Memory for own behaviour in pinnipeds.

Abstract

Pinnipeds are aquatic predators feeding on a vast range of prey, and their social behaviour differs greatly between species (from extreme polygyny in some sea lions to monogamy in some true seals). It has been hypothesised that the foraging and social complexity of their lifestyle should drive the evolution of their cognitive abilities. To investigate how aware pinnipeds are of their own behaviour, a grey seal (Halichoerus grypus), two harbour seals (Phoca vitulina) and four South American sea lions (Otaria flavescens) were trained to repeat their own behaviour on command. Three already trained behaviours were used, and the animal was asked to repeat the behaviour twice to ensure that the animal recalled its own behaviour and not the command given for the previous behaviour. All three species could recall their own behaviour significantly better than by chance. The duration for which the animals could recall their behaviour was tested using a staircase paradigm. A delay was implemented between the completion of the behaviour and the command to repeat it. The delay was increased after correct responses and decreased after incorrect responses. The performance of all species fell towards chance level after 12-18s, with no significant difference between species. These results indicate that sea lions and true seals are aware of their own behaviour and that true seals have similar short-term memory abilities. It also shows that pinnipeds have less developed short-term memory abilities compared to other aquatic predators, such as the bottlenose dolphin. The complexity of pinniped foraging and social behaviour does not seem to have driven the evolution of short-term memory abilities in these animals but might have contributed to their ability to recall their own behaviour.