Loggerhead Sea Turtle, Caretta caretta

Loggerhead Turtle, Caretta caretta, Juvenile. Turtle collected alive for a photo shoot and then returned to its native environment at the ocean’s edge adjacent the San José Rio, Baja California Sur, January 2011. Size:  6.5 cm (2.6 inches).

Phylogeny:  T he Loggerhead Sea Turtle, Caretta caretta (Linnaeus, 1758), is a member of the Chelonidae Family of Sea Turtles. The genus Caretta is one of seven genera in this family. This is the only species in this genus. Caretta is a latinization of the French word caret meaning turtle, tortoise, or sea turtle. In Mexico they are known as tortuga caguama. There is currently one accepted subspecies for this species, Caretta caretta gigas (Deraniyagala, 1939), from the western Indian Ocean.

Morphology:  Loggerhead Sea Turtles are the world’s largest marine turtle and are recognized by their large heads and strong muscular jaws. They have a large, bony heart-shaped shell (carapace), without ridges, with large rough non-overlapping scales that are reddish brown in color with olive and yellow tinges. They have five or more costal (lateral) scutes and twelve or more marginal scutes. The carapace is high in the front, and serrate on the posterior margin. They have two pairs of large scales (prefrontals) between their eyelids. The plastron is cream colored with darker gray blotches. The head and shell (both top and underside) have unique patterns which are key to identifying individuals. The front flippers are short and thick with two claws; the rear flippers have two or three claws. The Loggerhead Turtle reaches 2.8 meters (9 feet 2 inches) in length and can weigh up to 450 kg (1,000 pounds).

Habitat and Distribution: Loggerhead Sea Turtles inhabit all oceanic waters except the Polar Regions. They can be found in brackish water, bays, river mouths, estuaries, oceans (far out at sea), coasts, and reefs. The males spend their entire lives at sea, leaving land on the day they hatch. They spend most of their time in shallow water, but can be found at depths exceeding 61 m (200 feet). In the Eastern Pacific, Loggerheads are found from Southern California to Chile. In Mexican waters they are found along the entire Pacific coast, including the Gulf of California. Loggerheads found along the California and northern Mexico coasts were hatched in Japan. They travel across the north Pacific and remain in the Eastern Pacific for decades, until they reach maturity. At this time, they return to Japan to mate and nest. They then live out the rest of their lives in the Central Pacific.

Diet:  Loggerhead Sea Turtles feed in coastal bays and estuaries and in the shallow water along the continental shelf, eating fish, zooplankton and invertebrates such as crustaceans, mollusks, cnidarians, echinoderms, and marine worms.

Predators:  Adult Loggerhead Sea Turtles are prey for sharks, grouper and possibly crocodiles. While ashore laying eggs, they are prey for coyotes, wild dogs, jaguars, and other large predator mammals. Their eggs are also vulnerable to these species, as well as shore birds, insects and small mammals. Newly hatched, and juvenile sea turtles are prey for a wide variety of mammals, birds, fish, and invertebrates.

Reproduction:  Loggerhead Sea Turtles are gonochoric (male or female for life). Reproduction is sexual, with internal fertilization. Mating occurs in the spring and summer in surface waters offshore from the nesting beaches. After mating, the females crawl onto undisturbed, sandy nesting beaches during the night. After climbing above the high tide line, they dig holes with their front limbs, lay 40 to 140 eggs in the nest, and then bury the eggs. The eggs are white, approximately 22 grams and 4.1 cm (1.6 inches) in size. They incubate for 31 to 65 days and the hatchlings move quickly to the water under the cover of darkness. A female normally establishes three or four nests per year at two-week intervals and only nests every second or third year. They have life spans of up to 67 years.

Ecosystem Interactions:  Loggerhead Sea Turtles often host a variety of internal parasites such as nematodes and trematodes. The are also known to host over 200 epibionts including algae, crustaceans and cyanobacteria. They frequently host barnacles on their heads or shells. These barnacles are usually harmless, but some species of burrowing barnacles can damage a turtle’s skin and shell, causing open wounds that can lead to infection.

Human Interactions: Loggerhead Sea Turtles have been hunted by humans for millennia, as a food source and for their shells. The Loggerhead Turtle is currently listed in the United States as a Threatened Species and internationally as an Endangered Species. There has been a population reduction of at least 80% over the last ten years. Currently, the total population is estimated to be between 100,000 and 150,000. Key factors contributing to their decline are the loss of habitat due to human coastal development, pollution from human garbage, accidental capture by shrimp trawlers and long-liners, and nest-robbing by humans and predators. Coastal development has also added artificial light, which causes disorientation of nesting females.

Synonyms: Halichelys atra Fitzinger, 1843, Testudo caretta Linnaeus, 1758, Thalassochelys caretta Boulenger, 1886, and Thalassochelys corticata Girard, 1858.