Decisions during fights in the house cricket, Acheta domesticus: mutual or self assessment of energy, weapons and size?

During contests the outcome is ultimately determined by the difference in fighting ability or resource holding potential (RHP) of opponents and the loser may make the decision to give up by comparing its own fighting ability to that of the eventual winner. Such ‘mutual assessment’, however, may not be possible in all cases and an alternative mechanism is to withdraw when the costs of remaining in the contest cross a threshold. Thus, in contests where the opponents do not impose direct costs on each other the decision to give up is based on the absolute RHP rather than the relative RHP of the loser. The possibility for ‘mutual’ or ‘self’ assessment is a feature that distinguishes between different theoretical models of contests. Here I analyse relationships between contest duration and relative and absolute measures of RHP to determine whether contests in the house cricket are settled on the basis of mutual or self assessment. Although body size may contribute to RHP, additional traits such as weapons and energetic status may also influence fighting ability. Therefore, in this study I aimed to determine which features contribute to RHP before analysis of the effects of relative and absolute RHP on contest duration. Energy and body size strongly differ between winners and losers but differences in weapon size are marginal. Analysis of contest duration supports the idea that mutual assessment is a feature of these contests but also suggests that individual thresholds of energetic cost contribute to the decision to give up.