Who Is Likely to Cheat? Linking Personality to Worthless Gift Production in a Spider

Individuals may maximise fitness by adopting alternative reproductive tactics (ARTs) that are shaped by environmental conditions and reflect the individual's competitive ability. While variation in morphology or physiology in ARTs is well understood, the role of consistent behavioural variation is less clear. Yet, adopting certain ARTs can be driven by individual variation in personality traits and behavioural syndromes if individuals of certain behavioural types (e.g., shy, less aggressive) have lower competitive abilities, switching to tactics other than those used by competitive males. To investigate the relationship between ARTs and individual variation in behaviour, we focused on males of the spider Pisaura mirabilis, known for courting females with either a genuine tactic consisting of silk-wrapped nutritionally valuable (prey) or a cheating tactic using worthless (leftovers) gifts. Environmental and social conditions, such as prey availability and the intensity of sexual selection, are known to maintain flexible ARTs in this species, but the underlying behavioural types of males that are more likely to cheat remain unknown. We screened males for exploration, aggressiveness and body size-traits relevant for resource acquisition-and tested their likelihood of producing worthless gifts by offering them a prey carcass over repeated trials. We predicted behavioural traits to be repeatable, correlate in syndromes and be size-dependent, with larger, highly explorative-aggressive individuals, better at resource acquisition, to be less likely to produce worthless gifts. Personality traits were repeatable, especially exploration behaviour, but lacked an aggressive-exploration syndrome and size-dependency. The likelihood of taking a prey carcass was also repeatable, indicating between-male differences in response to worthless items, and was linked to higher male aggressiveness and larger size, suggesting a potentially higher capacity for exploiting scarce resources in these phenotypes. Our findings suggest that, despite not affecting gift production per se but only responses towards worthless prey items, size dependence and individual variation in aggressive behaviour may play a role in the initial acquisition of worthless items but are not decisive factors for ARTs.