Swimming with the current improves juvenile survival in southern elephant seals

Foo, D.; McMahon, C. R.; Hindell, M. A.; Fedak, M.; Biuw, M.; McConnell, B.; Raymond, B.

Understanding juvenile survival is crucial for the population ecology of long-lived species, where parental guidance can significantly influence survival rates of completely naive juveniles. In southern elephant seals (Mirounga leonina), however, offspring receive no knowledge from their parents, only fat reserves. This research focuses on how movement choices and physical characteristics affect the first trip and first year survival of naive southern elephant seal pups at Macquarie Island. We tracked 44 pups with satellite tags during their maiden foraging trip and compared their movements to the post-moult winter migrations of 58 adult females. We found that most pups (61.2%) moved southeast initially, in line with the Antarctic Circumpolar Current. Pups travelling with the predominant east-southeast current had a 1.5 times higher survival rate for their first trip than those swimming westward against it. Those that swam with the current and were heavier were more likely to survive their first year. Adult females showed different dispersal patterns, where they travelled southwards towards Antarctic waters, implying that learning from experience influences their direction. Future investigations into the role of the primary eastward current in the sub-Antarctic on circumpolar movement patterns of top marine predators could expand our understanding of Southern Ocean ecology.