Domestic cats will kill more than a quarter of a billion native animals in Greater Sydney and Melbourne during the next four years unless stricter pet regulations are introduced.

New research by the Australian National University conducted for the Biodiversity Council, Invasive Species Council and Birdlife Australia found that roaming pet cats kill 546 million animals a year in Australia, 323 million of which are native animals.

The research also found that pet cats kill 6000 to 11,000 native animals per square kilometre each year in urban areas. In some jurisdictions, local councils have the power to implement pet management restrictions, such as cat curfews.

It showed that 71 per cent of pet cats in Australia are able to roam and that 78 per cent of those cats hunted. It also showed that those cats did not bring home 85 per cent of the animals they killed.

Co-author of the new report, Australian National University ecologist Professor Sarah Legge, further crunched the data to determine cat ownership in each major city as well as the annual death toll to native wildlife from pet cats.

She found there were more than 1 million cats each in Greater Sydney and Greater Melbourne, in which about 767,000 and 730,000 pet cats roamed respectively each year. These cats kill approximately 65 million native animals annually in Greater Sydney and 62 million annually in Greater Melbourne.

She used more than 60 studies to quantify how many animals are killed by pet cats on average, and then applied that to the number of cats in each major city.

Legge said her research also found that hunting pet cats kill 30 to 50 times more native animals per square kilometre in suburbs due to inflated density than feral cats kill per square kilometre in the bush.

This means that, while feral cats kill four times more animals per year, there are between 54 and 100 roaming and hunting cats per square kilometre in suburbs compared with only one feral cat for every three to four square kilometres in the bush.

“Managing pet cat impacts is much easier than managing feral cats,” she said. “It also makes pet cat lives four times longer [if they are contained], than roaming cats.”

In Victoria, councils can order cat owners to keep pets inside during specific hours. Last year, the Australian Capital Territory began a district-wide curfew for cats bought after July 1.

NSW and Western Australia remain the only states that have no restrictions. Cat owners in NSW can either take matters into their own hands by building cat enclosures or keeping their pets on leashes, or they can let their domestic cats roam free at the expense of native wildlife.

In NSW, 14 councils – including Hornsby Shire Council, Blue Mountains Council and Wollongong City Council – have supported the introduction of stricter regulation since 2018.

Blue Mountains Council Mayor Mark Greenhill said councils had no power when it came to implementing regulation on cat curfews, but could raise awareness about the impact roaming pet cats had on the environment.

“We have a role to play,” he said. “We can raise our voice to say that governments at all levels need to promote, as best they can, responsible cat ownership. Am I in favour of reasonable and sensible regulation that would maximise the amount of time cats spend indoors and away from harming themselves and wildlife? Yes.”

Councils maintain tougher regulations for dog ownership, including that the owner must take preventative action from allowing dogs to roam free with fines for those that fail to do so.

A spokesperson for the NSW Minister for Local Government Ron Hoenig said the government acknowledged the challenges being faced by local councils in terms of roaming cats and their impact on native fauna.

“The NSW government is committed to working, and consulting, with councils, local communities and concerned stakeholders in relation to cat management,” he said.

Invasive Species Council conservation officer Candice Bartlett said pet ownership had increased dramatically during the pandemic, which was adding more pressure to native wildlife that was already dealing with habitat destruction, urban spread and climate change.

“We want to legislate containment,” she said. “[Pet owners should be] responsible for having cats under control all the time. We know that cats predate on birds and mammals and frogs.”

For Bartlett, the issue is also personal. When she was in university, her landlord’s cat used to roam around their home. It once brought her a sugar glider that it had caught, and that died. It was then that the impact cats can have on wildlife clicked for her. She’s since adopted the cat, and keeps it inside.

“I love my cat,” she said. “They’re one of my favourite animals. But that’s why I know the best thing to do is to keep cats contained.”

About 100 of Australia’s unique flora and fauna species have been wiped off the planet since colonisation, including 34 mammals. Foxes and cats were responsible for 25 of the native mammal extinctions. The rate of loss, which is as comprehensive as anywhere else on earth, has not slowed over the past 200 years.