Great Ape Juvenile Development and Digestive Physiology

人类和许多非人类灵长类动物都有很长的幼年发育时期，但这些模式的进化基础尚未完全了解。猩猩（Pongo pygmaeus）有着缓慢的生活史和极端波动的食物供应，是一个很好的物种，用于测试关于进化过程中可能有利于缓慢幼年发育的因素的假设。在本项目中，将采用多种方法对印度尼西亚古农帕隆国家公园的猩猩进行长期研究，以确定食物供应如何影响幼猩猩的生长发育，以及幼猩猩和成年猩猩在觅食行为、饮食和从食物中获取能量的整体能力方面的差异程度。该项目为本科生和研究生提供了研究机会，并增加了研究地点附近的科学能力。该项目与首席研究员的保护计划并行，该计划通过教育、替代生计、采用习惯森林以及与地方当局分享研究成果来帮助保护猩猩。该项目利用社交媒体、网站、Facebook、twitter、月度通讯和每周广播节目，向当地和世界各地的观众宣传猩猩保护的重要性，以及研究在解决保护问题方面的应用。项目团队成员还将制定一个特殊的女童子军贴片计划，向小学/中学高年级的女孩教授与科学领导、野外生物学和动物研究相关的技能，这些女孩是退出STEM学科的风险最高的群体。了解是什么限制了幼崽的发育，以及在繁殖开始之前，生长中的有机体将能量转化为生长和维持的能力，是我们理解动物生活史，包括人类进化研究的核心。有人认为，人类进化的特点是选择较慢的生命史。关于类人猿发展的现有比较数据有限，而且主要是基于生活在能源丰富环境中的圈养动物，因此可能经历了加速生长。这项研究通过研究对消化的发展和生态影响，阐明了生态风险规避的概念。研究人员将使用行为观察、生理测量、饮食和可用食物资源数据来确定：1)幼猩猩是否比成年猩猩面临更大的生态风险，幼猩猩是否能够从食物中提取更少的能量，咀嚼力在将食物分解成更小颗粒中的作用，以及体型如何决定肠道通过率和从食物中提取多少能量；2)幼鱼和成鱼在觅食行为、饮食组成和总能量消耗方面的差异；3)幼年发育对母亲行为和生理的影响；4)幼猩猩的生长速度，以及这是否因食物供应而异；5)幼猩猩生理随发育的变化及对食物能量摄入的依赖。如果在食物供应不足的时期食用高纤维食物会阻碍消化，我们可以更好地理解幼崽和它们的母亲为抵消热量和营养缺乏而采取的补偿行为。由于它们体型较小，肠道生物群落不完整，咀嚼发育不成熟，预计幼鱼更容易受到食物短缺的影响。此外，如果同一物种的体型较大的动物能够比体型较小的动物更有效地处理纤维，这可能会对体型的进化如何影响获得更高质量饮食的能力产生影响。

Humans and many non-human primate species have long periods of juvenile development, but the evolutionary underpinnings of these patterns are not fully understood. Orangutans (Pongo pygmaeus), which have a slow life history and extreme fluctuations in their food supply, are a good species for testing hypotheses about factors that may favor slow juvenile development during evolution. In this project, multiple methodologies will be applied in a long-term study of orangutans in Gunung Palung National Park, Indonesia, to determine how food availability affects juvenile growth and development, and the extent to which juvenile and adult orangutans differ in foraging behaviors, diets, and overall ability to extract energy from foods. The project provides research opportunities for undergraduate and graduate students and increases scientific capacity near the research site. The project runs parallel to the principal investigator's conservation program that helps conserve orangutans through education, alternative livelihoods, adoption of customary forests, and sharing of research with local authorities. Using social media, website, Facebook, twitter, monthly newsletter, and weekly radio programs, the project educates local and world-wide audiences about the importance of orangutan conservation and the application of research to solving conservation problems. The project team members also will develop a special Girl Scout patch program to teach skills related to scientific leadership, field biology and the study of animals to girls in the upper elementary/middle school range, the highest risk group of children for dropping out of STEM subjects. Understanding what constrains juvenile development and the ability of the growing organism to translate energy into growth and maintenance, before the onset of reproduction, is central to our understanding of animal life history, including the study of human evolution. It has been argued that human evolution has been marked by selection for a slower life history. Existing comparative data on great ape development are limited, and based primarily on captive animals living in energy-rich environment, thus likely experiencing accelerated growth. This study sheds light on the concept of ecological risk aversion by looking at both developmental and ecological influences on digestion. The investigators will use behavioral observation, physiological measures, and data on diet and available food resources to determine: 1) if juvenile orangutans are at greater ecological risk than adults, whether juveniles are able to extract less energy from their food, the role of masticatory force in breaking up food into smaller particles, and how body size determines gut passage rates and how much energy is extracted from food; 2) how juveniles and adults differ in their foraging behavior, diet composition and overall energy expenditure; 3) how juvenile development impacts maternal behavior and physiology; 4) at what rate juvenile orangutans grow and whether this differs depending on food availability; and 5) how juvenile orangutan physiology changes with development and depends on food energy intake. If digestion is impeded when consuming high fiber fallback foods during periods of poor food availability, we can better understand the compensatory behaviors that both juveniles and their mothers take to offset caloric and nutrient deficiency. Because of their smaller body size, incomplete gut biome, and masticatory immaturity, juveniles are predicted to be more vulnerable to periods of food shortage. Additionally, if larger-bodied animals of the same species are able to process fiber more efficiently than smaller-bodied animals, this has could have implications for how the evolution of body size impacts the ability to achieve a higher quality diet.