Integrating individual behavior and population ecology: the potential for habitat-dependent population regulation in a reef fish

We used the predictions of the ideal free and ideal despotic distributions (IFD and IDD, respectively) as a basis to evaluate the link between spatial heterogeneity, behavior, and population dynamics in a Caribbean coral reef fish. Juvenile three-spot damselfish (Stegastes planifrons) were more closely aggregated in patch reef habitat than on continuous back reef. Agonistic interactions were more frequent but feeding rates were lower in the patch versus the continuous reef habitat. Growth rates were lower in patch reef habitat than on the continuous reef, but mortality rates did not differ. A separate experiment using standard habitat units demonstrated that the patterns observed in natural habitat were the result of the spatial distribution of the habitat patches rather than resource differences between habitats. Our results do not follow the predictions of simple IFD or IDD models. This deviation from IFD and IDD predictions may be the result of a number of factors, including lack of perfect information about habitat patches, high movement costs, and higher encounter rates of dispersed patches. Our results demonstrate that behavioral interactions are an integral part of population dynamics and that it is necessary to consider the spatial organization of the habitat in both behavioral and ecological investigations.