Male mating success and risk of predation in a wolf spider: a balance between sexual and natural selection?

1.  Traits that benefit males through sexual selection are simultaneously expected to impair males by provoking costs through natural selection. If we consider the two male fitness components, mating success and viability, then we may expect that the increase in male mating success resulting from a larger trait size will be counterbalanced by an increase in viability costs.

2.  We studied the benefits and costs of male mate searching and sexual signalling activity in the wolf spider Hygrolycosa rubrofasciata. In the field, males search females actively and court them by drumming dry leaves with their abdomen. Females have been shown to prefer males with high drumming rate. Male moving and especially drumming is energetically highly demanding and drumming results in significant mortality costs.

3.  Our objective in this study was to determine whether male mate-searching activity or drumming activity affect male mating success and the risk of males being predated.

4.  It was evident that both higher mate-searching activity and higher drumming activity benefited males by increasing their mating success. Higher mate-searching activity clearly impaired males by causing direct increase in predation risk. There was also a slight tendency that more actively drumming males had higher risk of predation and from all of the predated males 13.3% were caught directly after they had drummed. Furthermore, male drumming activity decreased drastically in the presence of the predator.

5.  We conclude that in H. rubrofasciata both increased mate-searching activity and drumming activity benefit males through sexual selection, but at the same time natural selection provokes direct balancing costs on the same traits.