Habitat classification models for beaver (Castor canadensis) in the streams of the central Oregon Coast Range

Abstract

During 1988-1989, 22 stream habitat attibutes were measured and compared between 40 beaver-dam sites and 72 unoccupied stream sites to identify attributes associated with dam-site selection by beaver (Castor canadensis) in streams of the Drift Creek Basin, Lincoln County, Oregon. Beaver built dams in areas with wide valley-floors; narrow, low gradient streams; high grass/sedge cover; and low red alder (Alnus rubra) and shrub cover. Unoccupied sites lacked these characteristics. A discriminant function model correctly classified 83% of beaver-dam sites and 88% of unoccupied-stream sites with a chance-corrected classification rate of 69% (Cohen's Kappa statistic). We used 3 geomorphic attributes (stream width, gradient, and valley floor width) and developed a new Habitat Suitability Index (HSI) model for the basin. Land managers can use the discriminant function model or the HSI model to inventory potential beaver-dam sites along streams of the Oregon Coast Range. Information obtained from our habitat classification-models can be incorporated into plans to preserve unique riparian habitats maintained by beaver