Ecological Bases of Social Behavior in Capuchins: A Three-Way Comparative Study

University Of Florida, Gainesville FL

Investigators

Abstract

The evolution of the diverse array of primate social organizations is a fundamental issue in physical anthropology. Why are males dominant to females among many primate species, yet in a smaller proportion of species females typically dominate males? Why are some primate species highly aggressive, while others are best described as diffident and retiring? Why among most, but certainly not all, primate species do males typically emigrate to other troops in early adulthood, but all females pass their entire life in the same troop in which they were born? The answers to these questions are crucial to explaining the dramatic variation in social behavior exhibited by the more than 200 extant species of prosimians, monkeys, and apes. Furthermore, these questions are central to the eventual understanding of the evolution of social behavior among our hominid ancestors. Controversy exists regarding the underlying variables most important in explaining the variation social organization in primates. Ecological models of social evolution see competition for food as the key factor determining female grouping patterns, and thus the distribution and dispersal options of males. An alternate model attributes variation in social organization and female relationships to male competition with other males for control of mating with group females. What is clear at this point is that the most powerful tests of these models will need to be closely related species that vary in their social organization. Capuchin monkeys (genus Cebus) are noted for behavioral flexibility and variability and are a prime candidate for a successful study system. Major differences in mating system are reported among the four species. Brown (C. apella), and, wedge-capped capuchins (C. olivaceus)are essentially polygynous. On the other hand, females among the white-faced, C. capucinus, and white-fronted capuchins, C. albifrons, typically mate with multiple males during the period of conception. However, preliminary observations of brown capuchins at Raleighvallen Nature Preserve, Suriname suggest a multi-male mating system similar to that of the white-faced and white fronted capuchins. Researchers will perform a three-year field study of behavior, ecology and genetic relationships among the brown capuchins at Raleighvallen, Suriname. In conjunction with long-term field data for brown capuchins at other sites (Manu, Peru and Iguazu, Argentina) and for white-faced capuchins (Santa Rosa and Lomas Barbudol in Costa Rica), this will provide a powerful and important test of current models of primate social evolution. Researchers predict that the mating system and patterns of social interaction among brown capuchins at Raleighvallen will resemble Costa Rican white-faced capuchins rather than Peruvian or Argentinean brown capuchins. This would provide strong support for an ecological basis to capuchin social organization. A major goal of this study will be to determine the relative contributions of food distribution and mate competition in shaping capuchin social organization. Nevertheless, the implications of its findings have the potential to force dramatic reinterpretations of the past 30 years of investigations of primate social behavior.