Green Sea Turtle
Photo Credit: U. S. Fish and Wildlife Service
SCIENTIFIC NAME: Chelonia mydas (Linnaeus)
OTHER NAMES: Green Turtle.
DESCRIPTION: Largest of the hard-shelled sea turtles (Family Cheloniidae). Those nesting in Florida average approximately 101 centimeters (40 inches) straight-line carapace length (SLCL), and a weight of approximately 136 kilograms (300 pounds). However, some have been recorded to be much larger, with SLCLs to at least 120 centimeters (47 inches), and weights of 230 kilograms (500 pounds). Carapace is oval, smooth, and can vary in color from brown to greenish to grayish. Plastron normally yellowish. Have small rounded heads with one pair of long prefrontal scales above the nostrils; cutting edge on lower jaw serrated. Forelimbs and hindlimbs modified into long front flippers and short rear flippers, usually with only one claw on each; claws on front flippers of adult males long and curved. Adult males also have long muscular tails extending well beyond the carapace.
DISTRIBUTION: Tropical and subtropical oceans throughout the world, including the Atlantic, Pacific, and Indian Oceans (Ernst et al. 1994). In the continental United States, found along Atlantic and Gulf Coasts, and occasionally along the Pacific Coast. In the Atlantic and Caribbean, major nesting locations are in Costa Rica, Suriname, and on Aves and Ascension Islands. In the continental United States, nest from North Carolina to Florida, with the majority of nesting occurring along the Atlantic Coast of Florida (Ehrhart 1999). Occasionally nest in the northeastern Gulf of Mexico along the Florida Panhandle. In recent years, at least two nests have been recorded in Alabama.
HABITAT: Often found in relatively shallow coastal or bay waters, except when migrating. Appear to prefer protected bays, lagoons, or shoals with an abundance of algae or marine grass beds. Important feeding areas in the continental United States include bays along the Atlantic and Gulf Coasts of Florida, and bays in central and southern Texas (Magnuson et al. 1990). Although no major feeding areas have been found in Alabama coastal waters, grass beds along the Florida Panhandle do appear to act as feeding grounds. Normally nest on beaches with high-energy wave action, including many islands.
LIFE HISTORY AND ECOLOGY: Hatchlings and post-hatchlings assume a pelagic existence and are believed to be omnivorous (Ernst et al. 1994). During the pelagic phase, they may become associated with areas of convergent currents where floating plants and animals tend to collect. Once they attain a size of approximately 20 to 25 centimeters (eight to 10 inches) SLCL, they shift to benthic feeding grounds (Magnuson et al. 1990). In contrast to other sea turtles, juveniles and adults are herbivorous and feed on sea grasses and macroalgae. Growth is slow; age to maturity estimated to be 20 to 50 years (Balazs 1982). Adult females well known for reproductive migrations and many show strong nesting site fidelity. For example, some feed along the coast of Brazil and then migrate more than 1,000 kilometers (more than 600 miles) to nest on Ascension Island in the middle of the Atlantic Ocean (Ernst et al. 1994). Mating can occur near nesting beaches; females nest multiple times during a given nesting season, and lay from one to seven clutches at 12- to 14-day intervals (Magnuson et al. 1990). In the continental United States, the average is three to four clutches per female per season, and the nesting season generally extends from June through September. Normally do not nest every year, but return at two-, three-, or four-year intervals, when they dig a large body pit during laying. Clutch size varies greatly and ranges up to approximately 200 eggs per nest, but the average clutch size estimated in Florida was 136. Eggs can take from 45 to 75 days to hatch depending on nest temperature, and as in other sea turtles, gender is determined by incubation temperature. Hatchlings emerge at night, crawl down to the surf, swim away from shore, and begin pelagic phase of life history.
BASIS FOR STATUS CLASSIFICATION: Historically, over much of their distribution (including the continental United States), populations have been significantly depleted because of human demand for their eggs and meat. Additionally, incidental capture by shrimp trawlers, human-caused injuries, and degradation of nesting habitat due to coastal development are of concern (Magnuson et al. 1990). During recent years, an estimated 200 to 1,100 nest each year in the continental United States. During the 1990s there was an upward trend in the number of nestings on certain beaches in the southeastern United States coincident with the implementation of turtle excluder devices (Ehrhart 1999). Additionally, marine debris and derelict fishing gear (e.g., nets, fishing line, etc.) have caused injuries due to entanglement and ingestion (Magnuson et al. 1990). Populations nesting along the Atlantic and Gulf Coasts of the United States, and along the Pacific Coast of Mexico (which periodically travel up to the Pacific Coast of the United States) were listed as endangered by the U.S. Fish and Wildlife Service in 1978.
Author: Thane Wibbels