Mechanisms and effectiveness of predator detection by capuchin monkeys

这项研究旨在填补我们在理解灵长类与捕食者关系方面的关键空白。灵长类动物群居的一个最被广泛引用的原因是为了减少被捕食的风险。然而，一些遭受高捕食率的灵长类动物仍然独自或以非常小的群体觅食。这一观察和几个理论模型的预测表明，高捕食风险可能有利于非常小的群体，也可能有利于非常大的群体。这种结果的发生取决于1)不同大小的灵长类猎物群体检测捕食者的方法和有效性，以及2)猎物和捕食者相互检测的相对能力。尽管对灵长类动物的警觉行为进行了许多研究，但对于任何物种来说，关于警觉在检测捕食者方面的有效性、检测到的平均距离以及影响检测机会的变量，都只有零星的知识。关于灵长类捕食者的狩猎行为和检测能力更是知之甚少。为了衡量解释动物群体大小作为捕食风险函数的重要变量，阿根廷的五个不同大小的野生棕色卷尾猴群体将被生活(拴住)和模型捕食者放置在它们的家园中。观察者将跟踪单个猴子，并记录一系列背景变量(个体的性别和年龄、与捕食者的距离、猴子在森林中的高度、猴子看的方向等)，以及猴子是否发现了捕食者，这是通过发出警报或突然长时间而固定地直接盯着捕食者发出的信号。当一群猴子走近时，每只活的被拴住的猛禽都将被录像；它探测到这群猴子的距离以及是视觉还是声音将从录像带和相关的口头评论中确定。观测的细节和样本量将比以前的研究有很大改进，因为使用模型和圈养捕食者可以更好地控制探测过程，包括系统地改变探测条件，并在探测发生之前和之后记录观测。这项研究的结果将解决一个关于人类祖先的社会生活起源的重要问题，从而可能有助于解释当前人类社会的形式。该项目还将通过以下方式促进生物多样性保护：1)继续在研究地点长期驻扎研究人员以阻止偷猎者；2)促进关于这种长期生存物种的群体人口学的长期数据库；3)继续监测入侵物种和气候变化对当地生态的长期变化。这项研究将有助于培养至少一名美国研究生、几名大学本科生和一名或多名阿根廷生物学家。来自该项目的数据将被贡献给一个大规模的动物行为元数据库，以便使当前和未来的研究人员能够轻松地在线访问。从猴子种群中采样的遗传物质将被放置在公共生物材料库中，以供未来访问。

This study is designed to fill in critical gaps in our understanding of primate-predator relationships. One of the most widely quoted reasons that primates live in groups is to reduce the risk of predation. However, some primates that suffer high predation rates nevertheless forage alone or in very small groups. This observation and the predictions of several theoretical models suggest that high predation risk can favor either very small or very large groups. Which outcome occurs depends on 1) the method and effectiveness of detection of the predator by the primate prey in groups of different sizes, and 2) the relative ability of prey and predator to detect each other. Despite many studies of vigilance behavior in primates, there is only fragmentary knowledge for any species on how effective vigilance is in detecting predators, at what average distance detection occurs, and the variables that affect the chance of detection. Even less is known about the hunting behavior and detection ability of the predators of primates.To measure the important variables that explain group size in animals as a function of predation risk, five different-sized groups of wild brown capuchin monkeys in Argentina will have live (tethered) and model predators placed in their home ranges. Observers will follow individual monkeys and record a set of context variables (individual's sex and age, distance to the 'predator', monkey's height in the forest, direction the monkey is looking, etc.), along with whether or not the monkey detects the predator, as signaled by alarm calls or a sudden prolonged and fixed stare directly at the predator. Each live tethered bird of prey will be video-taped as a group of monkeys approaches; the distance at which it detects the group and whether the detection is by sight or sound will be determined from the video tape and associated verbal commentary. The detail and sample size of observations will improve greatly on prior studies because the use of model and captive predators permits greater control of the detection process, including systematic variation of detection conditions and recording observations both before and after detection occurs. The results of this study will address an important question about the origins of social living in human ancestors, and thus may help to explain the form of current human societies. The project will also contribute to biodiversity conservation by: 1) continuing the long-term presence of researchers in the study site to discourage poachers, 2) contributing to the long-term database on group demography of this long-lived species, 3) continued monitoring of long-term changes in local ecology due to invasive species and climate change. The research will help train at least one U.S. graduate student, several college undergraduates, and one or more Argentine biologists. Data from this project will be contributed to a large-scale meta-database for animal behavior, to allow easy online access to current and future researchers. Genetic material sampled from the monkey population will be placed in a public biomaterials repository for future access.