Marine Turtles are a successful group of animals that have witnessed the rise and fall of the dinosaurs. They have inhabited the earth for over 100 million years and survived in huge numbers until the recent past. They have evolved from large, land-living tortoise-like animals. Their body consists of a head, a short neck, a pair of long fore-flippers & a pair of short and rounded hind flippers, and a tail. The upper carapace and lower plastron make a protective structure (box) for internal organs. Unlike tortoises and freshwater terrapins, sea turtles cannot withdraw their head and limbs into their box. Instead of teeth, sea turtles have beak-like sharp jaws that can crush, tear or bite their prey and food items which vary according to species.
Turtles are cold-blooded reptiles (Class: Reptilia, Order: Chelonia), meaning their body temperature is determined by their environment. To warm up, marine turtles “sunbathe” at the sea surface, increasing their body heat. They breathe air through their lungs and must surface every 30 minutes to take a breath. Over millions of years, they have become highly adapted to marine life. With long, muscular fore flippers like oars, rudder-like hind flippers, and streamlined shells, they are agile and fast swimmers. The only time marine turtles leave the ocean is when females come ashore to nest, although some can be seen sunbathing on beaches or rocks. Males, however, remain at sea, and little is known about their behavior.
Most species are migratory, traveling long distances between nesting and feeding grounds, sometimes thousands of kilometers apart. Turtles are believed to live over 80 years, though their exact lifespan is uncertain. Sexual maturity varies by species—Olive Ridley turtles mature in 7-15 years, Green turtles take up to 50 years, while the largest species, the Leatherback, matures in 20-30 years. Male turtles develop long claws on each fore flipper and a longer tail upon reaching maturity. The way females find their nesting beaches remains a mystery, though some scientists believe they navigate using the Earth’s magnetic field. Turtles often return to the same stretch of beach each year to nest.
Seven species of marine turtles remain, representing two families—Cheloniidae and Dermochelyidae—all of which are threatened by human activity. Unlike some reptiles, mother turtles do not care for their young. After laying eggs, they leave them to incubate in the sand, heated by the sun. The incubation period lasts about 60 days, after which the hatchlings emerge. As they move in the nest, sand falls, creating an “elevator-like” platform that pushes the hatchlings to the surface. They emerge at night when it’s cooler and safer from predators like rats, crabs, and birds.
Upon reaching the ocean, the hatchlings are not free from danger. Inshore waters are home to sharks, large fish, and seabirds. They swim continuously for about 48 hours, relying on the remains of the egg yolk in their stomachs for nourishment. This “juvenile frenzy” helps them escape predator-rich inshore waters and get swept into open ocean currents. During this time, they feed on tiny sea animals. Much about their first year, often called the “lost year,” remains a mystery.
It is believed that once female turtles reach maturity, they return to the same beach where they hatched to nest. However, only one in a thousand eggs survives to become an adult turtle in the wild.
