Local enhancement via eavesdropping on courtship displays in male guppies, Poecilia reticulata

Courtship interactions often take place within the setting of a communication network, with signals sent from senders to target receivers also being detectable to third-party eavesdroppers. Potentially, eavesdropping males may be able to use signals produced by courting males to locate females indirectly. Furthermore, where male courtship vigour varies according to the quality of females (e.g. fecundity, receptivity or number), eavesdroppers observing multiple courting males may be able to use differences in courtship vigour to gauge indirectly the relative quality of the females. We tested these predictions in an experiment in which observer male guppies were presented with a binary choice between two demonstrator males courting differently sized groups of females, which were hidden from the observer. We found that the demonstrator males courted larger groups of females at a higher rate, and that observer males tested in the presence of the demonstrators spent more time and performed more courtship displays in the location of the demonstrator courting the larger group of females. Observers tested after the demonstrator males had been removed, however, showed no preference for either of the demonstrated locations and for the most part performed no courtship displays at all. Our results provide evidence for male-male local enhancement, but not delayed local enhancement, via demonstrator male courtship behaviour. Such behaviour may be adaptive, allowing eavesdropping observer males to locate females indirectly. We discuss how this system could be employed to explore social transmission of information further.