Ecologists are a step closer to understanding one of nature's most extraordinary sights the 'arribada' or synchronised mass nesting of female olive ridley sea turtles. The new study, published today in the British Ecological Society's Journal of Animal Ecology, is the first to combine three different approaches genetics, demography and behaviour, and the results should help conserve these vulnerable marine creatures.
The study, lead by Virginie Plot of the National Center for Scientific Research (CNRS) in France, gathered three sets of data. First, to get an accurate estimate of the size of the olive ridley population in French Guiana, the ecologists monitored nesting beaches at Cayenne and Remire-Montjoly every night during the nesting season (May to September) each year between 2002 and 2010.
Then, to learn more about how the turtles behave before coming ashore, they attached satellite data loggers to the shells of 10 individuals. By recording data every 10 seconds and sending them by satellite every time the turtles surface for breathing, these units gave a detailed picture of the turtles' geographic location, the depth and duration of their dives and the temperature of the water.
Finally, the team took skin samples from the turtles so they could investigate the variability of their DNA. These tests reveal the genetic diversity of the population and also allow researchers to estimate past population levels.
The results show that although olive ridley numbers in French Guiana have increased during the past 10 years, the population suffered a massive collapse in the past 2,000 years.
According to Ms Plot: "Looking at the DNA of these turtles tells us that they come from a much larger population, one that has collapsed by 99% over the past 2,000 years. This is one of the sharpest collapses ever reported in large species and their population in French Guiana remains at a critical level."
|Contact: Becky Allen|