Habitat use and terrestrial activity by red tree voles (Arborimus longicaudus) in Oregon

Several species of vertebrates may find optimal habitat for breeding, nesting, or foraging in old-growth (>200 years old) confierous forests in the Pacific Northwest. Old-growth forests are economically valuable, however, and most unprotected stands will be cut within 40 years (Franklin et al., 1981). Meslow et al. (1981) and Raphael (1984) identified a critical need to document habitat use and establish the relationship of wildlife species in these forests.

In 1983, we operated arrays of pitfall traps for six months to investigate habitat use by terrestrial herpetofauna and small mammals in four age classes of Douglas-fir (Pseudotsuga menziesii) forest in and near the H. J. Andrews Experimental Forest, Linn and Lane counties, Oregon. Red tree voles, Arborimus longicaudus, were among the mammals captured. This species is considered to find optimum habitat in old-growth forests (Franklin et al., 1981; Meslow et al., 1981), but quantitative data on the local occurrence of the species are lacking. Here we report on habitat use by A. longicaudus and document terrestrial activity for this presumably arboreal species.

A pitfall array was located in each of 18 stands dominated by Douglas-fir. Each array consisted of two sets of three 5-m aluminum drift fences each with pitfall traps (No. 10 tin cans; 6.4 l in volume) at the ends of the fences (see Bury and Raphael, 1983). The 18 stands represented four successional stages based on estimated age: 3 pre-canopy (clear cuts 5-9 years old), 3 young (30-69 years), 4 mature (76-150 years), and 8 old-growth (195-450 years). Additionally, old-growth stands were ranked on a general moisture gradient (wet, mesic, or dry) based on aspect, topographic position, and presence of indicator plant species. Pitfall traps were operated continuously for 180 days from late May to late November, 1983.