Cohabitation of juvenile females with mature males promotes sexual cannibalism in fishing spiders

Precopulatory sexual cannibalism, or female predation of a potential mate before mating, illustrates an extreme intersexual conflict. Unlike sexual cannibalism occurring after mating, precopulatory sexual cannibalism cannot be construed as a male strategy. Thus, research on the adaptive significance of this phenomenon has focused on female benefits. In the present study, I test the idea that precopulatory sexual cannibalism represents an adaptive female trade-off between the material costs and benefits of mating with a male (forgoing food, securing sperm) and preying on a male (forgoing sperm, securing food). I pay particular attention to the rarely tested prediction that precopulatory sexual cannibalism by virgin females should increase as each female's expectation of future mating opportunities increases. I use the phenomenon of cohabitation between adult males and juvenile females nearing sexual maturity as a means to manipulate female expectation of future mate availability. Results indicate that feeding on a male has significant positive effects on several measures of female fecundity. However, the likelihood of precopulatory attacks was not explained by a female's recent feeding history. Finally, as predicted, juvenile female cohabitation with mature males (expectation of future mating opportunities) heightens the prevalence of precopulatory attacks by virgin females, suggesting that juvenile experience can alter a female's propensity for sexual cannibalism. This is the first study to suggest that juvenile experience can alter a female's propensity for sexual cannibalism. This finding emphasizes the point that studies of sexual selection and mating systems need to consider the effects of juvenile experience on adult behavior.