Saturday, April 4, 2009

Testing photo ID of Hawksbill turtles

Following a recent visit to Seychelles by scientist from the Kelonia Marine Turtle Observatory in Reunion, MCSS is looking at regional cooperation in a new project to test whether or not Hawksbill turtles can be identified through photographs.

Photo-id, using natural marks on the body, has proved to be an effective means of identifying animals over their life span. Indeed, MCSS has been using photo-id on whale sharks since 2001. This method of identifying wild animals minimises stress to the animals, and allows researchers to track an individual longer than with conventional marker tags, which are prone to falling off and becoming fouled in the marine environment.

In turtles, this method is still being tested. Results from Green turtles photographed by divers around Reunion, Mayotte and Glorieuse islands have shown that individual animals can be reliable identified in their foraging grounds using head shots. To date, 42 Green turtles have been identified by researchers at Kelonia, with at least 5 individuals being re-sighted a few months later.

Each turtle is given an individual fingerprint based on the scale patter on its “cheek”, photo Kelonia.

The team at Kelonia have also used the photo-identification on Hawksbill turtles, but because this species is not abundant in Reunion, they have only been able to add 12 animals to their database. This is were MCSS comes in!

Seychelles host between 475 to 875 nesting females, which regularly visit our beaches to lay their eggs. If one assumes a 1: 1 ratio for males to females, then there are likely to be as many as 1,750 Hawksbill turtles just waiting to be photographed.

Over the years, Elke and various MCSS volunteers have photographed a number of nesting individuals, as well as foraging juveniles. While most of the photographs were not aimed at photo-id, a quick check has shown that there are at least 40 individual turtles that can be added to the database, allowing the Kelonia team to test and hopefully validate the Hawksbill photo-id database.

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