Distribution and abundance of Neotoma in western Oregon and Washington

Bushy-tailed woodrats (Neotoma cinerea) and dusky-footed woodrats (N. fusci pes) add substantially to the prey base of many avian and mammalian predato rs. High biomass of woodrats can reduce markedly area requirements of preda tors; thus, manage ment for woodrats has potential in conservation. But pat terns of abundance of woodrats in the Pacific Northwest are poorly understo od. Our objective was to determine local abundances and regional distributi ons of N. cinerea and N. fuscipes in forests west of the Crest of the Casca de Range in Oregon and Washington. We sampled a variety of forests from 1985 to 1997 in seven physiographic pr ovinces. 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 oc cur 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 occasional ly were abundant, but their abundances were negatively correlated. Neotoma cinerea was rare in mixed-conifer-mixed-evergreen forests bur N. fuscipes o ccasionally was abundant in early, and present in late stages of forest dev elopment. The distribution of N. fuscipes can be explained by its preferenc e for dense shrub cover and it ability to consume plants potentially toxic to other mammals; the only compelling explanation for the irregular distrib ution of N, cinerea is exceptional vulnerability to predation because of it s size and social behavior. Because of zoogeographic restrictions, limited opportunities exist in weste rn Oregon and Washington to manage habitat for woodrats as a means of assis ting in the recovery and maintenance of viable populations of predators sen sitive to loss or management of forests.