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Threat Abatement Plan for Predation by Feral Cats

Biodiversity Group Environment Australia, 1999
0 642 2546339

Introduction

Australia and Antarctica are the only continents without a native member of the cat family, Felidae. Felids are the most raptorial of mammals with body form, musculature, nervous coordination and senses highly specialised for stalking and capturing prey. Their nutrition and metabolism are such that they require large amounts of fresh animal protein, yet many felids can survive without drinking water. All species of wild cats prefer live prey and will rarely consume carrion except during droughts or when they are debilitated.

Cats (Felis catus) have a history of association with humankind dating back thousands of years. They have accompanied seafarers since the earliest times for vermin control, companionship and food (Jones 1989; Dickman 1996) and in this way the species has been distributed to virtually all inhabited parts of the globe as well as to many uninhabited islands. The species, which rarely exceeds eight kilograms in mass, is now the most widely distributed of all the world’s felids.

The first recorded instance of cats being brought to Australia is by English settlers in the 18th century. Cats may have arrived much earlier via trading routes from South-East Asia, shipwrecks or visits by European ships to the west coast (Baldwin 1980) but the available evidence for these origins is scant. Cats were deliberately released into the wild during the 19th century to control rabbits and mice (Rolls 1984) and feral cats are now found in all habitats, except some of the wettest rainforests, from the Torres Strait across the breadth of the mainland and Tasmania to sub-Antarctic Macquarie Island.

There is clear evidence that feral cats have caused the decline and extinction of native animals on islands through predation (Copley 1991; van Rensburg and Bester 1988). Dramatic recoveries of species on islands after the removal of feral cats is evidence of their impact (Dickman 1996). On the mainland, predation by feral cats is thought to threaten the continued survival of native species such as the eastern barred bandicoot in Victoria which currently persist in low numbers (Dickman 1996). Feral cats have been shown to thwart re-introduction programs for endangered species such as the numbat, golden bandicoot, burrowing bettong, mala and bilby in the arid and semi-arid zones of Western Australia and the Northern Territory (Johnson 1991; Gibson et. al. 1994; Dickman 1996). For these reasons predation by feral cats is listed as a Key Threatening Process under Schedule 3 of the Commonwealth Endangered Species Protection Act 1992 (the Act).

For each of the processes listed in Schedule 3 of the Act, a nationally coordinated threat abatement plan must be prepared and implemented. The Act prescribes the content of a threat abatement plan and the mechanisms by which plans are to be prepared, approved and published. Where a threatening process occurs in more than one jurisdiction, the Commonwealth must seek the cooperation of the relevant States and Territories in the joint preparation and implementation of a threat abatement plan.

Categories of Cats

In recent years the impact of cat predation on native Australian wildlife has become a prominent public issue with strongly polarised opinions, especially where domestic cats are implicated. Cats can be grouped into categories according to how and where they live. The definitions and categories used vary widely in the published literature and the following terms are used for the purposes of this plan:

These categories of cats in effect reflect a continuum and there is evidence that individuals may move from one category to another (Moodie 1995; Newsome 1991). In a given situation, the category of cats that causes the most damage to wildlife needs to be identified. Management actions may differ according to the different categories of cats causing the damage. Where domestic cats are the primary cause, management is likely to concentrate on owners and consist of education and legislation to promote responsible ownership. For feral cats the requirement is to reduce numbers or inhibit predation using mechanical, chemical or biological methods. The management of stray cats often requires a combination of technical and social approaches.

Domestic Cats

Concern about predation on wildlife by domestic cats developed in Victoria during investigations into the decline of the eastern barred bandicoot (Brown 1989). It has since become a national issue among cat owners, veterinarians, conservationists and wildlife managers. Results published in 1990 suggested that domestic cats in South Australia killed an average of 26 animals per year, many of them native birds (Paton 1990). Subsequent surveys have both supported (Trueman 1991) and contradicted (Reark 1994) Paton's conclusions. In urban areas of Victoria, traumatised small mammals are reported as usually being victims of cat attack (Dowling et al. 1994).

The quality of data on predation by domestic cats is poor and does not provide information about the impact on populations of prey species (Barratt 1995). Data obtained by written or telephone questionnaire have a number of identified areas of potential bias (Manly 1992). Too much reliance is placed upon the memory of cat owners, their ability to identify prey animals and their willingness to participate fully in a survey. Also, it may not be justifiable to assume that any small animal brought home by a cat has been preyed upon by that cat. There are other possible causes of injury or debilitation to small animals in urban areas.

Management of cats in cities is primarily an issue of urban amenity or animal welfare rather than an issue of wildlife conservation. Animals which live in cities, whether native or introduced, are generally common, adaptable species. With few exceptions, rare or threatened species do not occur in or near cities and are not directly at risk from domestic cats. Nevertheless, domestic cats in cities occur in very high densities because their requirements are primarily met by their human owners. As a consequence, even if each individual cat is taking only a small number of prey, the sum of that predation may depress populations of desirable urban wildlife.

The responsibility for managing domestic cats ultimately rests with their owners. State, Territory and local governments are supporting initiatives aimed at encouraging responsible pet ownership, including developing appropriate legislation, education and awareness programs, and management plans to address local problems with domestic and stray cats. Victoria has enacted the Domestic (Feral and Nuisance) Animals Act 1994 which requires cat owners to register their animals and gives councils the power to set fees and take remedial action when landowners experience problems with wandering cats. New South Wales has initiated the development of legislation to promote responsible ownership and improved welfare of companion animals.

Moves by some State and local governments to control cats present a range of opportunities to measure the conservation benefits to be derived from managing urban cats (Tidemann, 1994). Answers to questions surrounding domestic cat management are likely to be gained through rigorous monitoring and analysis of various management regimes that are currently being put in place. Suitably designed experiments could determine whether the enacting and enforcement of laws to control domestic cats leads to desirable outcomes for urban and peri-urban wildlife. However, because of the specific nature of the listing of predation by feral cats, the management of domestic cats will not be addressed in this plan.

Stray Cats

Irresponsible cat owners, and those who feed unowned cats, play a major role in maintaining populations of stray cats in urban and rural areas. Encouraging changes in the behaviour of these people has the potential to significantly reduce the numbers of free-ranging stray cats where these are causing damage. Control of unowned cats in these areas is primarily being promoted by groups such as the RSPCA, in order to address significant animal welfare concerns.

Capturing, sterilising and releasing is seen as an effective approach to managing colonies of stray cats in urban Europe (Hammond 1981) and has been used in parts of Adelaide (Pierson 1994). This approach has been promoted to achieve goals of cat welfare and enhanced urban amenity. No benefits to wildlife are derived from this approach, as the number of predators remains unchanged. Any programs to manage stray cats in urban and peri-urban areas should be subject to rigorous review to determine their effectiveness in achieving wildlife conservation goals.

Feral Cats

There is clear evidence that feral cats have caused the decline and extinction of native animals on islands through predation (Copley 1991; van Rensburg and Bester 1988). Sound evidence that feral cats exert a significant effect on native wildlife throughout the mainland is lacking (Dickman 1996; Jones 1989; Wilson et al. 1992). Feral cats have occupied tropical Australia, Tasmania and Kangaroo Island for at least a century and yet these areas have had virtually no extinctions, or none that could be attributed directly to feral cat predation. Yet there are a number of vulnerable and endangered species which are susceptible to feral cat predation in these areas.

The nature and extent of the threat posed to native wildlife by feral cats nevertheless remains poorly understood and the evidence relating to their impacts is largely inferred. Feral cats are mobile, especially during periods of food shortage (Newsome 1991) and can disperse widely. The feral cat population is self-sustaining and may breed at any time of the year under favourable conditions. Feral cats occupy virtually all Australian environments and the damage they cause to wildlife is likely to vary widely across this spectrum of habitats.

A review of recovery plans approved under the Act, and others in draft form, has identified feral cats as a confirmed threat or a perceived threat to a large number of listed endangered and vulnerable (threatened) species (Table 1).

This threat abatement plan focuses primarily on managing the impact of feral cats. In general, listed species which are susceptible to cat predation are found in remote parts of the country from which domestic and stray cats are absent. It is generally accepted that improvements in the management of domestic and stray cats are necessary to reduce recruitment to the feral cat population (Copley 1991), but there is little research demonstrating that populations of feral cats are significantly bolstered by such recruitment. Feral cats have self-sustaining populations and there is no evidence that they need recruitment from other categories to maintain their numbers over the long term.

Feral cats occur on Commonwealth land such as Department of Defence properties and in Commonwealth-managed national parks. On a national scale, however, management of feral cats on Commonwealth land is only a small part of the larger picture of conserving endangered or vulnerable species threatened by cat predation. State and Territory wildlife agencies have a long history of practical on-ground management of feral cats and it is largely through their efforts, often supported by Commonwealth programs, that major technical and strategic advances have been made. More recently, private sector and community initiatives have also contributed to feral cat control activities.

Table 1. Species listed on Schedule 1 of the Endangered Species Protection Act 1992 for which cats are a known or perceived threat.

 

Known Threat

Scientific Name

Common Name

Reference

Birds

Cyanoramphus novaezelandiae cookii

Norfolk Island Parrot

(Lane, B.A et. al. 1998)

Sterna albifrons

Little Tern

(Lane, B.A. et. al. 1998)

Mammals

Lagorchestes hirsutus

Rufous Hare-wallaby

(Lundie-Jenkins, G. & Moore, G. 1996)

Leporillus conditor

Greater Stick-nest Rat

(Copley, P.B. 1994)

Macrotis lagotis

Greater Bilby

(Southgate, R. 1997)

Myrmecobius fasciatus

Numbat

(Friend, J.A. 1994)

Perameles gunnii

Eastern Barred Bandicoot

(Driessen, M.M. & Hocking G.J. 1991)

 

 

Perceived Threat

Scientific Name

Common Name

Reference

Litoria aurea

Green and Golden Bell Frog

(Pyke, G. H. & Osborne, W.S. 1996)

Philoria frosti

Baw Baw Frog

(Hollis, G.J. 1997)

Birds

Geopsittacus occidentalis

Night Parrot

(Blyth, J. 1996)

DLathamus discolor

Swift Parrot

(Gaffney, R.F. & Brown, P.B. 1992)

Leipoa ocellata

Malleefowl

(Benshemesh, J. 1998)

Neophema chrysogaster

Orange-bellied Parrot

(Orange-bellied Parrot Recovery Team 1998)

Ninox novaeseelandiae undulata

Norfolk Island Boobook Owl

(Olsen, P. 1997)

Pezoporus wallicus flaviventris

Western Ground Parrot

(Burbidge, A.H., et. al. 1996)

Stipiturus malachurus intermedius

Mount Lofty Southern Emu-wren

(Littely, T. & Cutten, J. 1994)

Turnix melanogaster

Black-breasted Button-quail

(Smyth, A. 1995)

Mammals

Bettongia lesueur

Burrowing Bettong

(Short, J. & Turner, B. 1993)

cDasyurus maculatus gracilis

Spotted-tailed Quoll or Yarri (North Queensland subspecies)

(Burnett, S. 1993)

Isoodon auratus

Golden Bandicoot

(Graham, G. 1996)

Petaurus gracilis

Mahogany Glider

(Queensland Department of Environment, 1995)

DBurramys parvus

Mountain Pygmy-possum

(Broome, L.S. 1996)

Crocidura tenuata var. trichura

Christmas Island Shrew

(Meek, P 1997)

F/DDasycercus cristicauda

Mulgara

(Masters, P. & Baker, L. 1996)

Dasyuroides byrnei

Kowari

(Lim, L. 1992)

Dasyurus geoffroii

Western Quoll

(Orell, P. & Morris, K., 1994)

^Lasiorhinus krefftii

Northern Hairy-nosed Wombat

(Horsup, A. 1998)

Onychogalea fraenata

Bridled Nailtail Wallaby

(Clancy, T.F. 1994)

 

Parantechinus apicalis

Dibbler

(Start, A.N. 1996)

Petrogale lateralis

Black-footed Rock-wallaby

(Hall, G.P. & Kinnear, 1991)

Petrogale penicillata

Brush-tailed Rock-wallaby

(Hill, F.A.R. 1991)

^Petrogale persephone

Proserpine Rock-wallaby

(Rees, G. et. al. 1997)

Potorous longipes

Long-footed Potoroo

(Nunan, D. et. al. 1998)

Potorous tridactylus gilberti

Gilbert's Potoroo

(Courtenay, J.,et. al. 1998)

Pseudomys fieldi

Djoongari

(Morris, K. et. al. 1997)

Pseudomys oralis

Hastings River Mouse

(Smith, A.P. 1997)

Zyzomys pedunculatus

Central Rock-rat

(Burbidge, A. 1996)

Reptiles

Delma impar

Striped Legless Lizard

(Smith, W.J.S. & Robertson, P. 1997)

cCompetition for food by cats
DDomestic cat predation
F/DDomestic and feral cat predation
^Predation and disease dispersal.

While key threatening processes are listed because of their impacts on listed threatened species, impacts from cat predation are not restricted to these species. Best practice management of feral cats must involve not only action to reduce the threat to targeted threatened species, but to all native species which may be threatened by feral cat predation.

Fundamental to the approach taken in this plan is the recognition that feral cats cannot be eradicated over most of their Australian range using current techniques and financial resources. However, it is feasible to restrict their distribution and abundance. Eradication of feral cats has been achieved on a number of Australian islands (Copley 1991; Burbidge 1989), in New Zealand (Veitch 1985; Burbidge 1989) and in the sub-Antarctic (Bester 1993). This usually requires a sustained effort using a range of conventional and biological techniques. For example, in 1977 Feline panleucopenia was introduced to sub-Antarctic Marion Island by South African wildlife authorities to control feral cats (van Rensburg et. al. 1987). The disease caused a significant reduction in the island population, but feral cats were not eradicated until 1992 after a concerted effort combining trapping, baiting and shooting (Bester 1993).

Existing methods are not suitable for broadscale control of feral cats over most of Australia. However, it is possible to remove feral cats from small areas and to manage the effects of feral cats in localised areas with variable levels of success. Abatement of the threat that feral cats pose must initially be undertaken in discrete, manageable areas, selected according to national priorities. Feral cat control will have to continue for the foreseeable future and therefore must make the best use of available resources. The ongoing costs of feral cat control will, in most cases, be high. The construction and maintenance of exclusion fencing is expensive; for example, Coman and McCutchan (1994) report costs of $18 000 to $50 000 per kilometre have been incurred in constructing fox exclusion fences.

This plan delineates in broad terms the scope for national action and the apportionment of Commonwealth resources. It is intended that the plan will lead to changes in managing the impact of feral cats on endangered species, producing a more focused and strategic approach to reducing those impacts.

In accordance with the requirements of the Act this plan must be reviewed at intervals of no more than five years. At the end of the first five years, on-ground action will have increased protection for endangered species at high priority sites, and new techniques for controlling feral cat impacts will have been tested. The plan will also have assisted in documenting significant advances in knowledge, techniques and practice for abating the threat from feral cat predation. Towards the end of the period, the review required by the legislation will examine the plan, the supporting technical documents and the success or otherwise of management actions undertaken. Recommendations from the review will then be used to prepare another threat abatement plan for the next five-year phase.

During each five-year phase, knowledge will grow and efficiency and effectiveness of threat abatement actions should improve through information from well-monitored programs. The success of the plan will be dependent on the long-term commitment of resources by Commonwealth, State and Territory Governments, private landholders and community groups. The activities and priorities under the threat abatement plan will need to evolve with, and adapt to, changes as they occur.

By taking this measured approach, recognising the limitations and opportunities that exist, and ensuring that field experience and research are applied to further improve management of cats, the threat abatement plan process will ensure a responsible use of public resources and give the best outcome for wildlife threatened by cat predation.

The success of this threat abatement plan will depend on a high level of cooperation between all key stakeholders, including landholders, community groups, local government, State and Territory conservation and pest management agencies, and the Commonwealth Government and its agencies. The programs of the Natural Heritage Trust, particularly the National Feral Animal Control Program and the Endangered Species Program, will make significant contributions to implementing the plan. Success will only be achieved if all participants are prepared to allocate adequate resources to achieving effective on-ground control of feral cats at critical sites, improving the effectiveness of control programs and measuring and assessing outcomes.

Published June 1999 by Environment Australia under the Natural Heritage Trust.

Commonwealth of Australia