Evidence for assessment disappears in mixed-sex contests of the crayfish, Orconectes virilis

Abstract

During agonistic interactions, decisions about contest persistence can be informed by assessment of one’s own energy or time expenditure (self-assessment), one’s own expenditure combined with opponent inflicted costs (cumulative assessment), or through information exchange with an opponent (mutual assessment). Females and males can be expected to exhibit different strategies for contest resolution due to contrasting energetic requirements and resource valuation. We examined the assessment strategies crayfish employ during same-sex and mixed-sex fights. Two individuals interacted for 15 min, and fight duration and times spent at various intensity levels were quantified. Results indicated that both sexes employ a self-assessment strategy during same-sex fights. Evidence for assessment during mixed-sex fights was notably weaker, suggesting the resolution of mixed-sex fights involves different behavioural elements and/or sources of information. In species where mixed-sex fights are common year-round, the lack of common rules can lead to greater energy expenditure for both sexes.