Behavior and Ecology of Ateline Primates

Ateline primates – howler monkeys, woolly monkeys, spider monkeys, and muriquis – are a closely related group of New World monkeys that shared a common ancestor roughly 16 million years ago.  These primate taxa exhibit marked differences in foraging strategies and patterns of social organization, making them an excellent natural system for comparative study. Interestingly, however, all members of this clade of primates are characterized by a tendency for females to disperse from their natal social groups prior to reproduction and for some degree of male philopatry, which are both features of social organization that they share with the African great apes. Prompted by this convergence with African hominoids (and, presumably, with our earliest human ancestors), much of our lab’s field research to date has centered on ateline primates.

Our recent field work on atelines has focused on woolly monkey social behavior and population genetic structure and on comparing the social behavior, foraging strategies, seed dispersal behavior, and cognitive ecology of woolly monkeys (Lagothrix poepiggii) with those of sympatric white-bellied spider monkeys (Ateles belzebuth) a closely-related primate that differs markedly in social organization.

Evolution of Monogamy and Pair-Bonding in Primates

Since 2002, we have been conducting a long-term study of the evolution of “monogamous” or “pair-bonded” social systems in primates using three species of New World monkeys – owl monkeys, titi monkeys, and sakis – as models. This work represents an international collaboration with Dr. Eduardo Fernandez-Duque (Fundación ECO, Argentina and CRES (Conservation and Research for Endangered Species), Zoological Society of San Diego), who studies one of these taxa (owl monkeys) at his field site in Argentina.

Monogamy is a rare social system in mammals, and the specific pressures leading to its evolution are still debated. Early hypotheses forwarded to explain the evolution of monogamy tended to fall into one of two classes. Some proposed that monogamy evolved in response to the need for biparental care in order to successfully rear offspring, while others envisioned monogamy as the default social system imposed upon males in cases where the dispersion of females makes it difficult for single males to successfully defend access to more than one. More recently, emphasis has turned to the role of direct mate guarding of individual females by males and to the importance of specific male-female bonds as an infanticide-prevention strategy, with “monogamy” then emerging as a tradeoff between the competing reproductive strategies of males and females. In this project, we are trying to evaluate these various hypotheses for the origin and maintenance of monogamy in primates using a comparative approach, collecting comparable behavioral, ecological, demographic, and genetic data on all three genera at my study site in Ecuador and on one of the taxa (owl monkeys) at study sites in both Ecuador and Argentina. We have developed novel molecular genetic markers to allow paternity and population structure analyses for these monogamous species.

Tropical Forest Biodiversity and Phenology

Primatologists interested in how ecological conditions shape the behavior and social strategies of their study subjects must also collect detailed data on the diversity, abundance, and distribution of resources of potential importance. Thus, ongoing fieldwork includes documenting and understanding spatial patterns in plant diversity and temporal patterns of flowering and fruiting in neotropical forests. Since 1994, almost without interruption, our research team has collecting data every month on the phenological status of a large subset of the trees located in five hectares of botanical plots. This now represents one of the largest databases of phenological information available for an Amazonian rainforest site. Additionally, some of the plots are periodically recensused to look at temporal changes in floristic composition and biomass. These data form a part of the Amazon Forest Inventory Network (RAINFOR) database, which compiles information from a large set of Amazonian rainforest sites for the purposes of monitoring the long-term dynamics and productivity of these forests in response to global climate change.