RESEARCH ARTICLE Facial Recognition in a Group-Living Cichlid

The theoretical underpinnings of the mechanisms of sociality, e.g. territoriality, hierarchy, and reciprocity, are based on assumptions of individual recognition. While behavioural evi-dence suggests individual recognition is widespread, the cues that animals use to recognise individuals are established in only a handful of systems. Here, we use digital models to dem-onstrate that facial features are the visual cue used for individual recognition in the social fish Neolamprologus pulcher. Focal fish were exposed to digital images showing four differ-ent combinations of familiar and unfamiliar face and body colorations. Focal fish attended to digital models with unfamiliar faces longer and from a further distance to the model than to models with familiar faces. These results strongly suggest that fish can distinguish individu-als accurately using facial colour patterns. Our observations also suggest that fish are able to rapidly ( 0.5 sec) discriminate between familiar and unfamiliar individuals, a speed of recognition comparable to primates including humans