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Long-Term Monitoring of Green Turtle Nesting on Tromelin Island Demonstrates Stable Reproduction and Population Parameters
- Derville, Solène, Jean, Claire, Dalleau, Mayeul, Le Gall, Jean-Yves, Ciccione, Stéphane, Bourjea, Jérôme
- Chelonian Conservation and Biology 2015 v.14 no.1 pp. 11-20
- Chelonia mydas, coasts, data collection, eggs, females, hatching, monitoring, nesting, nesting sites, population size, progeny, reproductive behavior, surveys, turtles, Indian Ocean
- Situated about 500 km off the Malagasy east coast, the island of Tromelin is a key nesting site for the endangered green turtle, Chelonia mydas, in the south Western Indian Ocean. Nesting turtles found in this isolated island have been closely monitored since the 1970s, but the most recent estimates of nesting parameters date from 1986. Using mark–recapture data, track counts, and nests monitoring data collected over the 2009/2010 nesting peak, reproductive characteristics, population size, and offspring production were updated and discussed in the light of the track survey undertaken from 1986 to 2010. Females showed a consistent reproductive behaviour compared with previous studies in terms of clutch frequency (2.75 ± 1.46) and nesting success (0.65). Nest indices such as hatching success (0.76 ± 0.25) and emergence success (0.61 ± 0.33) were also included in the range of values calculated in the 1980s. Importantly, the estimated number of nesters and production in eggs and hatchlings were similar to older estimates, suggesting a relative demographic stability. For the 2009/2010 year-long nesting season, the size of the nesting population was estimated at about 1500 individuals, which produced around 480,900 eggs (± 103,900), resulting in 289,200 emerging hatchlings (± 152,000). These results are promising and support the effectiveness of conservation measures undertaken in the Iles Eparses, but further comparable monitoring is needed in the coming years to confirm the stability in Tromelin's green turtle nesting population.