Competition and opportunity shape the reproductive tactics of males in the ant Cardiocondyla obscurior

Abstract

Context-dependent adjustment of mating tactics can drastically increase the mating success of behaviourally flexible animals. We used the ant Cardiocondyla obscurior as a model system to study adaptive adjustment of male mating tactics. This species shows a male diphenism of wingless fighter males and peaceful winged males. Whereas the wingless males stay and exclusively mate in the maternal colony, the mating behaviour of winged males is plastic. They copulate with female sexuals in their natal nests early in life but later disperse in search for sexuals outside. In this study, we observed the nest-leaving behaviour of winged males under different conditions and found that they adaptively adjust the timing of their dispersal to the availability of mating partners, as well as the presence, and even the type of competitors in their natal nests. In colonies with virgin female queens winged males stayed longest when they were the only male in the nest. They left earlier when mating partners were not available or when other males were present. In the presence of wingless, locally mating fighter males, winged males dispersed earlier than in the presence of docile, winged competitors. This suggests that C. obscurior males are capable of estimating their local breeding chances and adaptively adjust their dispersal behaviour in both an opportunistic and a risk-sensitive way, thus showing hitherto unknown behavioural plasticity in social insect males.

Figure 1. Dispersal time of winged Cardiocondyla males from their natal nest.

A) In the presence of virgin queens, winged males stayed longer in the colony when being the single male in the colony (white) than when another male was present. They emigrated earlier when the second male was a wingless fighter male (black) than when it was a peaceful winged male (grey; mean ± s.d., significance groups marked with different letters). B) In the presence of a wingless fighter male, winged males always left the nest early. They prolonged their stay in nests without a wingless male only when virgin female sexuals were present (mean ± s.d., significance groups marked with different letters).