Do ecosystems need top predators?: A review of native predator-prey imbalances in south-east Australia

The role of native top predators in regulating terrestrial ecosystems in south-east Australia is briefly reviewed. Examples of ecological imbalance associated with overabundant native herbivores are identified. The cases of tree canopy loss due to excessive browsing by Koala and Common Ringtail Possum are discussed. The widespread loss of native top predators has left two introduced mesopredators, the Red Fox and Cat, to regulate both native and introduced herbivores in many areas. However, being ground-based predators, they are not efficient at controlling ringtail possums in dense vegetation, and without the top predator Dingo they may be ecologically released, increasing their impact on sensitive fauna. Management approaches to keeping a balance between predators and herbivores are outlined.