Estación Biológica Cocha Cashu
Scientific Visits
Site map


Mating strategies and territoriality of male spider monkeys (Ateles belzebuth chamek) in Manu National Park, Peru

Primary Investigator: Nicole Gibson
Department of Anthropology
Yale University
Web site:

My study investigates ecological and social factors that influence male reproductive strategies in white-bellied spider monkeys (Ateles belzebuth chamek). Spider monkeys exhibit several socioecological parallels with chimpanzees. Both have fission-fusion social systems in which individuals form fluid and non-permanent associations (e.g., foraging parties) within socially-bounded communities, but are generally hostile to conspecifics from other communities. This type of social system is rare in mammals. Shared reliance on ephemeral and often highly dispersed food sources, plus relatively low predation risk, presumably underlies fission-fusion sociality. Like chimpanzees, but unlike many other primates, males within a spider monkey community often cooperate and affiliate. This is not expected because male fitness depends most importantly on access to mating opportunities, for which males compete in various ways. Mating competition sets the stage for conflicts of reproductive interest between the sexes, with profound effects on social evolution. Males may protect females with whom they have mated, and protect those females’ infants, but may be aggressive towards other females and their infants. How and why male spider monkeys cooperate remains an open question, as does the extent to which distribution of females and food sources affects male relationships. This study is designed to use data on social behavior, habitat use, and genetic relatedness to explore how males balance within-community mating competition against possible gains from cooperative territorial defense.
My project will build on established theory in primate socioecology positing that conflicts of reproductive interest between the sexes have profoundly influenced primate social evolution. Data will be collected in collaboration with Peruvian student counterparts over a period of two years. My research results will contribute to a comparative understanding of the evolution of male bonding, territoriality, and fission-fusion sociality in primates and in mammals, generally. Results will also contribute to the overall goal of improving our understanding of ecosystems and biodiversity at the Cocha Cashu Biological Station. These, in turn, will help the field station maintain its role in assisting the Peruvian government in supporting, as well as protecting Manu National Park indirectly and directly.

Funding for this research provided by:

L.S.B. Leakey Foundation; John Perry Miller Fund; National Science Foundation; Organization for Tropical Studies; Williams Fund, Yale University; Fulbright Institute of International Education; Elizabeth S. and A. Varick Stout Fellowship Fund, Yale University.