Green Sea Turtle

Its appearance is that of a typical sea turtle. C. mydas has a dorsoventrally flattened body, a beaked head at the end of a short neck, and paddle-like arms well-adapted for swimming. Adult green turtles grow to 1.5 metres (5 ft) long. The average weight of mature individuals is 68–190 kg (150–419 lb) and the average carapace length is 78–112 cm (31–44 in). They are considered the second largest sea turtle in the United States, after the leatherback sea turtle.

Exceptional specimens can weigh 315 kg (694 lb) or even more, with the largest known C. mydas having weighed 395 kg (871 lb) and measured 153 cm (60 in) in carapace length.

The range of the green sea turtle extends throughout tropical and subtropical oceans worldwide. The two major subpopulations are the Atlantic and the eastern Pacific subpopulations. Each population is genetically distinct, with its own set of nesting and feeding grounds within the population's known range. One of the genetic differences between the two subpopulations is the type of mitochondrial DNA found in individual's cells. Individuals from rookeries in the Atlantic Ocean and Mediterranean Sea have a similar type of mitochondrial DNA, and individuals from the Pacific and Indian Oceans have another type of mitochondrial DNA. Their native range includes tropical to subtropical waters along continental coasts and islands between 30°N and 30°S. Since green sea turtles are a migrating species, their global distribution spans into the open ocean.

The diet of green turtles changes with age. Juveniles are carnivorous, but as they mature they become omnivorous. Young sea turtles eat fish and their eggs, sea hare eggs, hydrozoans, bryozoans, molluscs, jellyfish, small invertebrates, echinoderms, tunicates, insects, worms, sponges, algae, sea grasses, leaves, tree bark, and crustaceans. Green sea turtles have a relatively slow growth rate because of the low nutritional value of their diet. Body fat turns green because of the consumed vegetation. This diet shift has an effect on the green turtle's skull morphology. Their serrated jaw helps them chew green and red algae (such as filamentous red alga (Bostrychia), red moss (Caloglossa), freshwater red algae (Compsopogon), lobster horns (Polysiphonia), sea lettuce (Ulva lactuca), green seaweed (Gayralia), and crinkle grass (Rhizoclonium)) and sea grasses.

As one of the first sea turtle species studied, much of what is known of sea turtle ecology comes from studies of green turtles. The ecology of C. mydas changes drastically with each stage of its life history. Newly emerged hatchlings are carnivorous, pelagic organisms, part of the open ocean nekton. In contrast, immature juveniles and adults are commonly found in seagrass meadows closer inshore as herbivorous grazers.

Green sea turtles migrate long distances between feeding sites and nesting sites; some swim more than 2,600 kilometres (1,600 mi) to reach their spawning grounds. Beaches in Southeast Asia, India, islands in the western Pacific, and Central America are where green sea turtles breed. Mature turtles often return to the exact beach from which they hatched. Females usually mate every two to four years. Males, on the other hand, visit the breeding areas every year, attempting to mate. Mating seasons vary between populations. For most C. mydas in the Caribbean, mating season is from June to September. The French Guiana nesting subpopulation nests from March to June. In the tropics, green turtles nest throughout the year, although some subpopulations prefer particular times of the year. In Pakistan, Indian Ocean turtles nest year-round, but prefer the months of July to December.

Historically, the turtles' skin was tanned and used to make handbags, especially in Hawaii. Ancient Chinese considered the flesh of sea turtles a culinary delicacy, including and especially C. mydas. Particularly for this species, the turtle's fat, cartilage, and flesh, known as calipee, are sought as ingredients for making turtle soup, a popular 19th-century English and American dish.