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Feral felines: managing their impact on native fauna

Australian fauna have suffered serious declines since European settlement, with small- and medium-sized mammals being the worst affected. Feral cats depredate native birds, mammals and reptiles and are…

Feral cats are a significant threat to Australian fauna species. Tim Doherty / ECU

Australian fauna have suffered serious declines since European settlement, with small- and medium-sized mammals being the worst affected. Feral cats depredate native birds, mammals and reptiles and are listed as a Key Threatening Process under the Commonwealth EPBC Act. Reducing the harmful impact of feral cats on native fauna presents wildlife managers with a formidable challenge.

Domestic cats came to Australia with European settlers in the late 18th century and spread into the natural environment from coastal locations in the period 1824-86. Rabbits provided cats with a reliable food source during their dispersal. The intentional release of large numbers of cats to control rabbit plagues also furthered their spread.

By 1890 the feral cat had colonised the entire continent, including Tasmania and a number of offshore islands. Their successful invasion was aided by the species' flexible habitat use, adaptive diet and no requirement for free water. Moreover, feral cats have a high reproductive output and are threatened by few higher order predators in Australia.

Cats were valued as pest control agents and from 1918-21 it was illegal to kill feral cats in Western Australia. Their negative environmental impacts did not receive significant attention until at least 50 years later.

Fauna decline and extinction

Feral cats have been implicated in the decline and extinction of some 22 mammal species in the past 200 years. It is difficult to assess the relative contribution of feral cats to fauna declines as altered fire regimes, introduced herbivores, fox predation and climate change have also occurred in this time, and their impacts may be synergistic in nature - see here, here and here.

The first experimental evidence illustrating their impact was provided by research at Shark Bay, Western Australia. In that study, small mammals showed a positive population response where both cats and foxes were removed, but showed an 80% decline where foxes were removed, but cats remained.

Cat footprints on a vehicle track. Tim Doherty

Further evidence can be found in the failure of numerous reintroduction attempts of threatened mammal species.

In 1992, 40 burrowing bettongs were released into the Gibson Desert Nature Reserve. Sixty days later no live animals could be located and of the 11 carcasses that were found, all showed clear evidence of cat predation.

More recently, preliminary results from northern Australia have shown that cats decimated an unfenced population of reintroduced pale field rats, while a fenced population survived and successfully reproduced.

Protecting threatened species

The recognition of these impacts has led to a strong focus on control measures. Predator-free islands are an important nature conservation tool. A combination of trapping, shooting, baiting and sterilisation has been used to eradicate cats from islands.

Eradication of cats on Hermite Island allowed the establishment of insurance populations of the spectacled hare-wallaby and golden bandicoot. In similar fashion, four other threatened mammals have been translocated to Faure Island following removal of cats.

The remaining challenge now lies in protecting mainland fauna populations from an invasive predator that has high dispersal ability and an aversion to conventional baiting methods.

Two useful techniques have emerged: predator exclusion fencing and poison baiting using Eradicat or Curiosity baits.

Islands on the mainland

Predator-proof fences have become an invaluable tool for protecting threatened fauna. Fenced conservation properties, some greater than 5000ha, now protect at least 15 threatened mammal species in self-sustaining populations. These populations are a source of individuals for translocation to additional insurance populations, further strengthening their value.

Fencing, however, comes at a price; Long and Robley costed cat, fox and rabbit exclusion fencing at $8,000-$11,400 per km for materials only. The authors estimate that labour for planning and construction may make up 50% of the budget. The high cost of fencing and potential consequences of overabundance illustrate the need for sustained predator control at the landscape scale.

Baiting as a control measure

Eradicat and Curiosity baits were developed in response to the feral cat’s unwillingness to take conventional dog and fox baits. These cat baits are a sausage type medium of kangaroo meat mince, chicken fat, digests and flavour enhancers.

Broad-scale aerial application of Eradicat 1080 baits in semi-arid WA is used for the ongoing control of foxes and feral cats. The baiting targets high-value conservation areas such as Cape Arid National Park, the final stronghold for the critically endangered western ground parrot.

Baiting is helping protect the western ground parrot in Cape Arid National Park. Brent Barrett / DEC

The Curiosity bait has been developed for areas outside of south western Australia, where native fauna do not have a natural tolerance to 1080 poison. Curiosity contains the toxicant para-aminopropiophenone encapsulated in a “hard-shell delivery vehicle”, which may increase the bait’s target specificity.

Successful reduction in cat populations using Curiosity has been achieved on Christmas, French and Dirk Hartog Islands. Mainland trials at Flinders Ranges and Wilsons Promontory National Parks achieved some reduction in cat numbers, but may have been compromised by excess food availability and heavy rainfall respectively.

Eruptions of native and introduced mammals can compromise baiting operations. Christensen et al. have recently used a 14 year data set to show that a predator-prey index is potentially useful to land managers as an a priori predictor of the efficacy of planned baiting operations.

Control methods for feral cats are still in their infancy and will benefit from an improved understanding of feral cat ecology. Additional research will reveal whether habitat structure and higher-order predators can mediate feral cat impacts. Further investment in research, exclusion fencing and baiting will improve protection of Australian fauna from cat predation.

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20 Comments sorted by

  1. Russell Walton


    Encouraging developments.

    Cats are also a menace in the suburbs, my neighbourhood is infested with these diabolical, furry psychopaths, of course most of them are someone's "pet". All cats are feral, it's simply a matter of degree.

    What are the chances of a feline specific virus similar to calici?

  2. Keith Thomas


    My experience is that live trapping using dried fish is very effective.

    The cost of feral cat control may be seen by some as high, but it is minute compared with the benefit.

    Another issue that's off-topic here, but still relevant to the effect of cats on the environment, is that in Australia domestic cats eat more fish than do people. This is of huge significance for fisheries depletion.

    1. Neville Mattick
      Neville Mattick is a Friend of The Conversation.

      Grazier: ALP Member at A 4th Generation Grazing Station

      In reply to Keith Thomas

      Thank you Tim for the work above, there is hope, we bait foxes here regularly and suspect a few cats take the treatment at times too.

      Thank you Keith for exposing the appalling Human habit of feeding worthless cats on Fish, a shocking statistic, given that I am opposed to almost all Fishing of any kind apart from sustainable farmed ones.

  3. Dingo Simon

    Owner, Durong Dingo Sanctuary Qld

    You forgot to mention to ability of the Canis Lupus Dingo's role reducing cat numbers. Considering now it has been revealed the dingo has been living in Australia for about 18,000 years and co existed with all native wildlife, it's ability in keeping down the feral cat numbers should not be ignored.

  4. Mark Read

    Manager Species Conservation at Great Barrier Reef Marine Park Authority

    Interesting article and pleased to hear about some of the new control options.

    For many years I did vessel-based crocodile surveys at night in some of the most remote waterways in Queensland. It was staggering how often the spotlight would pickup the eyeshine of a feral cat instead of a crocodile. The cats would regularly be seen foraging in the riparian vegetation and mangroves at night, and I suspected they were after roosting birds, small mammals and geckos.

    I always wanted to see a crocodile take a cat, but sadly that opportunity never eventuated.

  5. Bernie Masters

    environmental consultant at FIA Technology Pty Ltd, B K Masters and Associates

    Thanks for this useful article. There is some evidence to suggest that feral cats came to Australia in the 17th century or earlier as a result of ship wrecks along our coast. It's also worth mentioning that feral cats are considered by some Aboriginal people to be a prized delicacy so maybe one further control option in inland and northern Australia is to employ Aboriginal people as cat trappers.....and they're allowed to keep and eat their successful catches!

  6. Pamela H.

    logged in via email

    The degredation that white man has done to this country is so sad. We brought the dogs, cats, foxes, boar, rabbits, rats, toads, horses, camels, cattle and sheep which all degrade the land, water, air and natural wildlife of this originally intact and beautiful land. In the relatively short time white man has been here we have managed to wipe out, that is, drive to extinction, over 38% of the Australian wildlife. We like to single out one species to blame, to vilify and label it 'feral', when that species never asked to be brought here and then abandoned in the first place. There are many humans that could be labelled 'feral' as well but we think we are so superior. Before we get all hysterical over cats, we need to stop for a minute and take a good look at what we've done.

  7. Pamela H.

    logged in via email

    It's topics like this that create hysteria and brings out all the cat-haters that are throwbacks from the days of the Inquisition. The hate is revealed in the calls for 'culling', shooting, baiting and even creating viruses. The worst virus on this planet is the human species which breeds uncontrollably, kills it's own species, exploits others, pollutes carelessly on a greater scale than any other species, spreads diseases, destroys the forests and oceans that are habitat to the vulnerable species that we pretend to care so much about. We pillage and plunder, raze the earth, build smoke stacks and petrol guzzling machines by the millions, turn the sea into plastic stew which is now coming back to us in the fish we catch. Even David Attinborough would attest to all this. Yet we still point the finger, just like the old days when they pointed and cried "Witch!"

    1. Bernie Masters

      environmental consultant at FIA Technology Pty Ltd, B K Masters and Associates

      In reply to Pamela H.

      Dear Pamela - two wrongs don't make a right. Please give some of us humans the credit to now see some of the things that we're doing wrong so that we can take steps to correct those mistakes. Controlling feral cat numbers in the bush is one action we now know we should take if we are to protect our biodiversity for future generations.

    2. Pamela H.

      logged in via email

      In reply to Bernie Masters

      Interfering humans have 'controlled' and 'managed' too many species to extinction. We need to first do something about 'controlling' our own populations and destruction before pointing the finger at a single other species. As I said earlier, the topic of abandoned or so-labelled 'feral' cats seems to whip up more hystia than that of any other species. This is speciescentrism at it's worst. Cat-haters often own savage dogs that kill all sorts of other species. Yet we love to hate the cats who have had a bad trot, to put it mildly, for many centuries.

    3. Michel Syna Rahme

      logged in via email

      In reply to Pamela H.

      I think you will find a little bit more research into the extreme damage caused by out of control populations of cats will change your mind. Yes, humans outdated affair with cats needs to be controlled, your right Pamela!

      Do you have an asbestos roof?

    4. Tim Doherty

      PhD Candidate at Edith Cowan University

      In reply to Pamela H.

      Pamela, control of feral cats is just one land management action amongst a suite of others currently being used to improve nature conservation in Australia. Fox control, fire management, herbivore removal, habitat restoration, captive breeding and translocations all play a role in reducing the fauna declines that you have described above.

    5. Russell Walton


      In reply to Pamela H.

      "Cat-haters often own savage dogs that kill all sorts of other species."

      "Often"? The majority of dog owners don't allow their animals to wander the neighbourhood 24/7, unlike many cat owners.

    6. Rochelle Steven

      PhD Candidate - International Centre for Ecotourism Research, Griffith University at Griffith University

      In reply to Russell Walton

      This is a very interesting and clearly heated debate.
      My research is about bird conservation, yet I own a cat, I unreservedly agree with culling feral cats, but if anyone hurt my pet, my heart would be broken. Many people find this very strange. But it isn't for a couple of reasons:
      1) Make no mistake, feral cats are a HUMAN problem, not a cat problem. Irresponsible cat owners are completely at fault for the damage domestic cats do to our native fauna.
      2) My cat is 100% indoors. By this I mean…

      Read more
    7. Tim Doherty

      PhD Candidate at Edith Cowan University

      In reply to Rochelle Steven

      Thank you for your insightful comment Rochelle.

      From personal experience I would agree that many cat owners are not willing to entertain the idea that their pet cat kills native fauna. However, I also recognize that there are many responsible cat owners out there.

      I think it important to make the distinction here that there are two separate, but related issues here. The first is the impact of pet cats on local wildlife in urban and semi-urban areas.
      See the following article for a good discussion on this

      The second is the very large and established population of cats that live in the wild, independent of human care, i.e. feral cats. This is the issue that my article is discussing, i.e. how do we manage populations of feral cats in the bush to protect native fauna, in particular those species that are listed as threatened.

    8. Russell Walton


      In reply to Rochelle Steven

      Rochelle Steven.

      "Ultimately the fault and responsibility lies with us, not the cats".

      Agree completely, that also, of course, applies to dog owners.

      I've noticed a gradual but steady improvement in canine control over the past 60 years, let's hope cat owners "get the message" as well.

    9. Rochelle Steven

      PhD Candidate - International Centre for Ecotourism Research, Griffith University at Griffith University

      In reply to Tim Doherty

      Thanks Tim.
      They are certainly to different issues. I am all for active control of feral cats in our natural landscapes. Managing domestic cat impacts is a harder sell. Largely because of the social complexities associated with it.
      Well done for getting the issues with feral cats out in the public sector via this forum. We need more of it !!

    10. Rochelle Steven

      PhD Candidate - International Centre for Ecotourism Research, Griffith University at Griffith University

      In reply to Russell Walton

      Thanks Russell.
      Yes, it certainly seems more headway is being made with canine control, though this is arguably due to the implementation and enforcement of laws around the issue. This is where more needs to be done with respect to cats. Bring on the fines and penalties for cats roaming the streets. Also bring on laws around being able to purchase an un-desexed dog or cat ,unless you are a registered breeder!

    11. Dingo Simon

      Owner, Durong Dingo Sanctuary Qld

      In reply to Tim Doherty

      I think many of us are aware of the problems with roaming cats, and some Council's suggest fining the owners of caught cats, but lets be serious here. Cats do most of their roaming and hunting at night. Council Rangers are sleeping then, so who is going to hunt and trap these problem cats ? They all say it is not cost effective, so the talk just goes round and round and nothing has been achieved. I have watched this behaviour over the last 40 years and there has been no improvement.
      Personally I find the use of baits as a lazy and dangerous way of curbing the feral cat problem. There is no guarantee the target animals will pick up the baits. What of birds, goannas and other wildlife taking the bait ?
      To me the only sure way is to get qualified people on the ground and cover all areas in a grid fashion and remove the cats that way. Failing that, the cats will keep breeding and keep killing wildlife.