Current-following behaviour during maiden foraging trips predicts survival in naive marine mammals.

Abstract

Identifying the determinants of juvenile survival is crucial for understanding the population ecology of long-lived species, where parental guidance can influence naive juvenile survival rates. In southern elephant seals (Mirounga leonina), offspring receive no foraging site knowledge from their parents, only fat reserves. We focus on how movement patterns during the pups' maiden foraging trip influence their survival at Macquarie Island. We tracked weaned pups with satellite tags during their post-weaning migration and compared their movements to the post-moult winter migrations of adult females. We found that pups travelled predominantly in an easterly to south-easterly direction, in line with the Antarctic Circumpolar Current. The Antarctic Circumpolar Current may provide a passive survival advantage for naive pups, with current-following predicting survival probability. We propose an "accessibility area" concept in which currents expand the foraging area accessible to energy-limited pups, providing a theoretical framework that may apply broadly to marine species with naive dispersing juveniles. Adult females showed different dispersal patterns, travelling southwards towards Antarctic waters, suggesting that learned experience may influence their direction.