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Chambault P.,CNRS Hubert Curien Multi-disciplinary Institute | Pinaud D.,CNRS Chizé 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.


De Thoisy B.,Institute Pasteur Of La Guyane | Matheus S.,Institute Pasteur Of La Guyane | Catzeflis F.,Institute Des Science Of Levolution | Clement L.,Association Kwata | And 8 more authors.
American Journal of Tropical Medicine and Hygiene | Year: 2014

A molecular screening of wild-caught rodents was conducted in French Guiana, South America to identify hosts of the hantavirus Maripa described in 2008 in a hantavirus pulmonary syndrome (HPS) case. Over a 9-year period, 418 echimyids and murids were captured. Viral RNA was detected in two sigmodontine rodents, Oligoryzomys fulvescens and Zygodontomys brevicauda, trapped close to the house of a second HPS case that occurred in 2009 and an O. fulvescens close to the fourth HPS case identified in 2013. Sequences from the rodents had 96% and 97% nucleotide identity (fragment of S and M segments, respectively) with the sequence of the first human HPS case. Phylogenetic reconstructions based on the complete sequence of the S segment show that Maripa virus is closely related to Rio Mamore hantavirus. Using environmental descriptors of trapping sites, including vegetation, landscape units, rain, and human disturbance, a maximal entropy-based species distribution model allowed for identification of areas of higher predicted occurrence of the two rodents, where emergence risks of Maripa virus are expected to be higher. Copyright © 2014 by The American Society of Tropical Medicine and Hygiene.


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.


PubMed | Collecte Localisation Satellites, CNRS Hubert Curien Multi-disciplinary Institute, British Petroleum, WWF Guianas and 4 more.
Type: Journal Article | Journal: 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 Cear 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.


Baudouin M.,French National Center for Scientific Research | de Thoisy B.,Association Kwata | Chambault P.,French National Center for Scientific Research | Berzins R.,Office National de la Chasse et de la Faune Sauvage Cellule technique | And 5 more authors.
Biological Conservation | Year: 2015

The green turtle (. Chelonia mydas) is classified as an endangered species on the IUCN Red List since 1986. This species is especially threatened in South America due to bycatch by fisheries along the northeastern coasts. It is particularly crucial to identify specific marine areas for conservation measures to safeguard green turtle rookeries in Suriname and French Guiana. Our study provides valuable information to attain this goal, describing the satellite tracking of post-nesting migration routes used by 16 green turtles fitted with Argos/GPS Fastloc satellite tags at the end of the nesting season. The data we obtained show a single migratory corridor: all the turtles followed a similar eastward route along the Guianan and the Brazilian coast. The GPS signal was lost for two individuals a few weeks after tracking commenced, suggesting that they were caught by fishermen. Thirteen turtles reached the coast of the state of Ceará (Brazil), where they spent at least one month. One turtle continued 700. km further to the coastal regions of Natal and Recife (Brazil), which are known feeding areas of the green turtle populations nesting on Ascension Island. The migratory corridor is essentially narrow, with a width of 22. km for most of the distance covered. It constitutes a major dynamic link between the nesting and feeding areas and crosses three Regional Management Units of the Atlantic basin. Since green turtles face a high risk of being caught in fishing nets, measures of protection should be implemented along this corridor. © 2015 Elsevier Ltd.


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.


Soubeyran Y.,Comite francais de l'UICN | 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.


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.


Chambault P.,CNRS Hubert Curien Multi-disciplinary Institute | De Thoisy B.,Association Kwata | Kelle L.,WWF Guyane | Berzins R.,British Petroleum | And 4 more authors.
Marine Ecology Progress Series | Year: 2016

Sea turtles adjust their behaviour according to the conditions of their habitat, thus saving or gaining energy during the energetically costly inter-nesting season. This study aimed to investigate how gravid green turtles Chelonia mydas nesting in Suriname and French Guiana have adapted to the unusual habitat of the Maroni River estuary, which has highly turbid and low salinity waters and a priori lacks seagrass, one of the main foods consumed by this species. Satellite telemetry was used to assess the behavioural adjustments of 26 adult females in terms of (1) home range and (2) diving behaviour, by recording the movements (location, dive depth, dive duration, surface duration) and environmental conditions (temperature and salinity of the water) experienced by each individual. The turtles exhibited limited movements, occupying a core home range of 512.7 km2 and remaining close to the shore (3.8 ± 3.1 km) and the nesting beach (18.6 ± 22.7 km). Dive data showed that individuals spent extended periods at the surface (210 ± 288 min), probably associated with diurnal resting activity. The turtles performed uncharacteristically short and shallow dives (<5 min and <2 m) which could result from lung volume issues linked to positive buoyancy. This species shows a unique ability to tolerate extreme environments in this internesting habitat, where large river outputs generate warm water (∼27 to 29°C) and highly variable salinities (range: 1.2 to 35.5 psu). These results highlight the various behavioural adjustments of this population in response to the atypical and estuarine habitat of the Maroni river mouth. © Inter-Research 2016.

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