Dissertation Research: Ecological Bases of Agonistic Coalitions in Capuchin Monkeys

在非人类灵长类动物的许多物种中，已经研究了成对攻击遭遇的生态基础。一些物种在寻找食物时也会形成侵略性的联盟，但这种联盟的生态相关性尚未得到研究。联盟被定义为两个或两个以上的个体在对抗一个或多个其他个体时的合作。本研究将重点研究白面卷尾猴（Cebus capucinus）在进食过程中的成对和联合攻击行为。本研究的目的是：(1)通过量化与资源竞争相关的成本和收益来衡量可能影响攻击性竞争率的生态因素；(2)检验非人类灵长类动物联盟行为进化的生态学解释。数据将在哥斯达黎加的两个干林研究地点收集。研究人员将研究与结成联盟相关的生态成本和收益是否与双配偶竞争中普遍存在的生态成本和收益存在系统性差异，以及雄性和雌性结成联盟的可能性是否相同。因为雄性通常对雌性处于优势地位，所以雌性会形成联盟来获得被雄性占据的食物区。争夺一块食物块的生态效益将以这块食物块上的参赛者获得的营养价值来衡量，而个人的成本则包括身体受伤的成本，以及在失败后寻找替代食物块所需的时间。生态学的解释将与简单的另一种解释进行检验，即战斗和联盟的频率反映了过度拥挤或在食物斑块中联盟伙伴的可用性。这项研究将帮助我们了解非人灵长类动物和人类合作行为的起源。

The ecological basis for pair-wise aggressive encounters has been investigated in many species of non-human primates. Some species also form aggressive coalitions while searching for food, but the ecological correlates of such coalitions have yet to be studied. A coalition is defined as cooperation by two or more individuals in an aggressive encounter against one or more other individuals. This study will focus on pair-wise and coalitional aggression in the white-faced capuchin, Cebus capucinus in the context of feeding. The objectives of this study are (1) to measure the ecological factors that may affect the rates of aggressive contests by quantifying the costs and benefits associated with resource competition and (2) to test an ecological explanation for the evolution of coalition behavior in non-human primates. Data will be collected at two dry-forest study sites in Costa Rica. The researchers will examine whether the ecological costs and benefits associated with coalition formation differ systematically from those that prevail during pair-wise contests, and whether males and females are equally likely to form coalitions. Because males are usually dominant to females in C. capucinus, one would expect females to form coalitions to gain access to food patches occupied by a male. The ecological benefit of fighting over a food patch will be measured as the nutritional gain available to contestants in the patch, whereas the cost to an individual includes both the cost of a physical injury and the time needed to find alternate food patches if it loses. The ecological explanation will be tested against the simple alternative that the frequency of fights and coalitions reflect overcrowding or the availability of coalition partners in a food patch. This study will help us to understand the origins of cooperative behavior in non-human primates and humans.