Proceedings of the Vertebrate Pest Conference

Since human arrival to the Hawaiian Islands, non-native predators have decimated native flora and fauna. In particular, native forest bird populations have suffered due to rat (Rattus sp.) depredation. To protect native species, conservation practitioners have been removing rats and other rodents from ecologically sensitive areas. Identifying reliable strategies for assessing the effectiveness of these control efforts is critical, particularly given limited resources for conservation. A common method used for monitoring rodents is baited ink-plates within a tunnel (hereafter ink-plates). While this method is widely used, its effectiveness has yet to be evaluated in many ecosystems, including montane rainforests. To evaluate the effectiveness of monitoring rat presence with ink-plates, we focused on the Alakai Plateau on the island of Kauai, which is home to several of Hawaii’s most critically endangered birds, and where over 300 Goodnature™A24 rat traps are currently in operation. The Alakai experiences approximately 11 m of annual precipitation, giving rise to areas of dense vegetation, which may affect how rats encounter and interact with ink-plates. We paired 116 Reconyx™ HyperFire cameras with individual ink-plates inside tracking tunnels in the summers of 2022 and 2023, at a site with an ungulate exclusion fence and at a site with no fencing, to monitor areas both with and without rat traps. Rats were detected on approximately twice as many cameras (34.5% presence) compared to ink-plates (16.4% presence). These results suggest that cameras could be a powerful tool for accurately assessing the efficacy of conservation interventions to mitigate the impact of invasive predators on Hawaii’s native birds. Increased investments in camera technologies are worth consideration, particularly in the case of critically endangered species. Further research into the cost-effectiveness versus the information gained by the two methods could help further refine conservation strategies.