Pattern and Adaptation in Individual Behavioral Differences

Abstract

The existence of individual differences in behavior is a well-documented but poorly understood phenomenon. On the one hand, individual variation could be attributable to nonadaptive evolutionary processes, such as genetic drift, or to stochastic environmental forces that act upon a single genotype to produce an array of observed behavioral phenotypes. On the other hand, behavioral differences may reflect the action of the process of natural selection on the form, degree, context, and origins of differences in behavior. The characteristics of behavioral variation in any given species may themselves represent an adaptation which increases individual success. The nonadaptive "explanation" is common, but generally untestable; it makes no specific predictions, although implicitly it suggests that many observed types will be maladaptive. The functional interpretation leads us to expect pattern in the occurrence of individual variation both between and within species such that an individual's behavior is more precisely fit for its peculiar circumstances. In this chapter, we explicitly pursue the possibility of functional and adaptive individuality. We review the reports of variation in social and foraging behavior and consider the existing explanations for this variation. We then try to develop a framework for further study which relates the appearance and controls on individuality to the life history of an organism and the dynamics of its foraging and social environments. This framework leads to some specific predictions both interspecific ally and intraspecifically.