High resource valuation fuels “desperado” fighting tactics in female jumping spiders

Opponent asymmetries often determine the probability of winning a fight in agonistic situations. In many animal systems, the asymmetries that drive the dynamics and outcome of male--male contests are related to resource holding potential (RHP) or territory ownership. However, recent studies have shown that this is not the case among females and suggest that resource valuation may be more important in that context. We studied contests between the female jumping spider, Phidippus clarus, and compared them with male--male contests in this same species. Our observations document several key differences between the sexes: Precontact and contact phases are longer in females, ritualized displays are rare in females but common among males, and female fights are more likely to end in injury or death. In sharp contrast with male contests, female weight and size do not correlate with signaling behavior, and the outcome of fights is predicted by differences in resource valuation rather than RHP. We interpret these differences in light of the different natural history of the sexes and discuss how the economics of fighting may lead to the evolution of ritualized displays in males and a "desperado effect" in females. Copyright 2010, Oxford University Press.