Relative impacts of cattle grazing and feral animals on an Australian arid zone reptile and small mammal assemblage

The effect of different levels of cattle grazing on an arid Australian small terrestrial mammal and lizard assemblage was assessed in a long-tem series of cross-fence comparisons. Cross-fenced sites were closely matched for edaphic and vegetation characteristics and experienced near identical weather patterns, to ensure that cattle grazing pressure was the principal determinant of any differences in fauna assemblages. In addition, the effects of removal of cattle, cats, foxes and rabbits from three of these long-term monitoring sites were assessed to determine the relative impacts of cattle grazing and feral animals. Small mammal captures, with the exception of Mus musculus, revealed a significant negative response to cattle grazing pressure but this response was of a considerably lower magnitude than the dramatic increase in rodent captures and species richness within the feral animal-proof Arid Recovery Reserve. Higher kangaroo numbers in ungrazed controls, compared with treatments grazed by cattle, possibly negated the benefits to small mammals of removing cattle grazing. No reptile species responded significantly to the grazing treatments although reptile richness and captures of geckos and skinks were the lowest and agamid captures were the highest at heavily grazed sites. Nephrurus levis was the only reptile species to increase significantly, while captures of some smaller geckoes declined, within the feral-proof treatment. Feral predation exerted a more significant effect on most small mammal species than the levels of cattle grazing assessed in this study, yet reptile responses to grazing or feral animals were less apparent and were likely primarily driven by changes in vegetation cover or secondary trophic impacts.