This project builds upon current models of male social relationships and contributes to a relatively scant literature on male bonding in multi-male groups of nonhuman primates. It provides a unique opportunity to investigate the factors influencing male cooperation and competition using a primate from outside the human-chimpanzee lineage and has relevance for understanding the emergence of warfare and coalitionary intergroup violence. Additionally, this project expands the researcher's long record of training undergraduates, post-graduate students, and field assistants from the US, Europe, and multiple primate habitat countries in field methods for behavior, ecology, and conservation research. The project also promotes conservation education about the largest and least disturbed national park in the western Amazon (the Yasuní National Park and Biosphere Reserve, in Ecuador) and of one of the world's most critically-endangered primate taxa (the brown spider monkey, in Colombia).

In the past few years, studies of wild spider monkeys -- a New World primate only distantly related to humans and chimpanzee -- have revealed striking convergences with these taxa in fundamental aspects of social structure and behavior. In these taxa, males typically remain in their natal groups throughout their lives while females leave their groups upon reaching adulthood, and groups of related males may develop strong, affiliative social bonds with one another. Male spider monkeys from the same social group also cooperate to patrol their territorial boundaries, participate in deep incursions or raids into neighboring territories, and engage in coalitionary attacks against members of rival groups. These behavioral patterns, shared by chimpanzees and spider monkeys as well as humans, are extremely rare in nature. This study takes an integrated look at factors influencing social interactions among male spider monkeys, focusing on both competitive and cooperative aspects of these relationships. The study will focus on two social groups of spider monkeys in each of two tropical forests, one in Colombia and another in Ecuador, where wild spider monkeys have been studied for several years. Behavioral follows of habituated groups will be used to assess patterns of cooperation and competition among males, particularly in the context of intergroup interactions. Genetic data will be used to evaluate the relatedness of males within each group and to determine paternities of infants born in these groups.

National Science Foundation (NSF)
Division of Behavioral and Cognitive Sciences (BCS)
Application #
Program Officer
Carolyn Ehardt
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Austin
United States
Zip Code