Vocal recognition of distance calls in a group-living basal bird: the greylag goose, Anser anser

Vocal communication in group-living animals represents a major challenge when multiple individuals call simultaneously and generate a complex soundscape. Decoding relevant information from a vocal signal and its emitter can determine the survival of the receiver. In hierarchical social groups, information on sex, size and age can provide relevant context for vocal signals. Ultimately, individual vocal recognition is a keystone in vocal communication systems, especially in the context of sociality. Greylag geese (Aves: Anseriformes) are a basal, gregarious and highly social species, and adults produce a distance call when approaching or leaving the flock. In this study we (1) quantified the acoustic properties of distance calls to test whether they can provide information on the sex, size and age of the emitter, (2) evaluated whether distance calls have individual properties, from the sender's perspective, (3) tested whether receivers discriminate distance calls depending on the emitter's identity and (4) explored whether an individual's response strength towards its partner's distance call is associated with fitness-related traits (i.e. pair bond duration and average number of offspring per year). We recorded distance calls of individually marked geese, quantified the variation in call acoustic properties and carried out a playback experiment in the wild. Distance calls encoded information about the sex of the goose, but not its age or size. From the emitter's perspective, we found some support for individuality in distance calls. From the receiver's perspective, geese were capable of recognizing distance calls from different individuals. Finally, the response strength towards playback of the partner's call was positively correlated with pair bond duration. Vocal recognition has been proposed to be tightly related to social structure, the evolution of sociality and vocal learning. Here, we uncovered vocal recognition of individual affiliative calls in a social bird from the most basal avian group studied so far.