Courtship interference by neighboring males potentially prevents pairing in fiddler crab Austruca lactea

Abstract

Courtship interference occurs when dominant males hinder female assessment of prospective males during female mate choice, leading to a more complex distribution of mating success. In this study, we describe and evaluate courtship interference in underground mating of the fiddler crab Austruca lactea. When a mate-searching female enters the burrow of a courting male, neighboring males frequently interfere in the female-male interaction. We thus identified mate-searching females and observed their interactions until pairing. The duration until females’ final decision for pairing increased with the number of interferences by neighboring males. The females reappeared more frequently from the burrow of the finally selected male when neighboring males interfered. These results suggest that courtship interference by neighboring males delays pairing between the mate-searching female and the finally selected male in this species. The number of interferences by neighboring males increased with female size, implying that large females with high fecundity potential induce interference by neighboring males. Moreover, in approximately half of the cases in which interference occurred at the burrow of the immediate last male before the finally selected male, the finally selected male was the interfering one. The distribution of mating success was therefore biased toward males that combined attractiveness (according to female preference) and dominance (which is associated with courtship interference) in this species. Courtship interference is a type of male-male competition and it may hamper female mate choice. In Austruca lactea, neighboring males often interfere in the interaction between a courting male and a mate-searching female. We demonstrated the effect of courtship interference by neighboring males in these interactions. The interferences prolonged the duration of female decision-making for pairing and temporarily expelled the female from the burrow of the finally selected male. These results imply that these interferences may potentially prevent pairing. Moreover, the finally selected males had often succeeded in interfering in the courtship interaction between the female and another male. Therefore, males with high mating success were not only attractive to the females of this species but also dominant in courtship interference.