Foraging habits of Castor canadensis: importance of girth, species, and distance from shore of attached trees.

Abstract

A young beaver dam in northern lower Michigan was selected for analysis. Girths, distances from shore and species of trees in a twenty by twenty transect were noted. We hypothesized that foraging preferences of Castor canadensis are independent of girth, distance from shore and species of attacked tree. Chi-squared tests showed that beavers prefer certain species of trees. All trembling aspens in our transects were attacked which agrees with Schoener's 1979 model based on maximun net rate of energy gain (Basey et. al, 1988). Another chi-square test showed that beavers prefer small distances from water. Using a Mann-Whitney U test and a chi-square test, we aslo showed that beavers preferred the same girth in near and far distances and that there was no difference in attack rates for large (>7.5) and small (<7.5) girths. Because these foraging preferences, the beavers are not optimally foraging as Schoener and Jenkins modeled. These foraging trends may be influenced by a need for preliminary dam material to build their young dam.