Woody plant foraging preferences of the beaver (Castor canadensis).

Abstract

Beaver can have a tremendous impact on their surroundings, altering the entire physical and chemical regime of the landscapes they inhabit. In this study we examined the effects tree size, tree distance from the waterway, and tree species have on beaver foraging habits. Because of past studies modeling optimum foraging patterns in central-place foragers (i.e. beaver), we chose null hypotheses that 1)beaver would show no preference in their tree species choice, that 2) beaver would harvest an equal number of trees both near to and far from the waterway, and that 3) the size of the trees harvested would be independent of their distance from the waterway. Transects were set up at Grapevine Point and Wilderness State Park near active beaver colonies. After data collection, analysis with a Chi square showed beaver to prefer sugar maple (Acer saccharum) and red oak (Quercus rubra) at Grapevine Point and trembling aspen (Populus tremuloides) and black ash (Fraxinus nigra) at Wilderness Park. Analysis with Mann-Whitney U tests showed that Grapevine point beaver harvested more trees closer to shore, but harvested equally large trees regardless of distance from shore. Wilderness park beaver harvested an equal number of trees near to and far from shore, but harvested larger trees farther from shore. These results seem to contradict an optimal foraging pattern, but may be due to biotic and abiotic factors such as beaver energetic constraints, predation risks, plant secondary chemical production, differential use of plant tissues, landscape topography and the thermal regime. Knowledge of these factors as they apply to an optimal foraging pattern can lead to the improved maintenance of our beaver populations and our waterways.