Department of Biological Sciences, Genetics and Ecology
Males and females often experience different optima in matingrate, which may cause evolution of female resistance to matingsand male counter adaptations to increase mating rate. Malesof the spider Pisaura mirabilis display a spectacular matingbehavior involving a nuptial gift and thanatosis (death feigning).Thanatosis in a sexual context is exceptional and was suggestedto function as an antipredation strategy toward potentiallycannibalistic females. If thanatosis serves as a protectionstrategy, males should death feign in response to female aggressionor when they are more vulnerable to attack. We tested thesepredictions in a factorial design: males that were handicapped(1 leg removed) and hence vulnerable and control males werepaired with females that were more or less aggressive intrinsically(measured toward prey). In mating trials, we recorded the tendencyof males to death feign, copulation success, and copulationduration. In addition, we investigated the effect of femalemating status (virgin or mated) on these male mating components.Intrinsically aggressive females showed increased mating aggressiontoward males. Neither female aggressiveness, mating status,nor male vulnerability increased the propensity of males toperform thanatosis. Instead, death-feigning males were moresuccessful in obtaining copulations and gained longer copulations.Hence, our results suggest that thanatosis functions as an adaptivemale mating strategy to overcome female resistance. All maleswere capable of performing thanatosis although some males useit more frequently than others, suggesting a cost of death feigningwhich maintains the variation in thanatosis during courtship.