As at May 2021, no study in urban Australia has determined that cats have a negative impact on native wildlife populations.

Research related to the ‘war on cats’ mostly refers to estimates of numbers, not population impacts. Interestingly, it fails to quantify numbers of wildlife we kill each day.

On this page

Research on this page mostly refers to urban and semi urban wildlife.

No impact

• No evidence cats impact wildlife populations in urban and peri urban areas

Mammals

• Medium-sized mammals not impacted by cats; Antechinus benefit

Birds

• Habitat destruction, not cats, impacts perching birds
• Birds protect nests from predation
• Up to 50% of bird species would die of other causes
• Urban cats do not cause additional bird deaths
• Cats are not impacting UK bird populations; habitat loss is

Preferred prey species

• Cats mainly prey on introduced and common species

Impact of desexing

• Desexed cats need 25% less energy

The federal government’s ‘war on cats’

• The ‘war on cats’
• 1080 poison
• So-called soft-jaw leg hold traps

Killing increases cat numbers

Throughout the world, it is commonly recognised that killing cats (and many other animals) leads to a rebound in population, due to what is called ‘the vacuum effect’.

Nature abhors a vacuum. When territory that has adequate food, water and shelter becomes available, cats (and other animals) will rapidly move into that area.

This perhaps explains why, despite more than one hundred years of killing rabbits and foxes, we still have rabbits and foxes. And cats, both in urban areas and in the bush.

Unfortunately, despite this being well known, the ‘war on cats’ seems to be ignoring this fact. Likely, much of the killing and the ‘dead cat count’ that is done each year by RMIT will achieve little for wildlife. But cost the nation a lot of money.

After all, it took 15 years to kill 2,000 to 3,000 cats on Marion Island, after cats were deliberately introduced to kill mice. Mice now have no nocturnal predator on the island and are harming the native wildlife.

• Killing cats increases their numbers: Tasmanian research
• Cat numbers restored three months after killing
• Conclusion

• References

Introduction

There is no peer-reviewed research that has found that cats in urban and peri urban areas impact wildlife populations.

In some cases, they provide a protective factor eg preventing predation of nests.

Research funded by the ‘war on cats’ has a clear purpose: to demonise cats. Any research funded by the war that is positive about cats would not be published. It would be censored, as it doesn’t suit the purposes of the ‘war’.

We encourage you to think critically when reading research funded by the ‘war on cats’. The Threatened Species Hub and ornithologist Dr Sarah Legge are some of the main people involved.  Legge appears to be a chief spokesperson for the ‘war’.

Medium-sized mammals not impacted by cats; cats increase Antechinus numbers

A 10 year Perth study (Lilith et al 2010) investigated species diversity across three different bushland areas in the City of Armadale where cats were either:

• prohibited;
• required to be inside at night and wear a bell; or
• unregulated.

The study found that medium-sized mammals, such as Brush-tailed Possums and Southern Brown Bandicoots, were not impacted by the presence or absence of cats.  The smaller Mardo (Antechinus flavipes), who look like house mice, and are highly susceptible to cat predation, was in higher numbers in areas where cats were unregulated.

Habitat destruction, not cats, impacts perching birds

A study of 57 metropolitan Perth sites found no link between passerine (perching) bird abundance, species diversity and cat (or dog) population. The study did, however, find that diversity of bird species declined with increasing number of houses, increasing distance from bushland and decreasing size of bushland (Grayson 2007).

The study concluded that habitat destruction and degradation, rather than cats (or dogs), were the main factors impacting birds (Grayson et al 2007).

Cats do not attack nests – they protect them

A Sydney study of nest predation in 24 forest patches in the Sydney metropolitan area found that no nests were attacked by cats (Matthews et al 1999). Black Rats, Ringtail Possums, Antechinus species and other birds were the main predators. Nest predation was reduced when cats were present.

Up to 50% of bird species cats predate on would not breed again

Most of the bird species that cats kill have an average life span of 2-4 years in the wild.  This means that 25-50% are dying of other causes every year and would not survive to the next breeding season (Australian Government Department of the Environment and Energy, 2017).

Urban cats rarely cause additional bird deaths

Research also shows that birds caught by cats in urban areas are on average less healthy than birds killed by flying into windows and cars (Baker et al 2008, Møller and Errotzøe 2000).  The researchers concluded that most cat-related bird deaths are not additive to the number dying each year.

UK RSPB: Cats are not impacting bird populations

In the UK, the Royal Society for the Protection of Birds has similarly concluded that there is no scientific evidence that cats are causing bird populations to decline. It also highlights that most birds who were killed by cats would have died from other causes before the next breeding season.

Just as in Australia, UK research has found that declines in bird populations are usually caused by habitat change or loss.

Cats mainly prey on introduced and common species

A further study (Franklin et al 2018) found that the main prey items of cats are mice, followed by rats, small lizards, then common species of birds. A Brisbane City Council analysis of the stomach contents of 25 cats found only one species – the Black Rat (Brisbane City Council 2015).

Threatened species impacted by humans and dogs

Between 2019 and 2020, 850 individuals from threatened species entered NSW wildlife rehabilitation facilities. 96.4% of those were impacted by humans or dogs. Just 3.6% were impacted by cats.

Cause of injury	No.	%
Habitat loss	402	47.3
Hit by person driving vehicle	290	34.1
Dog attack	127	14.9
Cat attack	31	3.6
	850	100

Desexed cats need 25% less energy

Desexed cats have reduced energy requirements compared with undesexed animals (Mitsuhashi et al 2011). This may also indirectly reduce wildlife predation.

Do cats kill wildlife? Some do; some don’t

Research by Franklin et al in 2021 found that not all companion cats catch wildlife. In contrast to oft-cited (gu)estimates that are rarely questioned, a median of three native animals were caught by a cat during the study. Most wildlife were common introduced or native species. The researchers concluded that cats (and dogs) are of relatively minor conservation concern, compared with habitat loss and urban development. .

If we truly care about wildlife, preserving their habitat will yield better protection than scapegoating cats (and dogs).

Conclusion

While cats may certainly kill individual native animals, they have not been found to have an overall impact on biodiversity or populations in urban and peri urban areas.

The principal cause of declining wildlife populations in urban and peri urban areas is habitat destruction, degradation and fragmentation by humans. Not cats.

The ‘war on cats’

Since the federal government launched its so-called ‘war on cats’, and a subsequent federal government continued with the war, large sums of money have been spent funding studies designed to vilify cats.

These studies are based on modelling and hypothetical situations, not field research.

Some of these studies have estimated the number of animals cats kill per year throughout Australia (not specifically in urban areas. In urban areas, there is markedly less available habitat, wildlife numbers and species diversity than in the bush).

However, these studies have consistently failed to indicate if this is significant at a population level. One can surmise why.

They have also failed to provide any long-term solutions. The only ‘solution’ proposed to date is to kill cats, including through the use of leg-hold traps and 1080 poison.

Killing cats increase their numbers

Australian research has found that killing cats causes a rapid rebound in population (Lazenby et al, 2014).

More research is required to determine how any impact wild cats in non-urban and peri urban areas have on wildlife can be reduced.

Cat numbers restored to pre-killing levels in just 90 days

In New Caledonia, 40% of cats on the semi-isolated New Caledonia peninsula were killed. In just three months, cat numbers were the same as they were before the killing (Palmas et al, 2020). Researchers believe this may be due to more cats moving into the territory – what is commonly known as the ‘vacuum effect’.

1080 poison

1080 is banned in most countries in the world because of the considerable suffering that occurs to any species who ingests it.

Contrary to claims by Australian governments and the poisons industry, native animals do die from 1080. It also poisonous to sheep, cows, horses, working dogs, companion dogs and cats.

This footage, taken by a farmer who has suffered the deaths of a number of his dogs to 1080, on his own property, shows how they die. (He lives far from a vet and had no gun to shoot the dog. There is no antidote, anyway).

Killing Shroedingers Feral Cat describes the suffering of a cat who had been poisoned by 1080 (Marks C, 2013). Although the scientist does not like cats, he chose to kill the cat rather than continue to witness their suffering.

1080-laced baits are known to be carried by birds such as ravens and dropped onto ‘non-target’ properties, including in farmed animal water troughs.

No property near where 1080 is being used is safe from 1080.

If you are concerned that 1080 is being used near you, you may like to obtain a free 1080 Legal Action Pack. This warns potential poisoners that you will sue should you suffer adverse effects from their use of 1080 near your property. These kits have been successful in preventing governments from using 1080.

So-called ‘soft jaw’ leg hold traps

Authorities and individuals who use so-called soft jaw leg hold traps claim that ‘non-target’ animals can be released from them unharmed.

Watch this video of a soft-jaw trap on a human hand. After carefully closing the trap on their hand, they could withstand the discomfort for all of five minutes 30 seconds.

Do you think an animal could be released unharmed after a trap being sprung on their leg, and them being left in it for several days?

As at 2021 in Victoria Australia, it is legal to force animals to suffer in these traps for three full days (72 hours).

References

Australian Government, Department of the Environment and Energy. What have we learned from banding studies? http://www.environment.gov.au/science/bird-and-bat-banding/about-banding/banding-studies (accessed 15/12/17).

Baker PJ, Molony SE, Stone E, Cuthill IC, Harris S. Cats about town: is predation by free-ranging pet cats Felis catus likely to affect urban bird populations? Ibis, 2008; 150: 86-99.

Brisbane City Council. The Invasive Times, Issue 4, October 2015-2016

Franklin M, Rand J, Marston L, Morton J. Prey captured by owned cats and dogs in Australia. Animals, 2018

Franklin M, Rand J, Marston L and Morton J (2021), Do Pet Cats Deserve the Disproportionate Blame for Wildlife
Predation Compared to Pet Dogs? Front. Vet. Sci. 8:731689. doi: 10.3389/fvets.2021.731689.

Grayson J, Calver M, Lymbery A. Species richness and community composition of passerine birds in suburban Perth: is predation by pet cats the most important factor? In: Lunney D, Eby P, Hutchings P, Burgin S, editors. Pest or Guest: The Zoology of Overabundance. Royal Zoological Society of New South Wales, Mosman, NSW, Australia, 2007: 195-207.

Lazenby B, Mooney N, Dickman C, Effects of low-level culling of feral cats in open populations: A case study from the forests of southern Tasmania, Wildlife Research 41(5):407, DOI:10.1071/WR14030

Lilith M, Calver MC, Garkaklis M. Do cat restrictions lead to increased species diversity or abundance of small and medium sized mammals in remnant urban bushland? Pacific Conservation Biology, 2010: 16(3): 162-72 (accessible at: http://researchrepository.murdoch.edu.au/id/eprint/6221/, accessed 15/12/17).

Marks C, Killing Shroedingers Feral Cat, Animal Studies Journal, 2013, 2(2)

Matthews A, Dickman CR, Major RE. The influence of fragment size and edge on nest predation in urban bushland. Ecography,1999; 22: 349-56.

Mitsuhashi Y, Chamberlin AJ, Bigley KE, Bauer JE. Maintenance energy requirement determination of cats after spaying. Br J Nutr, 2011; 106 suppl: S135-8.

Møller AP, Erritzøe J. Predation against birds with low immunocompetence. Oecologia 2000; 122: 500-4.

Palmas P, Gouyet R, Oedin M, Millon A, Cassan JJ, Kowi J, Bonnaud E, Vidal E, Rapid recolonisation of feral cats following intensive culling in a semi-isolated context,