The book synthesizes new field data on the biogeography, behavioral ecology, circadian biology, population biology and demography of owl monkeys spanning their entire continental range from Panamá to Argentina. It includes theoretical perspectives drawn from evolutionary biology, biological anthropology, anatomy, morphology and physiology, genetics, endocrinology and conservation biology to examine a specific set of adaptations that have allowed owl monkeys to exploit the nocturnal niche while functioning in a pair-living sexually monogamous system with remarkable patterns of paternal care. The expertise of Eduardo Fernandez-Duque (Editor), with 30 years of research experience with both captive and wild primates, makes this book one of a kind. The volume brings together a combination of senior researchers who during four decades have established captive owl monkeys as a system of study with a new generation of younger scientists who have, for the last 10-20 years, been spearheading their study in the wild. The 25 chapters (10 of them led by Latin American researchers) present the work of a remarkably diverse range of authors; the majority of them nationals of countries where owl monkeys are present, as well as researchers from the U.S and Europe.