Why Australia needs to kill cats

Introduced cats are a key threat to 123 of Australia’s threatened species.

The management of cats is challenging and divisive; many options such as rehoming, trap-neuter-release and euthanasia have been used around the world with varying success.

Australia’s recent commitment to killing 2 million feral cats to protect its native wildlife has attracted international attention and some have considered the project harsh.

While the actual target of 2 million has been rightly criticised as arbitrary and more based on public relations than rigorous science, it’s true non-lethal methods are not enough to stem the environmental havoc cats cause. Particularly in light of a UN report highlighting the world’s extinction crisis, Australia urgently needs well-targeted cat culls.

Read more: Feral cat cull: why the 2 million target is on scientifically shaky ground

Non-lethal methods

A range of effective non-lethal methods are already protecting wildlife from cats. Cat-exclusion fences have collectively improved the conservation status of many threatened species. In addition, an increasing number of Australian councils have created progressive cat management bylaws designed to protect pet cats, wildlife and humans from the effects of free-ranging cats.

The centrepiece of many of these bylaws, supported by the vast majority of animal welfare groups, is the containment of pet cats on their owner’s property. Indoor cats live longer, safer lives than cats that are allowed to roam.

Stray cats are harder to manage. These are the cats that do not have a home, but may be directly or indirectly fed by people.

Read more: A hidden toll: Australia's cats kill almost 650 million reptiles a year

Because they are unowned, no-one is officially accountable for their health or welfare. Groups of like-minded individuals feed and even provide veterinary assistance to some of these cats, further blurring the distinction between pet and feral cats.

A trend promoted by “no kill” shelters and advocacy groups in some US states and Europe is for clowders (groups) of stray cats to be desexed, vaccinated and released back onto the streets. This process is called trap-neuter-release (TNR).

A recent RSPCA best-practice cat management discussion paper proposed a trial of TNR in Australia too – but there are very good reasons why this would be counterproductive for cat welfare.

The risks of releasing unowned cats

Informed animal welfare advocate groups, including PETA, strongly condemn the release of unowned cats, neutered or otherwise, due to the welfare risks to these cats. Human health professionals and wildlife advocates also oppose maintaining groups of cats.

Dense outdoor cat clowders are hotbeds of toxoplasmosis infections. This cat-borne disease is increasingly being linked to a range of chronic mental health conditions including schizophrenia and Alzheimer’s disease.

“No kill” groups that promote TNR erroneously claim that neutered cats significantly reduce the breeding potential of erroneously named cat “colonies”, in the same way that release of neutered mosquitoes is a proven technique for controlling disease-bearing mosquitoes.

One of us (John) has recently written a book on protecting wildlife and cats that suggests five fatal biological flaws in this logic:

1. Neutering mosquitoes works because impotent individuals “swamp” short-lived wild insect populations that mate only once. By contrast, female cats typically mate repeatedly when on heat, so an encounter with a neutered tom is of little consequence.

2. Unlike lions, domestic cats evolved as solitary hunters. While domestic cats can tolerate living in high-density clowders, they do not form hierarchical colonies, packs or prides where alpha individuals restrict the feeding, breeding or survival of subordinate animals.

3. Although loud cat fights might make you assume males fight over the right to exclusively mate with a female, most litters of outdoor cats are sired by multiple males. Even supposedly “dominant” males seldom intervene when another male courts a female. Neutered male cats will not protect females in their clowder from non-desexed interlopers. This means that more than 90% of cats need to be neutered to restrict population increases, an incredibly challenging proposition.

4. Despite the misleading label “colony”, cat clowders are not closed populations. Rather, cats typically move around to take advantage of abundant food resources. And unwanted pets are often dumped at clowder sites. The failures of several well-studied TNR programs are attributed to cats migrating or being dumped at these sites.

5. Despite needing repeated vaccinations to protect them from debilitating diseases, few stray cats can be captured a second time. And many can never be captured at all. This leaves them and their clowder effectively unmanageable.

TNR is biologically flawed, cruel to cats – because it returns them to a hazardous environment – and ineffective when not accompanied by high levels of adoption.

Harming marine ecosystems

Not only do predatory cats harm native wildlife, but stray or feral clowders can also directly influence marine ecosystems and fisheries.

Many commercial cat foods contain increasingly threatened predatory fish that are high in the food chain and hence use more nutrients and biological energy than plants or herbivores. US dogs and cats consume one-third of the animal-derived protein eaten by humans, with accompanying greenhouse gas emissions.

The cat food provided to stray clowders adds to this biological expense. In 2009 alone, the US-based Best Friends Animal Society, one of the major promoters of TNR, distributed over 80,000 tonnes of cat food to unowned cats. There are no similar studies in Australia, and we appear to have far lower rates of stray-cat-feeding, but it is still part of the ecological impact of stray cats.

Even more insidiously, seals, otters and dolphins in oceans around the world die from cat-borne diseases spread mainly from clowders.

Read more: For whom the bell tolls: cats kill more than a million Australian birds every day

Humane euthanasia

Fortunately, both science and animal welfare standards are consistent about management of cats. All healthy domestic cats for which safe homes can be found should be adopted or rehomed, then kept indoors following neutering and vaccination. All other cats, including ferals and strays that cannot be rehomed quickly, should be humanely euthanased.

Feeding or releasing cats (neutered or otherwise) threatens our wildlife and perpetuates the cycle of suffering, disease, predation and social annoyance. Non-lethal options such as feral cat-proof fencing can still be part of the solution, but euthanasia remains an important part of controlling feral and stray cats to protect our native wildlife.

Among the Pigeons: Why our cats belong indoors (2019) by John Read is published by Wakefield Press.

John Read is a director of the ecological consultancy Ecological Horizons (www.ecologicalhorizons.com) and the conservation innovations not-for-profit Thylation (www.thylation.com). He receives government and NGO funding to develop and trial feral cat management tools.

Katherine Moseby receives funding from the Australian Research Council (ARC) to undertake research into the hunting behaviour of feral cats and methods to reduce the impact of feral cats on threatened species.