Cooperative human signals to honeyguides form local dialects

Abstract Human language enables the exchange of complex information and precise instructions for collaborative planning and action. It rapidly evolves through social learning, generating diverse cultural communication signals used not only with other humans, but also with domesticated animals bred or trained to respond. More rarely, humans communicate with untrained, wild animals to coordinate joint actions, yet little is known about how or why these human‐to‐wildlife signals diversify. Human‐wildlife cooperation allows us to investigate whether human signals directed at untrained, wild animals exhibit regional variation, akin to dialects in human language. We investigated regional variation in human signals used to cooperate with greater honeyguides ( Indicator indicator ): wild birds that guide people to bees' nests in exchange for access to beeswax. Across 13 villages in northern Mozambique, we tested whether human honey‐hunting calls varied with spatial distance, as expected if regional dialects had emerged, or with measures of the physical environment affecting sound propagation, as expected if calls were shaped by habitat acoustics. Our analyses showed that trills, grunts, whoops, and whistles used while cooperating with honeyguides (i) consistently varied with spatial distance between villages, (ii) varied irrespective of the local habitat, and (iii) appeared to be adopted by immigrant honey‐hunters to match local calls. These findings suggest that regional variation in human‐to‐wildlife signals is shaped primarily by human social factors, forming a landscape of interspecific signal diversity similar to human language dialects. Honeyguides cooperate effectively with honey‐hunters throughout this landscape, suggesting that they accommodate (and likely reinforce) cultural differences by learning the local interspecies dialect. Read the free Plain Language Summary for this article on the Journal blog.