Good fences make good neighbours: territorial male Cape fur seals use spatial acoustic map of neighbours

In territorial species, individual recognition among neighbouring males is likely to reduce energy expenses and risk of injury associated with the costly period of maintaining territory during the breeding season. This study explored neighbour–stranger vocal recognition in male Cape fur seals, one of the most colonial and polygynous mammals. Playback experiments revealed that territorial males were able to recognise the calls of their neighbours, in combination with their relative spatial position to their own harem. No ‘dear-enemy’ nor ‘nasty neighbour’ effects were detected. However, the strongest responses observed were towards the calls of familiar neighbours played back from an incongruent location, simulating a situation in which a neighbour is outside its own territory. The colony structure and movements of the seals across the day could explain such results. This study has implications for understanding how vocal signals regulate interactions among males in polygynous mammals, particularly during the competitive mating period.