Caretta caretta

Loggerhead Sea Turtle

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Loggerhead Sea Turtle Loggerhead Sea Turtle

 

Description

The Loggerhead Sea Turtle (Caretta caretta) has a distinctive large, yellow-orange head (hence its name), which is extremely broad posteriorly. It has dark brown eyes, a parrot-like beak and extremely powerful yellow jaws. The flippers are proportionately small, and the body length is up to 1.5 m; 0.3-0.5 m in juveniles. Both the carapace and flippers are reddish-brown in colour. The underside of the body is yellow. It commonly weighs up to 180 kg.This species is almost entirely carnivorous using their powerful jaw to crack open crustaceans and shellfish, as well as feeding on sponges, jellyfish and occasionally algae (Bustard, 1972). Sexual maturity can be reached as late as 37 years old. Females nest 3 - 5 times in one breeding season, returning to breed every couple of years. The female lays her eggs high up on specific tropical beaches. This can lead to predation from native species as well as humans. Hatchlings follow the light of the moon to the ocean. Light pollution from land can confuse the hatchlings diverting them away from the ocean resulting in desiccation, increased risk of predation and, hence, death. The hatchlings and small juveniles are pelagic, drifting amongst rafts of sargassum (brown algae) and flotsam of the open ocean before migrating to shallower coastal waters. Juveniles have small spikes along the spine of the shell.  

Loggerhead Sea Turtles are classified as Endangered (EN - A abd) on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List 2002, listed on Appendix I on Convention on the International Trade in Endangered Species of Flora and Fauna (CITES), Appendix I and II of the Convention of Migratory Species (CMS or Bonn Convention) 1979, Appendix II of the Bern Convention 1979, and Annex II of the EC Habitats Directive. All five species of turtles are protected under Schedule 5 of the Wildlife and Countryside Act 1981 and Schedule 2 of the Conservation (Natural Habitats & c.) Regulations 1994 (Anon. 1999(ii)). This species is particularly susceptible to: bycatch from shrimp trawlers; ingestion of marine debris, and predation on eggs.

Geography

The Loggerhead Sea Turtle is found in nearly all the world's temperate and tropical oceans: the Atlantic Ocean from Newfoundland to Argentina, the Indian Ocean from southern Africa to the Arabian Gulf to western Australia, the Mediterranean Sea, and the Pacific Ocean from Alaska to Chile and Australia to Japan. During winter months loggerhead sea turtles migrate to tropical and subtropical waters. 

Biogeographic Regions: Indian Ocean (Native); Atlantic Ocean (Native); Pacific Ocean (Native); Mediterranean Sea (Native)

Ecosystem

Preferred habitat of Loggerhead Sea Turtle individuals changes throughout the life cycle. Adult females go ashore to lay eggs and seem to prefer steeply sloped, high energy beaches. When hatchlings emerge from the nest, they head for the ocean. Young juveniles are typically found among drifting Sargassum mats in warm ocean currents. Older juveniles and adults are most often found in coastal waters and tend to prefer a rocky or muddy substrate over a sandy one. They may also be found near coral reefs and venturing into salt marshes, brackish lagoons, and the mouths of rivers. 

Range depth: 0 to 61 m.

Habitat Regions: temperate; tropical; saltwater or marine 

Aquatic Biomes: pelagic; reef; coastal; brackish water 

Other Habitat Features: estuarine

Conservation

The Loggerhead Sea Turtle, like all sea turtle species, is in decline. The greatest causes of decline world-wide is probably incidental capture in fishing gear such as long lines, gill nets, shrimp trawls, and direct exploitation of adult turtles and eggs for human food. Though in sharp decline in many parts of its range, and locally along North American coasts, loggerhead sea turtles are currently the most common and least-threatened marine turtle in North American waters. They are listed as threatened under the U.S. Endangered Species Act. 

Other important causes of decline include beachfront development, human disturbance of nesting females, pesticides, petroleum products (oil spills), and other ocean pollutants, human-influenced increases in nest predators such as raccoons, collisions with watercraft, and offshore and channel dredging. Artificial lighting near beaches can confuse emerging hatchlings, causing them to move away from the ocean and into hazardous urban areas. If predictions about global warming are realized, increased storms and rising sea levels could damage or destroy nesting areas and nests, and temperature changes could skew sex ratios. 

The United States has taken several measures to reduce bycatch of loggerhead sea turtles. Turtle exclusion devices (TEDs) are required in commercial fishing and shrimping nets. There have been other gear modifications, changes in practice, and area closures in fishing that have reduced bycatch. Also, other countries may harvest shrimp in a way that puts loggerhead sea turtles in danger and the U.S. has put an embargo on these shrimp. Despite these measures being taken, the numbers of loggerhead sea turtles in U.S. waters is still declining. 

US Federal List: threatened 

CITES: appendix i

State of Michigan List: no special status

IUCN Red List of Threatened Species: endangered

 

Threats

Threatened through direct exploitation for food (including eggs) and curio materials, incidental take (chiefly by drowning in shrimp trawls), and by habitat degradation, including beach development, beachfront lighting (Peters and Verhoeven 1994, Salmon and Witherington 1995), ocean pollution (including marine debris, which may be ingested), and dredging (direct kills and injuries). Beach armoring, including sea walls, rock revetments, riprap, sandbag installation, groins, and jetties, can result in loss of nesting beaches due to accelerated erosion, prevention of natural beach and dune accretion, and interference with females attempting to reach suitable nesting sites. Beach cleaning operations can destroy nests or produce tire ruts that inhabitat movement of hatchlings to sea. The effect of beach restoration may depend on sand type used and subsequent management. Additional threats include predation and/or trampling of eggs and young by raccoons and feral mammals, trampling/crushing of eggs or young by vehicles or human pedestrians, deaths caused by collisions with boats (e.g., in southeastern and southern Florida and shallow coastal bays of the Gulf of Mexico) and intentional attacks by humans (fishermen) (Mitchell 1991). Long-term threats include sea level rise which, coupled with inland urbanization, may reduce available nesting beaches. Since sexual differentiation depends on incubation temperature, there is concern that global warming may result in an imbalance in the sex ratio (Mrosovsky and Provancha 1989). Annual mortality due to drowning in shrimp nets has been estimated at 5000-50,000 in the southeastern U.S.; an additional 550-5500 may die each year from other human activities (CSTC 1990). The fall bottom fishery and black drum fishery may be having adverse effects on loggerheads that use Chesapeake Bay (Mitchell 1991). Susceptible to entanglement and drowning in pound net hedging in Chesapeake Bay (Lutcavage and Musick 1985). In Georgia, predation by the imported fire ant may be a serious threat to eggs and hatchlings (Moulis 1997). See USFWS (1998) for detailed information on certain threats, including beach erosion, beach armoring, beach nourishment, artificial lighting, beach cleaning, increased human presence, recreational beach equipment, exotic dune and beach vegetation, nest loss to abiotic factors, predation, and poaching.

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