Loggerheads have a characteristic large head, with more massive jaws and muscles than other sea turtles. This species is the largest hard-shelled turtle in the world. 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.

Adults and juveniles feed in shallow waters of the continental shelves, often in water only a few tens of meters deep. They spend much of their time around reefs, or along the bottom. Adults sometimes travel for thousands of kilometers. Hatchlings and young juveniles do not dive, staying near the surface, often in association with mats of floating seaweed. Loggerheads are frequently found in bays and estuaries, and may enter river mouths. Females nest on sandy beaches, usually just above the average high tide line. Many females nest at the same beach year after year, but a few nest a different beaches from one season to the next.

Biomes: pelagic; reef; coastal; brackish water; estuarine

Found in all but the most polar seas, as far north as Alaska, eastern Russia, and Norway, and as far south as Australia and South Africa. Females nest on sandy beaches in the tropical and temperate regions of their range. In North America nests are known on the Atlantic Coast from New Jersey south to Florida and west to Texas and south to Tabasco. The highest nesting densities along U.S. shores are along South Carolina, Georgia and Florida. Other loggerheads in North American waters may have nested along the coast of Central or South America. The northernmost nests on the Pacific Coast are in Central America.

These sea turtles reach sexual maturity when their shells are no longer than 50 cm. The eggs, which are 40 - 42 mm in diameter, are laid in the flood of spring tides. The eggs are placed in a nest, which is usually choosen in an undisturbed area of well-drained dunes or grassy vegetation. The female comes ashore and climbs up to the hightide line, she then stops and touches her snout to the sand, perhaps to test the site for temperature and chemical suitability. She then excavates a hole with her flippers. Once the hole is dug and the eggs are laid, the nest is then covered by the turtle using her hind flippers. Incubation lasts for a period of 31 - 65 days. There is usually 50 - 300 eggs per clutch, and the female lays two clutches at an interval of thirteen days. The females come ashore to nest only at night in the spring and summer. The females usually nest every other year with 3 - 4 nests per season. The eggs in the nest usually hatch around the same time, and the babies quickly move together to the water leaving behind their only terrestrial life stage.

Atlantic loggerheads are mainly carnivorous. They eat a wide variety of marine animals, including sponges, jellyfish, crabs, clams, fish, squid, and oysters. They have powerful jaws which enable them to crush the hard shells of some prey. They do ocasionally eat algae and other plants as well.

Except for western Caribbean populations, all of the nesting areas are located either north of the Tropic of Cancer or south of the Tropic of Capricorn. For reasons unknown, Atlantic loggerheads are unable to co-exist with the Olive Ridley Turtle. They migrate to nest by following vegetation laden ocean currents.

The worldwide population of loggerheads is declining, and has been for many years. Causes for this include due to local human harvesting (not such a problem in North America), incidental capture in shrimp trawls, loss of habitat due to coastal development, artifical light on coasts causing disorientation of nesting females, and beach sand mining The most concentrated population is in the Greater Antilles and the eastern United States with about 15,000 individuals frequenting the eastern U.S. yearly. However, the Carolinas record a three percent decrease in the occurence of C. caretta each year.

The species is considered Endangered by the International Union for the Conservation of Nature (IUCN) in their 2003 List of Threatened Species (the Red List), based on data indicating that the species is suffering an 80% or great decline in numbers over the last three generations.

The U.S. Fish and Wildlife Department has listed the species as Threatened in its Entire Range, since 1978.

Like all sea turtles, loggerheads are listed in Appendix One of CITES, making it generally illegal to trade in them internationally without special authorization.

McKeown, Sean. A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing Company, 1996