Niche Expansion and Terrestriality in an Arboreal Primate

大多数灵长类行为生态学的比较模型都假定野生灵长类动物的行为是适应性的，或者是过去生态条件下选择压力的产物。然而，人类活动改变环境的快速步伐导致了新的生态挑战，并使人们很难区分进化适应和更快获得的行为反应，这些行为反应可能会也可能不会随着时间的推移而适应。了解这种可塑性是分析进化机制的基础，也是评估生活在受干扰栖息地的濒危灵长类动物未来的当务之急。这项研究建立在一个独特的历史数据库的基础上，该数据库来自对巴西东南部大西洋森林野生北方短尾猴(Brachyteles Subxantus)的长期实地研究，以评估生态变化如何驱动行为创新，并确定新的行为模式在群体内和群体之间传播的社会路径。北部的Muriqui是极度濒危的物种，281只个体被限制在957公顷的受保护森林碎片中，研究种群占整个物种的25%以上。在过去的27年里，种群数量增加了五倍，种群密度现在是该物种已知的最高水平。之前对种群压力的行为调整包括从凝聚性分组模式转变为流动分组模式。最近，尽管它们生活在树上，但种群中最大的种群在使用地面方面经历了20倍的增长，其他三个较小的种群现在都从事陆地觅食。来自陆地捕食者和病原体的更大风险意味着，这种栖息地使用的变化是其生态位全面扩大的极端表现，这是由于种群在有限区域内的增长所必需的。通过收集这一拥挤种群中所有四个种群的系统行为数据，这项研究将量化生态位扩张的生态影响，以及新获得的行为模式通过分散雌性在种群之间传播并随后沿着已建立的社会网络在种群内传播的社会过程。这项研究的学术价值包括它将为其他灵长类动物与地面使用相关的生态条件提供新的比较视角，以及它将为当代灵长类动物的适应潜力和它们在快速变化的世界中的生存前景提供批判性见解。除了它的科学贡献外，这项研究将为唯一对这种极度濒危物种的长期研究提供必要的连续性，也是所有灵长类动物中运行时间最长的野外研究之一。它将有助于保存和保护北部仅存的据点之一，并保持研究人员为巴西学生提供培训机会的长期传统。合作研究和保护活动的既定记录，以及巴西在能力建设方面的成功，扩大了这项研究的更广泛影响，将国际保护和教育议程包括在内。

Most comparative models of primate behavioral ecology assume that the behaviors of wild primates are adaptive, or are the products of selection pressures under ecological conditions in the past. Yet, the fast pace at which human activities alter the environment results in new ecological challenges and makes it difficult to distinguish evolutionary adaptations from more rapidly acquired behavioral responses that may or may not be adaptive over time. Understanding this plasticity is fundamental to analyses of evolutionary mechanisms and represents an urgent priority for assessments of the future of endangered primates living in disturbed habitats. This study builds on a unique historical database from the long-term field study of wild northern muriqui monkeys (Brachyteles hypoxanthus) in the Atlantic Forest of southeastern Brazil to evaluate how ecological change drives behavioral innovations and to identify the social pathways by which new behavior patterns spread within and between groups. The northern muriqui is critically endangered, and with 281 individuals confined to a 957-hectare protected forest fragment, the study population represents more than 25% of the entire species. During the past 27 years, the population has quintupled in size and the population's density is now the highest known for the species. Previous behavioral adjustments to population pressures have included shifts from cohesive to fluid grouping patterns. More recently, and despite their arboreal lifestyle, the largest group in the population has undergone a 20-fold increase in its use of the ground and all three of the other smaller groups now engage in terrestrial feeding. The greater risks from terrestrial predators and pathogens imply that this change in the muriquis' habitat use is an extreme manifestation of an overall expansion of their ecological niche necessitated by the population's growth within a confined area. With the collection of systematic behavioral data on all four muriqui groups in this crowded population, this study will quantify the ecological implications of niche expansion and the social processes by which newly acquired behavior patterns are diffused between groups by dispersing females and subsequently spread within groups along established social networks. The intellectual merits of the study include the new comparative perspectives it will provide into the ecological conditions associated with ground use in other primates, and the critical insights it will provide into the adaptive potentials of contemporary primates and their prospects for survival in a rapidly changing world.In addition to its scientific contributions, this study will provide essential continuity for the only long-term study on this critically endangered species and one of the longest-running field studies of any primate. It will contribute to the conservation and protection of one of the last remaining strongholds for northern muriquis, and maintain the researcher's longstanding tradition of providing training opportunities for Brazilian students. The established record of collaborative research and conservation activities, and success with capacity building in Brazil, extend the broader impacts of this study to include an international conservation and educational agenda.