Fighting in rounds: males of a neotropical cricket switch assessment strategies during contests

摘要

How animals decide to withdraw from contests is central to understand the evolution of fighting behavior. Game theory models suggest 2 major types of decision criteria: 1) self-assessment, where individuals withdraw when they reach a cost-threshold determined by their own fighting ability that may or may not be affected by injuries, or 2) mutual assessment, where the decision is based on information about the relative fighting ability of the opponents. Many empirical studies have assumed that opponents use a single strategy throughout the whole fight. However, they often find partial support for a specific model. This might be due to individuals changing their strategy between phases of a contest. In this work, we addressed this issue by evaluating if males of the cricket Melanotes ornata switch their assessment strategy between phases. We used hind femur length as a proxy for fighting ability, as it was the attribute most strongly associated with contest outcome. Overall fight duration was positively associated with the loser's femur length and negatively associated with the winner's femur length, while the probability of escalation to physical aggression was negatively related to the difference in femur between opponents. However, such relationships held only at the first contest phase. During the escalated phase, fight duration was only correlated (although weakly) with femur length of losers. These results indicate that M. ornata males perform mutual assessment in the initial phase but switch their assessment strategy when fights escalate, suggesting a single strategy does not correctly explain how contests are settled.