Loggerhead Sea Turtle

The loggerhead sea turtle (Caretta caretta), or loggerhead, is an oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 centimeters (35 in) long when fully grown, although larger specimens of up to 270 centimeters (110 in) have been discovered. The adult loggerhead sea turtle weighs approximately 135 kilograms (300 lb), with the largest specimens weighing in at more than 454 kilograms (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish-brown. There are no external differences in gender until the turtle becomes an adult, the most obvious difference being that adult males have thicker tails and shorter plastrons than the females.

The loggerhead sea turtle is found in the Atlantic, Pacific, and Indian oceans as well as the Mediterranean Sea. It spends most of its life in saltwater and estuarine habitats, with females briefly coming ashore to lay eggs. The loggerhead sea turtle has a low reproductive rate; females lay an average of four egg clutches and then become quiescent, producing no eggs for two to three years. The loggerhead reaches sexual maturity within 17–33 years and has a lifespan of 47–67 years.

The loggerhead sea turtle is omnivorous, feeding mainly on bottom dwelling invertebrates. Its large and powerful jaws serve as an effective tool for dismantling its prey. Young loggerheads are exploited by numerous predators; the eggs are especially vulnerable to terrestrial organisms. Once the turtles reach adulthood, their formidable size limits predation to large marine organisms such as sharks.

Loggerheads are considered an endangered species and are protected by the International Union for the Conservation of Nature. Untended fishing gear is responsible for many loggerhead deaths. Turtles may also suffocate if they are trapped in fishing trawls. Turtle excluder devices (TEDs) have been implemented in efforts to reduce mortality by providing an escape route for the turtles. Loss of suitable nesting beaches and the introduction of exotic predators have also taken a toll on loggerhead populations. Efforts to restore their numbers will require international cooperation since the turtles roam vast areas of ocean and critical nesting beaches are scattered across several countries.

The loggerhead sea turtle is the world's largest hard-shelled turtle. Adult loggerheads have an average weight range of 80 to 200 kilograms (180 to 440 lb) and a length range of 70 to 95 centimeters (28 to 37 in). The maximum reported weight is 545 kilograms (1,200 lb) and the maximum carapace length is 213 centimeters (84 in). The head and carapace (upper shell) range from a yellow-orange to a reddish-brown, while the plastron (underside) is typically pale yellow. The turtle's neck and sides are brown on the tops and yellow on the sides and bottom.

The turtle's shell is divided into two sections: carapace and plastron. The carapace is further divided into large plates, or scutes. Typically, there are 11 or 12 pairs of marginal scutes which rim the carapace. Five vertebral scutes run down the carapace's midline, while five pairs of costal scutes border them. The nuchal scute is located at the base of the head. The carapace connects to the plastron by 3 pairs of inframarginal scutes forming the bridge of the shell. The plastron features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes. The shell serves as external armor, although loggerhead sea turtles cannot retract their head or flippers into their shells.

Sexual dimorphism of the loggerhead sea turtle is only apparent in adults. Adult males have longer tails and claws than females. The males' plastrons are shorter than the females', presumably to accommodate the males' larger tails. The carapace of males are wider and less domed than the females, and males typically have wider heads than females. The sex of juveniles and subadults cannot be determined through external anatomy, but can be observed through dissection, laparoscopy (an operation performed on the abdomen), histological examination (cell anatomy), and radioimmunological assays (immune study dealing with radiolabeling).

Lachrymal glands located behind each eye allow the loggerhead to maintain osmotic balance by eliminating the excess salt obtained from ingesting ocean water. On land, the excretion of excess salt gives the false impression that the turtle is crying.

Loggerhead sea turtles spend most of their lives in the open ocean and in shallow coastal waters. They rarely come ashore, with the exception of the females' brief visits to construct nests and deposit eggs. Hatchling loggerhead turtles live in floating mats of Sargassum algae. Adults and juveniles live along the continental shelf, as well as in shallow coastal estuaries. In the northwestern Atlantic Ocean, age plays a factor in habitat preference. Juveniles are more frequently found in shallow estuarine habitats with limited ocean access compared to non-nesting adults.[15] Loggerheads occupy waters with surface temperatures ranging from 13.3–28 °C (56–82 °F) during non-nesting season. Temperatures from 27–28 °C (81–82 °F) are most suitable for nesting females.

Juvenile loggerheads share the Sargassum habitat with a variety of other organisms. The mats of Sargassum contain as many as 100 different species of animals on which the juveniles feed. Some of the prey, such as ants, flies, aphids, leafhoppers, and beetles, are carried by the wind to these areas. Endemic prey of the Sargassum mats include barnacles, small crab larvae, fish eggs, and hydrozoan colonies. Marine mammals and commercial fish, such as tuna, dolphin fish, and amberjacks, also inhabit the Sargassum mats.

The loggerhead sea turtle has a cosmopolitan distribution, nesting over the broadest geographical range of any sea turtle. The loggerhead inhabits the Atlantic, Indian, and Pacific Oceans and the Mediterranean Sea.

In the Atlantic Ocean, the greatest concentration of loggerheads is along the southeastern coast of North America and in the Gulf of Mexico. Very few loggerheads are found along the European and African coastlines. Florida is the most popular nesting site, with more than 67,000 nests built per year. Nesting extends as far north as Virginia, as far south as Brazil, and as far east as the Cape Verde Islands. The Cape Verde Islands are the only significant nesting site on the eastern side of the Atlantic. Loggerheads found in the Atlantic Ocean feed from Canada to Brazil.

In the Indian Ocean, loggerheads feed along the coastlines of Africa, the Arabian Peninsula, and in the Arabian Sea. Along the African coastline, loggerheads nest from Mozambique's Bazaruto Archipelago to South Africa's St Lucia estuary. The largest Indian Ocean nesting site is Oman, on the Arabian Peninsula, which hosts around 15,000 nests, giving it the second largest nesting population of loggerheads in the world. Western Australia is another notable nesting area, with 1,000–2,000 nests per year.

Pacific loggerheads live in temperate to tropical regions. They forage in the East China Sea, the southwestern Pacific, and along the Baja California peninsula. Eastern Australia and Japan are the major nesting areas, with the Great Barrier Reef deemed an important nesting area. Pacific loggerheads occasionally nest in Vanuatu and Tokelau. Yakushima Island is the most important site, with three nesting grounds visited by 40% of all nearby loggerheads. After nesting, females often find homes in the East China Sea, while the Kuroshio Current Extension's Bifurcation region provides important juvenile foraging areas. Eastern Pacific populations are concentrated off the coast of Baja California, where upwelling provides rich feeding grounds for juvenile turtles and subadults (individuals past the juvenile stage that lack adult characteristics). Nesting sites along the eastern Pacific Basin are rare. mtDNA sequence polymorphism analysis and tracking studies suggest 95% of the population along the coast of the Americas hatch on the Japanese Islands in the western Pacific. The turtles are transported by the prevailing currents across the full length of the northern Pacific, one of the longest migration routes of any marine animal. The return journey to the natal beaches in Japan has been long suspected, although the trip would cross unproductive clear water with few feeding opportunities. Evidence of a return journey came from an adult female loggerhead named Adelita, who in 1996, equipped with a satellite tracking device, made the 14,500-kilometer (9,000 mi) trip from Mexico across the Pacific. Adelita was the first animal of any kind ever tracked across an ocean basin.

The Mediterranean Sea is a nursery for juveniles, as well as a common place for adults in the spring and summer months. Almost 45% of the Mediterranean juvenile population has migrated from the Atlantic. Loggerheads feed in the Alboran Sea and the Adriatic Sea. Greece is the most popular nesting site along the Mediterranean, with more than 3,000 nests per year. Because of this, Greek authorities do not allow planes to take off or land at night in Zakynthos due to the nesting turtles. In addition to the Greek coast, the coastlines of Cyprus and Turkey are also common nesting sites.
(credit: http://en.wikipedia.org/wiki/Loggerhead_sea_turtle)