Green sea turtle

Who is it?

The green sea turtle Chelonia mydas is one of the largest sea turtles.

Where does it live?

It is found in tropical and subtropical waters around the world, with two distinct populations in the Atlantic and Pacific Oceans, but it is also present in the Indian Ocean. Occasionally, it is also found in temperate areas. The adults usually inhabit shallow lagoons.

What does it eat?

The diet of a green turtle changes with age. Juveniles are omnivorous and then turn to mainly herbivorous as adults. The adult green turtle is the only strictly herbivore among the different species of sea turtles, feeding mostly on various seagrasses.

Why is its name “green turtle”?

Its common name refers to the usually greenish fat beneath its carapace, not to the colour of the carapace itself, which is olive to black. The body fat colour is due to the consumption of vegetation.

How can we recognize it?

It has a teardrop-shaped carapace and a pair of large, paddle-like flippers. The distinctive features are, on the head, one pair of pre-frontal scales between the eyes and, on the carapace, four distinct lateral scutes.

Does a green turtle migrate?

Like other sea turtles, it migrates for long distances between feeding grounds and the beach from where it hatched. Each population is genetically distinct, with its own set of nesting and feeding grounds within the population's known range. Mature female turtles often return to the exact beach where they were born. The males also return to their birthplaces in order to mate: they know they will be able to find mates because the females born there also return to breed. By doing this, the green sea turtles are able to improve their reproductive success and it is why they are willing to expend the energy to travel many km across the ocean to reproduce.

How does a green turtle orientate?

It has special adaptive systems to navigate. In the open ocean, it uses wave directions, sunlight and water temperatures. It also has an internal magnetic compass: the magnetic information is decoded by using magnetic forces acting on the magnetic crystals in its brain. Through these crystals, it can sense the intensity of Earth's magnetic field and make its way back to the nesting ground or preferred feeding sites.

How does a green turtle see?

Green sea turtles tend to have a good vision, well adapted to life at sea. The turtles can see many colours, but they are not able to see many shades from the orange to the red portion of the light spectrum. On land, however, sea turtles are nearsighted because the lenses in their eyes are spherical and adjusted to refraction underwater.

How does a green turtle hear?

All sea turtles have no external ear and only one ear bone, the columella. Thus, they can hear only low-frequency sounds, from 200 to 700 Hz.

How does a green turtle smell?

Sea turtles have two external openings that connect to the roof of the mouth through internal openings. The lower surface of the nasal passage has two sets of sensory cells called the Jacobson's organ. The turtle can use this organ to smell by pumping water in and out of its nose.

How does a pregnant green turtle act?

Like all the other sea turtles, female green turtles crawl out on beaches, dig nests, and lay eggs during the night.

How long does a green turtle can hold its breath?

During the routine activity, green and loggerhead turtles dive for about four to five minutes, and surface to breathe for one to three seconds.

Does a green turtle sleep?

Turtles can rest or sleep underwater for several hours at a time. Submergence time is much shorter while diving for food or to escape predators. This is because the breath-holding ability is affected by activity and stress. During the night while sleeping, to protect themselves from potential predators, green turtles hide under rocks. Many green sea turtles have been observed returning to the same sleeping location night after night.

Are green turtles endangered?

Depending on the place, green turtles are threatened by overharvesting of their eggs, hunting of adults, being caught in fishing gear, loss of nesting beach sites and seagrass habitat. They are also affected by pollution, and the newly hatched turtles have to deal with disorientation, when they try to reach the sea, mismatching the artificial lights along the coastline with the moonlight and thus taking the wrong way towards the land, instead of the sea.