Jaw-muscle electromyography during chewing in free-ranging mantled howling monkeys at La Pacifica, Costa Rica: A pilot study

灵长类动物咀嚼形式、功能和进化的研究通常分为两种研究方向。第一种方法是对圈养的灵长类动物进行实验室研究，使用肌电图（EMG）等技术来量化有节奏咀嚼的动态。第二项研究包括实地研究，旨在捕捉灵长类动物摄食行为和饮食的多样性。综合起来，这些研究项目提供了压倒性的和互补的证据，证明在灵长类动物的进化过程中，饮食和喂养导致了咀嚼器官形式的适应性改变。尽管他们对灵长类动物咀嚼进化有共同的见解，但这些研究项目从未完全整合。此外，由于颚肌的功能直接受到食物的机械特性的影响，实验室研究难免会有一种必要的假设，即它们可靠地复制了动物在野外的经历。为了整合这两条研究路线，pi将开发和测试一种新系统，以记录哥斯达黎加La Pacifica自由放生的披毛吼猴（Alouatta palliata）的颚肌活动。在这些猴子吃天然食物时收集的肌电图数据将与这些食物的机械特性相关联，以确定颚肌功能如何随着食物的机械特性而变化。La Pacifica的吼猴是一个理想的研究样本，因为它们的摄食生态在这个自然栖息地有很好的记录。此外，由于它们的饮食范围从树叶到水果，因此可以在咀嚼具有一系列结构和机械特性的食物时记录肌电数据。该项目的科学价值在于其综合的方法来研究灵长类动物咀嚼器肌肉骨骼设计的进化意义。这个项目将是同类项目中第一个将基于实验室的颚肌功能记录技术与灵长类动物摄食生态学的实地研究相结合的项目。本项目收集的数据将把咀嚼功能、饮食和自然摄食行为联系起来。通过结合这些不同的数据，我们可以对灵长类动物咀嚼器官的适应性提出生态和功能上强有力的假设。此外，这些数据将解决现有的实验室导出的肌电图数据是否是各种灵长类动物可能遇到的自然环境的合理代理。该项目更广泛的影响是，它将为哥斯达黎加学生提供教育机会，并为白斑叶蝉的保护做出贡献。学生将获得实地技术、肌电图、机械性能数据收集和分析方面的实践培训。这种综合方法将为未来灵长类动物生态学、功能形态学和保护的研究提供一个广泛的进化框架。这项研究还将有助于保护管理决策，以确定这些濒危灵长类动物在中南美洲不同微栖息地的长期可持续性。最后，该项目由一名少数族裔女性研究员领导，从而促进了少数族裔在科学领域的代表性。

Studies of primate masticatory form, function and evolution typically segregate into one of two lines of research. The first involves lab-based studies on captive primates, using techniques such as electromyography (EMG), to quantify the dynamics of rhythmic mastication. The second line of research involves field studies aimed at capturing the diversity of primate feeding behaviors and diets. Combined, these research programs provide overwhelming and complementary evidence that diet and feeding have led to adaptive modifications of masticatory apparatus form throughout primate evolution. Despite their mutual insight into primate masticatory evolution, these research programs have never been fully integrated. Moreover, because jaw-muscle function is directly influenced by the mechanical properties of foods, laboratory studies suffer from the necessary assumption that they reliably replicate what animals experience in the wild. In order to integrate these two lines of research, the PIs will develop and test a novel system to record jaw-muscle activity in free-ranging mantled howler monkeys (Alouatta palliata) at La Pacifica, Costa Rica. The EMG data collected from these monkeys while they eat their natural diets will be correlated with the mechanical properties of these foods to determine how jaw-muscle function varies with food mechanical properties. Howler monkeys at La Pacifica make an ideal study sample because their feeding ecology has been well-documented in this natural habitat. Additionally, because their diet ranges from leaves to fruits, EMG data can be recorded during the mastication of foods with a range of structural and mechanical properties.The scientific merit of this project lies in its integrative approach to studying the evolutionary significance of musculoskeletal design in the primate masticatory apparatus. This project will be the first of its kind to combine lab-based techniques for recording jaw-muscle function with field research on primate feeding ecology. Data collected in this project will link between masticatory function, diet and natural feeding behaviors. By combining these various data, we can develop ecologically and functionally robust hypotheses of primate adaptations of the masticatory apparatus. Furthermore, these data will address whether existing lab-derived EMG data are a reasonable proxy of the natural environment that various primates might encounter. The broader impacts of this project are that it will provide educational opportunities to Costa Rican students and contribute to the conservation of A. palliata. Students will get hands-on training in field techniques, electromyography, and mechanical properties data collection and analysis. This integrative approach will provide them with a broad evolutionary framework for future work on primate ecology, functional morphology and conservation. This research will also benefit conservation management decisions regarding the long-term sustainability of these endangered primates in different microhabitats in Central and South America. Finally, this project is led by a minority female researcher, thereby contributing to minority representation in the sciences.