Drivers of behavioural transition in foraging adult female southern elephant seals (Mirounga leonina) tracked from Bouvetøya

Abstract

Southern elephant seals are abundant top trophic predators with a circumpolar distribution in the Southern Ocean. They spend up to 80% of their life at sea on long-ranging migrations to remote foraging grounds. During breeding and moulting they haulout on subantarctic islands. During these migrations they dive continuously to great depth, encountering various environmental conditions. They are further known to target frontal areas and mesoscale eddies. Due to ecosystems changing, with high latitude areas being especially sensitive, it is of major importance to understand behavioural drivers in order to predict how they will react. They display site fidelity (breeding), allowing for retrieval of telemetry tags collecting high resolution data. In this study, data from five adult female southern elephant seals tracked from Bouvetøya in 2015 were analysed. This data covered their post-moult foraging migration. By identifying changes in move persistence values along the tracks, behavioural transitions periods were extracted to study the post-moult foraging behaviour of female southern elephant seals. More specifically, the dive and feeding efficiency during transition zones, defined as significant changes horizontal movement persistence, was analysed as a function of depth and physical features such as the mixed layer depth, top of circumpolar deep water as well as subsurface maximum.