Safer sex with feeding females: sexual conflict in a cannibalistic spider

Mating strategies are to a large degree shaped by conflictsbetween the sexes, causing a rapid antagonistic coevolutionof traits involved in reproduction. The view that sexual cannibalismrepresents a form of sexual conflict leads to the predictionof male traits that facilitate escape from cannibalistic females.A variety of traits have been suggested to serve this functionin spiders, where sexual cannibalism is comparatively common.Empirical evidence, however, is virtually absent. Here we showexperimentally that opportunistic mating with feeding females,which has been reported from several species of orb-weavingspiders, greatly reduces the risk of cannibalism and injuryfor males in the spider Nephila fenestrata. This has directconsequences for a male's fertilization success because survivingmales can reduce the female's remating probability by guardingher against rivals. Although copulation with previously matedfemales sometimes appears to be mechanically impossible, secondmales that do copulate can expect to fertilize on average 64%of a female's eggs. Our results support the view that opportunisticmating may have evolved as a male tactic in a context of sexualconflict over sexual cannibalism.