Shared predators between primate groups and mixed species bird flocks: The potential for forest-wide eavesdropping networks

A basic tenet of animal behavior is that animal groupings (e.g., schools of fishes or flocks of birds) are widely influenced by predators. Many studies have focused on communication between individuals within the same species or different species within a defined social group; but predators typically select from a number of different co-occurring species. To evaluate whether two distantly-related species with similar predators share vocal information regarding predator threats, we conducted a field experiment in the Amazonian rainforest involving an avian prey-species, a primate prey-species, and a shared predator. In our reciprocal field experiment, we elicited alarm calls from birds (Bluish-slate antshrikes, Thamnomanes schistogynus) and primates (Saddle-backed tamarins, Saguinus fuscicollis) by exposing them to a trained raptor (Bicolored Hawk, Accipiter bicolor). We then played all types of recorded alarm calls back to birds and tamarins, and measured 1) the time to respond (for both birds and tamarins), and 2) the distance moved across the substrate (for tamarins). Our results show that both birds and tamarins were significantly more likely to flee when hearing vocal alarms compared to a control (a common bird call, the Screaming Piha, Lipaugus vociferans), regardless of the species who produced the alarm. In addition, tamarins moved significantly more upon hearing bird alarm calls when compared to the control. We suggest that signals regarding shared predators may be highly valued across prey from distinct social groups. These data support the hypothesis that overlapping potential predators can drive communication between distinct prey groups, resulting in taxonomically diverse eavesdropping networks within tropical rainforests.

动物行为学的一项核心要义为：动物集群（如鱼群、鸟群）的形成与维持广泛受捕食者调控。诸多研究聚焦于特定社会群体内同种或跨物种个体间的通讯行为；但捕食者通常会从多种同域共存的物种中选择猎物。为验证两种亲缘关系较远且共享捕食者的物种是否会共享针对捕食者威胁的声学信息，我们在亚马逊雨林开展了一项野外实验，实验涉及两种被捕食物种：鸟类与灵长类，以及它们的共同捕食者。本实验为双向交叉野外实验：我们通过暴露受训猛禽双色鹰（Accipiter bicolor），分别诱导鸟类蓝灰蚁鵙（Thamnomanes schistogynus）与灵长类鞍背柽柳猴（Saguinus fuscicollis）发出警报叫声。随后我们将所有录制的警报叫声回放给鸟类与柽柳猴，并测量两项指标：1）两类受试对象的响应时延；2）柽柳猴在活动基质上的移动距离。实验结果显示：相较于对照组（一种常见鸟类鸣叫声——尖叫伞鸟（Lipaugus vociferans）），无论警报叫声的发出物种为何，鸟类与柽柳猴的逃逸概率均显著更高。此外，相较于对照组，柽柳猴在聆听鸟类警报叫声时的移动距离显著更大。我们据此提出推测：针对共享捕食者的声学信号，或可被不同社会群体的被捕食者高度重视。本研究数据支持以下假说：存在重叠潜在捕食者的情况，可推动不同被捕食物种群体间的通讯行为，进而在热带雨林中形成分类学跨度广泛的窃听网络。