Great Basin Naturalist


We compared physical and vegetative habitat characteristics at 14 dam sites occupied by beaver (Castor Canadensis) with those at 41 random unoccupied reaches to identify features important to dam-site selection in the Long Creek basin, Grant County, Oregon. Stream reaches with dams were shallower and had a lower gradient than unoccupied reaches. Beaver did not build dams at sites with a rock substrate. Bank slopes at occupied reaches were not as steep as those at unoccupied reaches; and occupied stream reaches had greater tree canopy cover, especially of thinleaf alder (Alnus tenuifolia), than did unused reaches. A discriminant model using transformations of bank slope, stream gradient, and hardwood cover classified all beaver dam sites correctly and 35 of 41 random sites as unoccupied sites. The 6 misclassified sites had rock substrates.

We also tested four habitat suitability models for beaver in this basin. Three models produced significantly different (P < .05) scores between occupied and random unoccupied reaches, suggesting that they might have some utility for this region.