Loggerhead sea turtle

The loggerhead sea turtle (Caretta caretta) is a marine reptile found across the globe, belonging to the Cheloniidae family. Fully grown, its shell averages about 90 centimeters in length.

Adults typically weigh around 135 kilograms, though the largest can reach about 200 kilograms. Its skin can be yellow to brown, while the shell is usually reddish brown. Males and females look alike until adulthood, when males develop thicker tails and shorter lower shells.

This turtle lives in the Atlantic, Pacific, and Indian Oceans, plus the Mediterranean Sea. It spends nearly all its time in saltwater or estuaries, with females only coming ashore briefly to lay eggs. Reproduction is slow: females produce about four clutches of eggs on average, then rest for two to three years without laying any. They reach sexual maturity between 17 and 33 years old and live for 47 to 67 years.

Loggerheads are omnivores, mostly eating bottom-dwelling invertebrates. Their large, strong jaws are perfect for crushing prey. Young turtles face many predators, and their eggs are especially vulnerable to land animals. As adults, their size protects them from most threats, leaving only large sharks as natural predators.

Conservation efforts

The International Union for Conservation of Nature lists the loggerhead as vulnerable. Under the Endangered Species Act of 1973, nine distinct population segments are protected: four are considered threatened, and five are endangered. Commercial international trade of loggerheads or their products is banned by CITES Appendix I.

Many loggerheads die from abandoned fishing gear. The biggest danger, though, is loss of nesting beaches due to coastal development, nest predation, and human disturbances like lights and housing that confuse hatchlings.

Threats

Turtles can also suffocate in fishing trawls, so turtle excluder devices have been introduced to give them an escape route. The loss of suitable nesting beaches and the arrival of non-native predators have also hurt populations. Because loggerheads roam vast oceans and their nesting beaches span many countries, international cooperation is needed to restore their numbers.

Taxonomy

Carl Linnaeus first named the species Testudo caretta in 1758. Over the next 200 years, 35 other names appeared, until Leonhard Stejneger introduced Caretta caretta in 1873. The common name "loggerhead" comes from its large head. It belongs to the Cheloniidae family, which includes all living sea turtles except the leatherback.

Whether it has subspecies is debated, but most experts consider it a single, variable species. Genetic studies show it has hybridized with Kemp's ridley, hawksbill, and green sea turtles. How often this happens naturally is unknown, but second-generation hybrids have been found, suggesting some hybrids are fertile.

Evolution

Modern sea turtles likely share a single ancestor from the Cretaceous period, though direct evidence is lacking. Like all sea turtles except the leatherback, loggerheads belong to the ancient Cheloniidae family, which appeared about 40 million years ago. Among the six living Cheloniidae species, loggerheads are most closely related to Kemp's ridley, olive ridley, and hawksbill turtles, and less so to flatbacks and greens.

About three million years ago, during the Pliocene epoch, Central America rose from the sea, cutting off currents between the Atlantic and Indo-Pacific Oceans. This shifted ocean currents and triggered climate changes as the Earth entered a glacial cycle. Cold water upwelling near the Cape of Good Hope and cooler temperatures at Cape Horn created barriers that isolated Atlantic and Pacific loggerhead populations.

During the last ice age, beaches in southeastern North America were too cold for sea turtle eggs. As the Earth warmed, loggerheads moved north, colonizing those beaches. As a result, turtles nesting between North Carolina and northern Florida form a different genetic group from those in southern Florida.

These distinct populations have unique traits and genetic differences. For example, Mediterranean loggerheads are smaller on average than Atlantic ones. North Atlantic and Mediterranean loggerheads descend from colonizers that came from Tongaland, South Africa, and South African loggerhead genes still appear in these populations today.

The loggerhead is the largest hard-shelled turtle in the world, slightly bigger at average and maximum adult weights than the green sea turtle and the Galapagos tortoise. It is also the second largest living turtle overall, after the leatherback.

Adults weigh between 80 and 200 kilograms, averaging about 135 kilograms, with a straight shell length of 70 to 95 centimeters. The largest recorded weight is 545 kilograms, and the greatest total length is 213 centimeters. The head and upper shell range from yellow to brown.