Castor canadensis: an analysis of foraging patterns in two different habitats of northern Michigan.

Abstract

This study compares two different foraging habitats for the American beaver, Castor canadensis, in Michigan. This study was designed to test optimal foraging theory's application to a field population. This study analyzes evidence of beaver activity in order to investigate efficiency in foraging. We expected to observe beaver preference for species and stem size, as well as decreased removal rates with respect to increased distance from the water's edge. Changing stem size selection as a function of increased distance from the water was also expected. All such observations would illustrate that beaver make economic decisions about maximizing energetic gains. Some debate has centered on foraging in beaver, and in review of the literature, one finds several conflicting reports. This research was modeled after past studies on beaver foraging in order to contribute commentary to the on-going debate in optimal foraging theory's application to central foragers, such as the beaver. In our study, beaver were found to show a species preference and a preference for stems located close to the water's edge. However, no significant relationship was found for stem size choice and distance. No overall stem preference was found either. Due to within and between site variation in species composition, these results show how foraging behavior can differ under different environmental circumstances. It is also discussed that beaver may not be optimal foragers, but rather are constrained by factors other than needs for energy maximization, such as predator avoidance. This study is unable to make a decisive conclusion that beavers forage optimally.