Short-term evaluation of two integrated pest management programs for mountain beaver (Aplodontia rufa) control

Abstract

In the Pacific Northwest, mountain beavers (Aplodontia rufa) are an impediment to reforestation efforts due to the damage they cause to seedlings. Trapping is currently the most effective method of reducing mountain beaver populations and seedling damage; however, mountain beavers can quickly reinvade harvested units, negating trapping efforts. Seedlings are most vulnerable to damage the first 3–4 months after planting, prior to emergence of forbs within timber harvest units. The integration of an additional tool to supplement trapping, such as baiting with a chlorophacinone rodenticide bait, may allow for additional seedling protection between trapping and forage green-up. Two integrated pest management (IPM) systems were tested in western Washington: treatment 1, baiting followed by trapping; and treatment 2, trapping followed by baiting. Using a cost effectiveness analysis we compared the costs of two different methods of mountain beaver management. In treatment 1, the units were baited and later trapped to remove remaining animals for a per acre cost of $42.47. In treatment 2, traps were placed in the units to remove mountain beaver, and then baits were placed in active areas for a per acre cost of $49.69. This indicates that the cost minimizing or efficient method of mountain beaver management was treatment 1. We found that seedling damage did not differ (P ¼ 0.61) between the treatments; however, overall activity based on fern monitoring demonstrated a greater overall reduction in activity on the treatment 2 plots. Retrapping efforts the year following planting demonstrated the ability of the species to reinvade units quickly. Treatment 1 units averaged 0.75–1.36 beavers/ha and treatment 2 units 0.36– 1.14 beavers/ha. Damage after 1 year remained similar between the treatments. Although higher in costs, fewer baits were placed on treatment 2 plots, since the population was reduced initially, than on treatment 1 plots. Treatment 2 may, therefore, be more socially acceptable because fewer baits are available in the environment with this treatment since the population is first reduced through trapping. Published by Elsevier Ltd.