Johnstone R A
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom.
Proc Natl Acad Sci U S A. 2001 Jul 31;98(16):9177-80. doi: 10.1073/pnas.161058798. Epub 2001 Jul 17.
Fights between pairs of animals frequently take place within a wider social context. The displays exchanged during conflict, and the outcome of an encounter, are often detectable by individuals who are not immediately involved. In at least some species, such bystanders are known to eavesdrop on contests between others, and to modify their behavior toward the contestants in response to the observed interaction. Here, I extend Maynard Smith's well known model of animal aggression, the Hawk-Dove game, to incorporate the possibility of eavesdroppers. I show that some eavesdropping is favored whenever the cost of losing an escalated fight exceeds the value of the contested resource, and that its equilibrium frequency is greatest when costs are relatively high. Eavesdropping reduces the risk of escalated conflict relative to that expected by chance, given the level of aggression in the population. However, it also promotes increased aggression, because it enhances the value of victory. The net result is that escalated conflicts are predicted to occur more frequently when eavesdropping is possible.
动物个体之间的争斗常常发生在更广泛的社会背景中。冲突期间的表现以及遭遇的结果，往往能被那些并未直接参与的个体察觉到。至少在某些物种中，已知这类旁观者会偷听其他个体之间的争斗，并根据观察到的互动来调整它们对争斗者的行为。在此，我扩展了梅纳德·史密斯著名的动物攻击模型——鹰鸽博弈，以纳入偷听者存在的可能性。我发现，只要升级争斗失败的代价超过了争夺资源的价值，某种程度的偷听行为就会受到青睐，并且当代价相对较高时，偷听行为的平衡频率最高。相对于根据种群攻击水平随机预期的情况，偷听降低了升级冲突的风险。然而，它也会促使攻击性增强，因为它提升了胜利的价值。最终结果是，当存在偷听可能性时，预计升级冲突会更频繁地发生。
