Hatching and Emergence

Almost all the eggs that have developed properly will hatch at the same time and the hatchlings combine their efforts to scrape at the walls and roof of their egg chamber. This brings down sand which filters through the struggling hatchlings and forms a new floor. The floor gets thicker as more sand falls and the hatchlings rise towards the surface rather like a lift! On nearing the surface those hatchlings at the top can tell if the surface of the beach is too hot and they will stop climbing until the beach cools down. Most hatchlings will emerge onto the surface of the beach at night.

The Rush to the Sea

When ready the hatchlings emerge onto the surface of the beach as rapidly as possible and sprint towards the sea guided by the light over the sea horizon. Speed is of the essence as many predators will try to catch and eat them. Frigate birds, kites, ghost and hermit crabs, feral dogs, mongoose, jackals and even leopards will kill and eat hatchlings.

Growth to Maturity

Depending on various factors such as temperature, availability of food, competition and individual characteristics marine turtles can take anything between 15 and 30 years to eventually reach nesting maturity. Green turtles, now almost totally herbivorous, will graze for hours building up their fat reserves to a point where they will feel the urge to reproduce.

Nesting Migrations

When the urge to reproduce has developed male and females return to the beaches on which they were hatched so many years before. This is a remarkable feat as it may require a swim of hundreds or even thousands of kilometres over open ocean and facing many dangers. Such migrations are amongst the longest in the world and are a source of wonder and much scientific research. It is thought that turtles are able to navigate using the Earth’s lines of magnetic force and also use their amazing sense of smell to recognise their original beaches.

Egg Laying

Females now ready to lay normally emerge onto the beaches after dark and make their way up the beach to above the high water mark. They are capable of walking hundreds of metres before finding a suitable site where they settle, dig a body pit in the sand with the fore flippers and then an egg hole using their hind flippers. Into this hole she will deposit between 100 and 150 soft shelled eggs about the size of a ping-pong ball. When she has completed laying she gently covers the eggs with sand using first her hind flippers and then disguises the entire nest with great sweeps of her fore flippers.

This entire operation can take up to two hours thereafter the female, by then very tired, will return to the sea leaving two clear tracks recording her visit. These tracks are valuable to scientists who by counting them can estimate how many females are nesting on any breeding beach. Normally a female will repeat this process at least 3 times but some very fecund females can lay as many as ten clutches of eggs per season.

Incubation

A clutch of eggs normally lies some 60 cm under the surface of the beach and will take between 45 to 75 days to hatch depending on the temperature and humidity of the surrounding sand. The sex of the hatchlings is determined by the temperature of the nest on the 19th day of incubation. This “pivotal” temperature varies from beach to beach but is normally about 28 degrees Celsius. Lower than that and the clutch will produce mainly males, higher than that and it will produce mainly females.

© Kélonia / SC

The Cycle Begins Again !

After a nesting season adult turtles will return to their foraging grounds and if they survive they may return again to lay more eggs after periods of 3, 4 or more years. Many will never return but having laid at least one full season’s worth of eggs they will have done enough to provide the population with some survivors and guarantee that the existence of these wonderful and harmless animals will continue into the future.