Doctoral Dissertation Improvement: The Juvenile Balancing Act: Survival, Skill-learning, and Growth in Phayre's Leaf Monkeys

灵长类的特点是幼年期异常长，从而产生延迟繁殖的代价。如此漫长的发育，在人类中最为明显，与培养大大脑的高昂成本有关。其他研究人员假设，长青春期是对学习复杂的生态或社交技能的必要性的反应，或者是青少年避险的结果。从这一理论角度出发，本研究旨在回答四个主要问题：(I)青少年是否利用时间获得生态技能，(Ii)他们是否使用空间策略来降低风险，(Iii)社会关系如何提供好处，(Iv)生长速度是否反映了青少年技能习得的差异。研究将在泰国东北部的Phu Khieo野生动物保护区进行，对22只Phayre幼年叶猴(Trachypithecus Phayrei)进行为期20个月的研究。除了收集食物的机械特性和营养含量外，还将收集喂养和社会数据。生长速度将使用摄影测量学方法进行非侵入性评估，以测量肢体长度。拟议研究的智力价值在于其对技能获得的作用的新视角。食物机械特性在觅食个体发育中的作用很少被详细研究。这项研究还迈出了重要的一步，将行为测量和生长测量结合在一起，这些因素在对非人类灵长类动物的研究中很少同时考虑。总体而言，大多数灵长类动物的研究都集中在成年研究对象上，因此忽视了在成年之前就可能存在的不同的选择压力。这个项目提供了一个机会，为任何关于灵长类动物幼体延长假说的讨论增加急需的数据。就更广泛的影响而言，这项研究将是第一个利用非侵入性方法测量野生灵长类动物生长的研究之一。大多数灵长类动物的生长数据只能从圈养动物那里获得，不受自然环境资源短缺的影响。为在野外研究中更实际和更常规地使用这些非侵入性方法铺平道路，特别是对树生物种，将提高我们对生长和发育以及与行为的相互关系的理解。这项研究也将成为当地助教攻读博士学位的基础。通过这种参与，该项目将帮助避难所工作人员获得行为数据收集和植物采样的所有方面的经验。国际保护协会将在泰国学生的保护和野外方法课程中担任积极的助理，该课程将由国际保护协会负责。与当地学生、科学家和保护区工作人员交流想法将有助于确保对这个拥有非凡生物多样性的地点的研究和保护做出长期承诺，其中包括8种灵长类物种。

Primates are characterized by an unusually long juvenile period generating costs in terms of delayed reproduction. Such a lengthened development, most distinct among humans, has been linked to high costs of growing large brains. Other researchers hypothesize that long juvenility is a response to the necessity of learning complex ecological or social skills or a consequence of juvenile risk aversion. Drawing from this theoretical perspective the proposed study aims at answering four main questions: (i) do juveniles use their time to acquire ecological skills, (ii) do they use spatial tactics to reduce risks, (iii) how do social relationships provide benefits, (iv) do growth rates reflect variation in juvenile skill acquisition. Research will be conducted at Phu Khieo Wildlife Sanctuary, Northeastern Thailand, following 22 juvenile Phayre's leaf monkeys (Trachypithecus phayrei) over a period of 20 months. Feeding and social data will be collected in addition to mechanical properties and nutrient content of food. Growth rates will be assessed non-invasively using photogrammetric methods to measure limb length.The intellectual merit of the proposed research is its new perspective on the role of skill acquisition. The role of food mechanical properties in foraging ontogeny has rarely been investigated in detail. This study also takes an important step by integrating behavioral and growth measures, factors rarely considered simultaneously in studies of nonhuman primates. Overall, most primate research has focused on adult subjects, thus neglecting the potentially different selective pressures operating well before adulthood. This project provides an opportunity to add much-needed data to any discussion concerning hypotheses for extended juvenility among primates.In terms of broader impacts this study will be one of the first to utilize non-invasive methods for measuring growth in wild primates. Most primate growth data are available only from captive animals not subject to resource shortages of natural environments. Paving the way for more practical and regular use of these non-invasive methods in field studies, particularly for arboreal species, will improve our understanding of growth and development and the interrelationship with behavior. The study will also form the basis for a Ph.D. involving local assistants. Through this involvement the project will help sanctuary workers to gain experience with all aspects of behavioral data collection and plant sampling. The co-PI will be an active assistant in a conservation and field methods course for Thai students, which will be conducted by the PI. Sharing ideas with local students, scientists and sanctuary workers will help to ensure a long-term commitment to both research and conservation at this site of extraordinary biodiversity including 8 primate species.