What do we mean when we say that a diet is nutritious? Why can some animals get all the energy they need from eating leaves while others would perish on such a diet? Why don't mountain gorillas eat fruit all day as chimpanzees do? Answers to these questions about food and feeding are among the many tasty morsels that emerge from this authoritative book. Informed by the latest scientific tools and millions of hours of field and laboratory work on species across the primate order and around the globe, this volume is an exhaustive synthesis of our understanding of what, why, and how primates eat. State-of-the-art information presented at physiological, behavioral, ecological, and evolutionary scales will serve as a road map for graduate students, researchers, and practitioners as they work toward a holistic understanding of life as a primate and the urgent conservation consequences of diet and food availability in a changing world.