Current-following behavior during maiden foraging trips predicts survival in naïve marine mammals

Understanding the determinants of juvenile survival is crucial for the population ecology of long-lived species, where parental guidance can significantly influence the survival rates of completely naïve juveniles. In southern elephant seals ( Mirounga leonina ), offspring receive no foraging site knowledge from their parents, only fat reserves. This research focuses on how movement patterns during maiden foraging trips influence the survival of naïve southern elephant seal pups at Macquarie Island. We tracked weaned pups with satellite tags during their postweaning migration and compared their movements to the postmolt winter migrations of adult females. We found that pups traveled predominantly southeast, in line with the Antarctic Circumpolar Current. The Antarctic Circumpolar Current provides a passive survival advantage for naïve pups, with current-following being the strongest predictor of survival probability. We propose an “accessibility area” concept where currents expand the foraging area accessible to energy-limited pups, providing a theoretical framework that may apply broadly to marine species with naïve dispersing juveniles. This mechanism operates largely independently of body condition, with current-following being a stronger predictor than initial body mass is, suggesting that behavioral strategies can compensate for physiological disadvantages during critical early life stages. Adult females presented different dispersal patterns, traveling southward toward Antarctic waters, suggesting that learned experience influences their direction. Understanding these dynamics becomes increasingly important as climate change alters ocean current patterns, potentially affecting the accessible areas that have shaped marine mammal evolution.