Marine turtle populations around the globe are threatened with extinction, having been heavily over-harvested by mankind throughout their range. In the Indian Ocean marine turtles have provided food at a subsistence level to fishermen and coastal dwellers since time immemorial. Turtles have also been used traditionally for their shell, fat and meat, and their eggs have fed hungry families dependent on the bounty of the sea. But with the advent of outboard motors, refrigeration and rapid transport to major urban areas, the harvesting of turtles and their eggs has reached a level from which populations are struggling to recover. Turtle eggs, which used to be collected on an occasional, irregular basis, are now collected nearly every single time a nesting female emerges on the beach.
In an effort to identify means through which the people of the Maldives working with scientists can help the few turtles that remain overcome the odds stacked against the turtles, this project investigated conservation strategies that are in keeping with their natural biological life-cycle. Specifically, the project included rearing a small number of turtles as an experiment to determine if natural predation rates decrease after growth in captivity, and to see if their dispersal patterns from shore are similar to first-born turtle hatchlings. If this project is successful, the results may point to a mechanism by which depleted populations can be given a helping hand to rebuild their once thriving presence in our seas.
This project had three main components/objectives: First, the project wanted to determine if keeping turtles in a controlled environment (free of predators) for a one-year period will significantly affect their overall survival. The theory is that once they were one year-old, they would be too big for most predators to bite and their hardened shells will deter most marine creatures from wanting to ruin their teeth! Secondly, there was an educational component, through which Maldivian schoolchildren and resort guests have the opportunity to learn firsthand about these magnificent marine mariners in a semi-natural habitat. Lastly, there was a scientific aspect, which aimed to determine growth rates and dispersal patterns (how the one year-old turtles swim away from the shore) and survival rates after they are released.
Under natural conditions sea turtle hatchlings are decimated as they crawl through the surf and swim through the near-shore waters. It is known that up to 50 % of all turtles never live to see their first sunrise. This project kept turtles for one and a half years in a mostly-natural habitat, free of predators, as they grew to a size at which they could not be eaten by most sharks, jacks and reef-dwelling groupers and snappers. During this time they were fed a diet equivalent to that which they would find in the open sea, and kept to a minimum of disturbance. While these turtles were growing, the project kept records of their growth in size and weight to assist turtle scientists to understand natural growth rates and patterns. They were then be released and a small subsample tracked with satellite transponders to determine their offshore migration paths.
Aware that interfering with the life-cycle of a creature such as the long-lived marine turtles can possibly have deleterious effects, we ensured that 90 % of hatchlings continue on their normal journey when they hatch, and only a very small number are kept for these trials. The education component involved Maldivian schoolchildren and guests of the two resorts. Through a series of lectures and visits, school children were provided with valuable information on marine turtles and their conservation needs, a message which is spread throughout the nation. Guests were encouraged to learn more, and have an opportunity to understand also the turtles’ behaviour, while being part of a long-term conservation programme.
Best-scenario estimates suggest only one in one thousand turtle hatchlings survives to adulthood under normal conditions. We feel that a helping hand to reverse the declining trend in numbers brought about by mankind’s intervention, is the least we can do to ensure our planet is handed down to our children in as good a state as it was handed down to us. The biological value of an egg or a hatchling pales in comparison to that of a large adult female, one which has survived the worst, who is of a size to be ignored by even the largest predators. An egg has a one in one-thousandth chance of surviving, while a one year-old has a much higher chance of surviving due to its larger size. For this reason we felt that keeping ten or twenty eggs for our trials was justified.
This work was funded by Banyan Tree Resorts (Maldives).