U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

July 1999


Reprinted from the Western Journal of Applied Forestry, Vol. 14, No. 3, July 1999. Permission to use.


Cambium-feeding behavior by black bears (Ursus americanus), or bear damage, is a major reforestation problem in the Pacific Northwest. Historically, studies have measured the cumulative effects of damage over time, but few have viewed damage in the frame of one season. Bear damage occurring in 1996 was surveyed in areas of radio-marked bears in western Washington. Fresh damage occurred on 48% of bear location plots (n = 96). Douglas-fir (Pseudotsuga menziesii) (69%), western hemlock (Tsuga heterophylla) (19%), and Pacific silverfir (Abies amabilis) (10%) with a mean dbh of 25.1, 29.5, and 30.7cm, respectively, were most frequently damaged. Random plots were surveyed from mid-July to mid-August to measure habitat availability. Stand and site variables were measured on freshly damaged bear location plots, random plots, and non-damaged bear location plots. This study identified several variables that make forest stands vulnerable to bear damage: conifer dbh, conifer density, stand age, and canopy cover. Awareness of such stand characteristics can assist natural resource managers with animal damage prevention and control programs.