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The Conversation: When feral cats are away, potoroos and bandicoots are more likely to play


Fidel Fernando/Unsplash

Euan Ritchie, Professor in Wildlife Ecology and Conservation, School of Life & Environmental Sciences, Deakin University; Amy Coetsee, Threatened Species Biologist, The University of Melbourne; Anthony Rendall, Lecturer in Conservation Biology, School of Life and Environmental Sciences, Deakin University, and Duncan Sutherland, Deputy Director of Research, Phillip Island Nature Parks; Research Fellow, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

All animals need to eat to survive, grow and reproduce. To do so, they also need to avoid being eaten. This is a big challenge for many of Australia’s native mammals, because when they search for food, they must also escape the attention of introduced predators, namely, feral cats and red foxes.

Tragically, many have been unable to overcome this test of survival, becoming one of the 40 native mammal species driven to extinction since European colonisation.

But what happens if we reduce the numbers of introduced predators? Do our surviving native species think there is less risk of being the next meal for a cat or fox? How do they respond? And how might we tell? With peanut butter balls, of course!

A deadly game of hide and seek


Long-nosed potoroos are vulnerable to predation by non-native feral cats and red foxes.
Leo Berzins/flickr, CC BY-ND

Natural environments contain predators and prey engaged in a deadly game of hide and seek, and – from the prey’s perspective – a landscape of fear. The extent to which the two groups are aware of each other and able to respond (hunting vs hiding and escape) varies across time and space. Prey might perceive some areas as a riskier proposition, such as more open habitats or times when predators are most active. They therefore reduce their activity to minimise the likelihood of being eaten.

But avoiding being eaten comes at an energetic cost. It may mean preferred areas or times to feed are reduced, which in turn limits rates of growth, reproduction and survival of prey species. Prey animals are constantly weighing up this tradeoff of risk vs reward as they go about their lives.

Tasty treats can assess risk appetite

We can’t know for sure how much animals fear being eaten, but we can assess it indirectly, through their willingness to eat. In our recently published study, we measured how much food animals don’t eat as a indicator of their fear of being eaten. The more food they give up, the greater the risk of predation those animals are assumed to perceive. These experiments are made easier by the fact many mammals are mad about gobbling up peanut butter.

French Island has long been fox free, but had thousands of feral cats. In 2010, authorities began a feral cat eradication, which made it a perfect place for our research.


Feral cat activity per month at one site on French Island, south-eastern Australia, across a 2-year period during a cat eradication program. The red arrow indicates when the cat eradication program began and the blue arrows indicate when we undertook our GUD experiments.
CC BY-NC-ND

Importantly, we were able to start our experiment prior to an eradication program of feral cats, which began in 2010 on French Island, Victoria. This means we were able to measure changes in long-nosed potoroos and eastern barred bandicoots habitat use and foraging as cat numbers and activity fell.

So, on fox-free French Island, we placed balls of peanut butter, rolled oats and golden syrup into trays with soil and dug them into the ground, ensuring they were below the soil surface. We did this in more open grassland areas (likely riskier habitat, with less cover and protection from feral cats) and more densely vegetated areas (less risky habitat, due to increased cover).

We used camera traps to measure how often potoroos and bandicoots visited these feeding trays to dig up the tasty treats, and how much of the peanut butter balls they left behind in different habitats and at different periods throughout the ongoing feral cat eradication program.

When feral cats are away, native animals play (more)

A deadly game of feral cat and long-nosed potoroo, as revealed by our camera trap. We can confirm that this potoroo survived, this time. Te Ao Marama Eketone (Deakin University), CC BY-NC-ND

As the number of feral cats on French Island was reduced, potoroos and bandicoots used both open and closed habitat types more frequently, and they increased their activity, giving up less food over time. This suggests bandicoots and potoroos do recognise feral cats as a threat, and are able to fairly rapidly change their habitat use and foraging accordingly.

Aside from the obvious benefits of fewer feral cats killing and eating potoroos and bandicoots on French Island, our study suggests there may be substantial benefits for native wildlife — namely increased access to habitats and foraging opportunities — even before the ultimate longer-term goal of cat eradication can be achieved.

Our study’s results are encouraging. Outside the safe havens of invasive predator-free islands and fenced sanctuaries, feral cats are notoriously hard to eradicate from large areas, and there is a constant threat of their return.

We need to do all that we can to give Australia’s native mammals, including eastern barred bandicoots, a helping hand. Zoos Victoria, CC BY-NC-ND

To change this, new and more effective ways to control and eradicate feral cats are needed. But until then, reducing and keeping feral cat numbers lower, while also carefully managing habitats to benefit wildlife, can still give native animals the helping hand they need to survive.

We would like to acknowledge that this work was led by former Deakin University Honours student, Te Ao Marama Eketone, and it occurred on the unceded Country of the Bunurong/Boonwurrung peoples.

The Conversation
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Science communication The Conversation

The Conversation: Yes, feral cats and foxes really have driven many Australian mammals to extinction

Lea Scannan/Getty

John Woinarski, Professor of Conservation Biology, Charles Darwin University; Euan Ritchie, Professor in Wildlife Ecology and Conservation, School of Life & Environmental Sciences, Deakin University; Katherine Moseby, Professor of Conservation Biology, UNSW, and Sarah Legge, Professor of Wildlife Conservation, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Millions of years of isolation have shaped Australia’s extraordinary mammal fauna into species unlike anywhere else in the world, from platypus to koalas and wombats.

Tragically, Australia is the world leader in mammal extinctions. About 40 species have gone extinct in the 238 years since European colonisation began, and nearly 80 species are now imperilled. It’s 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 key driver. 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’s mammals had confronted before.

Recently, some researchers have questioned whether these introduced predators really are responsible. In our new research, we lay out the clear lines of evidence implicating foxes and cats. For instance, extinct species tend to be small-to-medium mammals, the preferred prey size for these predators. When mammals are returned to fenced, fox- and cat-free areas, their populations often flourish.

The main lines of evidence implicating introduced predators in Australian native mammal declines and extinctions. Author provided, CC BY-NC-ND

Controversy in conservation

Last year, researchers questioned whether there was enough evidence to say feral cats and foxes had contributed to Australian mammal extinctions – 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:

  1. 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

  2. Lethal management programs aimed at reducing fox and cat numbers should result in an increase in native mammal numbers in an area

  3. Where cats and foxes are abundant, there should be fewer native mammals.

After testing these three ideas, the authors conclude the hypothesis foxes and cats cause extinctions “has come to be accepted with little evidence.”

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’s native mammal fauna depends on controlling cats and foxes. Many recent success stories in bringing native animals back from the brink are due to removing foxes and cats.

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.

An introduced eastern barred bandicoot population has thrived after foxes were eradicated on Phillip Island. Neil Bowman/Getty

What did we do?

A provocative claim in last year’s 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’t be held responsible.

Cats came with the First Fleet in 1788, augmented with many subsequent introductions. By the 1890s, feral populations had spread across the entire continent. Foxes came later, first introduced to southeastern Australia in the 1830s. They, too, spread out 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 documented record, especially in remote, sparsely populated areas of Australia.

First Nations peoples and Europeans have witnessed and recorded 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 greater stick-nest rat 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 now extinct.

After cats arrived in an area, historic data shows regional losses of mammals went up sharply, with the exception of two arbitrarily dated bones. Author provided, CC BY-NC-ND

Does fox and cat control work?

The authors argue fox and cat control doesn’t result in increases of threatened mammals. But this conclusion may stem from misreading data from feral cat and fox control programs. Not all control programs work to reduce cat numbers over long periods or even at all.

Instead, we can get far clearer evidence from what happens in safe havens – 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 are not excluded.

Eastern barred bandicoots now roam Victoria’s fox-free Phillip Island, while hare-wallaby numbers are rebounding on Western Australia’s 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’t always hold. After periods of good rainfall in inland Australia, populations of native mammals and feral predators all increase. During droughts, predator and prey numbers both fall.


This trail camera image captures a feral cat with two native hopping mice in its mouth.
Katherine Moseby, CC BY-NC-ND

Difficult truths

The original analysis and our new research have a broader context. Some have argued the impact of introduced species has been overstated, and that introduced species should be seen as a legitimate part of Australia’s ecosystems. Scientific evidence and conservation outcomes do not support this.

Australia supports about 8% of the world’s biodiversity as one of just 17 megadiverse nations. 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, necessary to protect many species near the brink of no return. It has to be done as humanely as possible and justified publicly. Stepping back would mean more and more extinctions.

We would like to acknowledge our research coauthors.

The Conversation
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Science communication The Conversation

The Conversation: In the most cleared state in Australia, Victoria’s native wildlife needs our help after fires

 joey found by firefighters near the Harcourt fire in Victoria. Glenlyon Rural Fire Brigade/Facebook

Euan Ritchie, Professor in Wildlife Ecology and Conservation, School of Life & Environmental Sciences, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Victoria has just suffered some of its worst bushfires since the Black Summer fires of 2019–20. Over 400,000 hectares are estimated to have burnt so far, an area more than five times larger than Singapore.

Regional communities have been deeply affected. They need support to recover and rebuild their homes, towns and lives. And what about the state’s unique plants, animals and ecosystems?

Both large and small fires erupted in Victoria, and were extraordinarily widespread across diverse environments. They burned in the Wimmera–Mallee region in the northwest, the Otways in the southwest, central Victoria, northeastern Victoria and eastern Victoria, including the alpine region. This means a correspondingly diverse range of native plants and animals has been affected.

Compounding this, Victoria is the most cleared state in Australia. This makes it more difficult for animals to find suitable habitat outside of burnt areas in a fragmented landscape as they recover.

A night image of fires lighting up the sky above Lake Eildon during the Victorian bushfires. Graeme Thomas/Facebook

How will these fires affect nature?

Fires have short and long-term affects on wildlife. While a high proportion of animals can survive fires, the total numbers of insects, birds, frogs, reptiles, mammals and others that have died during the fires or afterwards, will still be large. This is due to severe burns, smoke, radiant heat or other injuries as they try to escape. Many animals get caught on fences as they move across landscapes seeking refuge.

We might think animals that can fly, such as many insects, birds and bats, should be able to easily escape. But smoke and extreme heat makes it difficult to breathe and regulate their body temperature, and can disorient wildlife. Temperatures soared well above 40°C during the fires. Along with intense winds, this took a heavy toll on some animals. Tragically, thousands of flying foxes died.

Many animals will have survived fires by finding refuge in protected waterways, caves, rock and boulder piles, or by going underground, including into wombat burrows. Echidnas dig into the ground and go to sleep, a clever tactic to conserve energy and reduce stress on the body.

After fires, animals face additional challenges. Feral cats and foxes are known to rapidly take advantage of burnt areas. Hunting and capturing their prey in more open habitat is easier. Potoroos, bandicoots, lizards and many others that survive initially may be hunted in the hours, days and weeks after a fire.

The long-term effects

The impact of fire can last for decades, or even longer. Many Australian wildlife species depend on logs and hollows in trees for shelter and to raise young. Fire can both create and destroy hollows.

Importantly, Victoria is the most cleared state in Australia. Hence, hollows are already short in supply and patchily distributed. For some tree species, they can take more than 100 years to form. Their loss puts pressure on threatened species including greater gliders, barking owls and spotted-tailed quolls.

Aquatic life is not immune to the effects of fire either. Rains that occur in burnt landscapes can wash ash, debris and toxins into waterways. This smothers underwater habitats and reduces oxygen and water quality for native fish, crayfish and amphibians. In some cases it leads to mass mortality, including fish kills.

How to respond?

Once bushfires are contained and it is safe to enter, government agencies, scientists and wildlife carers will get a clearer picture of fire severity and native wildlife that need help. They will undertake population surveys and develop a management plan. This may include culling invasive herbivores such as deer, laying poison baits to control feral cats and foxes and installing artificial refuges for native animals.

Agencies should take a whole-of-ecosystem view to ensure well intended actions don’t have unexpected consequences. While 1080 poison may be needed in some areas to help control non-native predators, it also poses a risk to dingoes, a threatened species in Victoria.

This includes the Wilkerr (dingo) population in the Big Desert-Wyperfeld region in northwest Victoria, estimated to number fewer than 100 adults. Approximately 60,000 hectares of Wilkerr habitat has burned. The fires may push Wilkerr into agricultural land seeking cover and water, increasing contact and conflict with livestock graziers. This situation needs to be thoughtfully managed to protect graziers, livestock and Wilkerr.

What should I do?

We can help in a range of ways. These include:

  • putting out water dishes for animals with sticks or stones in them so small animals don’t drown
  • donating to charities and organisations that take care of injured wildlife
  • creating wildlife-friendly gardens that displaced animals may use.

Members of the public should not attempt to feed wildlife, and leave this to experts. Likewise, approaching injured animals is not advised, including kangaroos and snakes. Stressed animals can behave erratically and aggressively, and should only be taken care of by experienced wildlife experts.

Feeding wildlife after fire should be done by experts, such as occurred for rock wallabies following the Gariwerd–Grampians fires.

Governments must change course

As a wildlife ecologist and conservation expert, these fires bring an unwelcome but familiar mixture of deep sadness and intense frustration. As the climate gets hotter, such events will only become more likely and more severe.

Governments must substantially increase efforts to curb climate change, including a rapid transition away from fossil fuels. Likewise, we need far stronger environmental laws, and greater government investment to protect and recover the wildlife and places Australians love.

Fire has shaped Australia’s environments, and many species are adapted to survive and even benefit from fire. But the increasing regularity of severe fires will push some wildlife and ecosystems into oblivion. As with people and communities, we have a duty to provide Australia’s native plants, animals and other life with a safe and secure future.

The Conversation