Top-predator removal does not cause trophic cascades in Australian rangeland ecosystems

Abstract

Increased demand for livestock products is exacerbating conflict with predators in many parts of the world, fuelling an increase in predation management practices in many grazing systems. In Australia, exclusion fences are being erected across broad areas to facilitate the sustained eradication of dingoes, an apex predator, prompting concern for possible cascading effects on extant wildlife populations. We experimentally assessed population trends of mammals, reptiles and ground-dwelling birds inside and outside of two large, fenced areas over a five-year period subsequent to the erection of the fences and the removal of dingoes. Wildlife population abundances inside the fences were always higher or the same as outside the fences, and all wildlife species exhibited similar population trends within each treatment over time. The only exception to this was kangaroo populations, which fluctuated widely inside fenced areas but remained relatively low and stable outside fenced areas. Kangaroos exhibited negative relationships with dingoes, although unmeasured variables limited our ability to quantify specific causes for kangaroo population trends. Vegetation trends were virtually identical between treatments, indicating that wildlife population trends are closely linked to vegetation conditions and not predator abundances. These applied, experimental results demonstrate that top-predator removal does not routinely cause trophic cascades (including mesopredator releases) in Australian rangeland ecosystems. We therefore encourage exploration of opportunities for targeted threatened species recovery in predator-free areas on land used for livestock production.