Estimating the effect of toxic red meat baits on feral cat density in north-eastern New South Wales

Context The management of feral cats (Felis catus) is crucial to effective species conservation. One management approach is to aerially apply toxic baits (containing sodium monofluoroacetate) to achieve landscape scale control. However, limited bait types are available to target cats. Aims In the absence of specific baits (i.e. Eradicat® or Curiosity®) for the control of feral cats in New South Wales (NSW), we aimed to investigate the effectiveness of red meat baits, intended for canid control, to reduce local feral cat density. Methods We deployed a grid of 65 camera traps, spaced at approximately 1-km intervals, in the Guy Fawkes River National Park, NSW. The feral cat population was surveyed 7 weeks prior to and post-baiting, separated by a 4-week baiting period that was unmonitored. Cats detected by camera were individually identified and a spatial-mark-resight model was used to estimate the change in feral cat density. Key results In total, 34 individual feral cats were identified. The feral cats present after baiting were mostly different to those individuals detected prior to baiting. However, feral cat density was not substantially different between surveys (pre-baiting: 0.56 cats km−2, 95% CI: 0.39–0.81 cats km−2; post-baiting: 0.58 cats km−2, 95% CI: 0.40–0.84 cats km−2). Conclusions Aerially deployed red meat baits, intended for canid control, had a negligible effect on feral cat density. The density estimate reported was two times higher than the average cat density previously modelled for natural environments across Australia. Implications With a higher-than-expected density, and no clear population reduction from red meat baiting, it is possible the local feral cat population may be having a greater impact on regional biodiversity than previously expected. However, given the lack of replication, we caution against pre-emptively generalising the outcomes of this study across different seasons and ecoregions.