Differences in Townsend's chipmunk populations between second- and old-growth forests in western Oregon

Abstract

Because Townsend's chipmunks (Tomias townsendii) may be important in maintaining natural ecosystem processes in forests in the central Oregon Cascade Range, we compared their population characteristics in young second-growth and old-growth forests. We live-trapped Townsend's chipmunks in 5 young (30-60 yr old) second-growth and 5 old-growth (>400 yr old) Douglas-fir (Pseudotsuga menziesii) stands during spring and autumn 1987-90 in western Oregon. We tested the null hypothesis of no difference in characteristics of chipmunk populations in these 2 stand age-classes. Densities ranged from 0.4 to 10.3 chipmunks/ha and were greater (P < 0.05) in old-growth ( ± SE, 5.1 ± 0.4) than in second-growth (2.8 ± 0.3) stands. Chipmunk densities were related to large (≥50 cm diam at breast height [dbh]) snags in old- growth (P = 0.002) but not in second-growth (P = 0.6) stands. Chipmunks in old-growth stands moved shorter (P = 0.03) distances in autumn and had a greater proportion of young-of-the-year (P = 0.007) than those in second-growth stands. These differences suggest that old-growth stands provide better habitat for Townsend's chipmunks than young second-growth stands, and may reflect important functional differences in food chains and energy flow between the different stand age-classes.

Citation

Rosenberg, D.K.; Anthony, R.G. 1993. Differences in Townsend''s chipmunk populations between second- and old-growth forests in western Oregon. Journal of Wildlife Management 57(2):365-373