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LatestPhoto
Mating Green sea turtles off Aldabra.
Photo: Chris Johnson

December 16, 2002
A Night with a Nesting Green Turtle
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Log Transcript

This is Genevieve Johnson speaking to you from Aldabra Atoll in the western Indian Ocean.

The color of the water around Aldabra is striking in its aqua marine transparency. It is possible even while travelling at speed in a dinghy, to spot green turtles resting on the reef or swimming beneath the surface.

The abundance of turtles along the fringing reef is staggering. On average, the crew sighted one turtle almost every thirty seconds.

Mervin, a Ranger and our guide for the day pointed out something rolling in the water at a distance. "They are mating green turtles" he told us, and we moved in closer to take a look.

After mating with a male, a female green turtle may lay five to ten clutches of eggs every five years. After laying her first batch, she will return to the sea. However, there is no need for her to mate again. Instead, using stored sperm, the female will begin fertilizing new eggs immediately. It will take another two weeks before those eggs are ready for laying, at which point she will come back up the beach and the entire process will be repeated.

While most of the coastline of Aldabra is inhospitable, there are a few sandy beaches that provide nesting sites for green sea turtles.

LatestPhoto
After burying the eggs with her back flippers, the turtle sweeps sand over the nest with her front flippers.
Photo: Chris Johnson

Last night we were very lucky to see a green turtle come ashore on Picard Island to lay her eggs. By the time we arrived, she had just hauled herself up onto the sand and had begun to dig her nest above the high tide mark - this prevents the nest being swamped by the ocean.

The shell of a Green turtle (also called the carapace) can reach almost one and a quarter meters when fully mature. This is second in size only to the giant Leatherback turtle. This animal was an impressive size at 107 centimeters in length.

As soon as the female green turtle decided on the right place for her nest, she started moving the sand aside with her front flippers. She dug her entire body down into a pit until the top of her carapace was level with the sand. Next, she settled down and anchored herself with her front flippers.

She began to dig with her smaller back flippers, which were only about 30 centimeters long.

We watched in amazement as the female began to excavate her egg chamber. This is quite small and narrow, only 15 centimeters in diameter. She dug with her back flippers one at a time. We watched as she scooped and lifted out the sand. The turtle was very delicate and precise in her movements. The bone structure in her flippers is quite similar to those in the human hand.

The female green turtle continued to take sand out of the chamber until she couldn't reach any further. Finally, she was ready to lay her eggs, dropping an estimated 120 to 140 ping-pong sized eggs inside the hole.

Originally land-based reptiles, sea turtles still lay eggs with shells and have no option but to deposit them on dry land. The eggs are quite soft and leathery so they don't break when they hit the bottom of the chamber.

LatestPhoto
The female turtle pauses to take a deep breathe of air while covering up her eggs.
Photo: Chris Johnson

She laid her eggs surprisingly quickly. (We turned all camera lights off so as not to disturb her at this point).

When finished, the turtle began to fill in the hole, prodding and patting it gently with her back flippers. It was then that the real action began.

For the next hour we quietly watched as she dispersed sand across the top of her nest with her front flippers.

The female green turtle stopped periodically to lift her head and take a rejuvenating gulp of air. Her beautiful, moist eyes that have seen so many years at sea, were clogged with sand, but she was determined and did not rest until her task was complete. We marvelled at a creature struggling out of her natural buoyant element of the sea, nesting on the sandy shores as her ancestors have done for millions years.

She flicked sand violently backwards with her powerful flippers in an effort to conceal her nest. There are many predators that the female sea turtle may have to contend with while on land. Robber crabs as well as exotic species such as cats and rats can dig up her nest and take her eggs if they are able to find them.

By throwing excess sand over the nest she leaves behind, the chances of its precious contents being plundered are reduced.

Genevieve speaking in front of the nesting Green turtle.

"We're at zone two on on Picard Island on Aldabra Atoll. We have been sitting here for the last hour and a half watching a Green Turtle nesting and actually laying her eggs. When we first got here she tried unsuccessfully dig one nest and subsquently a second, but her third attempt has been successful. So we have just watched her lay her eggs and she has just about completed covering them up and hopefully, pretty soon, she will go back into the water. It is about midnight now and she is looking pretty exhausted."

Reports from the end of the 1800's describe scenes of more than 500 Green turtles nesting on a single strip of sand here. Over the years hundreds of thousands were taken from this region for export in response to an insatiable market for their meat. In 1970, less than a dozen females were counted nesting on Aldabran beaches.

LatestPhoto
The Green turtle returns to sea after laying and burying her eggs.
Photo: Chris Johnson

Hunted to extinction in many parts of the world or in decline almost everywhere else, Green turtles on Aldabra are termed to be 'safe' and their numbers here are actually increasing. Over two thousand green sea turtles are known to visit Aldabra to lay their eggs each year.

Green and Hawksbill turtles are now protected and find a last refuge on Aldabra.

The female green sea turtle will most likely head straight out to the reef, rest and gather her strength. We watched her as she reached the edge of the surf. How sweet it must be to return to the cool, familiar world of the ocean. We urged her on in the hope that she and her species, may survive long into the future.

Links

Listen to Dr. Jeanne Mortimer discuss more about sea turtles in this special 3 part Odyssey report - breeding patterns, the lifecycle and the threats to sea turtles.

Written by Genevieve Johnson

 
 
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