Vocal signature recognition of mothers by fur seal pups

Subantarctic fur seals, Arctocephalus tropicalis, come ashore to breed in dense colonies and lactating females have to alternate foraging trips at sea with periods ashore during which they suckle their pups. The effectiveness of vocal recognition between mothers and pups, has been shown experimentally. To see whether the recognition abilities of females differ from those of their offspring, we investigated how pups recognize their mother's calls. We used artificially modified signals in playback experiments to determine which acoustic parameters support the recognition process. Pups used both the energy spectrum and the ascending frequency modulation occurring at the beginning of each call. However, they seemed to rely mainly on spectral analyses. The vocal identification process at a perceptual level is therefore asymmetrical, as mothers mainly use temporal structures to recognize their pup's calls. (C) 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.