Sea Turtles of the Atlantic and Gulf Coasts of the United States

About Sea Turtles

About Sea Turtles All turtles are reptiles, and all have a shell consisting of two parts: the top is called the carapace, and the bottom, the plastron. Instead of teeth, turtles have a horny covering on the beak, the rhamphotheca. The front limbs of sea turtles are modified to serve as paddles and are longer and flatter than those of freshwater turtles; the hind limbs are used as rudders. Unlike most freshwater turtles and tortoises, sea turtles cannot withdraw the head and limbs inside the shell. Otherwise, the general body plan is similar to that of other turtles. Although sea turtles spend almost all of their lives in water, they must breathe air and lay their eggs on land. Sea turtles grow much larger than freshwater turtles. Their large size protects adults from most marine predators except for killer whales and large tiger sharks. But size is only a vague indication of age. Unlike mammals, which mature and stop growing at a certain age, reptiles grow and mature in relation to the amount and quality of food available. There is a minimum size for sexual maturity for each species, but the age at which that size is reached may vary dramatically from one individual to the next. Individual turtles have been recorded nesting for at least 20 years, and their life span may be similar to ours. Five species of sea turtles may be found along the U.S. Atlantic and Gulf coasts: leatherbacks, loggerheads, Kemp’s ridleys, green turtles, and hawksbills . Leatherbacks are present throughout the year, although some migrate as far north as Labrador and Baffin Island during the warm months. Loggerheads are found in temperate waters nearly worldwide, while Kemp’s ridleys are restricted to the Gulf of Mexico and Atlantic Ocean. Loggerheads and Kemp’s ridleys range northward to New England and the maritime provinces of Canada during warmer months. Green turtles and hawksbills inhabit tropical seas worldwide. Both species are occasionally found in New England waters, but they are much less common there than the other species . Hawksbills are generally restricted to tropical and subtropical waters, but green turtles range into temperate waters as well. A sixth species, the olive ridley, is not a regular inhabitant of the U.S. Gulf and Atlantic coasts, 2 about sea turtles but there are three recent (2003) records from Florida. All three of these animals had physical problems and may have been transported there by ocean currents. One was entangled in fishing gear, one was found dead and emaciated, and the third washed up covered with tar. Olive ridleys inhabit tropical oceans worldwide, but as they are not usually found in the area covered by this book, we will not address them in detail here. The Kemp’s ridley is the most endangered of the sea turtles and has the most limited nesting range—primarily Tamaulipas, Mexico. The other species nest worldwide, including on the beaches of the southeastern United States. All of our sea turtle species are listed as Endangered by the U.S. government and the International Union for the Conservation of Nature (iucn). Degradation of marine and beach habitats, overexploitation, and high rates of incidental death associated with commercial fishing make their longterm survival uncertain at best. In the United States the authority for their listing stems from the Endangered Species Act; internationally it stems from the Species Survival Commission of the iucn. Few people are aware of sea turtles in the waters off the northeastern United States because the turtles spend most of their time below the surface A leatherback (dermochelid), above, and a Kemp’s ridley (cheloniid), facing page. Courtesy of the National Park Service, Canaveral National Seashore, and Peter C. H. Pritchard, Chelonian Research Institute. 4 about sea turtles taking advantage of the abundant food there. From North Carolina southward , sea turtles are better known to the general public because they may be seen on summer nights when females come out of the water to lay eggs. Conducting research on a migratory species that spends much of its life in the open ocean is difficult, and there is still much to learn regarding the biology of sea turtles. When females come ashore to nest, biologists can easily observe their activities, so more is known of females and the nesting process than of males and of activities away from the nesting beach. In recent years, satellite telemetry has been helpful in...