LTREB Renewal: Social dynamics and fitness in a complex primate society

群居物种生活在群体中，它们的大小差别很大。对于任何物种来说，最大群体规模代表着一个临界点，在那里群体生活的成本超过了收益。然而，大多数关于群体社会动态的研究都集中在具有一个社会组织水平的社会。当面临竞争性的选择压力时，这些“单级社会”必然会采取一种妥协的解决方案——扩大规模以防止被捕食？或者，缩小体型以缓解饲养竞争？然而，一些社会已经通过“多层次社会”的进化解决了这个群体规模的难题——由许多模块化的核心群体组成，核心群体中的个人是一致的，而核心群体之间的联系可以迅速变化。本研究将通过调查野生灵长类动物狒狒的多层次社会，探索个体如何从单一社会过渡到多层次社会。这个项目提出了两个问题，每个问题都集中在狒狒社会的一个特征上。首先，是什么永久地将群体分开？其次，是什么让群体聚集在一起——形成更高的层次？这个项目之前已经证明，狒狒对陌生人有着异乎寻常的高容忍度。确定这种非凡的宽容背后的机制可以帮助我们理解另一个物种对陌生人的宽容的进化——人类。该项目的负责人将延续长期以来的国家和国际STEM推广传统（http://geladaresearch.org/db），并通过Save The Simiens(他们创建的501（c)(3)非营利组织，致力于保护研究发生地埃塞俄比亚塞米恩山脉国家公园的野生动物）在埃塞俄比亚的保护工作中投入大量时间。该项目由生物科学理事会的动物行为项目和社会、行为和经济科学理事会的生物人类学项目共同资助。本研究的目的是通过利用野生狒狒（Theropithecus gelada）多个核心群体的长期数据，确定个体相互作用如何导致多层次社会的高阶结构。具体来说，本项目将确定：(1)导致核心组分裂的原因（即分裂为两个或更多核心组）和(2)导致多个核心组保持在一起的原因（即保持更高级别的凝聚力）。本研究将探讨产生多层次社会的行为的适应性结果，并考察个体相互作用产生群体结构的机制过程。为了理解群体裂变的原因，有必要跟踪网络动态，检查裂变前后的女性社会网络，以确定社会关系的变化，这些变化可能预示着即将发生的裂变。为了理解更高层次的内聚，本研究将使用GPS项圈来跟踪发生（或未发生）裂变的核心组之间的同步运动。因此，这些结果将确定关联模式随时间的“衰减”。通过确定多层次社会的两个关键特征的起源——小的核心群体和这些群体之间的凝聚力——这项研究不仅将揭示狒狒单位裂变的原因，还将揭示它们是如何裂变的；这种进化途径可以在其他分类群中进行测试。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Social species live in groups that vary dramatically in size. For any species, the maximum group size represents a breaking point, where the costs of group-living outweigh the benefits. Yet, most research on the social dynamics of groups has focused on societies with one level of social organization. These "single-level societies" are bound to one compromise solution when faced with competing selective pressures - grow in size to protect against predation? Or, shrink in size to alleviate feeding competition? Yet, a few societies have solved this group-size conundrum through the evolution of "multi-level societies" - comprising many modular core groups where individuals within the core group are consistent while the associations between core groups can quickly change. This research will explore how individuals transitioned from single- to multi-level societies by investigating the multilevel society of a wild primate, the gelada. This project asks two questions that each focus on a hallmark of gelada society. First, what permanently splits groups apart? And, second, what keeps groups together - forming the higher levels? This project has previously demonstrated that geladas have an unusually high tolerance for strangers. Identifying the mechanisms behind this remarkable tolerance could help us understand the evolution of another species' tolerance for strangers - humans. The directors of this project will continue a long-standing tradition of national and international STEM outreach (http://geladaresearch.org/db) and significant time investment into conservation efforts in Ethiopia through Save the Simiens, a 501(c)(3) non-profit they created dedicated to protecting the wildlife of the Simien Mountains National Park of Ethiopia where the research takes place. This project is co-funded by the Animal Behavior Program in the Directorate for Biological Sciences and the Biological Anthropology Program in the Directorate for Social, Behavioral and Economic Sciences.The objective of this research is to identify how individual interactions lead to the higher-order structure of multi-level societies by harnessing long-term data on multiple core groups of wild geladas (Theropithecus gelada), an easy-to-observe primate with a multilevel society. Specifically, this project will identify: (1) what causes core groups to split up (i.e., fission into two or more core groups) and (2) what causes multiple core groups to remain together (i.e., maintain higher-level cohesion). This research will investigate the fitness consequences of behaviors that produce a multi-level society and examine the mechanistic processes by which group structure may emerge from individual interactions. To understand why groups fission, it is necessary to track network dynamics to examine female social networks before and after a fission to identify the changes in social relationships that may predict an impending fission. To understand higher-level cohesion, this research will use GPS collars to track simultaneous movement across core groups that have (and have not) undergone fission. Thus, these results will identify the "decay" in association patterns across time. By identifying the origin of two key features of multilevel societies - small core groups and cohesion among those groups - this research will uncover not just why gelada units fission but how they fission; and this evolutionary pathway can then be tested in other taxa.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.