Rapid increase of Australian tropical savanna reptile abundance following exclusion of feral cats

Abstract

Feral cats have been responsible, in part, for the extinction of many species of mammal, bird and reptile globally, especially on islands. Whilst there is extensive evidence of the predatory impacts of cats on mammals and birds, far less is known about their ecological impacts on reptiles, especially in continental situations. We conducted a field experiment to evaluate the impact of feral cats on terrestrial vertebrates in tropical savanna environments of northern Australia. Three experimental treatments were applied to six 64 ha plots to compare and contrast responses of reptile abundance and species richness to predator exclusion and the additive effects of frequent fire. Replicated pitfall-trapping was undertaken in each plot on seven sampling occasions between November 2013 and November 2015. We analysed relative abundance and species richness data using generalized linear mixed models. There was a significant increase in the abundance of reptiles over a two year period in cat-excluded plots with reptile abundance increasing at twice the rate in cat-exclusion plots compared with cat-accessible plots and there was an additive effect of time-since-fire. Cat exclusion had a positive effect on reptile species richness over time, however the evidence for this pattern was weak when seasonal variation was taken into account. Predation by cats, in synergy with other disturbance processes, could adversely impact reptile species and communities elsewhere in the world where feral cats have been established and warrants further investigation.