Current research

The Owl Monkey Project, started in 1996 by Dr. Eduardo Fernandez-Duque, is a multi-disciplinary research site in the Argentinean Chaco. In conjunction with the Anthropology Department at Yale University, we investigate the evolution of monogamy and paternal care in a pair-bonded primate.

In our history, the project has conducted studies on population biology, demography, behavior, genetics, endocrinology, and conservation. Our goal is to employ diverse biological and ecological methods to investigate the roles that males and females play in the maintenance of a monogamous social system.


The Owl Monkey Project continues to explore the genetic structure of the Guaycolec population. Genetic analyses, in combination with long-term behavioral observation, will allow us to test a number of hypotheses about the nature, evolution and maintenance of the social organization and mating system in this socially monogamous primate species.

Molecular genetic data allows us to examine the biological relatedness of individuals in groups of monogamous primates: how closely related the individuals are in various groups that make up the population; and the consequences, in terms of reproductive success, of copulations outside of the pair.

Understanding the genetic structure of a population, we can characterize maternal genetic variation, analyze the kinship structure of groups, asses paternity, and examine the possible effects of kin selection in the maintenance of social monogamy. During the last 10 years, we have collected high-quality DNA samples (hair, ear punches, skin biopsies) from 150 owl monkeys in Argentina and we have genetic data on 15 complete social groups.


We regularly collect individual (focal) and group behavioral data. In the field, we record, vocal, social, foraging and activity data using palm pilots, following an elaborately developed ethogram and coding system. The goal of the behavioral data collection is to evaluate the relative importance of paternal care, food resource distribution, and male and female reproductive strategies in favoring the evolution and maintenance of monogamy in primates.

The observation of owl monkey behavior allows us to test different hypotheses that explain the evolution and maintenance of monogamy. For example, in the owl monkeys, we see intense male care of offspring. It has been suggested that in monogamous species, given the relatively high costs to a female of raising and caring for offspring, males may care directly for infants or provide some kind of indirect services to females. The male-care hypothesis predicts that males should provide infant care when paternity certainty is high; moreover, it is predicted that in the absence of male care the development and survival of infants may be affected.

Among other things, we collect behavioral data on male-infant interactions (i.e. is the infant was independent or not, the position of the infant on the individual transporting it) before and after paternal male replacements and examine infant survivorship as it correlates to the intensity of such care.


In the quest to understand why some male monkeys mate in a monogamous relationship, presumably foregoing other reproductive opportunities and often investing heavily in the care of offspring they are not certain to have sired, we have recently begun to collect data to describe the possible hormonal mechanisms regulating monogamy in owl, titi and saki monkeys.

Using fecal samples, we can also evaluate male and female reproductive hormone profiles to test patterns in hormone and reproductive profiles. To what extent are males precluded from polygyny because of female reproductive synchrony? Are there differences in testosterone profiles that may be related to parental behavior? Do males make possible trade-off between parental care and territoriality as reflected in testosterone levels?

In collaboration with Dr. Valeggia’s Reproductive Biology Lab at the University of Pennsylvania we continue analyzing the endocrinology data of social monogamy and biparental care.


The Owl Monkey Project studies population biology and demography, as well as the spatial and temporal distribution of food resources. These demographic studies will help us elucidate how life-history traits are related to some of the behavioral patterns characteristic of social monogamy in the owl monkey population in Guaycolec, Formosa.

One possible explanation to the evolution and maintenance of monogamy is that females are a dispersed resource that males cannot monitor effectively; we test such a hypothesis by collecting data on the quality of territories as indicated by food resources (abundance and distribution of food resources in specific territories), infant production (continuous group demographic data) and female ability to make use of food resources.


With funding from the Waitt Program of National Geographic Society, Dr. Maren Huck, University of Pennsylvania Post Doctorate Fellow, is currently studying the influence of carnivores on the owl monkey population in Guaycolec. Maren currently has an extensive camera trap system in place that is capturing incredible pictures of the neighbors of the owl monkeys.


The study of the health of wild populations is a fundamental tool for the conservation of the animals, detecting potential threats to the animals that follow recent environmental changes. Wild animals are usually exposed to pathogens that are found in their natural environments and live with them in equilibrium; however, environmental changes, induced by man, can generate stress and reduce these wild animals’ resistance, putting them at health risks that may not have existed before.

With the objective to evaluate the health state of the owl monkeys at our study site, field veterinarians of the Global Health Program (GHP) at the Wildlife Conservation Society (WCS), take blood samples, fecal samples and samples of external parasites during monkey capture events. In the lab, the veterinarians later analyze basic hemoglobin levels, blood biochemicals composition, blood serum, parasite loads and by use of Polymerase Chain Reaction (PCR) evaluate illnesses and pathogen specifics. These analyses are done in order to understand the health status of the population under study. The investigation is carried out both in isolated forest patches, and in the gallery forest, looking to establish differences that lead to the understanding of how fragmented environments can affect the persistence of the owl monkey populations.

<p style=”text-align: right;”><span style=”color: #993300;”><strong><em><a href=””><span style=”color: #993300;”>Versión en castellano</span></a></em></strong></span></p>

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