Data from: Deconstructing the landscape of fear in stable multi-species societies

Animal distributions are influenced by variation in predation risk in space, which has been described as the “landscape of fear.” Many studies suggest animals also reduce predation risk by eavesdropping on heterospecific alarm calls, allowing them to occupy otherwise risky habitats. One unexplored area of study is understanding how different species’ alarms vary in quality, and how this variation is distributed in the landscape. We tested this phenomenon in a unique system of avian mixed species flocks in Amazonian rainforests: flock mates (eavesdropping species) strongly associate with alarm-calling antshrikes (genus Thamnomanes), which act as sentinel species. Up to 70 species join these flocks, presumably following antshrike behavioral cues. Since flocks in this region of the Amazon are exclusively led by a single antshrike species, this provides a unique natural system to compare differences in sentinel quality between flocks. We simulated predation threat by flying three species of live trained raptors (predators) towards flocks to compare sentinel probability to (1) produce alarm calls, and (2) encode information about magnitude and type of threat within such alarm calls. Our field experiments show significant differences in the probability of different sentinel species to produce alarm calls and distinguish predators. This variation may have important fitness consequences and shape the “landscape of fear” for eavesdropping species.动物的空间分布格局受空间捕食风险异质性的调控，这一现象被定义为“恐惧景观（landscape of fear）”。多项研究证实，动物可通过窃听异种警报叫声来规避捕食风险，进而得以占据原本具有捕食威胁的栖息生境。目前仍有一个未被探索的研究维度：即不同物种的警报信号在质量上存在何种差异，以及这种质量差异在空间景观中的分布规律。我们在亚马逊雨林的鸟类混合群这一独特自然系统中验证了这一科学问题：群内伴生的窃听物种与发出警报叫声的蚁鵙属（*Thamnomanes*）哨兵物种存在极强的协同关联。此类混合群最多可容纳70个物种，推测所有伴生物种均以蚁鵙的行为线索作为活动指引。由于该亚马逊区域的鸟类混合群均由单一蚁鵙物种领头，该系统为比较不同混合群间哨兵物种的信号质量差异提供了绝佳的天然实验平台。我们通过放飞三只经过训练的活猛禽（捕食者）逼近混合群来模拟捕食威胁，以此对比哨兵物种的两项核心指标：（1）发出警报叫声的概率；（2）警报叫声中所编码的威胁强度与威胁类型信息。本野外实验结果表明，不同哨兵物种在发出警报叫声以及精准区分捕食者的概率上均存在显著差异。这种信号质量的异质性可能会对物种的适合度产生关键影响，并进一步塑造窃听物种的“恐惧景观”。