Strongly interactive carnivore species: maintaining and restoring ecosystem function

Predators can have dramatic and lethal effects on individual prey, but they can also have subtle yet powerful effects on non-prey species via webs of indirect interactions. Top predators may, for example, suppress the activity of smaller predators and in turn provide a net benefit for the prey of the smaller predators; they can also reduce the impacts of herbivores and thus indirectly alter vegetation dynamics. Species that have such pervasive effects on their communities, and the broader ecosystems to which they belong, are termed ‘strongly interactive’. Here, we begin by reviewing the kinds of effects that theoretically can be engendered by the presence of strongly interactive carnivores, and then present examples of such species among the native reptiles, birds and mammals of Australia. The examples include elapid snakes, varanid (monitor) lizards, day-active raptors and owls, dasyurid marsupials and the dingo. The dingo, in particular, has been shown in many studies to suppress the activity of smaller mesopredators and herbivores and to have broadly beneficial effects on biodiversity and ecosystem function. Using the dingo as a case study, we propose that this important but persecuted species should be maintained in areas where it still occurs and that immediate consideration should be given to reintroducing it to areas from which it has been banished. We conclude that strongly interactive carnivores are key components of many ecosystems and should be retained where they still occur and reintroduced, where possible, elsewhere.