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Green sea turtle
Chelonia mydas
Conservation status
Endangered (IUCN)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Testudines Family: Cheloniidae Genus: Chelonia Latreille in Sonnini & Latreille, 1802 Species: C. mydas
Binomial name
Chelonia mydas (Linnaeus, 1758)

This page redirects from Chelonia, which is the genus name of this turtle, but has also been used for the order Testudines of all turtles and tortoises.

Chelonia mydas, more commonly known as the green sea turtle, is a large sea turtle belonging to the family Cheloniidae. It is the only species in the genus Chelonia.^[1]

Contents 1 Anatomy and Morphology 2 Range and Distribution 2.1 Atlantic subpopulation 2.1.1 Florida and the Caribbean 2.2 Pacific subpopulation 3 Ecology and Life History 3.1 Habitat 3.2 Feeding Ecology 3.3 Life History 4 Etymology and Taxonomic History 5 Importance to Humans 6 Conservation 7 Gallery 8 Bibliography 9 References 10 See also 11 External links

The appearance of the green sea turtle is that of a typical sea turtle. C. mydas has a dorso-ventrally flattened body, a beaked head at the end of a short neck, and paddle-like arms well-adapted for swimming.^[2] Unlike the closely-related hawksbill turtle, the green sea turtle's snout is very short and its beak is unhooked. The horny sheath of the turtle's upper jaw possesses a slightly-denticulated edge while its lower jaw has stronger, more defined denticulation. The dorsal surface of the turtle's head has a single pair of prefrontal shields. Mature C. mydas front appendages have only a single claw (as opposed to the hawksbill's two), although a second claw is sometimes prominent in young specimens. The carapace of the turtle is known to have various color patterns that change over time. Hatchlings of C. mydas, like those of other marine turtles, have mostly black carapaces and light-colored plastrons. Carapaces of juveniles are dark brown to olive, while those of mature adults are either entirely brown, spotted or marbled with variegated rays. Underneath, the turtle's plastron is hued yellow. C. mydas limbs are dark-colored and lined with yellow, and are usually marked with a large dark brown spot in the center of each appendage.^[3]
The green sea turtle is known to grow up to one and a half meters long. While individuals have been caught that reached weights of up to 315 kilograms, average weight of mature individuals is around 200 kilograms. The largest Chelonia mydas ever recorded weighed 395 kilograms (871 lbs.)^[4] The species is known to live up to eighty (80) years in the wild.^[5]

Its distribution extends throughout tropical, subtropical and some warmer temperate waters.

It can be found in tropical and sub-tropical oceans worldwide. There are two major subpopulations of C. mydas, the Atlantic and the Eastern Pacific ones.^[5]

Ascension Island in the mid-Atlantic hosts the second largest breeding ground for the Green Sea Turtle in the Atlantic, after Costa Rica. Each year, between 6,000 and 15,000 nests are laid by the turtle, and the turtles nesting on the island are the largest Green Turtles in the world, being 1.5 metres in length and weighing up to 300 kg. The turtles which breed in Ascension migrate from Brazil in what is one of the longest migrations of any creature on earth. The turtles repeat this every 3-4 years. The story of the turtles on Ascension has been a sad one, since the island's discovery in 1502, and up to the turn of the 20th century, turtling was one of the things the island was famous for. Now however, there is an active conservation programme taking place, and there has been an Ascension Island Green Turtle Fund set up to do this. Thankfully, due to low tourist numbers on the island's long beaches, there are plenty of nesting sites for the turtles there.

• Ascension Island Heritage Society page on the Green Turtle

Important feeding grounds for the green sea turtle in Florida include Indian River Lagoon, the Florida Keys, Florida Bay, Homosassa, Crystal River and Cedar Key.

The primary nesting sites in U.S. Atlantic waters are along the east coast of Florida, particularly Hutchinson Island, with additional sites in the U.S. Virgin Islands and Puerto Rico. Sites in Suriname and in Tortuguero, Costa Rica are also reported. This western Atlantic population reaches sexual maturity at anywhere from 20-50 years.

Before the inclusion of the turtles in the Endangered Species Act and the Convention on International Trade in Endangered Species, commercial farms such as the Cayman Turtle Farm in the West Indies bred them for commercial sale and held as many as 100,000 turtles at any one time. But when the markets were closed due to the new protections, some went bankrupt and drastically reduced their stock. They currently now operate only as tourist attractions with around 10,000 turtles at any one time. See http://www.turtle.ky/history.htm for further historical information.

The turtle is found throughout the Hawaiian Islands, all the way to Midway The native Hawaiian word honu is often used. Ninety percent of the Hawaiian population breed and nest at French Frigate Shoals, from April to November. Males apparently make the journey every year, while females make it at two to four year intervals. Sexual maturity comes at about 25 years.

The honu has made a remarkable comeback and is now the subject of eco-tourism and has become something of a state mascot. Students of Hawai'i Preparatory Academy (a high school) on the Big Island have tagged thousands of specimens over the past two decades.

Conservation efforts have been boosted by eco-tourism in Sabah, Borneo. The island of Pulau Selingaan (also known as 'Turtle Island') is home to a turtle hatchery. Staff on the island collect some of the eggs laid each night and place them in a hatchery to protect them from predators. Incubation is approximately 60 days. Once hatched, tourists are permitted to assist in the release of the baby turtles into the sea.

In the Arabian Sea, 'Hawksbay' and 'Sandspit' beaches off the coast of Karachi, Pakistan host some of the most important nesting grounds for the Green Turtles. The nests are laid throughout the year, but the frequency is higher in July and December. Apart from the populated beaches of Sindh, the turtle habitat has been recorded since 1877 on many inaccessible and unfrequented sandy beaches along the 700 kilometer coastline of Balochistan as well as on the Astola island, 25 km from the mainland.^[6] WWF-Pakistan has initiated various projects for safe turtle hatching since the 1980s. However, the population has been in decline due to populated beaches, urban developments, fishing activities, noise and other forms of pollution from the harbour and exploitation of turtle products.^[7]

Along with hawksbill turtles, green sea turtles are known to nest in the Turtle Islands in the Philippines.^[8]

The Green Sea Turtles on the Great Barrier Reef have two genetically distinct populations - one in the northern Great Barrier Reef, and the other in the southern Great Barrier Reef.^[9]

Green turtles usually inhabit shallow waters associated with seagrass beds.^[7] Seagrass meadows within inshore bays, lagoons and shoals are common locations where Chelonia mydas can often be found. This particular species is known to be very selective about their feeding and mating sites and entire generations will often alternately migrate between the same feeding and nesting areas.^[2]

Chelonia mydas is primarily herbivorous. It feeds almost-exclusively on various species of sea grasses and seaweed.^[7] While mature green turtles are entirely herbivorous, juveniles are known to subsist on a plethora of marine invertebrates. Their digestive intake of plant matter grows larger as they age, until as mature adults they become obligate herbivores.^[5]

Unlike most sea turtles, which spend most of their adult lives in the ocean, Pacific green turtles are known to willingly crawl onto secluded beaches during the day to bask in the sun.^[5]

Green turtles migrate long distances in-between their chosen feeding sites and the isolated islands from which they were hatched. Mature turtles will often return to the same exact beach from which they hatched from. Individual turtles will usually mate every two to four years.^[5] Mating seasons vary between populations, but for C. mydas in the Caribbean, mating season is from June to September.^[2]

Green turtles reproduce in the typical way that marine turtles do so. After a lengthy mating ritual in the water, the females haul themselves onto the beach above the high tide line. Upon reaching a suitable nesting site, the gravid female then digs a hole with her hind flippers and deposits a number of eggs in the nest. The number of eggs laid per litter depends on the age of the female and differs from species to species, but C. mydas clutches range between 100 to 200 eggs. After laying eggs, the female then covers the nest with sand and returns to the sea.^[5]

After around 45 to 75 days, the eggs hatch. As with other marine turtles, C. mydas eggs hatch during the night and the newly-emerged turtles head directly towards the water's edge. This undoubtedly is the most dangerous time in a turtle's life, as the hatchlings make their way to the water, various predators such as gulls and crabs pick off many turtles. A significant percentage of turtle hatchlings never make it to the ocean. Just like other sea turtles, little is known of the life history of juvenile green sea turtles. It is speculated that they take twenty to fifty years to reach mature size.^[2]

The species was originally described by Linnaeus in 1758 as Testudo mydas.^[10] In 1868, Bocourt described a particular species of sea turtle as Chelonia agassizi (and Chelonia agassizii - both were once valid names). ^[11] This "species" was referred to as the black sea turtle.^[12] These two separate species were then united in the same species, Chelonia mydas and were given subspecies status. C. mydas mydas referred to the originally described population while C. mydas agassizi referred to the Pacific population.^[13][14] This subdivision was later determined to be invalid and all members of the species were then designated Chelonia mydas.^[1]

The green sea turtle was so named because of the green color of its body fat. The adult turtle's algae diet is responsible for the color in its tissues.

Some debate exists about whether the Black Sea Turtle (Chelonia agassizi) is actually a separate species (bringing the total to 8), or a subspecies of the Green Sea Turtle. Black Sea Turtles are very similar to Green Sea Turtles, but are somewhat darker and smaller as a group. The habitat of this proposed species lies along the Pacific coast of Central America and northern South America.

Along with other sea turtles, Chelonia mydas are caught, intentionally and unintentionally in select regions of the world. In ancient China, the flesh of sea turtles including and especially C. mydas was considered a culinary delicacy.^[15]

Even though it is illegal to hunt members of the family, sea turtles continue to be caught throughout the world (see below).

A particular population of Chelonia mydas in the Mediterranean is listed as critically endangered.^[5]

There are various threats to the species' survival. These include direct threats to individual turtles such as being injured by boat propellers, becoming caught in fishermen's nets and drowning, and being hunted by humans for their flesh. The turtles' nests are also raided both by humans and other animals for their eggs. In addition, the turtles suffer a level of habitat loss from human development of their nesting areas.^[5]

Several population groups of this species exist, and all are in a vulnerable state. The Hawaii and Southern California green sea turtles are designated threatened, and the Florida and Mexico populations are endangered. In Pakistan, the status of Chelonia mydas japonica species has been termed as "Rare and declining" by WWF.^[16] In the United Kingdom the species is protected by a Biodiversity Action Plan, due to harvesting in excess from human overpopulation and marine pollution. They have long been used as a meat source by many different peoples, reducing their numbers. This species is used in turtle soup. They are also caught for their shells, leathery skin, and fat.

Other threats to the species' survival include habitat destruction on their beaches, being caught as by-catch by fishermen, egg poaching, trash pollution in the oceans, collisions with watercraft, and artificial lighting on nesting beaches, which confuses the hatchlings and lures them toward roads instead of toward the sea where they should go. A disease called fibropapillomatosis is also a problem in some green sea turtle populations.

Green Sea Turtle - Honu(Chelonia mydas)

A Sea Turtle resting on Punalu'u Black Sand Beach (Photo: Lisa Weber)

Two Sea Turtles mating underwater in the reefs of Ascension Island.(Photo: Jimmy Young)

A female green turtle returning to the sea after nesting in Redang Island, Malaysia. (Photo by P.N.Chen)

• Maria R. Audubon (ed.)(1897), Audubon and His Journals. New York: Scribner's Sons. (Dover Publications Reprint, 1986). ISBN 978-0486251448
• Seminoff (2004). Chelonia mydas. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 09 May 2006.
• Chelonia mydas (TSN 173833). Integrated Taxonomic Information System. Accessed on 21 February 2007.
• Glick, Daniel (September 2005). "Back from the Brink". The Smithsonian Magazine: 54-55. Retrieved on 2007-02-21. 

• Chelonioidea. The sea turtle superfamily.

• Caretta caretta. The loggerhead turtle.

• Dermochelys coriacea. The leatherback turtle.

• Eretmochelys imbricata. The hawksbill turtle.

• Lepidochelys kempii. The Kemp's Ridley turtle.

• Lepidochelys olivacea. The olive ridley turtle.

• Natator depressus. The flatback turtle.

• ARKive - images and movies of the green turtle (Chelonia mydas)
• US Fish and Wildlife Service sites:
  • Floridian and Mexican populations
  • Hawaiian population
• Green Sea Turtle Description of the species mentioning black sea turtle debate.