Sea Turtle

There are seven living species of sea turtle, divided into two families. Six belong to the family Cheloniidae: green, loggerhead, hawksbill, olive ridley, Kemp's ridley and flatback. The seventh, the leatherback, is the sole survivor of the family Dermochelyidae and lacks a hard shell. All seven share the same basic body plan and life cycle, though they differ widely in size, diet and habitat preference.

Sea turtles navigate using Earth's magnetic field, which acts like an internal compass. Hatchlings imprint on the magnetic signature of their birth beach before swimming out to sea, and females use that same signature years later to return and nest in almost the exact spot where they hatched. Scientists believe turtles also rely on visual and chemical cues once they get close to shore.

Diet varies a lot between species. The leatherback eats almost nothing but jellyfish, while the hawksbill specializes in sponges found on coral reefs. Green turtles switch from a varied diet as juveniles to mostly seagrass and algae as adults. Loggerheads and Kemp's ridleys prefer hard prey like crabs and mollusks, crushing them with strong jaws built for that purpose. Olive ridleys are the most opportunistic of all, eating whatever crustaceans, fish or jellyfish happen to be available nearby.

Six of the seven sea turtle species are listed as Vulnerable, Endangered or Critically Endangered by the IUCN. The main threats are accidental capture in fishing gear, egg poaching, loss of nesting beaches to coastal development and rising temperatures that affect how eggs incubate. All species are protected under CITES, and conservation programs around the world work to monitor nests and reduce these pressures.

Most sea turtles live between 50 and 100 years, though their slow growth makes exact ages hard to confirm. Many species take 20 to 30 years to reach sexual maturity, spending most of that time at sea before returning to nest for the first time. This long lifespan, combined with late maturity, makes population recovery especially slow once numbers decline.

The temperature inside a sea turtle nest determines the sex of the hatchlings rather than genetics alone. Warmer sand produces more females, while cooler sand produces more males. As global temperatures rise, many nesting beaches are now producing far more females than males, raising concern among scientists about the long term balance needed for these populations to keep reproducing successfully.

The leatherback is by far the largest sea turtle, with adults reaching up to 200 centimeters in length and weighing as much as 700 kilograms. Unlike the other six species, it lacks a hard bony shell, relying instead on a thick, leathery skin reinforced by small bony plates underneath. Its size and unique build allow it to dive deeper and travel farther than any other sea turtle species.