Did curiosity kill the cat? The impacts of aerial baiting and Felixer deployment on feral cat populations on Three Hummock Island, Tasmania

Context The eradication and control of feral cats (Felis catus) on offshore islands is a conservation priority in Australia to protect threatened species. However, this task is challenging and resource-intensive, particularly in remote and inaccessible locations. Aims This study aimed to evaluate the effectiveness of lethal aerial baiting and Felixer grooming traps in reducing feral cat activity on Three Hummock Island, Tasmania, to support the establishment of a hooded plover (Thinornis rubricollis) stronghold. Methods Two rounds of aerial baiting using Curiosity poisoned baits were undertaken in May 2021 and September 2023. Additionally, five Felixer units were deployed with a 6-month non-lethal period before being switched to lethal mode in November 2021. Felixers use image recognition to identify cats and apply a sodium fluoroacetate (1080) poison gel, which is ingested during grooming. A network of 20–60 camera traps, operating over 37,175 trap days during 2019–2024, was used to monitor changes in feral cat activity and site usage. Key results Feral cat relative activity (proportion of days with cat events) steadily declined following control efforts, with site usage halving after Felixer deployment in 2021 (dynamic-occupancy model slope for extinction without Felixers = −2.22, s.e. = 0.929, P = 0.0121). By contrast, aerial baiting did not significantly affect site usage (first round: estimate = 0.921, s.e. = 1.04, P = 0.378; second round: estimate = −1.021, s.e. = 0.687, P = 0.137) or activity. Despite targeting only nine cats, the Felixers contributed to a substantial decline in cat presence, suggesting a small, possibly inbred population prior to control. Camera trap images revealed that most cats were ginger, and many had kinked tails, further supporting the likelihood of inbreeding depression. Conclusions Felixers were effective in reducing feral cat activity with minimal intervention, whereas aerial baiting alone had limited impact. These findings highlight the potential of automated, low-effort control methods for managing feral cat populations on remote islands. Implications This study demonstrates that Felixers may be an effective alternative to traditional high-effort control methods, such as shooting, trapping, and baiting. However, ongoing monitoring and additional control efforts are required to ensure progress toward complete eradication.