Theory suggests that males should adjust courtship in response to a variety of factors, including female quality, the risk of male-male competition, and often in spiders, the risk of sexual cannibalism. Male black widow spiders demonstrate a behavior during courtship whereby they tear down and bundle a female's web in addition to providing other vibratory and contact sexual signals. This web reduction has been hypothesized to play a role in all three factors (sexual signaling, competition reduction, and cannibalism reduction), but rarely are these tested together. Here, we test these hypotheses by conducting mating trials using the western black widow (Latrodectus hesperus) and measuring both male and female quality and behavior. Our results indicate that amount of web reduction is best predicted by female aggression, and not aspects of either male or female quality (e.g., body mass), or by the potential for the web to attract other males (e.g., web mass). Yet, actual mating success was best predicted by the proportion of web reduced. Furthermore, there was no consistent among-individual variation in either reduction behavior or male success, indicating that all variation in both measures was due to plasticity and/or other unaccounted-for male or female traits. Collectively, we conclude that the primary function of web reduction behavior is to reduce female aggression and thus the risk of sexual cannibalism, and that any other functions such as signaling and reducing male-male competition have relatively lower importance.
|Date made available||2018|