Conclusion
Preliminary results of the validation of the method based on 106 profiles of green and 132 profiles of hawksbill turtles, indicate that this method based on a computer-assisted screening is reliable to identify individuals within these species. However, a more robust validation using a larger number of profiles per species and a multi-observer approach to avoid observer bias has to be done in order to finalize the validation of the method. This will be done as the next step in the development of this programme.
From a practical point of view, field experiences have indicated that photo-ID may be more suited for underwater images taken on the beach as sand may obscure parts of the head, especially with hawksbill turtles. For photographs taken on beaches, profiles should be clear of sand and washed off with seawater . One advantage for underwater fieldwork is that the entireprofile is most often visible, as the head and the neck of the turtle are extended during feeding. In addition , digital technology provides easy acquisition of high-resolution images and enables photography of the turtle without going close and disturbing them.
Analyses of images showing the facial profile of marine turtles at the three study sites (Mayotte, Mahe and Reunion) have shown the effectiveness of the technique for individual identification and site fidelity studies of foraging habitats. The use of the method in Reunion, where marine turtles cannot be conventionally tagged as they stay outside the reef barrier, should considerably increase our knowledge regarding home-range and habitat use of the resident population and, coupled with aerial survey, assessment of the foraging population. On a large geographic scale, the use of this method should contribute to study the origin of these turtles and their movements between different habitats in complement or in substitution to standard “capture-mark-recapture” studies.
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