Juvenile hormone influences precontest assessment behaviour in Polistes dominulus paper wasps

Theory on animal contests often assumes that individuals can rapidly and accurately assess their own resource-holding potential (RHP). In empirical work, individuals behave as if they 'know' their own RHP, but little is known about how such assessment occurs. Here, we test how juvenile hormone (JH) influences precontest behaviour in P. dominulus paper wasps. Previous work has shown that P. dominulus have variable black facial patterns that are a signal of agonistic ability and that JH influences fighting ability. In this experiment, we tested how JH influences rival challenge behaviour in the absence of direct social competition. Wasps were given the opportunity to challenge or avoid a model wasp guarding a patch of food. Individuals treated with the JH analogue methoprene were more likely to challenge rivals than were control individuals, and they also had a shorter latency to challenge than controls. However, hormone treatment was only one of multiple factors that influenced behaviour, suggesting that assessment prior to contests is based on the interplay between individual physiology and social context. Contest decisions were also dependent on a wasp's own facial pattern and mass, as well as the facial pattern of its rival. Interestingly, these complex assessment decisions occurred in the absence of direct social cues that could be acquired during a contest. These results are consistent with JH playing a role in self-assessment of RHP. Hormones such as JH are influenced by the physical and social environment, so they provide diverse information about relative RHP and may be commonly involved in assessment behaviour.