Mechanisms and effectiveness of predator detection by capuchin monkeys

这项研究旨在填补我们对灵长类动物与捕食者关系的理解中的关键空白。灵长类动物群居的一个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单独或在非常小的群体中觅食。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或非常大的群体。发生哪种结果取决于：(1)灵长类动物在不同大小的群体中发现捕食者的方法和有效性；(2)猎物和捕食者相互发现的相对能力。尽管对灵长类动物的警觉性行为进行了许多研究，但对于任何物种的警觉性在探测捕食者时的有效性、探测发生的平均距离以及影响探测机会的变量，人们的了解都是零碎的。灵长类动物捕食者的捕猎行为和探测能力更是鲜为人知。为了测量解释动物群体规模作为捕食风险函数的重要变量，阿根廷五个不同大小的野生棕色卷尾猴群体将在它们的家园范围内放置活的（系住的）和模型捕食者。观察者将跟踪每只猴子并记录一组环境变量（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，这是通过警报呼叫或突然长时间盯着捕食者看的信号。当一群猴子靠近时，每只被拴住的猛禽都会被录下来；它探测到群体的距离，以及探测是通过视觉还是声音，将由录像带和相关的口头评论决定。观测的细节和样本量将大大改善先前的研究，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和记录探测发生前后的观测结果。这项研究的结果将解决一个关于人类祖先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)继续让研究人员长期驻留在研究地点，以阻止偷猎者；2)为这种长寿物种的群体人口统计提供长期数据库；3)继续监测由于入侵物种和气候变化导致的当地生态的长期变化。这项研究将帮助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。这个项目的数据将提供给一个大型的动物行为元数据库，使当前和未来的研究人员可以方便地在线访问。从猴群中取样的遗传物质将放置在公共生物材料储存库中，以备将来使用。

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.