Sea turtles are gentle, ancient reptiles adapted to life in the ocean. There are seven species of sea turtle; six of them live in the Wider Caribbean Region. They are distributed between two taxonomic Families: the Dermochelyidae with one living species, the leatherback turtle (Dermochelys coriacea), and the Cheloniidae, including the green turtle (Chelonia mydas), hawksbill (Eretmochelys imbricata), loggerhead (Caretta caretta) , Kemp's ridley (Lepidochelys kempii) and olive ridley (Lepidochelys olivacea).
Most sea turtles inhabit tropical or subtropical waters. With the exception of Kemp's ridley (confined to the Gulf of Mexico and northern Atlantic) and the Australian flatback, Natator depressus (confined to the waters of northern Australia and adjacent Papua New Guinea), all sea turtle species have a global, albeit uneven, distribution. The leatherback has the widest biogeographical range of any reptile, with foraging grounds and migratory corridors that include subarctic waters. No geographical subspecies are currently recognized by the International Commission on Zoological Nomenclature for any species of sea turtle.
Sea turtles range in size from about 40 kg (adult ridley turtles) to nearly 1,000 kg in the case of an adult male leatherback. They are slow-growing, late-maturing, and long-lived with naturally high rates of egg and young juvenile mortality and low rates of adult mortality. No one knows for certain how long sea turtles live, but field studies demonstrate that they require 12 to 40 or more years, depending on the species, to reach adulthood.
Sea turtles, like all reptiles, have lungs and must come to the surface regularly to breathe air. All sea turtles are accomplished divers, with leatherbacks able to reach depths of 4000 ft or more. With few exceptions, the only time a sea turtle leaves the ocean is to lay eggs. During breeding years, adults depart their feeding grounds and migrate hundreds (sometimes thousands) of kilometers to mating grounds and nesting beaches.
An adult female may nest for two decades or more under natural circumstances. Eighty to 200 or more eggs are generally laid in each nest, 2-6 clutches of eggs are generally produced per gravid female per year (but leatherbacks have been known to nest 12 or more times in a single season!), and females return to their nesting grounds to lay eggs at 2-5 year intervals. After 50-65 days (on average) of incubation, during which time ambient temperature plays a significant role in determining hatchling gender, the tiny turtles emerge at the surface, orient to the sea, and engage in a swim frenzy toward oceanic convergence zones that will offer food and shelter during their early years.
Young juveniles (with the exception of the leatherback) eventually return to coastal Caribbean waters, assuming their characteristic diets, and may travel significant distances through multiple political jurisdictions during the decade(s) leading to sexual maturity. At maturity, adult females instinctively return to the general area where they were born, the signature of their natal coastline indelibly marked in their genetic code. Mothers pass the code to their daughters, who will repeat the cycle as long as the natal beach provides suitable habitat.
Sea turtles may produce several thousand eggs in a lifetime, but not all of these will hatch: some will be infertile, some will be lost to erosion or eaten by predators, and others will be collected for human consumption, often illegally. Hatchlings are eaten in large numbers by predators; young juveniles, too, face many oceanic dangers (predators, pollution, fishing nets). An adult has few natural predators. An estimated one egg in 1,000 will produce an adult turtle.
During non-breeding seasons, adult leatherback turtles travel extensively on the high seas in search of jellyfish and related prey. Loggerheads and ridleys are omnivores, consuming mollusks, crabs, jellyfish and other invertebrates; fishes (often associated with fisheries bycatch) and seaweeds are also eaten. The green turtle is an herbivore, preferring to graze in seagrass meadows and on various species of algae in tropical coastal waters. Hawksbills specialize on coral reef sponges and other invertebrates.