Do ecosystems need top predators? A brief review of predator-prey imbalances in south-east Australia with reference to tree dieback on the Mornington Peninsula

Summary The role of top predators in regulating terrestrial ecosystems in south-east Australia is briefly reviewed here. Examples of ecological imbalance associated with overabundant native herbivores are identified. The Mornington Peninsul a tree dieback phenomenon, which involves overbrowsing by Common Ringtail Possum, is discussed. Due to the widespread loss of native top predators, in many areas we are left with two unsatisfactory introduced mesopredators, the fox and cat, to regulate herbivo res. They have low efficiency in controlling ringtail possums in dense vegetation, a nd furthermore, 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.