Fences, Ferals and Fire: Compounding and Interacting Influences on a Variable Reptile Assemblage in North Australia

The impacts of feral cats on native fauna have received considerable attention in recent years. We previously reported a two‐fold increase in the abundance of reptiles at a site in Australia's tropical savannas in response to feral cat exclusion. There is also increasing understanding of important interactive effects on prey of invasive predators and disturbance processes, in particular fire. Australian tropical savannas are highly fire prone and their diverse reptile communities have co‐evolved with these fire regimes. However, these regimes have undergone marked changes since European settlement, in particular, increased fire frequency and intensity. These changes may not only directly affect important resources for reptiles, but in turn may also exacerbate the impact of feral cats and other predators on reptile diversity. We extended the experiment reported in 2018 (i.e., from 2 to 4 years) to attempt to further resolve the effects of exclusion‐fencing and fire frequency on reptile assemblage composition and abundance. We found few clear response patterns. Furthermore, our previous report of increase in reptile abundance after 2 years of exclusion was not apparent after a further 2 years of trial. Nonetheless, reptile species composition varied between fenced and unfenced plots. We found highly variable responses amongst reptile species and in overall reptile community composition to the effects of exclusion and fire history. These appear to reflect complex interactions between fire regimes, cat predation and meso‐predator responses which are difficult to unpack. This project has highlighted some of the complexities involved with understanding these processes and their potentially complex interactions. Although our experiment was carefully designed, it was not possible to definitively disaggregate the effects of feral cat exclusion from those of exclusion of ungulates and dingoes. The inability to contain fire activity to the original planned treatments and relatively small number of replicates challenged our ability to discern and interpret the complex interactions involved.