資源擁有狀態對打鬥決策之影響是否取決於個體之打鬥經驗與打鬥能力

Animals often fight to compete for resources. Fighting is costly especially to individuals that have bad fighting ability. Fighting ability therefore plays an important role in an individual’s contest decisions. An individual’s contest decisions are also affected by its previous winning/losing experiences and resource-ownership status. Winning/losing experiences modify an individual’s estimated fighting ability. Resource-ownership status could affect an individual’s estimated fighting ability and resource value. Competitors in natural environments often differ not only in their ownership status but also in their fighting ability and contest experiences. How fighting ability and contest experiences might affect owner advantage, however, remains unclear. Using the mangrove killifish (Kryptolebias marmoratus), this proposal aims to address these issues with two studies. Study 1 investigates the importance of fighting ability to owner advantage. Study 2 investigates how asymmetries in winning/losing experiences and shelter ownership jointly guide contest decisions. Previous studies of the fish suggest that individuals that have worse perceived and/or actual fighting ability are more responsive to fighting ability related information. Both winning/losing experiences and ownership status could affect an individual’s estimation of its relative fighting ability. Thus, individuals with different fighting ability and contest experiences should differ in their responsiveness to the influences of ownership status (fighting ability: worse > better; experience: losing > no > winning). Moreover, because ownership status affects the fish’s motivation to fight but not its actual fighting ability, fighting ability should have a greater influence than ownership status on contest outcomes. Furthermore, because ownership status affects the behaviors of both the owner and intruder, while winning/losing experience affects only an individual’s but not its opponent’s behaviors, ownership status should have greater influences than a winning/losing experience on the fish’s contest decisions. This was a 3-year project but was funded only for the 1st year. We completed the experiments outlined for Study 1. The results confirmed that better fighters behaved more aggressively and were more likely to win than worse fighters. Furthermore, how ownership status increased an individual’s tendency to win against a rival of the same fighting ability was different for better and worse fighters. For contests between better fighters, shelter ownership increased the chance of the owners winning non-escalated but not escalated contests. For contests between worse fighters, shelter ownership increased the chance of the owners winning both non-escalated and escalated contests. For the contests between a better and a worse fighter, when provided with a shelter, the worse fighters were more likely to escalate contests into physical interactions. The ownership status, although increased the worse fighters’ chance of winning non-escalated contests, did not increase their chance of winning escalated contests: the positive influence of the owner-status was not high enough to offset the negative effect of the worse fighting ability; intrinsic fighting ability is therefore more important than motivation to contest outcomes.