ABSTRACT
General ecological theory maintains that whereas male mammals are reproductively limited mainly by the number of mates available to them, a female’s reproductive success is limited by the availability of foods to her (Trivers 1972; Wrangham 1980). Therefore, patterns of food distribution and abundance are likely to exert a strong influence on a female mammal’s behavior. I undertook this study of vervet and patas monkeys in Kenya to test hypotheses derived from models based on these assumptions, which attempt to explain social behavior among adult female primates (Isbell 1991; van Schaik 1989; Sterck, Watts, & van Schaik 1997; Wrangham 1980). These models make predictions about the types of dominance hierarchies adult female primates will exhibit based on the distribution and abundance of foods available to them. The models assume that food availability influences competition among females and that such competition results in particular dominance styles. Feeding competition includes supplants at feeding sites or aggression during feeding (Isbell & Young 2002). Female primates are expected to compete aggressively when foods are both limited and usurpable (e.g., occurring in small patches) and despotic dominance hierarchies are predicted to emerge (Isbell 1991; van Schaik 1989; Wrangham 1980). To test the hypotheses derived from these models, I investigated the feeding behavior, social behavior, and food resources available to free-ranging vervet and patas monkeys from June 1993 to August 1995 at Segera Ranch, Laikipia, Kenya. The nature of the study site provided an excellent opportunity to examine contest competition and dominance relationships among adult females in two closely related species that use the same food resources.
