The effect of an audience on intrasexual communication in male Siamese fighting fish, Betta splendens

The evolution of signals has mainly been considered in the contextof an emitter-receiver dyadic interaction. However, communicationusually occurs in the presence of individuals (an audience)that are not directly involved in the communication interaction,and it is more realistic to assume that signal evolution occursin a network. Several types of information could be availableto an audience, and, therefore, the presence of an audiencecould have effects on the behavior of the communicating animalsand on signal evolution. We investigated whether the presenceof an audience of conspecifics affected intrasexual aggressivecommunication in male fighting fish. We found that if the audiencewas a female, males increased the intensity of conspicuousdisplays that can be used in communication with both males andfemales and decreased highly aggressive displays that are solelydirected to males. If the audience was a male of similar size,there was no significant change in the way in which males displayed.These results suggest that the presence of an audience couldbe one reason that many long-range and conspicuous signals areoften shaped to transmit information to both males and females