This will be the first time a volume will be compiled focusing on South American monkeys as models to address and test critical issues in the study of nonhuman primates. In addition, the volume will serve an important compliment to the book on Mesoamerican primates recently published in the series under the "DIPR" book series. The book will be of interest to a broad range of scientists in various disciplines, ranging from primatology, to animal behavior, animal ecology, conservation biology, veterinary science, animal husbandry, anthropology, and natural resource management. Moreover, although the volume will highlight South American primates, chapters will not simply review particular taxa or topics. Rather the focus of each chapter is to examine the nature and range of primate responses to changes in their ecological and social environments, and to use data on South American monkeys to address critical theoretical questions in the study of primate behavior, ecology, and conservation. Thus, we anticipate that the volume will be widely read by a broad range of students and researchers interested in prosimians, New World monkeys, Old World monkeys, apes, humans, as well as animal behavior and tropical biology.