Understanding factors affecting male mate choice can be important for tracking the dynamics of sexual selection in nature. Contextual variation in reproductive costs and benefits of different types of mates may predict male choice, but mating may also be opportunistic regardless of female reproductive value. Male brown widow spiders (Latrodectus geometricus) can mate with adult as well as immature (subadult) females. Matings with adults require costly courtship and typically end with cannibalism (‘self-sacrifice’ initiated by a male somersault), but matings with subadults involve more brief courtship and no risk of cannibalism. We examined whether there was evidence for male mate choice as a function of risks associated with different types of mates and the cues available to courting males. Previous studies showed male preference for adult females based on airborne pheromones. In our study, males preferred adult females based on silk-borne contact cues. We swapped adult and subadult females between webs to determine which cues trigger different components of courtship, and showed that contact with adult females’ webs triggers web reduction and contact with adult females’ bodies triggers mate binding and somersaulting, but vibratory courtship occurs regardless of the origin of the web or female developmental stage. We conclude that males can detect and recognize subadult females as potential mating partners, but are more likely to invest in costly courtship behaviours and mating attempts with adults. In our experiments, subadult females were less likely to mate than adults. We conclude that mating with adults could be the preferred option for males because of the higher likelihood of copulation, even at the cost of a higher risk of cannibalism.

Data were collected in two laboratory experiments:

1) Male responses to subadult vs. adult female silk cues in a Y-maze 2-choice experiment

2) Outcomes of mating trials in which males courted subadult or adult females placed on the webs of other females in a fully crossed design

All analyses were conducted in R version 4.0.0. See paper for full details of experimental design and analysis.