Loggerhead Sea Turtles, Caretta caretta
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Description & Behavior
Caretta caretta (Linnaeus, 1758) are commonly called "loggerhead" sea turtles due to their overly large heads with a horny beak that is significantly thicker than in other sea turtles. This species is the largest hard-shelled turtle in the world (the leatherback sea turtle is the largest of all turtles). Two subspecies have been recognized: Caretta caretta gigas, found in the Pacific and Indian Oceans, and C. caretta caretta, the Atlantic loggerhead. They may differ in the number of neural bones in the carapace and marginal scutes on the surface of the carapace, but the ranges overlap and many authorities do not support the distinction (Ernst, Lovich, and Barbour, 1994). Color patterns are reddish-brown with darker streaks and their front flippers possess two claws. Subadults have carapaces 45-90 cm in length and adults weigh between 77-227 kgs and have a carapace 0.9-1 m in length.
Sea turtles live in almost every ocean of the world. Their smooth shells and paddle-like flippers help them speed through the water as fast as 24 kph. These long-distance travelers have been known to swim up to 4,828 km.
Although sea turtles cannot withdraw their heads into their shells, the adults are protected from predators by their shells, large size and thick scaly skin on their heads and necks.
Sea turtles spend almost all their lives submerged but must breathe air for the oxygen needed to meet the demands of vigorous activity. With a single explosive exhalation and rapid inhalation, sea turtles can quickly replace the air in their lungs. The lungs are adapted to permit a rapid exchange of oxygen and to prevent gasses from being trapped during deep dives. The blood of sea turtles can deliver oxygen efficiently to body tissues even at the pressures encountered during diving. During routine activity green and loggerhead sea turtles dive for about 4 to 5 minutes and surface to breathe for 1 to 3 seconds. A female loggerhead tracked at sea made up to 500 dives every 12 hours.
Turtles can rest or sleep underwater for several hours at a time but submergence time is much shorter while diving for food or to escape predators. Breath-holding ability is affected by activity and stress, which is why turtles drown in shrimp trawls and other fishing gear within a relatively short time.
Because sea turtles are difficult to study in the open ocean, scientists are just beginning to learn about the life history of sea turtles. Today, radio transmitters, attached to nesting turtles, help track the sea creatures on their travels and provide valuable information.
World Range & Habitat
Loggerhead sea turtles are found in coastal tropical and subtropical waters often extending to temperate waters in search of food. Found in the Atlantic Ocean from Argentina to Nova Scotia. The highest populations in North America are found on barrier islands from North Carolina to the Florida Keys. These Florida loggerheads migrate to the Bahamas in the winter. Small populations of the Atlantic loggerhead are also found on barrier islands off of the Texas coast. Primary habitat is in southeastern United States ranging southward to South America and extending eastward to Africa and the Mediterranean as well as areas of the western Pacific and Indian Oceans.
Hatchling habitat is primarily in warm ocean currents among flotsam such as sargassum mats. Adult habitat includes rock outcroppings and reefs near shore as well as in brackish lagoons and the mouths of inlets. Long migrations often occur, especially to return to nesting beaches.
Feeding Behavior (Ecology)
Primarily carnivorous during most of their lives. Hatchlings often eat sponges, jellyfishes, sargassum weed, small gastropods and crustaceans. Juveniles, sub-adults and adults feed upon conch, clams, horseshoe crab as well as other crustaceans. They have powerful jaws that enable them to easily crush the hard shells of their prey. During migration through the open sea, loggerheads eat jellyfishes, pteropods, floating mollusks, floating egg clusters, squids and flying fishes.
Although sea turtles move swiftly in the ocean, they are slow and defenseless on land. Male sea turtles almost never leave the water. Female sea turtles leave the ocean only to lay eggs and, for most species, nest only at night. A female may nest every two to three years.
Nesting can take between one and three hours. After a female turtle drags herself up the beach, she hollows out a pit with her back legs and deposits from fifty to two hundred eggs the size of golf balls. When the last egg is laid, the turtle covers the eggs with sand, tamps down the sand with her plastron, and flings more sand about with her flippers to erase any signs of the nest.
After about two months, the hatchling turtles emerge at night. The light reflected off the water from the sky guides them to the sea. These days, car headlights, street lamps, or lights on buildings near the beach cause some hatchlings to travel in the wrong direction. Waiting herons make fast meals of other hatchlings. Any babies still on the beach in the morning are easily picked off by predators or die in the hot sun. It is thought that when the surviving hatchlings reach maturity, they return to the beach where they hatched to lay their eggs.
Loggerhead sea turtles reach sexual maturity when adults and their shells are longer than 90 cm in length (thought to occur when they are from 12-30 years of age). In the United States, the southeastern region from North Carolina to Florida hosts the majority of the nesting. In Florida, Brevard County beaches receive the most nesting females per year than generally any other county in Florida. Nesting also occurs in some areas of the northeastern coasts of Mexico and minor beaches in the Caribbean. In the Mediterranean nesting is reported in Greece, Turkey, Israel as well as Italy. The Indian Ocean's major nesting sites are in South Africa as well as large nesting colonies on the Arabian Peninsula on Masirah Island, Sultanate of Oman.
Nesting occurs during late spring and summer. Females renest approximately every two weeks during the nesting season laying between two and fives times a season with an average clutch size of 100 eggs. Egg diameter is from 34.7-55.2 mm. Incubation period varies, but 49 days at the least and 69 days at the most dependent upon the location of nesting. Sex determination is dependent upon the incubation temperature, therefore there is an optimal incubation temperature that ranges between 26°C-32°C. The male sex is determined at cooler temperatures.
Nests are often lost to predators such as raccoons, dogs, ghost crabs, sea birds and ants as well as to shoreline erosion and human predation. Hatchlings are preyed upon by mammals, sea birds, crabs and carnivorous fishes. Predation continues to be high until the turtles are big enough to avoid being swallowed by large carnivorous fishes such as groupers, snappers and jacks. Sharks are a formidable predator throughout the life cycle of sea turtles, although larger turtles can often avoid a shark attack by presenting the flat side of the plastron or carapace to prevent biting. Life Span: At least 30 years and up to 50 years or more. Population Numbers: Unknown.
Conservation Status & Comments
WARNING: Eating sea turtles and their eggs, anywhere, can cause severe illness and even death, especially to children. The flesh has been found to contain chelonitoxin which may cause a number of symptoms including nausea, vomiting, diarrhea, burning sensation of lips, tongue and mouth, chest tightness, difficulty swallowing, hypersalivation, skin rash, coma and death. See the following for more information:
Chelonitoxism: new case reports in French Polynesia and review of the literature
Turtle meat kills six in Micronesia
Listed as "Threatened" on the United State Fish and Wildlife Service Endangered Species List since July 28, 1978. Most loggerhead deaths occur due to drowning in shrimp nets, as well as due to longline fishing practices.
Other reasons for being federally listed are due to predation of eggs in countries who utilize them as a primary means for food as well as sell them on the black market. Loggerheads are a big part of the diet of some rural communities, such as in the Antillean and Caribbean areas. Much money is paid for their meat and eggs, which are used to make turtle burgers and turtle soup and the eggs are even used to make cakes. In Cuba, the eggs are dried in the oviduct and sold like sausage. The turtles also provide oxidizing oil, which acts like varnish. In Honduras, boat paddles are made out of their shells.
Loggerhead sea turtles, Caretta caretta, are now listed as Endangered (EN A1abd) on the IUCN Red List of Threatened Species due to:
"Documentation about the rationale for listing, habitats, threats, etc. is not yet available."
A taxon is Endangered when it is not Critically Endangered but is facing a very high risk of extinction in the wild in the near future, as defined by any of the criteria (A to E) as described here.
References & Further Research
Center for Biological Diversity: Loggerhead sea turtles
FAO Species Catalogue Volume 11 Sea Turtles of the World: An Annotated and Illustrated Catalogue of Sea Turtle Species Known to Date. FAO Fisheries Synopsis No 125, Volume 11
Loggerhead Sea Turtles - Office of Protected Resources - NOAA Fisheries
EuroTurtle - a website for marine turtle education
U.S. Fish & Wildlife Service Endangered Species
Dodd Jr., Kenneth C. Synopsis of the Biological Data on the Loggerhead Sea Turtle Caretta caretta (Linnaeus 1758), Biological Report 88(14) May 1988, (FAO Synopsis NMFS-149) Fish and Wildlife Services, U.S. Department of the Interior, 119 p.
The State of the World's Sea Turtles (SWoT)
Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington, District of Columbia, USA: Smithsonian Institution Press.
IUCN/SSC Marine Turtle Specialist Group 1996. Caretta caretta. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. www.iucnredlist.org. Downloaded on 23 December 2009.
Research Caretta caretta » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
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