Finding One's Mate in a King Penguin Colony: Efficiency of Acoustic Communication

Abstract

Abstract In the king penguin, during the three months of incubation and the brooding stage, members of a pair alternate care duties on land with foraging trips. Contrary to most of the species of birds that nest at a fixed location, the king penguin carries its egg on its feet during incubation. This allows the incubating parents to move in the colony. Brooding or incubating parents moved on average 4.4 meters between egg-laying and the end of the brooding stage. This movement in a group of thousands of other birds reduced the reliability of visual cues for recovering the pair mate during the change-over. We showed that the difficulty in relocating the mate was more important during the brooding stage than during incubating. We confirmed earlier findings that acoustic communication was the main mode of communication during a change-over, and showed that the omnidirectional properties of sound allowed birds to reach more than five hundred other birds with each emitted call. Our experiments proved that the communication system is performed at short or medium range. On average, the birds identified their mate at a distance of 8.8 m. Seventy percent of the birds started the acoustic search of their mate when the distance was shorter or equal to this discrimination range, and so acoustic communication is a particularly efficient strategy in the king penguin. Chez le manchot royal (Aptenodytes patagonicus) le male et la femelle participent tous deux a l'incubation et a l'elevage du poussin. Si en general les oiseaux possedent un nid dont la position fixe aide les deux partenaires a se retrouver lors des releves, le manchot royal est une des rares especes sans nid. En effet, l'adulte incube et protege son oeuf ou son poussin sur ses pattes ce qui lui permet de se deplacer dans la colonie. Nous avons mesure un deplacement moyen de 4.4 metres entre le moment de la ponte et la fin de l'elevage individuel. Ce deplacement parmis des milliers d'autres oiseaux morphologiquement semblables rend tous reperes visuels inutilisables lors des releves entre male et femelle. Pour se reconnaitre individuellement, les manchots utilisent une signature acoustique. Nous avons montre que les proprietes omnidirectionelles du son permettent au manchot qui cherche son partenaire de communiquer potentiellement avec plus de 500 oiseaux pour chaque chant emis. La degradation rapide de la signature lors de la propagation du signal dans la colonie ne permet pas une communication a longue distance: les oiseaux identifient le chant de leur partenaires a une distance moyenne de 8.8 metres. La majorite des manchots royaux (70%) commencent a chanter a une distance inferieure ou egale a la portee du signal ce qui revele une strategie de communication particulierement efficace.