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Saint-Denis-d'Oléron, France

Ballorain K.,University of Strasbourg | Ballorain K.,French National Center for Scientific Research | Ballorain K.,University of Reunion Island | Ciccione S.,Kelonia | And 6 more authors.
Marine Biology | Year: 2010

We investigated the habitat use in green turtles exploiting a 13-ha multispecific seagrass meadow at Mayotte Island, south-western Indian Ocean. A phyto-ecological survey shows the occurrence of eight seagrass species, dominated by Halodule uninervis and Syringodium isoetifolium, distributed according to four distinct seagrass communities along the depth gradient. Direct underwater censuses show that green turtles occurred all over the meadow. Yet when community relative surface area was taken into account green turtles preferentially frequented the most seaward, biomass-richer S. isoetifolium-dominated community, suggesting that green turtles compensate for their intrinsically nutrient-poor herbivorous diet. Additionally, smaller (<80 cm standard curved carapace length, SCCL) individuals also preferentially occurred in the most shoreward H. univervis-dominated community where no larger (>80 cm SCCL) individuals were sighted, suggesting habitat use is indicative of diet selection and may reflect size-specific food requirements and physiology. © 2010 Springer-Verlag. Source


Dalleau M.,University of Reunion Island | Dalleau M.,Center dEcologie Fonctionnelle et Evolutive | Dalleau M.,French Research Institute for Exploitation of the Sea | Ciccione S.,Kelonia | And 5 more authors.
PLoS ONE | Year: 2012

Changes in phenology, the timing of seasonal activities, are among the most frequently observed responses to environmental disturbances and in marine species are known to occur in response to climate changes that directly affects ocean temperature, biogeochemical composition and sea level. We examined nesting seasonality data from long-term studies at 8 green turtle (Chelonia mydas) rookeries that include 21 specific nesting sites in the South-West Indian Ocean (SWIO). We demonstrated that temperature drives patterns of nesting seasonality at the regional scale. We found a significant correlation between mean annual Sea Surface Temperature (SST) and dates of peak nesting with rookeries exposed to higher SST having a delayed nesting peak. This supports the hypothesis that temperature is the main factor determining peak nesting dates. We also demonstrated a spatial synchrony in nesting activity amongst multiple rookeries in the northern part of the SWIO (Aldabra, Glorieuses, Mohéli, Mayotte) but not with the eastern and southern rookeries (Europa, Tromelin), differences which could be attributed to females with sharply different adult foraging conditions. However, we did not detect a temporal trend in the nesting peak date over the study period or an inter-annual relation between nesting peak date and SST. The findings of our study provide a better understanding of the processes that drive marine species phenology. The findings will also help to predict their ability to cope with climate change and other environmental perturbations. Despite demonstrating this spatial shift in nesting phenology, no trend in the alteration of nesting dates over more than 20 years was found. © 2012 Dalleau et al. Source


Scott R.,University of Exeter | Scott R.,University of Swansea | Hodgson D.J.,University of Exeter | Witt M.J.,University of Exeter | And 15 more authors.
Global Ecology and Biogeography | Year: 2012

Aim Tracking technologies are often proposed as a method to elucidate the complex migratory life histories of migratory marine vertebrates, allowing spatially explicit threats to be identified and mitigated. We conducted a global analysis of foraging areas of adult green turtles (Chelonia mydas) subject to satellite tracking (n= 145) and the conservation designation of these areas according to International Union for Conservation of Nature criteria. Location The green turtle has a largely circumtropical distribution, with adults migrating up to thousands of kilometres between nesting beaches and foraging areas, typically in neritic seagrass or algal beds. Methods We undertook an assessment of satellite tracking projects that followed the movements of green turtles in tropical and subtropical habitats. This approach was facilitated by the use of the Satellite Tracking and Analysis Tool (http://www.seaturtle.org) and the integration of publicly available data on Marine Protected Areas (MPAs). Results We show that turtles aggregate in designated MPAs far more than would be expected by chance when considered globally (35% of all turtles were located within MPAs) or separately by ocean basin (Atlantic 67%, Indian 34%, Mediterranean 19%, Pacific 16%). Furthermore, we show that the size, level of protection and time of establishment of MPAs affects the likelihood of MPAs containing foraging turtles, highlighting the importance of large, well-established reserves. Main conclusions Our findings constitute compelling evidence of the world-wide effectiveness of extant MPAs in circumscribing important foraging habitats for a marine megavertebrate. © 2012 Blackwell Publishing Ltd. Source


Dalleau M.,University of Reunion Island | Dalleau M.,Center dEcologie Fonctionnelle et Evolutive | Dalleau M.,French Research Institute for Exploitation of the Sea | Benhamou S.,Center dEcologie Fonctionnelle et Evolutive | And 3 more authors.
Marine Biology | Year: 2014

While our understanding of the early oceanic developmental stage of sea turtles has improved markedly over recent decades, the spatial context for this life history stage remains unknown for Indian Ocean loggerhead turtle populations. To address this gap in our knowledge, 18 juvenile loggerheads were satellite tracked from Reunion Island (21.2°S, 55.3°E) between 2007 and 2011. Nine turtles swam north toward Oman (20.5°N, 58.8°E), where one of the world's largest rookeries of loggerheads is located. Three individuals traveled south toward South Africa and Madagascar, countries that also host loggerhead nesting grounds. Fourteen of the transmitters relayed diving profiles. A dichotomy between diurnal and nocturnal diving behavior was observed with a larger number of shorter dives occurring during the day. Diving behavior also differed according to movement behavior as individuals spent more time in subsurface waters (between 10 and 20 m) during transit phases. The study provides an understanding of the oceanic movement behavior of juvenile loggerheads in the Indian Ocean that suggests the existence of an atypical trans-equatorial developmental cycle for the species at the ocean basin scale in the Indian Ocean. These results address a significant gap in the understanding of loggerhead oceanic movements and may help with the conservation of the species. © 2014 Springer-Verlag Berlin Heidelberg. Source


Enstipp M.R.,CNRS Hubert Curien Multi-disciplinary Institute | Ballorain K.,CNRS Hubert Curien Multi-disciplinary Institute | Ciccione S.,Kelonia | Narazaki T.,University of Tokyo | And 2 more authors.
Functional Ecology | Year: 2016

Measuring the energy requirements of animals under natural conditions and determining how acquired energy is allocated to specific activities is a central theme in ecophysiology. Turtle reproductive output is fundamentally linked with their energy balance so a detailed understanding of marine turtle energy requirements during the different phases of their life cycle at sea is essential for their conservation. We used the non-invasive accelerometry technique to investigate the activity patterns and energy expenditure (EE) of adult green turtles (Chelonia mydas) foraging year-round at a seagrass meadow in Mayotte (n = 13) and during simulated oceanic migration (displacement from the nesting beach) off Mohéli (n = 1), in the south-western Indian Ocean. At the foraging site, turtles divided their days between foraging benthically on the shallow seagrass meadow during daylight hours and resting at greater depth on the inner side of the reef slope at night. Estimated oxygen consumption rates (sV˙O2) and daily energy expenditures (DEE) at the foraging site were low (sV˙O2 during the day was 1·6 and 1·9 times the respective resting rate at night during the austral summer and winter, respectively), which is consistent with the requirement to build up substantial energy reserves at the foraging site, to sustain the energy-demanding breeding migration and reproduction. Dive duration (but not dive depth) at the foraging site shifted significantly with season (dive duration increased with declining water temperatures, Tw), while overall activity levels remained unchanged. In parallel with a significant seasonal decline in Tw (from 28·9 ± 0·1 °C to 25·3 ± 0·4 °C), there was a moderate (˜19%) but significant decline in DEE of turtles during the austral winter (901 ± 111 kJ day-1), when compared with the austral summer (1117 ± 66 kJ day-1). By contrast, the turtle moved continuously during simulated oceanic migration, conducting short/shallow dives in the day, which (predominately at night) were interspersed with longer and deeper 'pelagic' dives. Estimated oxygen consumption rates during a simulated migration (1·25 ± 0·16 mL O2 min-1 kg-0·83) were found to be significantly increased over the foraging condition, equal to ˜3 times the resting rate at night (0·42 ± 0·02 mL O2 min-1 kg-0·83), and daily energy expenditure amounted to 2327 ± 292 kJ day-1, underlining the tremendous energetic effort associated with breeding migration. Our study indicates that the accelerometry technique provides a new and promising opportunity to study marine turtle energy relations in great detail and under natural conditions. © 2016 British Ecological Society. Source

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