Part I. Paleontology, Phylogeography, Taxonomy and Historical Perspectives on the Study of Owl Monkeys -- Cebid or Pitheciid: An Evolutionary History of Aotus, the Owl Monkey -- Phylogeography of the Owl Monkey -- Indigenous Records of Owl Monkeys, Early Explorers, Historical and Current Review of the Studies of Owl Monkeys (15th-20th centuries) -- The Owl Monkey Project of Argentina: 30 years of field research, education and conservation -- Taxonomy and Distribution -- Part II. Morphology, Genetics, Endocrinology, Circadian biology -- Genomics -- Diet, Dentition, and Jaw Shape in Aotus -- Molecular Phylogenetics -- Reproductive Ecology and Behavioral Endocrinology of Owl Monkeys -- Behavioral, Physiological and Morphological Thermoregulatory Adaptations -- Part III. Behavioral Ecology -- Field Methods for the Study of Owl Monkeys -- Patterns of nocturnal activity by night monkeys (Aotus spp.) in the tropics -- Cathemerality in Azara's owl monkeys of Argentina. -- Social Behavior in Owl Monkeys -- Paternal care in owl monkeys -- Dispersal: a critical life-history stage influencing populations, social dynamics, and individual fitness -- The great unknown - what we (do not) know about floaters. -- Intraspecific communication among owl monkeys. -- Owl Monkey Diet and Feeding Ecology. -- Part IV -- Correlates of population densities and occupancy rates in night monkeys -- Population Status and Conservation of the Panamanian Night Monkey Aotus zonalis. -- Population assessment and strategies for the conservation of Nancy Ma's night monkey populations at the Colombian-Peruvian Amazon border -- Conservation of Aotus sp. in anthropogenic habitats in the Andes -- Trade in owl monkeys -- Part V. Integration of Research on Captive and Wild Populations -- The owl monkey colony at the Michale Keeling Center for Comparative Medicine -- The owl monkeys of the DuMond Conservancy in Miami, USA - a scientific, educational and community asset.