My research focuses on decision-making in animals. I study how an individual's foraging, mating and social behavior are influenced by its phenotype, by ecological circumstances, and by the actions of other individuals in the population. I develop simple mathematical models to generate predictions that can be tested using data gathered from structured field observations or experimental manipulations. In this way I search for general principles, or 'rules', that underlie complex patterns of behavior. Much of my recent research on the adaptive value of behavior has centered on understanding the social dynamics of equids—horses, zebras and asses. My studies have shown that as the distributions of forage and water change, the patterns of female movement and association change. In turn, the ways in which males compete to mate with females also change. Thus ecological features play a large role in shaping equid core social groups.