Squirrel Monkeys: A Test of Primate Social Evolution Theory

与其他哺乳动物目相比，组成灵长目的200个物种在社会组织中表现出极大的多样性。目前的理论表明，灵长类物种内部对食物的竞争程度是该物种社会组织的唯一最佳预测因素。例如，随着食物竞争的加剧，预计会出现更严格的统治等级，更多的女性与男性的优势，女性之间更紧密的联系，以及很少的女性分散。松鼠猴是一种分布在新热带地区的物种，它对食物竞争在灵长类社会组织进化中的重要性提供了一个独特而有力的测试。没有其他灵长类分类群在社会组织上有如此大的种群差异。之前的两项实地研究与预测完全一致。哥斯达黎加松鼠猴的队伍内部食物竞争可以忽略不计，表现出几乎不存在的雌性社会关系和雌性移民。相比之下，秘鲁松鼠猴之间的食物竞争非常激烈，雌性松鼠猴形成了密切的社会纽带，雌性松鼠猴从未被发现移民。我在苏里南的初步观察表明，还有第三种社会组织形式，其他部队成员以男性为主，女性从属关系很少。然而，这一群体中存在的极其激烈的食物竞争显然与理论相矛盾。如果得到证实，苏里南的松鼠猴社会系统为灵长类动物中食物竞争和社会行为之间密切联系的假说提供了强有力的检验，并为我们理解影响和构建灵长类社会系统的机制提供了重要的窗口。

The 200 species that comprise the Order Primates exhibit extreme diversity in social organization compared to other mammalian orders. Current theory suggests that the extent of competition for food within a primate species is the single best predictor of that species' social organization. With greater food competition, for example, more rigid dominance hierarchies, greater female versus male dominance, closer affiliations among females, and little female dispersal are expected.. Squirrel monkeys, a species distributed throughout the Neotropics, offer a uniquely powerful test of the importance of food competition in the evolution of primate social organization. No other primate taxon has such widely divergent population differences in social organization. Two previous field studies were entirely consistent with predictions. Costa Rican squirrel monkeys, with negligible within-troop food competition, exhibit almost non-existent female social bonds and females emigrate. In contrast, food competition is high among Peruvian squirrel monkeys, females form close social bonds, and females have never been known to emigrate. My preliminary observations in Suriname indicate yet a third form of social organization with strong male dominance of other troop members, and little female affiliation. Yet the extremely intense food competition that exists in this population is in apparent contradiction to theory. If confirmed, the squirrel monkey social system of Suriname provides a powerful test of the hypothesis of close linkage between food competition an social behavior in primates, and provides an important window to our understanding of the mechanisms that affect and structure primate social systems.