A shelled night time visitor arrives on Cousin Island

 

A report from Nature Seychelles International Volunteer Program

On Hawaiian beaches, some parts of the Pacific and Australia, and the Galapagos Islands, Green turtles (Chelonia mydas) come onto land to bask. The reason for this peculiarity is unknown; most turtles get close to the surface of shallow waters to take in the sun and only clamber onto land to nest.

Hawksbill turtles (Erechmotelys imbricata) nesting behaviour in Seychelles is also unique. Unlike in most other places, females lay their eggs in daytime. Throughout the Seychelles during turtle season, on nesting beaches favoured by hawksbills, you will be treated to the sight of a female crawling to and from a nest in broad daylight. It is a spectacle we have become accustomed to on Cousin Island Special Reserve.

Not typically seen here are nesting green turtles. More common and in larger numbers in the outer islands, green turtles don't appear with the same intensity as hawksbills, which nest yearly on Cousin between September to March. Being nocturnal, green turtles are also likely to come and go without being spotted, leaving only the evidence of tracks and eggs behind.

We were therefore thrilled to see a green turtle on the reserve twice within the space of ten days.

 A rare sighting on Cousin but a much welcomed treat 

Turtles follow a regimented process of laying: they emerge from the water, crawl up a beach, find a suitable spot to hold their eggs, prepare a body pit to settle into, dig an egg chamber, and lay their eggs. They then cover the chamber, conceal it against predators and crawl back to the ocean. Because they are sensitive to disturbance, turtles are approached when they enter a trance-like state during laying. 

We'd found our visitor at dusk, just after she'd established her nesting spot and was organising a body pit. As we waited for her to lay, we enumerated the differences between green and hawksbill turtles: The former has larger paddle-like flippers, it crawls with a simultaneous as opposed to alternate gait of the hawksbill leaving behind a symmetrical print in the sand, it is larger - the second largest sea turtle after the leatherback, despite its name, their colour can be anything from olive to green-brown, its name is from the colour of its fat, carapaces are smooth and heart-shaped, and it cannot retract its flippers and head into the shell.

When it was safe to approach, we were able to get a closer look at our new mama and she was beautiful. Cheryl, Nature Seychelles’ Science Coordinator, collected vital data from the turtle that contributes to a long-term turtle conservation programme on the island. She measured the length and width of her carapace, determined her clutch size (number of eggs laid) and applied numbered tags to her flippers to identify her each time she comes back to this and other Seychelles' beaches.

Finally, after disguising her nest, our nocturnal visitor's time on land was up, and she began her journey back to the water. She will return: during this season as green turtles visit nesting sites 3-5 times in a season, and in two to five years time ready to nest and to enchant once more.

By Liz Mwambui

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Seychelles Nature, Green HealthClimate Change, Biodiversity Conservation & Sustainability Organisation

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