This project will examine why and how owl monkeys live in a monogamous relationship. Owl monkeys live in groups that include only one pair of reproducing adults and male owl monkeys are heavily involved in infant care, carrying the infant most of the time. Why do male owl monkeys mate in a monogamous relationship presumably foregoing other reproductive opportunities? Why are they such good fathers, investing heavily in the care of offspring they may have not even sired? The evolution of monogamy and paternal care in primates remains largely unknown, despite its profound implications for understanding human behavior.
There are three possible explanations that the study will evaluate: 1- males are unable to monopolize more than one female because females are spread too far apart from each other, 2- the care and services the male provides to the female are necessary for the survival of the offspring and, 3- social monogamy occurs because of the successful guarding of mates done by males and females. A team of doctoral and undergraduate students from the USA and Argentina will collect data from 22 owl monkey groups in the forests of the Argentinean Chaco. Among other things, they will collect data on the abundance and distribution of food resources to evaluate how females distribute themselves in the forest and on infant survival to evaluate the benefits of paternal care. Finally, they will conduct experiments simulating the presence of predators and the presence of sexual competitors to evaluate how males and females may respond to a threat to their monogamous relationship.
This project will make a substantial intellectual contribution to the understanding of how ecological and social factors affect the evolution of social monogamy in primates, including humans. It will also allow us to examine the differences between males and females in behavior and both parental and mating tendencies. From a more applied perspective, the long-term demographic data on owl monkeys will be useful in informing management decisions for other less well-known primate and mammal species. For example, it may be possible to model the viability of other more endangered primate populations based on the information collected from this project.
The broad impacts of this project are numerous. The owl monkey project maintains collaborations with NGOs in Argentina that are responsible for educating the local people about conservation issues, as well as with national and provincial government offices. The PI has already offered (and will continue to offer) training and educational opportunities to 85 students from the US and to 84 students from seven Latin American countries, England, and Japan in situations ranging from field internship to MA and PhD dissertations. The study will continue to generate valuable biological samples that will be shared with numerous researchers and institutions. The PI is also involved in conservation activities, and he founded a conservation-related organization (of which he is scientific director) for the region. In addition, he has organized field training courses for Latin American students.
Dr. Eduardo Fernandez-Duque, Assistant Professor in the Department of Anthropology of the University of Pennsylvania, is the Principal Investigator of the Owl Monkey Project. Between 1996-2005, Dr. Fernandez-Duque spent 70 months in the field, getting off the ground this international and multidisciplinary research program. Under the guidance of the PI, the year-round field activities have been coordinated, conducted, and expanded by a team of young Argentinean biologists, among them Marcelo Rotundo (Field Manager), Cecilia Juárez (doctoral student) and Victor Dávalos (botanist). The project has also largely benefited from the participation of more than 200 students (52% females, 48% males) from the US (100 students), Argentina (120 students) and 14 other countries (30 students). Some of the data and samples collected led to studies and publications in collaboration with colleagues from institutions worldwide. The Owl Monkey project has provided crucial information on the behavior, demography and reproductive ecology of these small neotropical monkeys, one of the few socially monogamous primates in the world. A recent NSF-funded evaluation of three hypotheses to explain the maintenance of monogamy generated revealing insights. For example, differences in the infant production of each group or in the age at natal dispersal by young individuals were not associated with differences in the abundance and distribution of food resources among territories. On the other hand, the hypothesis that the mother’s energetic costs are lessened by the male’s contribution to infant care was supported: putative fathers tended to lose more weight than the mothers during the time they provided care. It was also found that the presence of adults who range solitarily in search of reproductive opportunities constitutes a concrete source of intrasexual aggression that may be favoring the maintenance of close proximity between pairmates. Field work takes place primarily in Estancia Guaycolec, a 25,000 ha cattle ranch in the Province of Formosa in the Argentinean Chaco. In the last few years, the work has been expanded to Pilcomayo National Park (58,000 ha), the only park in Argentina where owl monkeys are protected. The Penn Field Station in the city of Formosa houses the project offices, labs, and lodging facilities, whereas the local not-for-profit organization Fundación ECO provides logistical and administrative support. The Centro de Ecología Aplicada del Litoral (CONICET, Argentinean National Council of Research), the National Parks Administration and the Department of Anthropology of the University of Pennsylvania all provide institutional support. Owl monkeys offer a unique opportunity to evaluate hypotheses on the evolution of social monogamy, infant care, and activity patterns among primates. Why do male owl monkeys mate in a monogamous relationship presumably foregoing other reproductive opportunities? Why do they invest heavily in the care of offspring? Why are owl monkeys the only anthropoids with nocturnal habits? The Owl Monkey Project is helping us understand how ecological and social factors regulate social monogamy and infant care in primates, including humans. It is also allowing us to examine some of the environmental factors that may have been key in triggering evolutionary switches between diurnal and nocturnal habits in primates. The broader impacts have been numerous. Being the only long-term program on any mammal species in the Argentinean Gran Chaco, it has had multiplying effects on the conservation of this ecosystem and its fauna. It has also contributed substantially to local education programs. In 1999, Fernandez-Duque co-founded Fundación ECO of Formosa (www.fundacioneco.org.ar) and since then he has collaborated with them in developing primate conservation field courses, establishing the Mirikiná (local name for owl monkeys) Reserve (1,500 ha) in Guaycolec Ranch and launching a National Program for the Conservation of Owl Monkeys. Several REU-NSF sponsored students have benefited from educational opportunities and in the near future the project plans to establish an REU site that will offer a Semester Abroad on Biological Anthropology.
