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The Journal of Experimental Biology 205, 3793-3798 (2002)
Copyright © 2002 The Company of Biologists Limited

Localisation of an acoustic signal in a noisy environment: the display call of the king penguin Aptenodytes patagonicus

Thierry Aubin1,* and Pierre Jouventin2

1 CNRS-NAMC, UMR 8620, Université Paris-Sud, F-91405 Orsay Cedex, France
2 CNRS-CEFE, UPR 9056, 1919 Route de Mende, 34293 Montpellier, France

* Author for correspondence (e-mail: thierry.aubin{at}ibaic.u-psud.fr)

Accepted 19 September 2002

King penguin chicks identify their parents by an acoustic signal, the display call. This call consists of a succession of similar syllables. Each syllable has two harmonic series, strongly modulated in frequency and amplitude, with added beats of varying amplitude generated by a two-voice system. Previous work showed that only one syllable of the call is needed for the chick to identify the calling adult. Both the frequency modulation pattern of the syllable and the two-voice system play a role in the call identification. The syllabic organisation of the call, the harmonic structure and the amplitude modulations of the syllables apparently do not contribute to individual recognition. Are these acoustic features useless? To answer to this question, playback experiments were conducted using three categories of experimental signals: (i) signal with only the fundamental frequencies of the natural call, (ii) signal with the amplitude of each syllable kept at a constant level and (iii) signals with only one syllable, repeated or not. The responses of chicks to these experimental signals were compared to those obtained with the calls of their natural parents. We found that these acoustic features, while not directly implicated in the individual recognition process, help the chicks to better localise the signal of their parents. In addition, the redundant syllabic organisation of the call is a means of counteracting the masking effect of the background noise of the colony.

Key words: sound localisation, communication in noise, individual recognition, king penguin, Aptenodytes patagonicus






© The Company of Biologists Ltd 2002