Recovery Plan for the Northern Spotted Owl - DRAFT

Woodrats.-The dusky-footed woodrat (N.Jfiscipes) is limited in distribution toparts of western Oregon and most of western California (Figure D.5.b), whilethe bushy-tailed woodrat (N. cinerea) is found throughout Washington andOregon, and in parts of northern California (Figure D.5.c). Woodrats areassociated with seral stages that have abundant understory vegetation andcoarse woody debris, such as early successional stages (recent clear-cuts) andolder seral stages (Thomas et al. 1990); bushy-tailed woodrats also are associatedwith rocky areas, such as talus slopes (Thomas et al. 1990).Deer mice.-The deer mouse (Peromyscus maniculatus) is one of the mostwidely distributed mammal species in North America and is found throughoutOregon, Washington, and California. Such a wide-ranging species would beexpected to be a habitat generalist, and data from the Pacific Northwest supportthis contention. Deer mice do not show consistent preferences for particularstand ages (Thomas et al. 1990). The forest deer mouse (P. oreas)inhabits older forests in western Washington and southern British Columbia(Figure D.5.c). Because of its extensive use of tree canopies, it is probably animportant prey species for owls in Washington (West 1991).Red tree vole.-The red tree voles (Phenacomys ssp.) have the most restricteddistribution of all the species preyed upon by spotted owls. Before the Californiapopulation (P. pomo) was recognized to be a species separate from theOregon (P. longicaudus) species (Johnson and George 1991), the range of thered tree vole included parts of western Oregon and northwest California (FigureD.2). The California population now is considered a separate species based onmorphometric and genetic data. Habitat associations of these species arebased on relatively small sample sizes, but there is a trend of greater relativeabundance with increasing stand age, with the highest densities in old-growthforests (Corn and Bury 1991, Ruggiero et al. 199 lb).Rabbits and Hares.-Brush rabbits occur in most of western Oregon andCalifornia, and appear to be absent from Washington (Figure D.5.A. Snowshoehares are found in western Oregon and Washington, and into north-centralCalifornia (Figure D.5.e). No research has been conducted to specifically studyhabitat associations of lagomorphs in relationship to spotted owl habitat. Ingeneral, these species occupy brushy, densely vegetated habitats (Thomas etal. 1990) and are not more abundant in older forests. It is primarily young ofthe year that are preyed upon by spotted owls (Forsman et al. 1984:41), sodispersal habitat may be most important when considering these species asspotted owl prey.Red-backed voles.-Westem red-backed voles occur throughout westernOregon and northwest California, and the southern red-backed vole (C.gapperO occurs in western Washington (Figure D.5.1). Western red-backedvoles live in a variety of forested habitats, but densities are low in recentlyburned clear-cuts and their occurrence may be positively associated withwoody debris (reviewed by Alexander and Verts, In press). No differences inabundance of Cleithrionomys spp. were found in unmanaged young (30 to 70years) Douglas-fir stands compared to older seral stages (Corn and Bury 1991,Gilbert and Allwine 1991, West 1991), but abundance was much lower inmanaged young stands than in old-growth stands (Rosenberg and Anthony1990).Managing prey for the northern spotted owl.-Recent research on preyspecies was motivated, in part, by an interest in increasing prey abundancethrough silvicultural prescriptions. The results to date do not show consistentpatterns that would allow this to be achieved. This, combined with the difficultyin assessing the relationship between prey abundance and availability,makes the feasibility of manipulating prey densities to increase owl use of368