Not friends, just roommates: social organisation of two South American sea lion non-breeding colonies

Abstract

Groups of male South American sea lions (Otaria flavescens; SSLs) congregate in harbours on the northern coast of Argentina. These groups are very dynamic, with a high degree of habituation to human activities and the ability to colonise different types of artificial substrates, making them an interesting subject for understanding individual association patterns and spatio-temporal variations in this species. In the present study, we recorded the associations between individual bleach-marked SSLs in the harbours of Mar del Plata (PM) and Puerto Quequén (PQ) on four different substrate types during four non-breeding seasons. We found that the association pattern differed between the harbours, with a well-differentiated social structure being evident in PM but very little social differentiation occurring in PQ. The observed social structure in PM may have resulted from passive habitat preference rather than genuine social behaviour, as the association pattern disappeared when SSLs moved to sandy beaches within the harbour. Given that these colonies are must-see tourist attractions but may have negative interactions with human activities, we recommend considering the association between SSLs and artificial habitats to design effective management strategies and reduce potential conflicts.