Aspects of Castor canadensis foraging patterns in two aquatic systems of northern Michigan.

Abstract

Efficient management of energy is important to the survival of all organisms. Optimal foraging theory suggests that an organism will seek to forage such that energy gain is maximized while energy loss is minimized. The beaver, Castor canadensis, is a good model system for studying foraging strategies because of their method of attaining food and housing material in a radiate-and-return pattern. Because the beaver choose large, stationary prey and are required to transport that prey back to their lodge or dam makes measurements of their foraging patterns relatively easy to obtain. Through this research, we addressed several aspects of beaver foraging behavior including relationships between preference and size, size as a function of distance from the water, species preference, and proportion of trees taken as a function of distance from the water. We studied beaver foraging at two sites in northern lower Michigan--Carp Creek near Pellston and O'Neal Lake in Wilderness State Park near Mackinaw City. We foudn no significant preference for tree size taken or any relationships between size of tree selected and its distance from water. This finding contradicts both previous research and the optimal foraging model. There was, however, a significant preference for specific species of trees taken. There also was a difference between proportion of trees cut nearer the water than farther away. The latter two findings suggest species type and distance from the water are important factors in tree choice. From these data, it is evident that many variables are involved in the foraging behavior of beaver.