Green Sea Turtles
Last Updated: May 17, 2012
Green sea turtles are named for the green colored fat underneath their shell, which is thought to be the result of their herbivorous diet. The largest of all hard-shelled sea turtles, the species has a smooth oval carapace and single-clawed flippers. Their upper shell varies from dark green or brown to light yellow, with different color patterns that change over time.
Scientific Name: Chelonia mydas
Status in the Wild: Endangered
Adult green sea turtles measure about three feet long, and weigh 300-350 pounds. They are omnivorous early in life, favoring aquatic insects, crustaceans, algae and worms. When green sea turtles reach 8-10 inches in length, they transition to a strictly vegetarian diet of sea grasses and algae, making this the only sea turtle species to be completely herbivorous as an adult. They are believed to live an average of 80 years in the wild.
Green sea turtles live in tropical and subtropical waters worldwide between 30° North and 30° South, with heavy concentrations in the Pacific Ocean, Caribbean Sea, Atlantic Ocean, Indian Ocean, and the Mediterranean Sea. Juveniles spend their first five years at sea often unobserved by humans, as they swim deep in pelagic waters, but adults typically prefer shallow coastal waters. The most important nesting sites for green sea turtles include the coasts of Pakistan, Australia, Somalia, Brazil, Ecuador and Costa Rica.
Costa Rica Nesting Sites:
Tortuguero, located in the northern Caribbean, is one of the world's most important nesting sites for green sea turtles, hosting approximately 22,500 females per season. Here, these marine reptiles lay eggs from July-October, with peaks from June through August. Evening turtle tours are very environmentally friendly, employing only licensed guides and ensuring that the turtles are not interrupted during the nesting process.
Mating season varies by population, but most green sea turtles in the Caribbean breed from June-September with peaks in June and July. Scientists believe that females return to their natal beaches to mate, while males travel independent of their birthplace, searching only for large populations of nesting females. Females nest every two to four years and lay eggs four to seven times per season, with about 14 days in between nesting episodes. A healthy female lays 100-125 eggs each time, so by the end of her nesting season she will have laid 600-700 eggs.
Eggs incubate for 45-75 days and typically hatch at night, when the new babies make their way to the ocean. Predators are many, and a large percentage of the hatchlings fall prey to seagulls, dogs, crabs, sharks and other hunters. It is estimated that green sea turtles reach sexual maturity anywhere from 20-50 years in age.
Status in the Wild:
With less than 90,000 nesting females worldwide, green sea turtles are classified as an endangered species. The greatest threat to their survival is from poachers hunting for turtle meat or eggs, which are considered a delicacy in many countries. For over 50 years, the Sea Turtle Conservancy (STC) has conducted research and promoted conservation programs in Tortuguero, Costa Rica. Through turtle tagging, surveys, nest monitoring, and data collection, the STC has stopped the decline of marine turtles in the Caribbean. Green sea turtles also face the threat of commercial fishing nets, which may cause accidental death, as well as habitat pollution and destruction.