Green Sea Turtle Facts

Chelonia mydas

Green sea turtle, Caribbean
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Green sea turtles (Chelonia mydas) inhabit the beaches and offshore locations of 140 countries throughout the world. They are graceful and serene swimmers who migrate thousands of miles through warm subtropical and tropical oceans. All species of these beautiful reptiles are endangered or threatened.

Fast Facts: Green Sea Turtles

  • Scientific Name: Chelonia mydas
  • Common Name(s): Green sea turtle, black sea turtle (in the eastern Pacific)
  • Basic Animal Group: Reptile
  • Size: Adults grow to between 31–47 inches 
  • Weight: 300–440 pounds
  • Lifespan: 80–100 years
  • Diet: Herbivore
  • Habitat: In warm subtropical and tropical ocean waters. Nesting occurs in over 80 countries, and they live in the coastal waters of 140 countries
  • Population: Two largest are the Tortuguero population on the Caribbean coast of Costa Rica (22,500 females nest there each season) and Raine Island in the Australian Great Barrier Reef (18,000 females nest).
  • Conservation Status: Endangered


Green sea turtles are distinguished by their streamlined shell or carapace, which covers their entire body except for flippers and head. The adult green sea turtle has an upper shell that blends several colors, gray, black, olive, and brown; its undershell, called a plastron, is whitish to yellow. Green sea turtles are named for the greenish color of their cartilage and fat, not their shells. While sea turtles have fairly mobile necks, they cannot withdraw their heads into their shells. 

The flippers of sea turtles are long and paddle-like, making them excellent for swimming but poor for walking on land. Their heads are light brown with yellow markings. The green sea turtle has four pairs of costal scutes, large, hard scales which assist in swimming; and one pair of prefrontal scales located between its eyes.

Green Turtle
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There are seven recognized species of sea turtles, six of which are in the Family Cheloniidae (the hawksbill, green, flatback, loggerhead, Kemp's ridley, and olive ridley turtles), with only one (the leatherback) in the family Dermochelyidae. In some classification schemes, the green turtle is divided into two species—the green turtle and a darker version called the black sea turtle or Pacific green turtle. 

All sea turtles migrate. Turtles sometimes travel thousands of miles between cooler feeding grounds and warm nesting grounds. A leatherback turtle was tracked by satellite traveling over 12,000 miles for 674 days from its nesting area in Jamursba-Medi beach in Papua, Indonesia to feeding grounds off Oregon. Habitats, diet and the number and arrangement of these scutes are the primary ways to distinguish different sea turtle species.

Habitat and Distribution

Green sea turtles are found throughout the world in warm subtropical and tropical ocean waters: They nest on the beaches of over 80 countries and live on the coasts of 140 countries.

Efforts continue to emphasize the tracking of sea turtle movement using satellite tags to learn more about their migrations and the implications their travels have for their protection. This may help resource managers develop laws that help protect turtles in their full range.

Diet and Behavior

The only herbivore of the extant sea turtle species, green sea turtles graze on seagrasses and algae, which in turn maintains and fortifies the seagrass beds. They migrate long distances between a wide range of broadly separated localities and habitats during their lifetimes. Tagging studies suggest that ones that nest at Ascension Island in the Atlantic Ocean west of Brazil feed on the Brazilian coast, up to 1,430 miles or more away. 

Reproduction and Offspring

Sea turtles mature at around age 25–30. The males spend their whole lives at sea, while females mate with the males at sea and then go to selected beaches to dig a hole and lay between 75 to 200 eggs. Female sea turtles may lay several clutches of eggs during a single season, then cover the clutches with sand and return to the ocean, leaving the eggs to fend for themselves. The breeding season occurs in late spring and early summer; the males can breed every year but the females only breed once every three or four years.

After a two-month incubation period, the young turtles hatch and run to the sea, facing attack by a variety of predators (birds, crabs, fish) along the way. They drift at sea until they are about a foot long and then, depending on the species, may move closer to shore to feed.


Climate change, the loss of habitat, and diseases such as fibropapilloma—which causes benign but ultimately debilitating epithelial tumors on the surface of biological tissues—threaten green sea turtles today. Sea turtles are protected by a variety of national and state laws and international treaties, but hunting of live turtles and harvesting of eggs is still underway in many places. Bycatch, the accidental entanglement in fishing gear such as gillnets or shrimp trawling nets, is responsible for hundreds of thousands of turtle deaths and injuries each year. In addition, oceanic pollution and marine debris have been known to disturb and disrupt migration patterns. Vehicle traffic and development of beaches and light pollution of nesting regions disturbs hatchlings, who often go towards the light rather than towards the ocean.

Rising sea temperatures from climate change also affect turtle populations. Because the incubation temperature of eggs determines the animal's sex, populations in the northern Great Barrier Reef have experienced imbalances of populations with 90 percent or greater females.

Conservation Status

All seven species of sea turtles are listed under the Endangered Species Act. Due to conservation efforts, some populations are recovering: Between 1995 and 2015, the Hawaiian green sea turtle increased at a rate of 5 percent per year.


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Your Citation
Kennedy, Jennifer. "Green Sea Turtle Facts." ThoughtCo, Apr. 5, 2023, Kennedy, Jennifer. (2023, April 5). Green Sea Turtle Facts. Retrieved from Kennedy, Jennifer. "Green Sea Turtle Facts." ThoughtCo. (accessed June 10, 2023).