The Oahu Army Natural Resources Program Adaptive Rat Control Strategy: Protecting Endangered Hawaiian Species

Since 1995 the Oahu Army Natural Resources Program (OANRP) has managed over 60 federally endangered Hawaiian species, including plants, invertebrates, and one forest bird. An adaptive rodent control program is essential for the stabilization of many of these species. OANRP has utilized and experimented with various rodent control methods in remote settings on Oahu, including using small grids of bait stations containing rodenticide coupled with snap traps; deploying small grids of snap traps only; constructing predator-proof fence exclosures; and maintaining large-scale grids of snap traps for ecosystem-wide protection. In 2012, the program began to phase out the use of rodenticide in bait stations and transitioned to using kill-traps only, including the use of automatically self-resetting rat traps. To gauge the effectiveness of rat control methods, resources are monitored for changes in rat predation. Rat activity (both black rats and Polynesian rats) is also monitored with tracking tunnels inside and outside of management areas. This study discusses rat control and monitoring methods utilized by OANRP in the past and present. It also reviews investigations into the use of automatic rat traps, the transition to using kill-traps only instead of bait station grids, and highlight some strengths and weaknesses of various rat control methods. OANRP is working towards integrating multiple control methods for adaptive management in an effort to determine the most effective means to control rats in Army-managed areas on Oahu