Julian Kapoor: Cornell University

Among animals that develop signals through social learning, dialects – shared signals among a subset of individuals within a larger population – are nearly ubiquitous. Despite the prevalence of dialects across social animal species ranging from hummingbirds to whales to humans, the functional significance of such variation remains elusive; do dialects reflect an evolutionarily adaptive process, or are they simply the result of randomly generated variation in signals? The majority of scientific attention has focused on the broad-scale patterns of regional dialects, where it is thought that the process of cultural drift is a major driver of divergence. Relatively little work, however, has sought to explain the existence of fine-scale dialects between sets of individuals within social groups. In my talk, I will explain the evolutionary mechanisms leading to microgeographic vocal dialects among a group-living species of tropical hummingbird, the little hermit. Specifically, I will address tests of the ideas that microgeographic dialects might represent 1) strategic avoidance of superior competitors, 2) the effects of spatial and temporal queuing for status within the social group, 3) the result of sexual selection for increased signal salience to receivers, or 4) the effects of deceptive mimicry. Finally, I will discuss the implications of my findings for the evolution of vocal learning in social organisms.