| Individual variation in a population may be the result of natural selection. A first step toward determining the adaptiveness of individual differences is to find predictors of such differences. Little is known about the predictors of individual variation in the antipredator behavior of primates. In this dissertation, I investigated individual variation in the responses of captive rhesus macaques (Macaca mulatta) to models of a leopard ( Panthera pardus) and a python (Python molurus), and to other threatening situations. I examined whether or not individual differences were consistent across time and context, and if maternal status, age, social rank, or social behaviors were predictors of these differences. A preliminary study (Chapter 1) showed that the leopard and python models were effective in eliciting antipredator behaviors from the captive monkeys. The monkeys reacted differently to the leopard and python, indicating that they perceived the models as different types of threats. Clear individual differences were detected in the monkeys' responses to the predator models. Females with or without infants did not respond differently to the leopard (Chapter 2). An exploratory analysis of these subjects showed that sociable and subordinate behaviors were correlated with responses to the leopard. A principal components analysis of directly observed social behaviors revealed the components Excitable, Sociable, and Inactive (Chapter 3). These components predicted some of the female monkeys' responses to the python model, but not the leopard model. Individuals were mostly consistent in their behaviors toward the two types of models. Adult females were also consistent in their responses to another type of threat, the approach of animal keepers' vehicles (Chapter 4). Age and social rank were not associated with a subject's type of response to the vehicles or consistency of responses. The consistency of individuals' behaviors toward different types of threats in these studies indicates that an inherent characteristic of individuals mediates individual variation in antipredator behavior. These studies also provide some evidence that social behaviors, but not maternal status, age, or social rank, are linked to individual differences in the antipredator behaviors of primates. |
