Vocal learning in seals, sea lions, and walruses.

The pinnipeds provide a variety of clues to those interested in the vocal learning capabilities of non-human animals. Observational and experimental studies of seals, sea lions, and walruses reveal elements of vocal development, contextual control, plasticity in expression and learning, and even imitation of complex sounds. Consideration of the factors that influence the expression of these capabilities informs understanding of the behavioral and structural mechanisms that support vocal learning in mammals and the evolutionary forces shaping these capabilities.