African penguins utilize their ventral dot patterns for individual recognition

Birds are known to be highly social and visual animals. Yet no specific visual feature has been identified to be responsible for individual recognition in birds. Here, using a differential looking paradigm across five experiments, we demonstrated that African penguins, Spheniscus demersus, spontaneously discriminated between life-size photographs of their monogamous, lifelong partner and a nonpartner colonymate using their ventral dot patterns. Our findings challenge the assumption of limited visual involvement in penguin communication and suggest a rather complex and flexible recognition process in these birds. The combination of our current results and previous findings, which showed cross-modal (visual/auditory) recognition in these animals, suggests that African penguins use their ventral dot patterns to individually recognize their colonymates. Our results provide the first evidence of a specific visual cue responsible for spontaneous individual recognition by a bird, and highlight the importance of considering all sensory modalities in the study of animal communication.