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.动物的分布格局受空间捕食风险异质性的影响，这一现象被称为“恐惧景观（landscape of fear）”。诸多研究表明，动物可通过偷听异种警报叫声降低自身捕食风险，借此得以进入原本存在较高捕食风险的栖息环境。目前尚有一个未被充分探索的研究方向：厘清不同物种的警报叫声在质量上存在何种差异，以及这类差异在景观中的分布规律。我们以亚马逊雨林中一类独特的鸟类混合群为研究系统开展验证：该混合群中的伴生个体（即偷听者物种）与发出警报叫声的Thamnomanes属蚁鵙（哨兵物种（sentinel species））存在极强的关联关系。该鸟类混合群最多可容纳70个物种，推测这些物种均通过跟随蚁鵙的行为线索加入种群。由于亚马逊该区域的此类混合群均由单一蚁鵙物种统领，这为我们比较不同混合群间哨兵物种的质量差异提供了独一无二的天然实验系统。我们通过向混合群放飞3种经过活体训练的猛禽（捕食者）以模拟捕食威胁，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）在警报叫声中编码的威胁强度与威胁类型相关信息。野外实验结果显示，不同哨兵物种在发出警报叫声以及区分捕食者的概率上存在显著差异。这类差异可能会对偷听者物种的适合度产生重要影响，并进而塑造其所处的恐惧景观。