Abstract
Animals that live together in groups often face difficult choices, such as which food resource to exploit, or which direction to flee in response to a predator. When there are costs associated with deadlock or group fragmentation, it is essential that the group achieves a consensus decision. Here, we study consensus formation in emigrating ant colonies faced with a binary choice between two identical nest-sites. By individually tagging each ant with a unique radio-frequency identification microchip, and then recording all ant-to-ant ‘tandem runs’—stereotyped physical interactions that communicate information about potential nest-sites—we assembled the networks that trace the spread of consensus throughout the colony. Through repeated emigrations, we show that both the order in which these networks are assembled and the position of each individual within them are consistent from emigration to emigration. We demonstrate that the formation of the consensus is delegated to an influential but exclusive minority of highly active individuals—an ‘oligarchy’—which is further divided into two subgroups, each specialized upon a different tandem running role. Finally, we show that communication primarily occurs between subgroups not within them, and further, that such between-group communication is more efficient than within-group communication.
Highlights
One of the most important life challenges faced by any animal is to find a new place to live when the current nest site becomes uninhabitable
The mechanisms that coordinate nest-site selection and colony emigration have been most thoroughly studied in ants of the genus Temnothorax [2,3,4] and in the honey bee [5,6]
In colonies of Temnothorax ants a key stage in colony emigration—disseminating information about potential nest-sites—is organized via stereotyped physical interactions in which a knowledgeable individual physically leads a naive nestmate back to a new nest site, in what is called a tandem run [7,8,9,10]
Summary
One of the most important life challenges faced by any animal is to find a new place to live when the current nest site becomes uninhabitable. In colonies of Temnothorax ants a key stage in colony emigration—disseminating information about potential nest-sites—is organized via stereotyped physical interactions in which a knowledgeable individual physically leads a naive nestmate back to a new nest site, in what is called a tandem run [7,8,9,10]. Such followers learn the location of the new nest site to which they were led, and later lead other ants back to the same site. We examine how the role specializations of the leader and follower within each tandem pair, interact to determine the quality of the tandem run
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