Sexual size dimorphism mediates the occurrence of state-dependent sexual cannibalism in a wolf spider

Most research on sexual cannibalism has focused on factors influencing female motivation to engage in cannibalism. However, a critical factor that may mediate the actual occurrence of sexual cannibalism is male vulnerability to female attacks. We tested whether sexual size dimorphism (SSD) affected whether hungry females were successful in sexual cannibalism in a moderately size dimorphic wolf spider, Hogna helluo. Experimentally food-limited females cannibalized males more frequently than did well-fed females. However, in a correlational study, female body condition was only a significant predictor of the occurrence of sexual cannibalism if SSD was included in the model. Our results suggest that SSD is an important factor mediating the occurrence of sexual cannibalism in H. helluo by affecting male vulnerability to female attacks. Consideration of factors affecting male vulnerability to cannibalistic attacks by females may be critical to understanding the occurrence and evolution of sexual cannibalism.