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Providing evidence to improve practice

Individual study: Bat activity in thinned, unthinned, and old-growth forests in western Oregon

Published source details

Humes M.L., Hayes J.P. & Collopy M.W. (1999) Bat activity in thinned, unthinned, and old-growth forests in western Oregon. The Journal of Wildlife Management, 63, 553-561


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Thin trees within forest and woodland Bat Conservation

A replicated, paired sites and site comparison study in 1994–1995 in 11 pairs of forest stands and nine old growth forests in the Oregon Coast range, USA (Humes et al. 1999) found that thinned tree stands had higher bat activity than unthinned tree stands, and there was no difference in bat activity between thinned stands and old growth forest. Overall bat activity (of at least nine bat species) was higher in thinned (average 10 bat passes/night) than unthinned stands (6 bat passes/night). There was no significant difference in bat activity between thinned stands and old growth forest (average 13 bat passes/night). Surveys were carried out in 11 pairs of stands (10–63 ha, 50–100 years old) that were thinned (in 1971–1985, average 184 trees/ha) or unthinned (average 418 trees/ha), and in nine old growth forest stands (20–70 ha, >200 years old, average 155 trees/ha). All 31 tree stands were dominated by Douglas fir Pseudotsuga menziesii. Bat detectors recorded bat activity at one random location in each of 11 pairs of tree stands and in a nearby old growth forest stand simultaneously for two consecutive nights on four occasions in June–September 1994 or May–September 1995.

(Summarised by Anna Berthinussen)