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Micro-scale nest-site selection of leatherback turtles in French Guiana

2010Micro-scale nest-site selection of leatherback turtles in French Guiana.BEDEAU Caroline (France)
Organisation:University of Poitiers, Poitiers (FR) - Institut Hubert Curien, Univ. of Strasbourg (FR) - Réserve naturelle de l’Amana, Guyane françaiseSupervisor :Jean-Yves GEORGES (US)
Summary: Sea turtles do not exhibit postovipositional care, as female investment is limited to egg production and deposition, and progeny is left to face the ecological conditions associated with the specific environment surrounding the nest site. Sea turtles represent therefore relevant models for studying both the mechanisms involved in the nest-site selection and the adaptability to changing environmental conditions encountered on these sites. This study aims to characterize the spatial and temporal nesting pattern of a known population of leatherback turtles at Awala-Yalimapo beach, French Guiana, one of the last major rookeries for the species. This study has highlighted that the distribution of turtles and nests on the beach follow a non-random and aggregated distribution. This suggests a phenomenon of nest- site selection at the population scale, and / or the existence of favorable breeding areas and / or favorable to nest survival areas. However, such aggregated distribution is evolutionarily counter-intuitive, since it implies a marked density of nests at the locations of the beach that are preferentially used by turtles, and thus a priori more favorable, potentially leading to an increased destruction of nests, eggs and / or hatchlings by a phenomenon of density-dependence, described, so far, only at the scale of the entire beach. Our study suggests that the aggregated nesting pattern may be related to different determinants: terrestrial determinants: 98% of clutches are above the high tide line (at an average distance of 0.84 ± 2.80 m from the line), the majority (60% of nests) on the sandy zone, with a preferential utilization of specific areas of the beach relatively throughout the season, month, and night temporal scales. this aggregated distribution of nests on these areas seems to be partly related to the absence of constraints (barriers , human activities) that can interrupt the normal nesting behavior or limit hatchling survival. marine determinants: arrival of turtles is subject to tidal influences that govern the time and the distribution of beach ascents during the night and the nesting season. Turtles follow the coastal currents to arrive or come back to the beach, taking also into account the presence of sandbars that evolve over time. However, it appears that at the individual level, the breeding experience of females does not influence the temporal pattern of ascents, and that individuals do not seem to exhibit fidelity to a specific area of the beach. This study suggests for the first time that sea turtles nest distribution would result mainly from environmental, and not behavioral, factors, which it is necessary to precise using long-term monitoring of the coastal dynamic and population dynamic. This approach, which exists for not other population of sea turtles, can also provide original information to improve management plans and conservation of areas and species.