Optimal foraging behavior by Castor canadensis: examining preferences for tree size, distance of tree to water, and tree species.

Abstract

Optimal foraging theory attempts to simplify complex foraging behaviors into formulaic models from which simpler trends can be observed and tested. In the present study, I examine the foraging behavior of a beaver (Castor canadensis) in an area of forest near a beaver lodge on Douglas Lake in Cheboygan County, northern lower Michigan. The three major variables examined are species of trees, diameters of trees, and the distance of trees to the waterline. Optimal Foraging Theory predicts that the beaver would show preferences with respect to all three of these variables. Small trees should be preferred over large, and near trees over far. Additionally, difference should exist between species. In all cases, it is assumed that the beaver will act to maximize net energy gained from a foraging event. My results show that beavers prefer big toothed aspen (Populus grandidentata) to all other species present. Also, small trees are shown to be preferred over large. However, the data show that no distance preference exists. The results of the distance measurements contain too many uncertainties to reach firm conclusions about such preferences. Many theoretical aspects of the system under study are explored and several problems with the study and future directions for research are contemplated. The study is very informative about the foraging behavior of beaver and offers new perspectives on theoretical ecology. More importantly, it demonstrates the effectiveness of Optimal Foraging Theory in offering simplified models of complex foraging behavior. The future prospects for uses of such theory are promising.