Harnessing the power of ecological interactions to reduce the impacts of feral cats

Cats (Felis catus) are globally one of the most widespread invasive predators and are identified as one of the top 100 invasive species (Lowe et al. 2000). The effects of cats are particularly severe on islands (Medina et al. 2011; Courchamp, Chapuis, and Pascal 2003) and isolated landmasses without native felines. The impacts of cats on native wildlife are exemplified in Australia, whose fauna evolved in isolation from placental predators.

Cats were introduced to Australia in ∼1788 and now occupy 99.8% of Australia’s land area (Legge et al. 2017). Cats are implicated in most of Australia’s ∼29 mammal extinctions, representing 35% of global mammal extinctions since 1500 (Woinarski, Burbidge, and Harrison 2015). Of Australia’s remaining mammal species, ~29% are vulnerable to predation by cats and foxes (Radford et al. 2018).

Growing awareness of the threat posed by cats to Australian wildlife led the Australian government to ‘declare war’ on feral cats in 2015 (Tharoor 2015). The war plan included a target to kill two million feral cats by 2020 and eradicate cats from five islands (Australian Government 2015d). We commend the government’s willingness to reduce the harm caused by cats and recognise that targets can be important in achieving conservation goals, raising public awareness and promoting investment (Doherty et al. 2018). We also agree that predator-free islands and fenced reserves are valuable tools to increase populations of threatened species (Australian Government 2015d). However, we argue for a stronger emphasis on the important role that ecological interactions play in reducing the impacts of cats in the vast landscapes outside enclosures and islands. We need a more self-sustaining, holistic approach – one that places greater focus on harnessing the power of ecological interactions and addresses the mechanisms by which cats cause harm to biodiversity. The gains for biodiversity of experimentally testing and implementing management that uses natural levers in trophic networks (see Figure 1) are potentially enormous.