Modelling Southern Elephant Seal Foraging Behaviour: Influences of Primary Production Variability and Oceanographic Conditions

• Main Author: Dragon, Anne-Cécile
• Other Authors: Centre d'Études Biologiques de Chizé (CEBC), Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS), Mathématiques Appliquées à Paris 5 (MAP5), Institut National de la Recherche Agronomique (INRA)-Université Paris Descartes - Paris 5 (UPD5)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris VI, Christophe Guinet
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2011
• Subjects: area-restricted search; mesoscale structures; drift dive; fine scale behaviour; movement analysis; recherche en zone restreinte; structures meso-échelle; plongées de dérive; comportement à fine échelle; analyses de mouvement; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Southern Ocean; Austral; Tourbillons; Elephant Seal; Elephant Seals; Southern Elephant Seal; Southern Elephant Seals
• Online Access: https://theses.hal.science/tel-00661545; https://theses.hal.science/tel-00661545/document; https://theses.hal.science/tel-00661545/file/AC-Dragon_PhD-thesis.pdf

In the polar frontal zone of the Southern Ocean, fronts and mesoscale eddies were shown to have a significant impact in structuring and enhancing the primary productivity. They are therefore likely to influence the spatio-temporal structure of prey fields and play a key role on the creation of preferred foraging regions for oceanic top-predators. The optimal foraging theory predicts that predators should adjust their movements' behaviour in relation to prey density. While crossing areas with sufficient prey density, it is thought that those predators would change their behaviour by decreasing their displacement speed and increasing their turning frequency. Our aim was to investigate the changes in fine scale movement and diving behaviour of southern elephant seals equipped with satellite-relayed data loggers. Various statistical methods were used to estimate the foraging effort and success along tracks and dives of the seals. We finally correlated the detected foraging zones with \textit{in situ} and satellital oceanographic variables. The most favourable foraging zones were related to the presence of both cyclonic and anti-cyclonic eddies. Elephant seals used the centre and edges of cyclonic eddies but only the edges of the anti-cyclonic ones and adjusted their diving behaviour accordingly. A physical characterisation of favourable and unfavourable eddies was thus obtained which will help us to understand the foraging strategies that have been optimised along time by this population of top-predators in this complex and dynamic environment. Dans la zone interfrontale de l'Océan Austral, de grandes structures agencent la distribution spatio-temporelle des blooms phytoplanctoniques. Ces structures, à grande (fronts) et moyenne (tourbillons) échelles, amènent à une agrégation des ressources des échelons trophiques supérieurs dans les zones favorables. L'approvisionnement des prédateurs parmi ces champs repose sur une maximisation du gain énergétique net. Ainsi la concentration de la recherche d'un prédateur dans ...