Group-living animals gain fitness benefits from intergroup aggression, but also incur costs. Advertisement behaviors, such as long-distance calls and scent marking, help animals avoid disadvantageous, or less rewarding, fights. However, it remains unclear how species that lack advertisement behaviors respond to auditory information from other groups. We hypothesized that such species use auditory information prior to visual contact with the opponent group to determine its relative resource holding potential. Here, we aimed to identify the behavioral responses of Japanese macaques to simulated intergroup encounters. We conducted a vocal playback experiment and behavioral observations of 11 adult males and females from two groups intermittently from October 2015 to June 2017. In response to vocalizations of other groups, the macaques stopped feeding, decreased contact calling, and increased visual scanning, which could enable them to make timely and accurate decisions as to whether to fight or flee. The spatial cohesion of the group did not change. These results partly support our hypothesis and suggest that the onset of increased vigilance to opponents is prior to visual contact with them. The present study highlights the importance of investigating early phases of intergroup encounters in species lacking advertisement behaviors to obtain new insights on intergroup conflicts in animals.

中文翻译：

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日本猕猴对回放模拟群际相遇的行为反应

群居动物从群际攻击中获得健康益处，但也会产生成本。广告行为，例如长途电话和气味标记，可以帮助动物避免不利的或没有回报的打架。然而，尚不清楚缺乏广告行为的物种如何对来自其他群体的听觉信息做出反应。我们假设这些物种在与对手群体进行视觉接触之前使用听觉信息来确定其相对资源持有潜力。在这里，我们旨在确定日本猕猴对模拟群际相遇的行为反应。我们从 2015 年 10 月到 2017 年 6 月间断地对两组 11 只成年雄性和雌性进行了声音回放实验和行为观察。为了响应其他组的发声，猕猴停止进食，减少接触呼叫，增加视觉扫描，这可以使他们能够及时准确地决定是战斗还是逃跑。群体的空间凝聚力没有改变。这些结果部分支持了我们的假设，并表明对对手的警惕性增强是在与他们进行视觉接触之前。本研究强调了在缺乏广告行为的物种中调查群际相遇的早期阶段以获得对动物群际冲突的新见解的重要性。这些结果部分支持了我们的假设，并表明对对手的警惕性增强是在与他们进行视觉接触之前。本研究强调了在缺乏广告行为的物种中调查群际相遇的早期阶段以获得对动物群际冲突的新见解的重要性。这些结果部分支持了我们的假设，并表明对对手的警惕性增强是在与他们进行视觉接触之前。本研究强调了在缺乏广告行为的物种中调查群际相遇的早期阶段以获得对动物群际冲突的新见解的重要性。