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 mating behavior of the
Mediterranean black widow. Instead, body size affects male mating success
and occurrences of sexual cannibalism in females.