This Chapter considers how feral and domestic cats are defined under state and territory legislation, their prevalence across Australia and impact on Australia’s biodiversity, habitats and urban environments.
Classifying feral and domestic cats
All cats belong to the same species, Felis catus, however for the purposes of cat management instruments, governments across Australia have adopted different terminology to classify cats, often based on characteristics such as ‘ownership’ status or the circumstances in which the animal lives or is cared for.
The Australian Government Department of Agriculture, Water and the Environment (DAWE), advised the Committee that classifications for cats vary widely between jurisdictions, but that for the purposes of its own work administering key environmental legislation and coordinating national-level responses, it uses three definitions to classify cats:
feral cats are those that live and reproduce in the wild (e.g. forests, woodlands, grasslands, deserts) and survive by hunting or scavenging; none of their needs are satisfied intentionally by humans;
stray cats are those found in and around cities, towns and rural properties; they may depend on some resources provided by humans but are not owned; and
domestic cats are those owned by an individual, a household, a business or corporation; most or all of their needs are supplied by their owners.
DAWE cited research which concluded that these ‘… categories of cats are artificial and reflect a continuum, and individuals may move from one category to another …’
Evidence to the inquiry highlighted different legislative definitions used across Australia. Some jurisdictions used three cat classifications in a similar manner to DAWE. Others made distinctions between ‘domestic’ and ‘non-domestic’ cats, or made no distinction at all.
Table 2.1: Outline of the terminology used across Commonwealth, state and territory jurisdictions
Defines ‘feral’, ‘stray’ and ‘domestic’ cats
Does not differentiate by ‘feral’ or ‘stray’
New South Wales
Defines ‘cat’ as ‘an animal of the species Felis catus, whether or not domesticated’
Australian Capital Territory
Groups all cats together as an example of ‘domestic’ animals
Does not explicitly define ‘feral’ or ‘domestic’
Defines ‘stray and ‘feral’ cats
Defines ‘feral animals’ but not specifically cats
Defines ‘cat’ as ‘an animal of the species Felis catus
Does not refer to ‘feral’, ‘domestic’ or ‘stray’ animals except in relation to powers to destroy ‘feral’ cats
Inquiry contributors argued that there was a need for clear and consistent legislative definitions for cats across Australia. The Western Australian Biodiversity Science Institute (WABSI) told the Committee that:
There is a clear need for consistency of terminology nationally in Australia …. To achieve this consistency, there is a need for a balanced, evidence-based and fully inclusive conversation around the pros and cons of chosen terminology, and the implications for management that this choice creates.
WABSI argues that the ‘… lack of consistent terminology for these categories causes confusion and disagreement, creating inconsistencies in legislation and challenges with implementing management strategies and enforcing regulations.’ Local governments also argued that a clear definition for cats would improve their ability to manage cats within communities.
Some inquiry participants submitted that the definitions used for classifying cats should be further disaggregated. The Australian Veterinary Association, for example, suggested that any definition of ‘stray cats’ should include those cats that were ‘semi-owned’ and ‘unowned’. Another submitter, Heather Crawford, made the point that:
The management of stray cats is currently a grey area in the legislation of various states because of the difficulty in determining whether a stray is actually owned or was ever owned by a person.
In relation to domestic cats, RSPCA Australia was of the view that:
Cat management strategies should recognise three subcategories of domestic cats using the following definitions:
Owned – these cats are identified with and cared for by a specific person and are directly depending on humans. They are usually sociable although sociability varies.
Semi-owned – these cats are fed or provided with other care by people who do not consider they own them. They are of varying sociability with many socialised to humans and may be associated with one or more households.
Unowned – these cats are indirectly depending on humans with some having casual and temporary interactions with humans. They are of varying sociability, including some who are unsocialised to humans, and may live in groups.
The RSPCA’s proposed definition was supported by a range of inquiry contributors.
The prevalence of feral and domestic cats
The prevalence of feral and domestic cats in Australia is difficult to accurately determine due to a range of factors, including the availability of prey and climate variability. Research shows that cats are found all over Australia, but cat prevalence varies over time and location. According to the National Environmental Science Program’s Threatened Species Recovery Hub (TSRH) ‘… cats are absent in Australia only from a set of mostly small islands and a network of relatively small mainland exclosures: i.e., cats are present over 99.9% of the Australian land mass.’
TSRH submitted to the Committee that the total population of feral cats in Australia is about 2.8 million, comprising a population size in natural landscapes of 2.1 million and in modified (or urban) landscapes of about
While estimates of feral cat prevalence across all states and territories were not readily available, some jurisdictions did provide the Committee with more localised information. The Tasmanian Government submitted to the Committee that:
The density of feral cat populations varies across the State. A number of published and unpublished reports (~28) on feral cats in Tasmania have estimated density between (0.02 – 68.20 cats/km²) … Generalised trends in the density estimate data suggest a gradient of relatively lower densities in the southern and western wilderness areas (~ 0.02- 0.1 cats/km²) through to high densities in the eastern part of the state (~0.5- 1.5 cats/km²).
The NSW Government noted that state government surveys ‘found that feral cats occur across the entirety of NSW.’
In terms of the prevalence of domestic cats, the Tasmanian Government submitted to the Committee that based on research:
Australia has one of the highest rates of pet ownership in the world, and cats are the second most common pets with 29% of households owning a cat (Animal Health Alliance 2013).This equates to 15 in every 100 people in Australia having a cat. In Tasmania, it is estimated that 34% of households own a cat, the highest rate in Australia …
Animal Medicines Australia told the Committee of its research which found:
Domestic cats are one of the most popular pets in Australia. Approximately 27% of households have a cat. Overall, there are approximately 3.77 million pet cats. Cat owning households have an average of 1.4 cats each. 43% of households have had a cat at some point. AMA’s survey found that 77% of pet cats are microchipped and 89% of pet cats are desexed.
Factors influencing prevalence of feral cats
According to evidence presented to the inquiry, a range of environmental factors determine the prevalence of feral cats including the availability of prey, climate variability and rainfall.
Commenting on the variability of feral cat populations due to climate, Australia’s Threatened Species Commissioner, Dr Sally Box told the Committee that:
When times are lean, you'll have feral cat populations at the lower end …When times are plentiful, when you've got good rainfall in the desert and there's high prey availability, you'll see an increase in feral cat population…
TSRH similarly stated that:
Densities [of feral cats] vary in inland Australia with decrease during drought periods and rapid increase (aided by the cat’s high potential reproductive output and capability for long-distance movement) after widespread rains…
Dr Andy Sheppard from the CSIRO told the Committee that:
… there are many factors that determine the abundance and impacts of feral cats in the landscape, which are pretty well documented … the main ones are the state of the environment, the habitat, the amount of habitat, the prevalence of fires in the landscape—which provide an opportunity for feral cats to forage more openly—but also the availability of other prey such as rabbits in the landscape …
Understanding cat population distributions
Inquiry contributors told the Committee that a better understanding of the distribution of feral cats in Australia would improve population management strategies.
Dr Sheppard from CSIRO was of the view that understanding and measuring feral cat impacts and movements, along with those of other feral animals, was vital:
… as most control programs simply focus on population reduction. Feral cat populations are often sustained by populations of other feral animals, such as rabbits, and it is therefore also vital to understand and utilise these interactions in the design of management programs …
Dr Tony Buckmaster from the Centre for Invasive Species Solutions (CISS) advised that understanding the prevalence of feral cats would require examination beyond simply cat populations, while effective management strategies should be assessed on measureable outcomes:
It involves identifying the problem in terms of damage. For native species, rather than the number of cats or the area that cats inhabit, it would be better to look at how many native species are being impacted or, if you're measuring the increase in native species, what level of increase is obtained through cat management…
The impact of feral and domestic cats
Inquiry contributors impressed upon the Committee that both feral and domestic cats have contributed to significant impacts on native wildlife and their habitats. A major concern was evidence pointing to the significant involvement of cats in the extinction of many Australian mammal species since European settlement.
On native wildlife
Evidence to the inquiry provided the Committee with an insight into the impact that feral and domestic cats have had on Australia’s native wildlife (including threatened species), with many emphasising concerns about the overall decline in native animal populations. Cat predation occurs in a number of ways including through direct predation of individual animals, competitive exclusion, and disease transmission.
Some inquiry contributors viewed predation by cats as the key threat to Australia’s native wildlife. While cats are not the only cause of the decline in native animal populations, the NSW National Parks and Wildlife Service offered the Committee a stark reminder:
For our mammal fauna, which has suffered the most substantial decline of any faunal group, feral cats and foxes are identified as the greatest threat, along with changed fire regimes.
The NSW National Parks and Wildlife Service cited research estimating that predation by cats is responsible for the loss of 1.6 billion native animals every year, with feral cats responsible for some 1.4 billion of this figure. The Australian Government’s Threat Abatement Plan for Predation by Feral Cats advises that feral cats are ‘recognised as a potential threat to 74 mammal species and sub-species … 40 birds, 21 reptiles and four amphibians.’ Some submissions to the inquiry also provided numerous examples of the impacts on individual species, although it is beyond the scope of this report to examine each of these in detail.
In further examining the impacts of feral cats on native wildlife, the TSRH estimated that:
… on average a single feral cat in the bush kills about 370 invertebrates,
44 frogs, 225 reptiles, 130 birds and 390 mammals per year; and the collective toll of Australian animals killed per year by all feral cats (including unowned stray cats, but excluding pet cats) in Australia is ca. 1.1 billion invertebrates,
90 million frogs, 600 million reptiles, 320 million birds and 960 million mammals …
The CSIRO’s Dr Andy Sheppard was blunt in his assessment of the impact of feral cats, stating that:
… feral cats are increasingly the final nail in the coffin of some endangered vertebrate species rather than the original driver of decline. … it is widely accepted that controlling feral cats nonetheless will provide significant benefits to Australian threatened and endangered species.
In terms of pet cats, TSRH cited research concluding that ‘… collectively pet cats in Australia kill 390 million animals per year (i.e. more than one million animals per day) … ‘.
According to the Australian Veterinary Association’s assessment of the impacts of stray cats:
It is likely that the abundance of native and non-native wildlife, as well as the relative proportions of different species in any given area, are altered by the presence of cats. Cats are opportunistic hunters preying upon species in proportion to their availability.
Evidence to the Committee presented a disturbing picture of the involvement of cats in the extinction of native mammals since the European settlement of Australia. While the figures vary slightly, inquiry contributors provided evidence that largely corroborated the view of the TSRH, which concluded that:
… cats were a major cause of the extinctions of 25 of the 34 Australian mammal species lost since 1788, and a likely contributing factor for a further three of those species; and a likely contributing factor to three of the nine extinctions of Australian bird species since 1788.
The impact of feral and domestic cats on the habitats of Australia’s native wildlife and threatened species may be more difficult to quantify than estimates of individual animals killed by cat predation.
Professor Christopher Dickman told the Committee about the importance of habitats:
Habitat is crucial. Species that have survived the impacts of cats and other predators do occur in structurally complex areas. They occur in areas like rock pile habitats, such as the MacDonnell Ranges. They occur in areas where there is very dense ground level vegetation. Until there were fires and development in parts of the southwest of Western Australia things like the dibbler had small but fairly secure populations. When that habitat was removed those species disappeared as the predators began to move in.
Evidence to the Committee made it clear that habitat destruction through human activity and natural disasters such as bushfires contributed to species decline and also improved the ability of cats to hunt native wildlife.
The inquiry was told that human-induced factors had contributed to the impact on habitats making it easier for cats to hunt. The Cat Protection Society of NSW observed that the ‘… environment (and its animals) are significantly threatened by habitat loss, land clearing, climate change and extreme weather events including bushfire and drought.’
Other factors cited in evidence included urban housing development, logging, mining, and livestock grazing. The Australian Mammal Society’s submission to the inquiry advised that:
A major reason why cats are able to suppress their mammal prey is that native mammals are exposed by habitat degradation, particularly intensified fire regimes and inappropriate grazing that continually remove ground cover, understorey plants and fallen timber that mammals use for shelter.
Some inquiry contributors sought to provide the Committee with an understanding of how the damage caused to Australian landscapes during regular summer bushfires made it easier for feral cats to hunt, not least because it made it harder for native fauna to hide.
The TSRH concluded that in relation to bushfires:
Cats occur at higher density and/or hunt more efficiently in recently burnt areas, in fragmented landscapes, and in heavily grazed landscapes, mostly because these factors lead to reduction in ground cover and hence shelter for many native animals … For example, it is likely that in the aftermath of the 2019-2020 wildfires, any surviving wildlife in burnt areas will be much more susceptible to cat predation than they were before the fires …
Dr Tony Buckmaster from the CISS told the Committee that:
… following fires, the native species are more at risk from predation by feral cats. They have less food available to them. They become less fit. They have less shelter so they can't hide as well. And feral cats are incredible predators.
Threatened Species Commissioner, Dr Box told the Committee that:
… while feral cats also perish in fire alongside the native species, they're much more effective hunters in a burnt landscape because the native species have lost that protection. Some of the things that we can do immediately after a fire—and this is being supported through the government's investment in bushfire recovery—is target feral cat management around the unburnt patches on the edges of the burnt areas to try to protect the native species that are left.
On urban environments
Australia’s urban environments vary widely and include natural features such as ‘creeks, waterways, rivers and streams, reserves, and remnant native vegetation on public and private residential land’ and also modified features such as residential and industrial developments. These environments are often home to large numbers of wildlife, particularly birds, which may fall prey to feral and domestic cats.
According to BirdLife Australia the predation rate of ‘… roaming pet cats per square kilometre in residential areas is 28–52 times larger than predation rates by feral cats in natural environments … ‘. BirdLife Australia’s submission to the inquiry cites examples of research that conclude that pet cats have been complicit in the decline of local populations of birds in Victoria, some 47 bird species in urban Canberra and another 13 bird species in suburban Perth.
BirdLife Australia advises of the importance of urban environments for bird populations:
Urban landscapes are used by and important for 634 bird species in Australia, from our most common birds through to 71 state and/or federally listed threatened species … Despite pressures from cats, our urban spaces can be important refuges for birds, particularly those impacted by recent fire and drought events … Appropriate management of threats such as cats is required for these areas to remain a viable refuge for our native fauna.
Pathogens and disease control
Cats can carry and spread a variety of pathogens including those that cause toxoplasmosis, cryptosporidiosis, giardiasis, bartonellosis (cat scratch disease), salmonellosis, and visceral larval migrans. Evidence to the Committee focussed mainly on the impact that the cat-borne disease toxoplasmosis may have on human health, wildlife and agricultural food production.
Some inquiry contributors focussed on toxoplasmosis (T. gondii), which is caused by a protozoan parasite of which cats are the only definitive host.
Dr Jasmin Hufschmid informed the Committee that:
Toxoplasmosis is caused by the parasite Toxoplasma gondii and can infect any mammal, including humans, or birds (Dubey 2010). Infection occurs after ingestion of either an infective oocyst (=parasite egg), which can only be shed by a cat, from the environment, or through ingestion of muscle tissue including the cyst stage of the parasite …
According to TSRH, ‘this parasite would disappear from Australia in the absence of cats (or other felines)’.
Some inquiry contributors discussed the impacts that toxoplasmosis can have on human health. According to the Australian Veterinary Association:
Toxoplasmosis is a public health problem due to the presence of bradyzoites (tissue cysts) in meat … In Australia this most often affects pork, sheep and chicken meat. Toxoplasmosis, although rare, can result in neurological damage in immunocompromised people and abortion or stillbirth when immunologically naïve women are exposed for the first-time during pregnancy.
Further, the Australian Veterinary Association stated that T. gondii:
… infects about 25% of the world’s human population … Human infection occurs via ingestion of oocysts directly from the environment (for example, on unwashed vegetables) or improperly cooked meat. Cats are typically infected by Toxoplasma in their first year of life and shed oocysts for 2-3 weeks before becoming immune.
Animal Management in Rural and Remote Indigenous Communities told the Committee that given the immunocompromised health status of many of Australia’s Aboriginal and Torres Strait Islander community residents, zoonotic conditions, such as toxoplasmosis, are of significant concern, potentially contributing to the high burdens of illness experienced by many residents.
In relation to the impacts of toxoplasmosis on agricultural livestock and the farming industry, Australian Pet Welfare Foundation submitted to the Committee that in Australia ‘16% of lambs and 32% of sheep have evidence of prior infection with Toxoplasma gondii … ‘.
WoolProducers Australia elaborated on the impact that toxoplasmosis has on sheep, advising the Committee that:
Ewes infected during early pregnancy will suffer resorption of the foetus, while ewes infected during late gestation will abort the foetus if perinatal death has not occurred. If the lamb is born alive, it may be weak or it could be affected by complications caused from infection with the parasite. There is no treatment for toxoplasmosis in sheep. Once infected, ewes become immune.
The Australian Veterinary Association submitted to the Committee that:
Toxoplasma gondii infections in farm cats may result in environmental contamination and contribute to toxoplasmosis in livestock, particularly sheep. Cats predate rodents and produce litters of immunologically naïve kittens, which become infected and shed oocysts around areas where the sheep are corralled for husbandry procedures e.g. shearing sheds and yards.
The Committee was apprised of evidence that pointed to significant financial losses in the agricultural industry as a result of toxoplasmosis in livestock.
Inquiry submitters also considered the impacts of toxoplasmosis on the health of Australian wildlife. TSRH advised that:
Toxoplasmosis infection is now known to occur in many Australian bird and mammal species, with many consequences including spontaneous abortions, changed and aberrant behaviours and increased mortality.
The Tasmanian Government advised the Committee that toxoplasmosis was a reported cause of death for Tasmanian marsupials including the eastern barred bandicoot, pademelon, Bennett’s wallaby and eastern quoll. Predation by cats was also an issue for seabirds and Little Penguin colonies in Tasmania.
According to many inquiry contributors, the impacts of T. gondii are poorly understood and there remains significant scope for more research to understand how the disease impacts native wildlife, farm animals and humans.
Improving the survival of Australia’s native animals and their habitats
While the Committee was presented with a grim view about the future of Australia’s native wildlife, there remained hope that these animals could learn to adapt to the threat of cat predation in some circumstances. Professor Woinarski told the Committee that:
… many of these species may eventually be able to tolerate or live with cat predation, but that cat predation is compounding the impacts of many other threats, such as fire, habitat loss, rabbits and a whole range of other factors. Native species may be able to survive with cats, but the combined impacts of cats and those other factors is sufficient to continue to drive decline.
As to the question of ‘how’ this could be done, Professor Woinarski suggested that:
… we can prevent extinction of the most cat-susceptible native mammal species through the use of predator-proof exclosure fencing and through the use of translocation of those species to islands. These mammal species that have proven most susceptible to cats—and foxes as well— can thrive in the absence of foxes and cats. So there is hope. It is not entirely a gloomy picture. We can remove these mammals from predation in specified circumstances, and those mammals will then recover.
Dr Box provided the Committee with an example, stating that through:
… the strategic use of fire and other indirect tools. … the brush-tailed rabbit rat on Melville Island, as a threatened species, appears to be able to use parts of the island where the shrub density is high and feral cats are rarely detected … and reduce the efficacy of feral cat hunting.
The Society for Conservation Biology Oceania Section stated that:
… artificial refuges are one method currently being trialled to provide small mammals with movement pathways and protection from cats and foxes in fire-affected areas, in an attempt to reduce the risk of predation and improve population persistence … The artificial refuges are wire mesh tunnels that allow small mammals to enter and exit from any point, whilst physically excluding cats and foxes …
Inquiry contributors supported the need to conduct further research into the impact and prevalence of cats on native wildlife and habitats.
Research on prevalence, impact and control
Throughout the inquiry, the Committee heard examples of innovative and world-leading research projects.
Dr Sarah Legge from the TRSH told the Committee about its work:
In light of the broad-scale impacts of cats on threatened species, our hub included a major research program on the ecology impacts and management of cats. Our research team has provided the best assessment of the number of feral cats in Australia and the distribution. We've catalogued the impacts of cats in detail, including the extinction they've already caused to our mammal fauna and their ongoing predation toll on mammals, birds, reptiles, frogs and invertebrates. We've revealed underappreciated components of cat impacts, including the very high predation rates of pet cats on native animals and the fact that cat-dependent diseases like toxoplasmosis and macrocytosis, which affect people and livestock and cost Australia over $6 billion each year. We've documented how the pressure from cats is exacerbated by other threats like rabbits overgrazing and extensive severe fire, showing it's essential that we manage cats holistically with the management of these other threats.
The CISS is equally involved in leading and conducting innovative Australian research:
CISS plays a leadership and enabling role in relevant National Biosecurity System collaborative RD&E initiatives and develops new knowledge, tools and practices to continually improve best practice invasive species management. We currently facilitate 40 collaborative projects involving environmental, community and agriculturally based invasive species issues across the entire invasion curve. CISS is maintaining the knowledge and innovation momentum gained through the national collaborative research pursued through the Invasive Animals Cooperative Research Centre and its participants.
The Committee also heard that there is a need for further research in a number of areas. Dr Andy Sheppard of the CSIRO told the Committee that:
… we see the need for better understanding of impacts, benefits and the efficacy of control in different management and environmental settings linked to monitoring; better understanding of feral cat ecology and population genetics to support future management strategies, including potential genetech based approaches; better understanding of the drivers of cat abundance and developing our ability to track them to inform management strategies; and integration of the human dimension around cats into management, both Indigenous and non-Indigenous.