Castor canadensis: optimal foraging in relation to preference, distance, and size of trees utilized.

Abstract

Castor canadensis (beaver) build dams and lodges which have profound effects on locan ecosystems. C. canadensis forage trees from distances near and far to build dams. One would expect that such energy intensive work would place constraints on characteristics of trees chosen. In this study, we examined predictions of the optimal foraging theory. We studied preference of a tree genera, proportion utilized, and size and selectivity at various distances. We collected tree genera, circumference at gnawing height, and distance from shoreline for trees in our study area. In coniferous dominant canopies such as Wilderness State Park, aspen was found to be preferred tree for harvesting. In deciduous forests such as Grapevine Point, sugar maple was found to be the preferred species. At Wilderness State Park, diameter was correlated to distance. ""Far"" trees were had a greater girth than those closer to the shoreline. At Grapevine Point, no correlation between diameter and distance was found. There was no difference statistically in the number of trees harvested in ""near"" versus ""far"" locations at Wilderness State Park. At Grapevine Point, there was a statistical difference in the number of ""near"" versys ""far"" trees harvested. This study could have been further elucidated if tree genera among canopies of the two sites were similar. Further investigations of beaver foraging in relation to optimal foraging theory should consider factors such as potential tree chemical defense when attempting to quantify relationships between size and distance from the shoreline.