Complex interactions among mammalian carnivores in Australia, and their implications for wildlife management

Abstract

Mammalian carnivore populations are often intensively managed, either because the carnivore in question is endangered, or because it is viewed as a pest and is subjected to control measures, or both. Most management programmes treat carnivore species in isolation. However, there is a large and emerging body of evidence to demonstrate that populations of different carnivores interact with each other in a variety of complex ways. Thus, the removal or introduction of predators to or from a system can often affect other species in ways that are difficult to predict. Wildlife managers must consider such interactions when planning predator control programmes. Integrated predator control will require a greater understanding of the complex relationships between species.In many parts of the world, sympatric species of carnivores have coexisted over an evolutionary time scale so that niche differentiation has occurred, and competition is difficult to observe. Australia has experienced numerous introductions during the past 200 years, including those of the red fox (Vulpes vulpes) and the feral cat (Felis catus). These species now exist in sympatry with native mammalian predators, providing ecologists with the opportunity to study their interactions without the confounding effects of coevolution.Despite an increasing body of observational evidence for complex interactions among native and introduced predators in Australia, few studies have attempted to clarify these relationships experimentally, and the interactions remain largely unacknowledged. A greater understanding of these interactions would provide ecologists and wildlife managers world-wide with the ability to construct robust predictive models of carnivore communities, and to identify their broader effects on ecosystem functioning. We suggest that future research should focus on controlled and replicated predator removal or addition experiments. The dingo (Canis lupus dingo), as a likely keystone species, should be a particular focus of attention.

Experimental evidence of competitive release in sympatric carnivores

“…In the wider ecological context, controlled experimental manipulations of predator populations have frequently been advocated in order to better understand carnivore communities and their role in ecosystem functioning (Polis et al 1989;Glen & Dickman 2005). However, such manipulations are scarce, despite the profound importance of carnivore interactions on community structure.…”

Phylogenetic structure of mammal assemblages at large geographical scales: linking phylogenetic community ecology with macroecology

“…In mammals, interspecific competition has been shown to reduce population densities, or cause local extinction, of weaker competitors within local sites (e.g. [33][34][35]). It is therefore reasonable to expect that local-scale mammal assemblages are sometimes structured by competition.…”

Could controlling mammalian carnivores lead to mesopredator release of carnivorous reptiles?

“…The predatory impact of introduced carnivores on native prey has been widely documented; however, only recently has much attention been given to the indirect effects that result from competitive interactions between predators [1,2]. Competitive interactions can be complex and shifts in their dynamics have resulted in unpredictable and sometimes profound impacts on lower trophic levels [3,4].…”