Analyzing Shapes of Foraging Areas: Some Ecological and Economic Theories

A recent increase in research on the evolutionary consequences of foraging behavior has produced a diversity of approaches for evaluating feeding rates and energetic efficiency. Many of these investigations have been reviewed, and broad ecological principles formulated (10, 14, 17, 34, 53, 84, 102, 105). In this review I consider some economic concepts of consumer behavior in order to investigate several of the mechanisms that determine shapes of foraging areas. Out of the very large number of foraging studies, I focus on only a few that specifically deal with spatial configurations in relatively homogeneous habitats. Of primary concern is the development of equilibrial locational boundaries among individual consumers as they compete for resources. This initial discussion raises some basic questions: How does the intensity of predation on consumers affect the distances they can travel from centralized refugia? How is foraging mobility influenced by the use of a number of nutritionally different food resources? A series of graphical analyses is introduced to answer these questions and to emphasize the importance of different types of resource combinations required by consumers. These graphical methods yield testable predictions and are useful for relating the interactions of several major variables. Distances traveled by foragers are thus measurable in terms of both feeding activities and predator avoidance by considering proportionate costs and gains. Values such as the time a consumer is exposed to predators (or the energy required to escape predators) can be placed in a spatial context so that relative distances between food resources and refugia are measures of readily comparable interacting variables.