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Chambault P.,CNRS Hubert Curien Multi-disciplinary Institute | Pinaud D.,CNRS Chize Center for Biological Studies | Vantrepotte V.,CNRS Laboratory of Oceanology and Geosciences | Vantrepotte V.,French National Center for Scientific Research | And 9 more authors.
PLoS ONE | Year: 2015

In response to seasonality and spatial segregation of resources, sea turtles undertake long journeys between their nesting sites and foraging grounds. While satellite tracking has made it possible to outline their migration routes, we still have little knowledge of how they select their foraging grounds and adapt their migration to dynamic environmental conditions. Here, we analyzed the trajectories and diving behavior of 19 adult green turtles (Chelonia mydas) during their post-nesting migration from French Guiana and Suriname to their foraging grounds off the coast of Brazil. First Passage Time analysis was used to identify foraging areas located off Ceará state of Brazil, where the associated habitat corresponds to favorable conditions for seagrass growth, i.e. clear and shallow waters. The dispersal and diving patterns of the turtles revealed several behavioral adaptations to the strong hydrodynamic processes induced by both the North Brazil current and the Amazon River plume. All green turtles migrated south-eastward after the nesting season, confirming that they coped with the strong counter North Brazil current by using a tight corridor close to the shore. The time spent within the Amazon plume also altered the location of their feeding habitats as the longer individuals stayed within the plume, the sooner they initiated foraging. The green turtles performed deeper and shorter dives while crossing the mouth of the Amazon, a strategy which would help turtles avoid the most turbulent upper surface layers of the plume. These adjustments reveal the remarkable plasticity of this green turtle population when reducing energy costs induced by migration. © 2015 Chambault et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Soubeyran Y.,Comite francais de lUICN | Meyer J.-Y.,British Petroleum | Lebouvier M.,French National Center for Scientific Research | De Thoisy B.,Association Kwata | And 3 more authors.
Biological Invasions | Year: 2014

Invasive alien species (IAS) are one of the most serious threats to the rich and unique biodiversity of the 13 French overseas territories (FOTs) scattered across three oceans and two continents. To address this critical issue, a dedicated Initiative has been conducted since 2005, with the support of a large panel of national and local experts and stakeholders. This paper summarizes the main results and benefits of this project after 7 years. As a first phase, an unprecedented overview of IAS and their impacts in all the FOTs was achieved. A total of 630 alien taxa were recorded, among which 258 plants, 52 terrestrial vertebrates and 32 invertebrates were identified as a threat, or a potential threat, to native species and/or natural habitats. Gaps in the knowledge about invasive species were also highlighted and a comprehensive set of recommendations was developed. Using a range of targeted collaborative actions and promoting the exchange of information and regional cooperation, the Initiative raised awareness of invasive species issues, improved access to information and strengthened local and regional capacities. In this paper, we report on the outcomes of the Initiative and what remains to be done with regards to the prevention of new introductions, early detection, rapid response and public awareness, as well as future challenges. © 2014 Springer International Publishing Switzerland. Source


Chambault P.,CNRS Hubert Curien Multi-disciplinary Institute | de Thoisy B.,Association Kwata | Heerah K.,LOCEAN UMR 7159 | Conchon A.,Collecte Localisation Satellites | And 8 more authors.
Progress in Oceanography | Year: 2016

The circulation in the Western Equatorial Atlantic is characterized by a highly dynamic mesoscale activity that shapes the Guiana continental shelf. Olive ridley sea turtles (Lepidochelys olivacea) nesting in French Guiana cross this turbulent environment during their post-nesting migration. We studied how oceanographic and biological conditions drove the foraging behavior of 18 adult females, using satellite telemetry, remote sensing data (sea surface temperature, sea surface height, current velocity and euphotic depth), simulations of micronekton biomass (pelagic organisms) and in situ records (water temperature and salinity). The occurrence of foraging events throughout migration was located using Residence Time analysis, while an innovative proxy of the hunting time within a dive was used to identify and quantify foraging events during dives. Olive ridleys migrated northwestwards using the Guiana current and remained on the continental shelf at the edge of eddies formed by the North Brazil retroflection, an area characterized by low turbulence and high micronekton biomass. They performed mainly pelagic dives, hunting for an average 77% of their time. Hunting time within a dive increased with shallower euphotic depth and with lower water temperatures, and mean hunting depth increased with deeper thermocline. This is the first study to quantify foraging activity within dives in olive ridleys, and reveals the crucial role played by the thermocline on the foraging behavior of this carnivorous species. This study also provides novel and detailed data describing how turtles actively use oceanographic structures during post-nesting migration. © 2016 Elsevier Ltd. Source


Soubeyran Y.,Comite francais de lUICN | Meyer J.-Y.,British Petroleum | Lebouvier M.,French National Center for Scientific Research | De Thoisy B.,Association Kwata | And 3 more authors.
Biological Invasions | Year: 2014

Invasive alien species (IAS) are one of the most serious threats to the rich and unique biodiversity of the 13 French overseas territories (FOTs) scattered across three oceans and two continents. To address this critical issue, a dedicated Initiative has been conducted since 2005, with the support of a large panel of national and local experts and stakeholders. This paper summarizes the main results and benefits of this project after 7 years. As a first phase, an unprecedented overview of IAS and their impacts in all the FOTs was achieved. A total of 630 alien taxa were recorded, among which 258 plants, 52 terrestrial vertebrates and 32 invertebrates were identified as a threat, or a potential threat, to native species and/or natural habitats. Gaps in the knowledge about invasive species were also highlighted and a comprehensive set of recommendations was developed. Using a range of targeted collaborative actions and promoting the exchange of information and regional cooperation, the Initiative raised awareness of invasive species issues, improved access to information and strengthened local and regional capacities. In this paper, we report on the outcomes of the Initiative and what remains to be done with regards to the prevention of new introductions, early detection, rapid response and public awareness, as well as future challenges. © 2014, Springer International Publishing Switzerland. Source


Clement L.,Association Kwata | Catzeflis F.,Montpellier University | Richard-Hansen C.,ONCFS Direction Etudes et Recherches | Barrioz S.,Association Kwata | de Thoisy B.,Association Kwata
Tropical Conservation Science | Year: 2014

Species Distribution Models (SDMs) have become increasingly useful for conservation issues. Initially designed to predict distributions of species from incomplete datasets, SDMs may also identify environmental conditions associated with higher occurrences and abundances of widely distributed taxa. Using sighting records of 15 widely distributed mammals from French Guiana, including primates, carnivores, rodents and ungulates, we used three SDMs --based on (i) entropy, (ii) genetic algorithm, (iii) Mahalanobis distance -- to investigate relationships between species occurrence and predictive variables such as vegetation, biogeographic units, climate, and disturbance index. Maximal entropy procedures resulted in more accurate projected conditions: the accuracy of the predicted distributions was higher than 90% in nine species among the 15 tested, and predicted occurrences were correlated to fieldmeasured abundances for nine species. The Genetic algorithm implemented with GARP had lower accuracy, with predicted occurrences correlated to abundances for three species only. Finally, Mahalanobis distance had a much lower performance and failed to find any correlation between occurrences and abundances. In the case of MaxEnt modelling, since map projection summarized more appropriate environmental conditions and identified areas likely to act as sources and/or corridors, we propose to use those appropriate environmental conditions as a proxy of conductance for landscape connectivity planning. We provide evidence here that SDMs can identify not only more suitable environmental conditions, but also areas hosting higher abundances for a large set of species with key ecological roles. Further management applications of this environmental suitability index could help in designing corridors between protected areas. © Luc Clément, François Catzeflis, Cécile Richard-Hansen, Sébastien Barrioz, Benoit de Thoisy. Source

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