Forage Use by White-Tailed Deer in Northwest Montana from a Historical Perspective

Abstract

We evaluated forage use by white-tailed deer (Odocoileus virginianus) that occupy montane forests of northwest Montana over a period spanning the 1940s through the 1990s. Several studies provided food habit information, but most came from the Thompson River, Swan Valley, Kootenai River, and Salish Mountains. Use of Douglas-fir (Pseudotsuga menziesii) and Oregon grape (Berberis repens) by deer during winter was consistent over the 60-year period despite habitat alteration or loss due to construction of large hydroelectric facilities, logging and other silvicultural treatments, and fire suppression. The relative importance of conifer browse and low-growing species such as Oregon grape probably varied with amount of winter snowpack. Douglas-fir and Oregon grape probably have not represented emergency or starvation forage as traditionally believed but rather a very important dietary component on deer winter ranges in northwest Montana. Availability and use of arboreal lichens by deer might also increase digestibility and importance of browse available to deer during winter. Further, the observed pattern of forage use over time was consistent with a strategy of overwinter survival that favors energy conservation whereby value of overhead cover might override that of forage in winter resource selection.