Body Size, Not Personality, Explains Both Male Mating Success and Sexual Cannibalism in a Widow Spider

Theory suggests that consistent individual variation in behavior relates to fitness, but few studies have empirically examined the role of personalities in mate choice, male-male competition and reproductive success. We observed the Mediterranean black widow, Latrodectus tredecimguttatus, in the individual and mating context, to test how body size measures and two functionally important aggressive behaviors, i.e., male aggression towards rivals and female voracity towards prey, affect mating behaviors, mating success and sexual cannibalism. We specifically selected voracity towards prey in females to test the "aggressive spillover hypothesis", suggesting that more voracious females are more sexually cannibalistic. Both females and males exhibit consistent individual differences in the examined aggressive behaviors. While larger males win contests more often and achieve more copulations, neither male nor female size measures correlate to aggression. Female voracity does not correlate with aggression towards mates and sexual cannibalism, rejecting the "spillover hypothesis". However, occurrence of sexual cannibalism positively relates to longer insertion duration. Furthermore, the smaller the ratio between male and female body length the more likely a female attacked and cannibalized a mate. We show that individual variation in aggression levels plays no direct role in the mating behavior of the Mediterranean black widow. Instead, body size affects male mating success and occurrences of sexual cannibalism in females.