By Dr John Kanowski, Chief Science Officer
Imagine being a little bush animal – a native mouse, or an antechinus. You are sniffing around, digging up seeds or grubs for a meal, when suddenly you are in the grip of a massive predator – a feral cat, or fox – 100 times your size. That’s like a human in the jaws of Tyrannosaurus rex. What’s the likely outcome?
Sadly, the outcome for Australian mammals has been wholesale extinction and decline of species in the ‘critical weight-range’– anything from the size of a native mouse to a rock-wallaby. Most of the vulnerable species – bettongs, bandicoots, bilbies, quolls, small wallabies and native rodents – have been eaten out of extensive tracts of the country, with declines especially acute in the arid zone, where options for hiding from predators are limited. The species that survived the onslaught were lucky enough to have natural protection, such as the Echidna, or to be living on islands, or in parts of the country where the ‘poison pea’ Gastrolobium was common such that they were afforded some protection by the naturally occurring ‘1080’. Mammals occupying the tropics have escaped the fox, but their decline at the claws of the cat – aided by the removal of ground cover by wildfires and introduced herbivores – continues apace.
So, how do we protect the remnants of our natural heritage, our precious remaining native mammals, from introduced predators? Clearly, one option is to build a fence to the specifications required to keep cats and foxes away from our wildlife. Another is to acquire an island and eradicate any feral predators from it. AWC has embraced both these approaches to protecting critical weight-range mammals. To date, we have established feral cat- and fox-free areas on Faure Island (4,600 hectares) and within eight fenced areas, ranging in size from 252 hectares at Karakamia to 9,570 hectares at Mallee Cliffs National Park.
AWC’s safe havens currently protect a total of 15 nationally threatened mammal species, as well as a number of locally extinct mammals. The removal of foxes and cats from AWC’s fenced areas and Faure Island has also benefited a range of birds, reptiles and mammals that are vulnerable to fox or cat predation on these properties, such as the ground-active, nationally threatened, Malleefowl (Leipoa ocellata). For some species, such as the Numbat (Myrmecobius fasciatus), Bilby (Greater Bilby; Macrotis lagotis) and Burrowing Bettong (Bettongia lesueur), AWC’s reintroduction program makes a major contribution to their conservation, with multiple secure populations comprising a substantial proportion of the global population. For example, the Numbat has been successfully reintroduced to AWC’s fenced areas at Mt Gibson, Scotia, Yookamurra and most recently Mallee Cliffs. These sites collectively support several hundred individual Numbats, while remnant populations in south-west Western Australia are thought to number fewer than 1000 individuals.
At present, AWC is in the middle of a major burst of activity in our reintroduction program. At Mt Gibson, south-west WA, we are in the final stages of the most comprehensive rewilding project yet attempted in Australia. To date, we have released eight species of nationally threatened mammals to the 7,838-hectare fenced feral predator-free area, with follow-up translocations of one species, and reintroductions of a further two species, proposed for 2021 and following years. Importantly, the two last reintroductions – of the Brushtail Possum (Trichosurus vulpecula) and Chuditch (Western Quoll, Dasyurus geoffroii) – will involve attempts to establish populations outside the fence, in conjunction with a sustained feral predator control program.
At Newhaven in Central Australia, we are in the early stages of the reintroduction program, having reintroduced two species to date, with another eight to come. Like other recent AWC projects, the fenced feral predator-free area at Newhaven is sufficiently large (nearly 9,450 hectares) that we anticipate the reintroduced species will be able to establish populations in the hundreds to thousands of individuals. These large populations are more resilient to the boom-and-bust conditions characteristic of arid Australia, facilitating persistence and the maintenance of genetic variation. Our team of ecologists are currently planning reintroductions of the Burrowing Bettong and Golden Bandicoot (Isoodon auratus) to Newhaven. Both species were formerly abundant in the arid zone – in fact, remnant warrens made by the Burrowing Bettong can still be found on Newhaven.
Bettong warrens also provide important habitat and thermal refuge for a range of other species in the desert, including several mammals we hope to reintroduce to Newhaven in coming years. The burrows and diggings made by small mammals are a fundamental component of the ecology of arid Australia, trapping water and nutrients, and facilitating plant regeneration. This highlights the fact that rewilding projects, while important for species conservation, actually involve the restoration of entire ecosystems.
Our two projects conducted in partnership with the NSW Government, in the Pilliga and at Mallee Cliffs National Park, are also still in the early phases of reintroductions. To date, four of a total of 11 regionally extinct mammal species have been reintroduced to these sites, as part of the Saving our Species program. Another four or five reintroductions are planned for 2021, depending on the availability of founders (an unpredictable element of these programs, influenced by factors ranging from environmental conditions at source sites to the granting of regulatory approvals). As at Newhaven, the reintroduction of ‘ecosystem engineers’ such as the Bilby has important consequences for the restoration of ecosystems in the Pilliga and Mallee Cliffs, with diggings and burrows now starting to pit the soil surface.
AWC’s newest fenced area project, the Western River Refuge on Kangaroo Island (KI), is helping protect the threatened KI Dunnart (Sminthopsis aitkeni) and other locally endemic species, in the face of severe predation by feral cats after the 2019-20 bushfires burnt 93 per cent of the Dunnart’s known range.
AWC is in the final stages of preparing for the on-ground work required to establish a 900-hectare fenced area at Mount Zero-Taravale Wildlife Sanctuary, in north Queensland. This work is being done to facilitate the reintroduction of the endangered Northern Bettong (Bettongia tropica), which has declined to just two populations. We expect the safe haven on Mount Zero-Taravale to support a population of around 500 bettongs – the habitat within the fence includes locations where the species was last recorded in the area, some 20 years ago.
AWC’s network of feral predator-free areas is a nationally significant piece of conservation infrastructure that makes a major contribution to the protection of Australia’s critical weight-range mammals. Reintroductions to these and other predator-free areas were called out as rare examples of positive outcomes for our native mammals in the Action Plan for Australian Mammals (Woinarski et al. 2014), in the Threatened Mammal Index (developed by the Threatened Species Recovery Hub of the Australian Government’s National Environmental Science Program) and by a recent House of Representatives Inquiry into tackling the feral cat pandemic. In fact, the Inquiry called for an expansion of feral predator-free areas, and AWC was specifically commended for our work addressing the problem of feral cats.
Bayraktarov, E. and Jackson, M. 2021. Threatened Mammal Index. National Environmental Science Program (NESP) Threatened Species Recovery Hub < https://tsx.org.au/growing-the-index/threatened-mammal-index/>.
House of Representatives Standing Committee on the Environment and Energy. 2020. Tackling the feral cat pandemic: a plan to save Australian Wildlife. Report of the inquiry into the problem of feral and domestic cats in Australia.<https://www.aph.gov.au/Parliamentary_Business/Committees/House/Environment_and_Energy/Feralanddomesticcats/Report>.
Woinarski, J.C.Z., Burbidge, A.A. and Harrison, P.L. 2014. The action plan for Australian mammals 2012. CSIRO Publishing, Collingwood, Australia.
Read and download this full issue of Wildlife Matters here.
Donate to help save Australia’s threatened wildlife and wild places.