Étude de la biologie et de la vulnérabilité au développement anthropique des oiseaux marins nocturnes à La Réunion

The biodiversity is currently threatened by human activities. As they depend both of marine and terrestrial habitats, seabirds are particularly exposed to human pressures. In Reunion Island, the consequences of the urbanization on populations are unknown. For conservation and environmental assessment purposes, accurate information on the species repartition, flight patterns and vulnerability to infrastructure is required. The goals of this thesis are to update biological information on species and to assess the vulnerability of nocturnal seabirds of Reunion Island exposed to infrastructure. We studied the evolution of the size and the repartition of the colonies of tropical shearwater Puffinus bailloni at the scale of the entire island over a 19-years period. The flight patterns of tropical shearwater and Barau's petrel Pterodroma baraui were described with radar technology at different spatial and temporal scales. Our results show an apparent stability of the tropical shearwater population despite an important light pollution. Tropical shearwater and Barau’s petrel present specific flight patterns. The estimated census of Barau's petrel suggests a population size higher than current estimation whereas the estimated census of tropical shearwater is reliable to current estimations. Barau's petrels' juveniles mostly take off during the first hours of the night. Decision making tools have been produced. Our study also highlights the need to conduct further fundamental and applied researches.La biodiversité est actuellement fortement menacée par les activités humaines. Dépendant des milieux marins et terrestres, les oiseaux marins sont particulièrement exposés aux pressions anthropiques. À La Réunion, les conséquences des impacts des aménagements sur les populations restent méconnues. Dans une optique de conservation et de réalisation d'études environnementales pertinentes, des informations fiables sur la répartition des espèces, sur leur comportement de vol et une évaluation de leur vulnérabilité vis-à-vis des aménagements sont nécessaires. Les objectifs de cette thèse sont de préciser des données biologiques et d'évaluer la vulnérabilité des oiseaux marins nocturnes de La Réunion face aux aménagements. Nous avons étudié l'évolution de la taille et de la répartition des colonies de puffin tropical Puffinus bailloni à l'échelle de l'île sur une période de 19 ans. Les patterns de vol du puffin tropical et du pétrel de Barau Pterodroma baraui ont été caractérisés par imagerie radar à différentes échelles temporelles et spatiales. Nos résultats montrent une stabilité apparente de la population de puffin tropical malgré la forte pollution lumineuse. Le puffin tropical et le pétrel de Barau présentent des patterns de vol spécifiques. Les effectifs estimés de pétrel de Barau suggèrent une population plus importante que celle connue actuellement. Les effectifs estimés de puffin tropical sont cohérents avec les estimations actuelles. Les jeunes pétrels de Barau s'envolent principalement durant les premières heures de la nuit. Des outils d'aide à la décision ont été produits. Nos travaux soulèvent la nécessité de poursuivre des recherches fondamentales et appliquées

Breeding status affects the hormonal and metabolic response to acute stress in a long-lived seabird, the king penguin

International audienceStress responses are suggested to physiologically underlie parental decisions promoting the redirection ofbehaviour away from offspring care when survival is jeopardized (e.g., when facing a predator). Besidesthis classical view, the ‘‘brood-value hypothesis” suggests that parents’ stress responses may be adaptivelyattenuated to increase fitness, ensuring continued breeding when the relative value of the broodis high. Here, we test the brood-value hypothesis in breeding king penguins (Aptenodytes patagonicus),long-lived seabirds for which the energy commitment to reproduction is high. We subjected birds atdifferent breeding stages (courtship, incubation and chick brooding) to an acute 30-min capture stressand measured their hormonal (corticosterone, CORT) and metabolic (non-esterified fatty acid, NEFA)responses to stress. We found that CORT responses were markedly attenuated in chick-brooding birdswhen compared to earlier stages of breeding (courtship and incubation). In addition, NEFA responsesappeared to be rapidly attenuated in incubating and brooding birds, but a progressive increase inNEFA plasma levels in courting birds suggested energy mobilization to deal with the threat. Our resultssupport the idea that stress responses may constitute an important life-history mechanism mediatingparental reproductive decisions in relation to their expected fitness outcom

First automatic passive acoustic tool for monitoring two species of procellarides (Pterodroma baraui and Puffinus bailloni) on Reunion Island, Indian Ocean

International audienceHere are proposed two automatic detectors of Barau's petrel (Pterodroma baraui) and tropical shearwater (Puffinus bailloni) vocalisations in noisy audio recordings (1) trained with a low number of positive training instances, and (2) whose performances would be the highest possible. To do so, acoustic recordings were performed in one Barau's petrel colony between February and May 2014 (85 h) and in two tropical shearwater colonies in March and April (21 h). Manual and automatic methods of segmentation were combined. Manual segmentation allowed (1) to miss a very few number of positive segments and (2) to avoid introducing false positive instances. Automatic segmentation provided quickly a diversified set of negative instances. Manual labelling must be regarded as an investment, for current and future works. A random forest classifier and classical methods of acoustic signal characterisation (cepstral coefficients, spectral moments, etc.) were tested. Best models were able to discriminate each target species calls from other sounds of its colony with F1 scores of 88% (Barau's petrel, 1015 samples) and 85% (tropical shearwater, 1217 samples). The acoustic monitoring of nocturnal burrow-nesting seabirds based on (1) data collected by autonomous recording units in harsh, windy and wet environments and (2) automatic analysis tools is feasible. The size of our database was limited. Consequently further works will be necessary to study robustness of models on long time-series data

Energy expenditure of freely swimming adult green turtles (Chelonia mydas) and its link with body acceleration.

International audienceMarine turtles are globally threatened. Crucial for the conservation of these large ectotherms is a detailed knowledge of their energy relationships, especially their at-sea metabolic rates, which will ultimately define population structure and size. Measuring metabolic rates in free-ranging aquatic animals, however, remains a challenge. Hence, it is not surprising that for most marine turtle species we know little about the energetic requirements of adults at sea. Recently, accelerometry has emerged as a promising tool for estimating activity-specific metabolic rates of animals in the field. Accelerometry allows quantification of the movement of animals (ODBA/PDBA, overall/partial dynamic body acceleration), which, after calibration, might serve as a proxy for metabolic rate. We measured oxygen consumption rates ( ) of adult green turtles (Chelonia mydas; 142.1±26.9 kg) at rest and when swimming within a 13 m-long swim channel, using flow-through respirometry. We investigated the effect of water temperature (T(w)) on turtle and tested the hypothesis that turtle body acceleration can be used as a proxy for . Mean mass-specific ( ) of six turtles when resting at a T(w) of 25.8±1.0°C was 0.50±0.09 ml min(-1) kg(-0.83). increased significantly with T(w) and activity level. Changes in were paralleled by changes in respiratory frequency (f(R)). Deploying bi-axial accelerometers in conjunction with respirometry, we found a significant positive relationship between and PDBA that was modified by T(w). The resulting predictive equation was highly significant (r(2)=0.83, P<0.0001) and associated error estimates were small (mean algebraic error 3.3%), indicating that body acceleration is a good predictor of in green turtles. Our results suggest that accelerometry is a suitable method to investigate marine turtle energetics at sea