Assessment strategies in the contests of male crickets,Acheta domesticus(L.)

Abstract

Game theoretical models predict that the assessment of relative fighting ability and motivation is a process fundamental to resolving most contests. Demonstrations of assessment must (1) identify characters associated with fighting success and (2) establish a correlation between opponent asymmetry in these characters and the costs of fighting. Pair-wise contests between male house crickets revealed that winners were generally heavier than their opponents, although this effect varied with the degree of asymmetry in mass and the presence or absence of burrows. Prior burrow residency and initiating a fighting bout provided additional, but small advantages in fighting success. Fight winners performed a larger repertoire of agonistic tactics, more total acts, and escalated more frequently to energetically costly tactics than did their opponents. As a result, the winner's total energy expenditure usually exceeded the loser’s. In accordance with the core prediction of assessment models, the cumulative energetic costs of combat for both opponents increased with decreases in asymmetry of mass and energy expenditure rate. These results suggest that house crickets resolve contests by assessing asymmetries in both body size and their relative use of costly tactics. The relative energetic costs incurred by combatants may reliably signal relative energy reserves and contribute to the active assessment of fighting ability, rather than simply accrue as a by-product of combat.