The species frequents a variety of habitats on the continental shelf, including beaches, estuaries, bays, lagoons, coastal hard bottom habitats, seaweed driftlines, and the open ocean. As bottom-feeders in bays, estuaries, and reefs, their diet may include plants and fish, but consists mainly of invertebrates like mollusks and crustaceans. Upon reaching sexual maturity around 20-25 years old, loggerhead females return to their natal beach every two or three years and lay their eggs at night. They lay 2-6 clutches of 60 to 150 eggs per clutch throughout the summer season, though only a few of every thousand hatchlings reach adulthood. The hatchlings inhabit mats of floating seaweed for the first few years of their lives, and then return to coastal areas as adults around age 7-12.
Loggerheads are migratory and circumglobal, ranging from temperate to subtropical and tropical waters, as far north as Newfoundland and Alaska and as far south as Argentina and Chile. The west coast of Baja California near Baja Magdalena, Mexico is reported as the largest known aggregation of the species in the eastern Pacific, possibly to feed on pelagic red crab. The nesting beach aggregation found along the Atlantic coast of Florida is thought to be one of the largest in the world. The species also nests along the coasts of Georgia, South Carolina, and North Carolina, western Florida, as well as the Caribbean coast of Quintana Roo, Mexico. The turtles that forage in the Gulf of California or along Mexico’s Pacific coast are thought to be from the Japanese and Australian populations.
The worldwide population of loggerheads is likely in the hundreds of thousands. In North America, serious declines have taken place in northwestern Atlantic, especially in the Yucatán Peninsula of Mexico. The number of nesting females in South Carolina and Georgia may also be declining; however, the number of nesting females in Florida appears to be stable. Harvest of loggerhead eggs remains a threat in many parts of their range, however, a much greater threat has been incidental catch in bottom trawl nets, such as those used in shrimping. Their habit of scavenging on bycatch discarded from fishing boats has also made the loggerhead particularly vulnerable to entanglement in fishing gear. Development and destruction of nesting beaches and associated artificial lighting is a problem for loggerheads, as well as threats like oil and gas exploration, dredging, marina and dock development, chemical pollution, boat collisions, and ingestion of marine debris. In addition, a viral tumor-causing disease called fibropapilloma affects loggerheads, potentially killing them as the tumors grow and inhibit movement, feeding, and vision.