Millions of years of isolation have shaped Australia鈥檚 extraordinary mammal fauna into species unlike anywhere else in the world, from platypus to koalas and wombats.
Tragically, Australia is the in mammal extinctions. About 40 species have gone extinct in the 238 years since European colonisation began, and species are now imperilled. It鈥檚 essential we understand what factors caused these extinctions and ongoing decline.
Over many years, scientists have gathered compelling evidence demonstrating predation by introduced cats and foxes has been a . Australian mammals have had millennia living alongside other predators such as wedge-tailed eagles and dingoes. But foxes and cats are extraordinarily capable and ecologically flexible hunters, quite unlike anything Australia鈥檚 mammals had confronted before.
Recently, some researchers whether these introduced predators really are responsible. In our , we lay out the clear lines of evidence implicating foxes and cats. For instance, extinct species tend to be , the preferred prey size for these predators. When mammals are returned to fenced, fox- and cat-free areas, their populations .
Controversy in conservation
Last year, whether there was to say feral cats and foxes had contributed to Australian 鈥 and, by implication, their role in the ongoing decline of other threatened mammal species.
Their research drew on three premises relating to extinct and surviving mammals. If cats and foxes caused these extinctions, they argued that these should follow:
The last recorded sighting of a now extinct mammal from an area must come after the arrival of one or both of these predator species
Lethal management programs aimed at reducing fox and cat numbers should result in an increase in native mammal numbers in an area
Where cats and foxes are abundant, there should be fewer native mammals.
After testing these three ideas, the authors the hypothesis foxes and cats cause extinctions 鈥渉as come to be accepted with little evidence.鈥
The research caused a major stir among the conservation community, as it took aim at longstanding accumulated knowledge and questioned whether the evidence base was strong enough to justify efforts to control feral cats and foxes.
As experts with many decades experience working to protect threatened Australian mammals and other wildlife, we had a duty to evaluate their evidence.
Claim and counterclaim is essential to test, shape and hone science, and to provide a robust foundation for conservation management. It may seem like an academic argument, but it has clear real-world implications.
The survival and recovery of much of Australia鈥檚 native mammal fauna depends on controlling cats and foxes. Many recent in bringing native animals back from the brink are due to .
If this objective is abandoned because of arguments feral cats and foxes are simply innocent bystanders, we risk rapidly losing many of these imperilled species.
What did we do?
A provocative claim in last year鈥檚 research was that some Australian mammal species may have gone extinct before foxes and cats ever got to the area. If this was true, cats and foxes couldn鈥檛 be held responsible.
Cats came with the First Fleet in 1788, augmented with many subsequent introductions. By the 1890s, feral populations had . Foxes came later, first introduced to southeastern Australia in the 1830s. They, too, across most of the continent over decades.
We re-ran analysis of the historic data and found the last record of a now-extinct native mammal in an area was always dated after the arrival of cats. The picture is less clear for foxes, though this is understandable given the earlier arrival of cats would already have caused losses.
Further, the actual date of extinction may occur long after the last , especially in remote, sparsely populated areas of Australia.
First Nations peoples and Europeans have many cases where a native mammal species disappeared from an area soon after one or both non-native predators arrived.
Fate provides further evidence. Many mammals were wiped out from their entire mainland ranges but survived on islands that cats and foxes never colonised. For instance, all mainland populations of the have disappeared. But the species survives because it also had an island population. By contrast, the lesser stick-nest rat had no island population. It is .
Does fox and cat control work?
The authors argue fox and cat control doesn鈥檛 result in increases of threatened mammals. But this conclusion may stem from misreading data from and control programs. Not all control programs to reduce cat numbers over long periods or even at all.
Instead, we can get far clearer evidence from in safe havens 鈥 islands or fenced areas where foxes and cats are completely excluded. Threatened mammal species almost always increase in these areas and almost always decline at comparable sites where foxes and cats .
Eastern barred bandicoots now roam Victoria鈥檚 , while hare-wallaby numbers are rebounding on Western Australia鈥檚 Dirk Hartog Island following the eradication of feral cats.
The assumption that native mammals should typically be less abundant when and where cats and foxes are more common doesn鈥檛 always hold. After in inland Australia, populations of native mammals and feral predators all increase. During , predator and prey numbers both fall.
Difficult truths
The original analysis and our new research have a broader context. Some have argued the impact of introduced species has been , and that introduced species should be seen as a . Scientific evidence and conservation outcomes do not support this.
Australia supports of the world鈥檚 biodiversity as one of just . Protecting our unique species is not easy. But the task for conservationists and policymakers will be even harder if feral cats and foxes are given a free pass to keep killing.
Lethal control is, unfortunately, to protect many species near the brink of no return. It has to be done as humanely as possible and . Stepping back would mean more and more extinctions.
We would like to acknowledge our .
, Professor of Conservation Biology, ; , Professor in Wildlife Ecology and Conservation, School of Life & Environmental Sciences, ; , Professor of Conservation Biology, , and , Professor of Wildlife Conservation,
This article is republished from under a Creative Commons license. Read the .
