Distribution and abundance of Neotoma in western Oregon and Washington

Bushy-tailed woodrats (Neotoma cinerea) and dusky-footed woodrats (N. fuscipes) add substantially to the prey base of many avian and mammalian predators. High biomass of woodrats can reduce markedly area requirements of predators; thus, management for woodrats has potential in conservation. But patterns of abundance of woodrats in the Pacific Northwest are poorly understood. Our objective was to determine local abundances and regional distributions of N. cinerea and N. fuscipes in forests west of the Crest of the Cascade Range in Oregon and Washington. We sampled a variety of forests from 1985 to 1997 in seven physiographic provinces. In Washington, we found that N. cinerea was rare in upland forests, but abundant along rocky streams on the eastern Olympic Peninsula and in rock bluffs on the west slope of the Cascade Range; N. fuscipes does not occur in Washington. In Oregon, N. fuscipes is at the northern limits of its range and we found that it was rare in Douglas-fir (Pseudotsuga menziesii)-western hemlock (Tsuga heterophylla) forests; N. cinerea was common in old forests and along streams. In mixed-conifer forests both species occasionally were abundant, but their abundances were negatively correlated. Neotoma cinerea was rare in mixed-conifer-mixed-evergreen forests but N. fuscipes occasionally was abundant in early, and present in late stages of forest development. The distribution of N. fuscipes can be explained by its preference for dense shrub cover and it ability to consume plants potentially toxic to other mammals; the only compelling explanation for the irregular distribution of N. cinerea is exceptional vulnerability to predation because of its size and social behavior. Because of zoogeographic restrictions, limited opportunities exist in western Oregon and Washington to manage habitat for woodrats as a means of assisting in the recovery and maintenance of viable populations of predators sensitive to loss or management of forestsCarey et al "Distribution and abundance of Neotoma in western Oregon and Washington." Northwest Science. 1999; 73(2): 65-8