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Of the seven sea turtle species found throughout the world, four appear seasonally in the Chesapeake Bay. The loggerhead turtle, named for its log-like head, is the most numerous of the Bay turtles and accounts for close to 90% of the summer sea turtle population. Between 2,000 and 10,000 young loggerheads visit the Bay each summer. The loggerhead is the largest hardshell sea turtle and may weigh over 500 pounds. A significant portion of the world's most endangered sea turtle, the Kemp's ridley, also summers in the Chesapeake. On occasion, leatherbacks and green turtles find their way into the Bay, but never in any great number. The leatherback may top 2,000 pounds--hard to believe considering the main ingredient in its diet is jellyfish. The green, a medium-sized turtle, was named not for the color of its shell but for its characteristic green fat. Sea turtles are truly prehistoric; about 150 million years ago, they settled into an evolutionary form that has remained essentially unchanged since this time. These turtles are reptiles--air-breathing, cold-blooded animals which reproduce by internal fertilization. Although some reptiles produce live young, sea turtles lay their eggs on land. Egg-laying is the only time Atlantic sea turtles come onshore; their legs and shells are adapted to an aquatic existence. Their shells are streamlined while their legs are flipper-like and designed for rapid swimming. The amount of time spent on a dive varies with water temperature; if the water is cold, the turtle minimizes its metabolic activity and may remain underwater for hours. Sea turtles mate while floating at the ocean's surface. To secure a grip on the female, the male hooks his flipper claws under the shell at her shoulder, often leaving her scratched and bleeding from the encounter. When an Atlantic female is ready to nest, she clambers high onto a suitable sand beach, usually in Georgia or Florida, digs a hole and lays up to 100 eggs. As she strains with the effort, apparent tears flow from a gland near her eyes. Lore has it that she cries knowing the perils her children face; in actuality, she is secreting excess salt from her body. With the eggs laid, she fills in the hole and drags herself back to the sea, leaving the eggs to incubate in the sand. About two months later, the young turtles peck their way out of the leathery shells. After most eggs have hatched, the young turtles simultaneously emerge at night; their trek down to the sea and beyond is often a hazardous one with predators poised to take advantage of this bounty of food. Only a tiny fraction of those hatched (.1-1%) will survive to adulthood. At the end of each spring, many sea turtles --especially juveniles-- which have overwintered in the tropics and subtropics move north along the Atlantic coast. While leatherbacks generally continue north past the Chesapeake Bay, the loggerheads and some Kemp's ridleys veer into the Bay as water temperatures warm to about 68 degrees Fahrenheit. The Bay, with its rich food supply and extensive shoals, provides ideal habitat for the development of these young animals. Although occasionally sighted in Maryland waters, most turtles remain in the Virginia portion of the Bay where salinities are higher. Loggerheads eat a variety of foods including horseshoe crabs, jellyfish and mollusks. They concentrate their feeding around river mouths and areas of the Bay deeper than 13 feet. Kemp's ridleys inhabit the shallower areas, grazing in the flats and feeding on blue crabs amidst the eelgrass beds. The turtles remain in the Bay for the summer and early fall, leaving only when the first major northeasterly storm of the season drives water temperatures down. All sea turtles are on the "endangered" or "threatened" species lists. Years of exploiting these turtles for their meat, shells and eggs has taken a devastating toll on their population numbers. It is now illegal to harm sea turtles or even to collect the shells of dead turtles. Despite this protection, natural predation from sharks and other animals, along with injury and death from boat propellers, accidental capture in the leader portions of pound nets, intentional injury, capture by shrimp trawlers, destruction of nesting sites, and ingestion of plastic refuse continue to pose risks to the turtles. Bay scientists are researching the behavior, migration and other habits of sea turtles to provide a better understanding of these creatures and how they may be saved from extinction. Using small airplanes, the Virginia Institute of Marine Science (VIMS) records the distribution and migration of sea turtles. Metal tagging of healthy turtles also reveals migratory movements. Results of the early research indicated that transplant of eggs from southern U.S. beaches to Virginia was most likely futile and possibly detrimental to loggerhead populations.
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For
many of us, the earliest recollection of a turtle is the tiny, green,
pet shop variety which swam lethargically around a water-filled tray
complete with plastic palm tree and island. The first glimpse of a giant
sea turtle, then, may catch us off-guard. These primeval, beaked creatures
can weigh over 1,500 pounds and seem to bear little resemblance to the
small, green turtles of our childhood.
