Reptiles

Sea Turtle

Chelonioidea · also called marine turtle

Endangered ↓ carnivoreherbivoreomnivore Ocean Coasts & shorelines

A sea turtle spends its whole life in the ocean, except for the hour or two when a female drags herself up a beach to lay eggs — usually the same beach where she hatched, 20 to 50 years earlier, found across an entire ocean by reading the Earth’s magnetic field. Its limbs are flippers that cannot be pulled into the shell, and it cries salt.

Overview

Sea turtles are the superfamily Chelonioidea, just seven species — six hard-shelled ones (green, loggerhead, hawksbill, Kemp’s and olive ridley, flatback) plus the leatherback in its own family. They live in all warm oceans, are permanently marine except for nesting, and swim with paddle-shaped flippers. Diet ranges from the green turtle’s seagrass to the leatherback’s diet of almost pure jellyfish.

Homing across an ocean

A female navigates by the magnetic field and returns to her natal beach to nest — natal homing — tying each population to one region. Nest sand temperature sets the sex of the young, warmer nests female. Salt glands behind the eyes shed excess salt as thick “tears”.

The leatherback

The leatherback is the largest turtle at 2 m and 700 kg, has a leathery ridged skin instead of a hard shell, dives below 1,000 m, and stays warm in cold seas through its size, fat, and a heat-exchange blood system.

Long odds

Sea turtles live 50 to 100 years and mature slowly, but roughly one hatchling in a thousand reaches adulthood — eggs and young are eaten by crabs, birds, and fish, and the young drift for years in open-ocean weed lines.

Status

Sea turtles are assessed as Endangered overall, trend decreasing. Six of seven species are threatened, with the hawksbill and Kemp’s ridley Critically Endangered. The threats are fishing bycatch, egg collection, developed and lit beaches, plastic mistaken for jellyfish, boat strikes, and warming that skews nests toward all-female.

Sea Turtle: common questions

How many kinds of sea turtle are there?

Seven. Six belong to the family Cheloniidae, the hard-shelled sea turtles, which are the green turtle, the loggerhead, the hawksbill, the Kemp's ridley, the olive ridley, and the flatback, the last found only around Australia. The seventh, the leatherback, is in its own family, Dermochelyidae, and is very different, with a barrel-shaped body, a flexible skin-covered shell reinforced by a mosaic of small bones, and the ability to keep itself warm in cold seas. All seven are marine for their whole lives except that females come ashore to lay eggs, and in a few populations the green turtle also basks on land.

Why do sea turtles come onto land, and how often?

Only to nest, and only the females. A female sea turtle mates at sea, then hauls out onto a sandy beach at night, drags herself above the high-tide line, digs a chamber with her hind flippers, lays around 80 to 120 eggs, covers and disguises the nest, and returns to the sea, all in one or two hours. She repeats this several times in a season, at roughly two-week intervals, then does not breed again for two to several years while she rebuilds her reserves. The hatchlings dig out together about two months later, usually at night, and scramble to the sea, orienting toward the brighter, lower horizon over the water.

Are sea turtles endangered, and why?

Most are. Six of the seven species are listed as threatened, and two, the hawksbill and Kemp's ridley, are Critically Endangered. The pressures are almost all human. Turtles drown in trawl nets, on longlines, and in gillnets as bycatch. Eggs are dug up for food, and nesting beaches are built on, lit up, and eroded. Turtles eat floating plastic bags that look like jellyfish, and hatchlings crawl toward streetlights instead of the sea. Boat strikes kill adults in coastal waters. And because sand temperature sets the sex of the young, warming is producing nests that are almost entirely female on many beaches, threatening future breeding.

How do baby sea turtles know which way the sea is?

They use light and slope. On hatching at night, a baby turtle heads toward the direction where the horizon is brightest and lowest, which on a natural beach is the open sky over the sea reflecting starlight and moonlight, away from the dark silhouette of dunes and vegetation. Once in the water it swims into the waves, which on most beaches come from the open ocean, and then it switches to a magnetic compass for the long journey offshore. This light-based cue is why artificial lighting near nesting beaches is so damaging, as hatchlings crawl toward roads, houses, and car parks and die of exhaustion, dehydration, or predation before reaching the water.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 10, 2026. Last updated September 10, 2026.

Quick facts

Scientific name: Chelonioidea
Diet: Varies by species, with the green turtle grazing seagrass and algae as an adult, the hawksbill eating sponges from reefs, the loggerhead crushing crabs and shellfish, the leatherback feeding almost entirely on jellyfish, and the young of most species omnivorous in the open ocean
Flippers instead of feet: A sea turtle's limbs are long, flattened, paddle-like flippers with the toes bound together, superb for swimming but useless for walking, so a nesting female drags herself up the beach with enormous effort and cannot retreat quickly, and none of the seven species can pull its head or limbs inside the shell
They return to their natal beach: A female sea turtle navigates the open ocean partly by sensing the Earth's magnetic field and returns, after 20 to 50 years at sea, to nest on the same stretch of coast where she hatched, a feat called natal homing that ties each nesting population to a specific region
The nest temperature sets the sex: Sea turtles have no sex chromosomes, and the temperature of the sand around the eggs during a middle window of incubation decides the sex, with warmer nests producing females, so on many beaches the hatchlings are already heavily skewed female as sand temperatures rise
The leatherback is a warm-blooded outlier: The leatherback is the largest turtle, reaching 2 m and 700 kg, has a leathery ridged skin instead of a hard shell, dives below 1,000 m, and keeps its body temperature well above the surrounding water through its size, insulating fat, and a heat-exchange blood system, letting it feed in cold seas
A long life with terrible early odds: Sea turtles can live 50 to 100 years and take decades to mature, but only around one hatchling in a thousand is thought to survive to adulthood, since eggs and hatchlings are eaten by crabs, birds, fish, and mammals, and the young spend years drifting in open-ocean weed lines
They cry salt: A sea turtle takes in a lot of salt with its food and seawater, and it excretes the excess through large salt glands behind the eyes, producing thick, salty tears that on land make a nesting female look as though she is weeping
Range: All the world's tropical and warm-temperate oceans, with the leatherback ranging into cold water as far as Norway and Alaska, feeding over seagrass beds, coral reefs, and the open ocean and gathering at scattered nesting beaches, chiefly in the Caribbean and Gulf of Mexico, the eastern Pacific, West Africa, the Indian Ocean, Southeast Asia, and northern Australia.
Conservation status: Endangered ↓ ≈ Assessed species by species rather than as a group, and of the seven sea turtle species six are listed as threatened, with the hawksbill and Kemp's ridley Critically Endangered, the green turtle Endangered, and the leatherback Vulnerable and declining steeply in the Pacific; some individual nesting populations have recovered well under protection while others continue to fall, with the main threats being bycatch in fishing gear, egg collection, coastal development of nesting beaches, plastic and light pollution, boat strikes, and warming that skews the sex ratio in the wild