests.
The poaching of adult sea turtles is harder to control. The meat makes its way into “informal” markets that are more difficult to track.
Poachers target adults at their nesting sites and on their foraging grounds. Sea turtles are most vulnerable in these areas.
Green sea turtle meat is more highly prized than the meat of other sea turtle species.
Sometimes, green sea turtles end up in the nets of fishermen. While these fishermen usually let sea turtles go, they are less likely to let green sea turtles go. By keeping and selling green sea turtles at the market, they can make a lot of money.
These sea turtles are also in danger from the fishing and shrimping industries. They get caught in nets and lines and are unable to break free. The most common culprits are shrimp trawling, dynamite fishing, drift netting, and long-lining.
Bycatch is the leading cause of death among green sea turtles after poaching.
Plastic and Chemical Pollution
Plastic bags, fishing lines, and other plastic pollution are killers of sea turtles.
Green sea turtles sometimes feed on jellyfish, which have translucent, gelatinous bodies. The transparent appearance of plastic resembles jellyfish as it drifts through the water. The sea turtles attempt to eat the plastic and suffocate.
Chemicals can be as damaging as plastics, particularly those from oil spills.
For example, the Deepwater Horizon oil spill was the worst oil spill in United States history. Turtles of all ages and their eggs suffered.
Turtles are likely to ingest the spilled oil when they surface for air, which can be fatal.
Decreasing Nesting Sites
Even worse, green sea turtles are finding it harder to find nesting sites.
Very few sea turtles make it to adulthood, and it takes decades for them to reach adulthood. That means that their reproductive rates are already low.
Now, real estate along beaches is destroying sea turtles’ natural nesting areas.
Plus, climate change is causing ocean levels to rise. As the waters rise, more and more beaches are being washed out. Fewer beaches mean fewer nesting sites for turtles.
Climate change is also causing temperatures to steadily rise across the globe.
Male vs Female Turtles
Sand temperature determines the sex of turtle eggs. Cooler temperatures produce more males, while warmer temperatures produce more females.
If temperatures continue to rise, we will have more female sea turtles than males. An uneven number of males and females can make breeding tricky.
Fewer Nesting Sites
The warming climate is also changing the landscape of sea turtle nesting beaches. Rising water levels and storms cause flooding and erosion, causing nests to wash away.
Climate change may also affect their foraging territories. The changing temperatures will affect the amount of food in some areas.
Hatchlings are in even greater danger.
Predators already make it difficult for hatchlings to make it to the water. Artificial lighting along beaches makes it even more difficult, as it confuses hatchlings.
Rather than heading straight for the water, the hatchlings turn toward the light. The predators have more time to scoop up the hatchlings before they find their way.
Sea turtles often spend time at the surface of the ocean to get air.
Boats and other vessels often strike unsuspecting animals, especially in high-traffic areas. Accidents most often occur in marinas, inlets, and ports.
Larger juveniles and adults are more likely to be victims than smaller turtles.
Disease, Parasites, and Degradation
Many green sea turtles develop fibropapillomatosis, which causes internal and external tumors.
Research suggests there is a link between the disease and the degradation of habitat.
Depending on location, the tumors can make it challenging to swim and eat. Many turtles eventually succumb to the disease.
Green sea turtles are also susceptible to parasitic flukes—trematode eggs. They infect the turtles and cause inflamed cardiovascular tissue. The infection is severe and often causes death.
Sea Turtle Protections
Fortunately, many worldwide laws and treaties offer sea turtle protection.
The most notable protections include the following:
- Endangered by the World Conservation Union
- Annex 2 of the SPAW Protocol to the Cartegena Convention
- Appendix 1 of CITES
- Appendices 1 and 2 of the Convention on Migratory Species
The protections have helped slow the illegal poaching of turtles and their eggs.
They have also implemented “turtle excluder devices” for fishing. Fishermen must use these devices to prevent sea turtles from getting stuck in their nets and lines.
Here’s How Researchers Study Green Sea Turtles
Researchers are constantly studying green sea turtles. By understanding them better, they hope to offer further protections.
The National Oceanic and Atmospheric Administration (NOAA) and the World Wildlife Fund (WWF) both work to protect sea turtles.
They aim to better understand the turtles’ physiology, demographics, and resource needs. They understand these better by studying the turtles’ reproductive and foraging habits.
They keep track of various populations for their research. They do this by utilizing boats, satellites, flipper tagging, and aerial surveys. They also study the turtles’ genetics and track their nesting sites.
They also watch fisheries’ behaviors and design gear that decreases sea turtle bycatch.
By doing these things, researchers can better understand many things. They can observe the turtles’ life histories and population health. They can also see how the changing environment affects them.
What We Can Do To Help Sea Turtles
Sea turtles need help on a large scale, and many countries and organizations are working to do that. Every day, people can do their own part to protect sea turtles by reducing their dangers.
Consider cutting down on your use of single-use plastics. Doing so reduces the amount of trash in the ocean, helping sea turtles and other marine animals.
Likewise, consider participating in beach clean-up events. They help prevent discarded trash from entering the ocean.
Don’t release balloons. Intentional balloon releases are common during ceremonies, memorials, and other events.
The balloons don’t simply disappear. Eventually, they pop and fall back to earth, where they cause devastation to the animals that eat them.
Leave Turtles Alone
Stay away from sea turtles and their eggs. Even those with the best intentions can cause harm. Instead, keep your distance and observe or take pictures instead.
Take part in turtle watches for a better view.
Contact the authorities for an injured turtle rather than trying to help it yourself.
Watch Out For Them While Boating
Look out for sea turtles during boating activities. Slow down and go around them when you see them; aim to stay at least 50 yards (45.7 m) away. If a turtle gets closer than that, put the engine in neutral and wait for it to swim away.
Leave The Beach How You Found It
When enjoying a nesting beach during the day, make sure to take everything with you.
Don’t leave any equipment or trash behind for the turtles to eat or become trapped in. Knock down sand castles to remove obstacles. Fill in holes; smaller turtles can fall inside and become trapped.
Avoid Artificial Lights
Those who live near nesting beaches can protect hatchlings. Turn off any lights that you can see from the beach.
How Sea Turtles Help The Environment
Green sea turtles are important to the ecosystem. They act like gardeners by continually grazing on seagrass beds.
Their constant eating keeps seagrass beds healthier. When seagrass is healthy, it is better able to absorb carbon and help reduce carbon in the atmosphere.
After the turtles eat the grass, it passes through their system. Then, it becomes recycled nutrients. Those nutrients are available for many animals and plants within the seagrass ecosystem.
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Green Sea Turtle FAQs
Are Green Sea Turtles Asexual?
Green sea turtles are not asexual and cannot reproduce asexually. Both male and female turtles are necessary to reproduce.
Males and females come together to mate, and after fertilization, the mother lays her eggs in a hole in the sand.
It takes many years for green sea turtles to become sexually mature. This is one reason their reproduction rates are low.
Can You Touch Green Sea Turtles?
While green sea turtles are not toxic to the touch, they are still wild animals. People should never touch endangered animals unless they have the authority to do so.
It’s unlikely a green sea turtle will harm someone who touches it, though it’s possible. They are large, strong animals with powerful beaks for biting.
Touching a green sea turtle may also injure the turtle or cause distress.
Further, endangered species are under the law’s protection. It is illegal to harm or harass sea turtles, and the offense is punishable.
Do Green Sea Turtles Sleep On The Beach?
Green sea turtles do not sleep on beaches because they are most vulnerable on land. They may come on land to bask, though it’s rare they will sleep during this time.
Instead, they sleep in the water. They lift their heads above the surface when they need to breathe.