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Life Cycle of the Galapagos Sea Turtle

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The Galapagos sea turtle (Chelonia mydas agassizii) is a subspecies of the green sea turtle that nests almost exclusively in the Galapagos Islands. It is smaller than other green sea turtles, with adults averaging a shell length of 3 feet and a weight of 240 pounds. Its shell, or carapace, is more domed than those of other sea turtles and is darker in color, ranging from dark gray to black. Like all sea turtles, the female Galapagos sea turtle returns to the beaches where her life began to lay her own eggs.


The Galapagos sea turtle's eggs incubate under the sand for an average of 60 days. Once hatched, the young turtles dig their way out of the nest and scramble for the ocean. This begins the most dangerous period of their lives, as predators wait to snatch them before they can reach the water. The sea offers safety from birds, crabs and mammals but the hatchlings are still heavily preyed upon by fish. Unlike the adults, young sea turtles are omnivorous and will eat plankton, sea worms, small crustaceans and mollusks as well as algae and sea grass. They stay in shallower waters where they are protected from larger predators.


Juvenile Galapagos sea turtles move farther out to sea as they grow larger. This period of the turtle's life cycle can last anywhere from 10 to 25 years, depending on the availability of food. At this size they become largely herbivorous, feeding on sea grasses and algae and an occasional mollusk. The larger they get, the less risk they face from predators, but even as adults they may be preyed upon by large sharks and killer whales.


It takes the Galapagos sea turtle quite some time, 25 years or more, to reach adulthood. Once they reach full size they will spend the remainder of their lifetime, as long as 100 years in total, roaming the open ocean. They travel vast distances to return to their breeding grounds, off the coast of the Galapagos Islands, only every two or three years. Once the females have successfully bred they can lay as many as nine individual clutches of eggs in a single season without needing to breed again.


Eggs are laid between December and June in nests the female turtle digs in the sand above the high tide mark. The very dry, light sand on the beaches of the Galapagos Islands has led to a behavior unique to the subspecies: the females dig with only one hind leg while the other remains in the hole to prevent cave-ins. Once the hole is dug the female will lay an average of 100 eggs, cover them with sand and return to the ocean. The eggs hatch about two months later and the cycle begins again as the new hatchlings make a mad dash for the sea.