The ontogeny of southern elephant seal foraging migration strategies: finding their way as they go

Abstract

The roles of innate navigational abilities, environmental cues and individual learning in shaping animal habitat selection and migration strategies are poorly understood. Naïve juvenile southern elephant seals (Mirounga leonina) depart from their natal islands after weaning unaccompanied by experienced conspecifics and immediately undertake long foraging migrations into the Southern Ocean, before survivors return to their natal islands several months later. We describe 35 foraging migrations undertaken by 21 recently weaned (< 1 yr old) southern elephant seals from Marion Island and compare these with 161 foraging migrations undertaken by more experienced (71 sub-adults, 15 adult male and 37 adult females) seals. Foraging migrations of underyearlings were shorter in duration and they remained nearer to Marion Island than older seals. Subadults and adult female seals displayed similar directional travel, foraging over deep water south of the Subantarctic Front. However, underyearlings travelled in multiple directions away from the island, showing little evidence of common directional travel. Underyearlings tracked over multiple migrations during their first year at-sea displayed little repeatability in foraging ranges and substantial variation in direction and distance of travel among tracks. In contrast, older seals displayed consistency in their use of foraging ranges and high levels of repeatability in direction and distance of travel. The overall dissimilarity in movement patterns exhibited by the underyearling elephant seals when compared with more experienced seals suggest that individual foraging strategies of this species are strongly influenced by individual learning, especially during the first year of life.