Vocal repertoire of South American fur seals, Arctocephalus australis: structure, function, and context

We describe the vocal repertoire of male and female South American fur seals (Arctocephalus australis) breeding at Punta San Juan, Peru, the first such description for any member of the genus. We distinguished 11 call types, which we grouped into four functional classes: investigative, threat, submissive, and affiliative calls. Barking is used during non-agonistic investigation of other individuals. Threat calls of South American fur seals show gradation of structure, form, and apparent meaning, and are grouped into two series: nontonal or respiratory sounds, and pulsed or guttural sounds that sometimes include a terminal tonal component. This might be adaptive in enabling display behavior to be flexible in agonistic situations, allowing participants to interpret situations on the basis of contextual cues and their own physical ability and experience. In contrast, vocal displays such as submissive, full-threat, and affiliative calls tend to have a discrete acoustic structure. Of these, full-threat, female-attraction, and pup-attraction calls share acoustic characteristics: all are long, loud calls composed of both pulsed and tonal components, and show sufficient variation to allow individual recognition. We attempt to establish a base line for standardizing nomenclature and acoustic analysis, to facilitate further comparative research on the vocal repertoire of Arctocephalus species.