DUSKY-FOOTED WOODRAT ABUNDANCE IN DIFFERENT-AGED FORESTS IN NORTHWESTERN CALIFORNIA

Because dusky-footed woodrats (Neotoma fuscipes) are important prey species of northern spotted owls (Strix occidentalis caurina), we estimated their abundance in Douglas-fir (Pseudotsuga menziesii)/tanoak (Lithocarpus densiflora) forests of different ages in northwestern California. We surveyed and trapped woodrats in 6-8 stands in each of 5 seral stages during the summers of 1988-90. We used belt transects to compute nest density, and livetrapped at nest sites to estimate woodrat numbers per nest. Combining these 2 sources of information provided an estimate of woodrat densities, which were highest in sapling/brushy poletimber stands, followed by seedling/shrub and large old-growth stands. Woodrats were not found in small sawtimber stands and rarely occurred in large sawtimber stands. Because of within- and among-stand heterogeneity in woodrat abundance, the combined method may provide a more reliable estimate of woodrat abundance within a seral stage than live trapping on a grid. Because woodrats cross ecotonal boundaries, sapling/brushy poletimber stands adjacent to mature and old-growth Douglas-fir/tanoak forests may be source areas for woodrats preyed upon by northern spotted owls. Our data suggest that adopting specific silvicultural procedures that provide source areas for woodrats adjacent to suitable spotted owl habitat may directly benefit spotted owl populations; we recommend that specific hypotheses regarding these procedures be tested.