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Chelonia mydas (Linnaeus, 1758)Green turtle |
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| Following modified from Animal Diversity Web, University of Michigan |
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Chelonia mydas
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By Janel Crite
Green turtles are found in tropical and portions of subtropical oceans worldwide. They are found in the Atlantic Ocean from the eastern United States along coastal South America to South Africa. They are found throughout the Caribbean Sea and portion of the Mediterranean. They are also found throughout the warm waters of the Indian and Pacific Oceans. ( Ernst, Barbour, and Lovich, 1994 )
Biogeographic Regions:
indian ocean (
native
);
atlantic ocean
(
native
);
pacific ocean
(
native
); mediterranean sea (
native
).
Green sea turtles live in tropical waters all over the world. The only time they emerge from the water is when they are nesting. The only time males are not at sea is when they were first born. C. m. agassizii are sometimes found with seals and albatrosses basking on the beach (Pritchard 1967). When it is time to mate they migrate from several hundred to over a thousand miles across the ocean to where they hatched. Female green turtles use the same beaches to nest as their mothers and grandmothers.
Aquatic Biomes:
coastal
.
They are called green turtles because of the color of the flesh. Chelonia mydas are one of the largest turtles ranging from 71 to 153 centimeters. They can weigh up to 205 kilograms. They have limbs that are paddle-like, which are used to swim. Their heads seem small compared to their body size. Males are larger than females and the tail is longer, extending well beyond the shell. The carapace can be olive to brown, or sometimes black, depending on the geographic location of the species. Green turtles cannot pull their heads inside of their shells. There are two sub-species which include Chelonia mydas mydas and Chelonia mydas agassizii . The common name for Chelonia mydas mydas is the Atlantic green turtle, which lives in the Atlantic ocean and has been see off the shores of Europe and North America. Chelonia mydas agassizii , or Eastern Pacific green turtle and sometimes black sea turtle because of its dark colored carapace, has been see off the coasts of Alaska, through California, and to Chile. Some features that distinguish C. m. agassizii from C. m. mydas are that the shell of C. m. agassizii is higher, the shell is narrower, the marginals are more constricted over the hind legs, and the postcentral lamina are longer relative to their width (Ernst 1994). The Pacific and Atlantic populations have been separated for millions of years.
Some key physical features:
ectothermic
;
bilateral symmetry
.
Males and females mature between 10 and 24 years. The breeding season depends on the latitude. Internal fertilization takes place when the male and female copulate. This is the only time there is vocalization. Like many species, there is male competition. One male may try to bite another male who is copulating with a female. Mating occurs underwater or on the surface about one kilometer from the shore. Sometimes the female will retain enough sperm to nest several times that year. Nesting occurs every three to six years. When the female is ready to lay her eggs, she leaves the water, crawls onto the sand and starts digging for hour and hours until her flippers will not allow her to dig deeper. She then lays 100 to 200 eggs. This group of eggs is called a clutch. She covers them with sand to protect them from the sun, heat, and predators. Pacific green turtles lay fewer eggs than Atlantic green turtles. The gestation period is 40 to 72 days, depending on the location.
Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate).
Baby turtles use their egg tooth when they hatch to break the shell of the egg. Females lay so many eggs because the chance for their survival is very low. Sometimes animals such as raccoons, foxes, coyotes, ants, and even people will dig up the eggs and eat them. But if the eggs are successful, when they hatch they start moving their flippers. When they do this, the sand starts to fall below them, pushing them up out of the hole so they can start making their way to the sea. As soon as they get to the sea, they start to drift off. They spend a few years floating at sea eating plankton at the surface. During this time, their shell is soft and they are very subject to predation by fish. After a few years of eating plankton, they move to shallow waters to feed on sea grasses.
To avoid predation, they dive and swim away. Young green turtles that have just hatched are the most vulnerable. They may get eaten from the time they hatch, crossing the sand on their way to the ocean, and during the first couple of years at sea. Predators in the sand include ghost crabs, ants, snakes, gulls, opossums, rats, and vultures. There are many more in the water such as sharks, dolphin fish, kingfish, needlefish, and bottle-nosed dolphins (Ernst 1994).
Key behaviors:
motile
.
Green turtles are mostly herbivorous. They spend most of their time feeding on algae in the sea and the grass that grow in shallow waters. As juveniles, they eat plants and other organisms such as: jellyfish, crabs, sponges, snails, and worms. As adults, they are strictly herbivorous (Ernst 1994).
According to "The Official World Wildlife Fund Guide to Endangered Species of North America," in some areas of the world such as the Caribbean, Mexico, and South America, green sea turtles are an important source of food for humans. They are captured and their meat is used for turtle soup (Behler, 1998).
IUCN Red List:
[link]
:
Endangered.
US Federal List:
[link]
:
Endangered.
CITES:
[link]
:
Appendix I.
Green turtles are an endangered species because they have so many predators--including humans. Even though a female can lay over 200 eggs in on clutch, some will not hatch, and many will be eaten. Even if they do hatch, they get eaten on their way to the water, and in the water. So only a few will survive if any. If the they do survive, they can live to be over 100 years old. Sometimes eggs are laid on a public beach. When this happens conservationists come and move them to a safer place. In the United States, green turtles are protected by the Endangered Species Act.
Find Chelonia mydas information at
Janel Crite (author), University of Michigan.
Tanya Dewey (editor), Animal Diversity Web, University of Michigan Museum of Zoology.
To cite this page: Crite, J. 2000. "Chelonia mydas" (On-line), Animal Diversity Web. Accessed February 09, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Chelonia_mydas.html.
Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students . ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.
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| Following modified from turtles.org |
The Atlantic Green Turtle (Chelonia mydas)
The following is based on information from the Recovery Plan for U.S. Population of Atlantic Green Turtles , U.S Fish and Wildlife Service and National Marine Fisheries Service, 1991. Obtained from the U.S. National Marine Fisheries Service, and used with their kind permission. Current StatusThe green turtle is listed as endangered by the International Union for the Conservation of Nature. Under the U.S. Endangered Species Act of 1973, the green turtle was listed as threatened except for the breeding populations in Florida and on the Pacific coast of Mexico, where it is listed as Endangered. Green turtles continue to be heavily exploited by humans, and the destruction and loss of nesting and foraging sites is a serious problem. Humans have already caused the extinction of large green turtle populations, including those that once nested in Bermuda and Cayman Islands. The status of green turtle populations is difficult to determine because of our lack of knowledge about their life cycles. The number of nests deposited in Florida appears to be increasing, but we don't know whether this is due to an increase in the number of nests or because we have started to monitor nesting beaches more closely. DescriptionThe green sea turtle is the largest hard-shelled sea turtle. Adults of this species commonly reach 100 cm in carapace length and 150 kg in mass. The average size of a female nesting in Florida is 101.5 cm straight carapace length, with an average body mass of 136 kg. Hatchling green turtles weigh about 25 g (about a handful of Smarties) and have a carapace about 50 mm long. Hatchlings are black on top and white underneath. The plastron of Atlantic green turtles remains a yellowish white throughout life, but the carapace changes colour from black to various shades of gray, green, brown and black, forming swirls and irregular patterns on their shells. GrowthGrowth rates of pelagic -stage green turtles have not been measured under natural conditions; however, growth rates of green turtles have been measured at their feeding grounds. Green turtles grow slowly. In the southern Bahamas, green turtles grew from 30 to 75 cm in 17 years, and according to Bjorndal and Bolten, growth rate decreased with increasing carapace length. Growth rates measured in green turtles from Florida and Puerto Rico fall within the range of growth rates measured in the southern Bahamas. Based on growth rate studies of wild green turtles, the researchers Balazs, Frazer and Ehrhart estimate the age at sexual maturity range anywhere from 20 to 50 years. HabitatGreen turtles occupy three habitat types:
Females deposit egg clutches on high energy beaches, usually on islands, where a deep nest cavity can be dug above the high water line. Hatchlings leave the beach and apparently move into convergence zones in the open ocean where they spend an undetermined length of time (Carr, 1986). When turtles reach a carapace length of approximately 20 to 25 cm, they leave the pelagic habitat and enter benthic feeding grounds. Most commonly these foraging habitats are pastures of seagrasses and/or algae, but small green turtles can also be found over coral reefs, worm reefs and rocky bottoms. Some feeding areas, such as Miskito Cays, Nicaragua, support a complete size range of green turtles from 20 cm to breeding adults. Coral reefs or rocky outcrops near feeding pastures are often used as resting areas, both at night and during the day. DietScientists assume that post-hatchling, pelagic-stage green turtles are omnivorous, but there are no data on diet from this age class. Our personal experience with a juvenile Hawaiian green confirms this theory. Our first turtle encounter resulted when a juvenile swam up to us and attempted to take some of the cuttlefish we were using to attract eels for photographic purposes. Scientists do know that once green turtles shift to benthic feeding grounds, they are herbivores. They feed on both seagrasses and algae. Population Distribution and SizeThe green turtle can be found throughout the world in all tropical and sub-tropical oceans. In the U.S., Atlantic green turtles can be found around the U.S. Virgin Islands, Puerto Rico, and continental U.S. from Texas to Massachusetts. Important feeding areas for green turtles in Florida include Indian River Lagoon, Florida Keys, Florida Bay, Homosassa, Crystal River and Cedar Key. Major green nesting colonies in the Atlantic are located on Ascension Island, Aves Island, Costa Rica and Suriname. In the U.S., green turtles nest in small numbers in the United States Virgin Islands, and in Puerto Rico. Greens nest in larger numbers in Florida but actual data is presently not helpful in assessing trends in nesting. ReproductionFemale green turtle emerge at night to deposit eggs, the process taking an average of two hours. Up to seven clutches are deposited at 12 to 14 day intervals, but the average is probably two or three clutches. Accurate counts of the number of clutches per season are difficult to get. The average clutch size is usually 110-115 eggs, but this varies among populations. It is uncommon for females to produce clutches in successive years. Usually 2, 3, 4 or more years intervene between breeding seasons. Mating occurs in the water off the nesting beaches. Little is known about the reproductive biology of males, but evidence is accumulating that males migrate to the nesting beach every year. The hatching success of undisturbed nests is usually high, but on some beaches, predators destroy a high percentage of nests. Large numbers of nests are also destroyed by inundation and erosion. One interesting discovery in recent years is that incubation temperatures determine the sex of hatchling turtles. In 1985, Standora and Spotila reported this effect on green turtles. Eggs incubated below a pivotal temperature--which might vary among populations--produce primarily males, and eggs incubated above this temperature produce primarily females. MovementsThe navigation feats of the green turtle are well known, but poorly understood. We know that hatchlings and adult females on the nesting beach orient toward the ocean using light cues. For a long time, no one knew what cues were employed in pelagic movements, in movements among foraging grounds, or in migrations between foraging grounds and nesting beaches. Recently published work, however, has suggested that the earth's magnetic field plays a role in these feats. Because green turtles feed in marine pastures in quiet, low-energy areas, but nest on high energy beaches, their feeding and nesting habitats are, of necessity, located some distance apart. Green turtles that nest on Ascension Island forage along the coast of Brazil, some 1,000 km away! The location of the foraging grounds of green turtles that nest in Florida is still unknown. It has been generally accepted, but not proven, that green turtles return to nest on the beach where they were born. Green turtles do exhibit strong site-fidelity in successive nesting seasons. Our personal experience with Hawaiian green turtles is that they also exhibit strong site fidelity for their foraging grounds. Atlantic Green Turtle Quick FactsGreen sea turtles are listed as threatened or endangered throughout their habitat.
Last modified 04/01/24
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Phylum Chordata 
Class Reptilia 
Discover Life
World Register of Marine Species 
