Collaborative research: Physiological signatures of variable weaning strategies in wild primates

过早断奶可导致婴儿发育不良和婴儿死亡率增加；然而，导致过早断奶的社会条件及其后果仍然知之甚少。该项目的中心目标是研究与新成年雄性移民和/或不良母亲状况相关的压力社会条件如何影响过早断奶的可能性，以及反过来，在非人灵长类动物模型中，过早断奶如何影响婴儿生长、肠道微生物定植和免疫系统的发育。考虑到早期断奶作为人类进化标志的重要性，开发这种早期生命过渡的综合纵向模型是有价值的。此外，这些发现可以作为一种动物模型，用于了解现代人缩短或延长母乳喂养的成本和收益。该项目将为至少一名博士后和几名研究生和本科生提供严格的科学培训。这些保护区还将参与地方和国际两级的公众宣传活动，为国内外的科学教育和保护工作作出贡献。该项目研究了社会因素、不同断奶策略与狒狒婴儿生长和免疫系统发育之间的联系。它利用从0-2.5岁婴儿收集的横断面和纵向数据来解决以下目标：(1)确定与压力人口变化和/或母亲状况相关的社会因素如何影响停止哺乳的时间；(2)确定相对于婴儿尺寸的早期断奶与出生后发育迟缓、肠道微生物多样性和组成改变以及尿新蝶呤（细胞炎症的生物标志物）浓度的关系。狒狒是这项研究的理想对象，因为它们的社会系统的特点是频繁而紧张的社会动荡，这会破坏婴儿的发育，甚至导致婴儿死亡。此外，雌性狒狒形成了强大的统治等级制度，决定了获得食物的途径，从而使研究人员能够解决与母亲营养不良相关的社会因素如何与不同的断奶策略相关联。总之，这些特征使狒狒成为研究过早断奶的一个极好的模型系统。这项研究将是第一个整合同位素/元素化学、基因组学、内分泌学和数字摄影测量学的创新方法来研究野生灵长类婴儿过早断奶的原因和后果的研究之一，从而确定一些连接早期社会逆境与长期发育和健康的关键机制。学员将有机会学习行为数据收集方法以及各种湿实验室方法，以表征肠道微生物组的组成，并通过在无创收集的粪便样本中发现的牛奶与植物源碳和氮的数量来定义断奶。

Premature weaning can result in poor infant developmental outcomes and increased infant mortality; however, the social conditions that lead to premature weaning and its consequences are still poorly understood. The central goal of this project is to examine how stressful social conditions linked to the immigration of new adult males and/or poor maternal condition influence the likelihood of premature weaning, and, in turn how premature weaning then influences infant growth, gut microbial colonization, and the development of the immune system in a nonhuman primate model. Given the importance of early weaning as a hallmark of human evolution, developing comprehensive longitudinal models of this early life transition are valuable. In addition, the findings may serve as an animal model for understanding the costs and benefits of truncated or extended breastfeeding in modern humans. The project will provide rigorous scientific training to at least one post-doctoral fellow and several graduate and undergraduate students. The PIs will also engage in public outreach at local and international levels, contributing to scientific education and conservation efforts both domestically and abroad. This project examines the links between social factors, variable weaning strategies, and infant growth and immune system development in geladas. It draws on both cross-sectional and longitudinal data collected from infants aged 0-2.5 years to address the following goals: (1) Determine how social factors related to stressful demographic changes and/or maternal condition influence the timing of nursing cessation; (2) Identify how earlier weaning relative to infant size is related to stunted postnatal growth, altered gut microbial diversity and composition, and the concentration of urinary neopterin, a biomarker for cellular inflammation. Geladas are ideal for this research because their social system is characterized by frequent and stressful social upheavals that disrupt infant development and can even lead to infant mortality. Further, gelada females form strong dominance hierarchies that determine access to food, thus allowing researchers to address how social factors linked to poor maternal nutrition are associated with variable weaning strategies. Together, these attributes make geladas an excellent model system in which to study premature weaning. This study will be one of the first to integrate innovative methods in isotopic/elemental chemistry, genomics, endocrinology, and digital photogrammetry to examine the causes and consequences of premature weaning in wild primate infants, thus identifying some of the key mechanisms bridging early life social adversity to long-term developmental and health. Student trainees will have the opportunity to learn methods in behavioral data collection as well as various wet lab methods to characterize the composition of the gut microbiome and define weaning by the amount of milk vs. plant-origin carbon and nitrogen found in noninvasively collected fecal samples.