Methods for Studying the Ecological Physiology of Feeding in Free-Ranging Howlers (Alouatta palliata) at La Pacifica, Costa Rica

We lack a general understanding of how primates perform physiologically during feeding to cope with the challenges of their natural environments. We here discuss several methods for studying the ecological physiology of feeding in mantled howlers (Alouatta palliata) at La Pacifica, Costa Rica. Our initial physiological effort focuses on recording electromyographic activity (EMG) from the jaw muscles in free-ranging howlers while they feed in their natural forest habitat. We integrate these EMG data with measurements of food material properties, dental wear rates, as well as spatial analyses of resource use and food distribution. Future work will focus on incorporating physiological measures of bone deformation, i.e., bone strain; temperatures; food nutritional data; and hormonal analyses. Collectively, these efforts will help us to better understand the challenges that howlers face in their environment and the physiological mechanisms they employ during feeding. Our initial efforts provide a proof of concept demonstrating the methodological feasibility of studying the physiology of feeding in free-ranging primates. Although howlers offer certain advantages to in vivo field research, many of the approaches described here can be applied to other primates in natural habitats. By collecting physiological data simultaneously with ecological and behavioral data, we will promote a more synthetic understanding of primate feeding and its evolutionary history.