The owl monkey project, started in 1996 by Dr. Eduardo Fernandez-Duque, is a multidisciplinary research program on the owl monkeys of the Argentinean Chaco. Some of the major questions being explored are: How are physical and behavioral dimorphism related in monogamous species? What are the ecological and social correlates of monogamous relationships? What are the ecological and behavioral correlates of paternal care in owl monkeys? Why do male owl monkeys invest heavily in the care of offspring? To answer those questions, an international group of biologists, anthropologists and primatologists conduct studies on population biology, demography, behavior, genetics, chronobiology endocrinology and conservation in collaboration with numerous institutions and with the support of international and Argentinean funding agencies.