Efficacy of Cholecalciferol Baits for Pocket Gopher Control and Possible Effects on Non-Target Rodents in Pacific Northwest Forests

Abstract

Author(s): Rizor, Suzanne E.; Arjo, Wendy M.; Bulkin, Stephan; Nolte, Dale L. | Abstract: Population reduction measures need to be implemented to reforestation plots infested with pocket gopher in the Pacific Northwest. This 1-year investigation assessed the efficacy of 0.15% cholecalciferol (vitamin D3) bait application to reduce pocket gophers and the long-term effects on non-target small rodent populations within treated plots. The study site was a reforested clear cut containing pocket gopher populations of 10 to 14 animals per ha. Six plots (2.8 ha each) were randomly selected at the study site, 3 plots of untreated controls and 3 plots baited with cholecalciferol. A trap-and-release program was used to assess non-target populations. Radio telemetry and the open hole method were used to monitor pocket gopher activity before and after the fall application of cholecalciferol bait. A 70-80% reduction of pocket gopher activity from telemetered animals occurred in the treated plots, whereas only 10-20% mortality occurred on the control plots. Pocket gopher activity in most of the plots increased by June, and by September of the following year, activity was back to original levels. Time, not treatment, had a significant effect on yellow pine chipmunk, Townsend chipmunk, and golden-mantled ground squirrel populations. We conclude that 0.15% cholecalciferol bait appears to have application for pocket gopher control. Risks to non-target species may exist.