Space in the lives of vertebrates: On the ecology and psychology of space use.

Abstract

I develop a theory of animal space use that integrates behavioral ecological and neuropsychological approaches. Specifically, I present a theory of space use for animals that create and use cognitive maps; and I test the hypothesis that the size of the hippocampus (a brain structure essential to cognitive mapping) varies with selection pressures on cognitive mapping abilities both within and between species. Chapter 1 introduces and justifies the approach with an overview of space-use theories in behavioral ecology, psychology, and neurobiology. I argue that integrating these disparate approaches benefits each. In Chapter 2 I develop a theory of space use for cognitive mapping foragers by imbuing optimal foraging theory with recent findings from psychology and neurobiology. The theory views foragers as integrators and users of two types of spatial information: information about the geometric relations among places (cognitive maps), and information about what is likely to be in places (site-specific information). I formalize the value of spatial information as the increment to foraging rate in an area of an informed versus an uninformed forager. Information value is dynamic and usually declines with time since learning. I show how incorporating this dynamic view of information into foraging models predicts animal home ranges and movement patterns within them. In Chapter 3 I apply the theory to models that make predictions about space use patterns of animals constrained to use linear cognitive maps. Chapter 4 introduces some models for two-dimensional foraging situations. In Chapter 5 I review the important predictions of the theory, discuss its assumptions and applications, and present a series of case examples from the literature. In Chapter 6 I test the hypothesis that the hippocampus of the mammalian brain should vary in size with the relative selection pressure on cognitive mapping abilities. I compare relative hippocampal size between two species of kangaroo rat, and between sexes within each of the two species. The species most reliant on cognitive mapping has a larger hippocampus. Likewise, within each species, the sex (male) most reliant on cognitive mapping has the larger hippocampus. Hippocampal size is apparently affected by both natural and sexual selection.