U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Crop Protection 143 (2021) 105561



U.S. gov't work


Mountain beaver (Aplodontia rufa) is the most primitive rodent species in North America and is endemic to the Pacific Northwest, USA. Within their range, mountain beaver cause more conflict with conifer forest regeneration than any other vertebrate species. Most damage occurs as a result of clipping and browsing new seedlings, which reduces stocking density and delays stand development. An integrated approach using trapping and a registered toxicant (baiting) has been suggested as the most efficacious means to reduce seedling loss during stand initiation. We evaluated this management strategy in intensively managed conifer stands across two mountain ranges in western Oregon. Harvest units were divided equally and management (trapping and baiting) was implemented on a randomly selected half of each unit; the remaining halves served as an experimental control. We conducted damage assessments in fixed 0.04 ha circular plots at approximate 1, 6, and 12 month intervals after planting and initiation of management activities. After 12 months, we observed mountain beaver damage in 100% of control plots and 95% of treatment plots; however, there was a 79% decrease in the estimated odds of damage for plots where trapping and baiting was implemented (95% CI 43–92). Mean seedling height was 10.6 cm taller in treated plots than control plots 1 year post-planting (95% CI 4.1–17.1). Reoccupation of vacant burrows began within 1 month; within 12 months, only 5% of trapped plots remained unoccupied. Reported costs and benefits varied among harvest units, but management was less expensive ($154.09/ha) than the cost of interplanting gaps created by mountain beaver damage ($182.13/ha). Although trapping and baiting may not offer a one-time solution to damage problems, it is an effective tool in reducing damage, saving management costs, and meeting compliance with forest regulations and certification requirements.