A nocturnal rail with a simple territorial call eavesdrops on interactions between rivals

The behaviour of most animals has evolved in a communication network environment, in which signals produced by senders are perceived by many intended and unintended receivers. In this study, we tested whether the corncrake (Crex crex), a nocturnal rail species with innate (non-learned) calls, is able to eavesdrop on the interactions of conspecific males and how this eavesdropping affects subsequent responses by the eavesdropper to territorial intrusion. In the first step, simulated aggressive or neutral interactions between male dyads were presented to a focal male. In the second step, the calls of winning, losing or neutral males from the first step were played within the territory of the focal male. We measured behavioural and vocal responses of focal males. We found that corncrakes eavesdropped on signal exchange between rivals. Males often began responding to distant aggressive interactions during the eavesdropping phase, and they responded strongly during the intrusion phase of the experiments. The response was significantly weaker to playback of males from neutral interactions than to those involved in aggressive interactions, and we found no differences between the responses to Winners and Losers entering a focal male territory.

绝大多数动物的行为均在通讯网络环境中演化形成，信号发送者产生的信号会被众多有意或无意的接收者感知。本研究以长脚秧鸡（Crex crex）——一种鸣唱先天固有、无需后天学习的夜行性秧鸡类——为研究对象，探究其是否能够窃听同种雄性个体间的互动行为，以及该窃听行为如何影响窃听者后续对领地入侵的响应。实验分为两个阶段：第一阶段，向目标雄性个体播放模拟的雄性成对个体间攻击性互动与中性互动的音频；第二阶段，在目标雄性的领地内播放第一阶段中获胜雄性、落败雄性及中性互动雄性的鸣唱回放录音。研究人员记录了目标雄性的行为与鸣唱响应。结果显示，长脚秧鸡能够窃听同类竞争者间的信号交流。在窃听阶段，雄性个体往往会对远距离的攻击性互动作出响应；而在实验的入侵阶段，它们则会表现出强烈的响应。相较于中性互动雄性的鸣唱回放，目标雄性对攻击性互动雄性鸣唱回放的响应强度显著更高；且针对入侵领地的获胜者与落败者的响应，未发现显著差异。