That's the question 27 per cent of households that own cats in Australia must consider.

Whether you keep your cat contained or not could have far reaching implications for your pet and Australia's wildlife.

RSPCA Australia senior scientific officer Sarah Zito said the issue should be considered as containing cats, not simply keeping them indoors.

"There are various ways to contain cats, including indoors," Dr Zito said.

"But also allowing them access to a controlled outdoor environment, which is the ideal situation."

Dr Zito said the "detrimental impact" roaming cats have on wildlife is a major concern.

"Not only on wildlife numbers but also welfare because even if the animals are not killed, they're being hunted or played with and that's obviously a real welfare problem," Dr Zito said.

Several recent studies have looked into the toll domestic and feral cats have on Australia's fauna.

A 2020 study estimated roaming pet cats kill 390 million animals per year in Australia, with an individual roaming pet cat killing 186 reptiles, birds and mammals per year - most of them (86 per cent) being native species.

The average feral cat was estimated to kill 748 reptiles, birds and mammals a year.

As well as posing a risk to wildlife, roaming cats face several risks to their own safety if uncontained.

Those include infectious disease, like the feline immunodeficiency virus, which can be contracted when fighting with other cats.

"They're also more likely to get parasites like fleas and worms because they're in an environment other cats frequent," Dr Zito said.

Cats face being prey to dogs, poisons and the greatest risk, traffic.

"I think we would all know people who have lost cats or had cats injured being hit by a car, particularly in urban areas," Dr Zito said.

Factors like disturbance, fear, competition and disease transmission were also concerns with roaming cats hunting.

"I think we also need to remember that it's not just owned cats that are impacting wildlife," Dr Zito said.

"One of the things with cat containment is that people assume it's going to solve all of the issues like wildlife predation, community nuisance, fighting, digging, defecation, urination, vocalisation."

Many of those issues can occur because of feral, un-owned or semi-owned cats, meaning pet cat containment is not a "silver bullet".

The ACT is at the forefront of cat containment in Australia, with laws introduced on July 1.

Part of the ACT Cat Plan 2021-2031, the laws mean all cats obtained after July 1 must be contained to a home at all times.

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Dr Zito said two of her three cats were stray for the first six months of their lives but adjusted to being contained to an indoor/outdoor home setting.

A contained setting, she said, should consider the physical and mental needs of a cat.

"Those would be things like making sure that the cat has good resources such as food, litter, trays, water but also opportunities to rest, hide, perch, play, scratch, stalk, pounce and leave scent," Dr Zito said.

Cats also need the opportunity to express their natural hunting behaviour, with interactive toys, playtime and using food helping stimulate their instincts.

"Like hiding food and toys around the house, so that they're actually foraging for food," Dr Zito said.

Dr Zito warned against national mandatory cat containment laws which could have unintended consequences such as an inequitable impact on owners who can't afford enclosures or are renting.

Biologist and animal carer Adriana Simmonds said keeping domestic cats contained at all times was the only way to ensure the safety of Australia's native wildlife.

"Cats kill 24/7," Ms Simmonds said.

More than 50 per cent of the native animals brought to Ms Simmonds' former animal rescue shelter in Wonga Park, Victoria, were attacked by cats.

"Cats are fantastic creatures, they adapt to everything," Ms Simmonds said.

"That's why they're so dangerous, because wherever you put them, they adapt.

"There are many different ways to keep your cats indoors, keeping them happy and healthy and sane."

Director of Human Seeds, a project that delivers seminars and workshops on ecology and conservation, Ms Simmonds said the problem is that many cat owners are ignorant to how dangerous their cats can be.

"We love our pets but we are very irresponsible," she said.

"I think many people are just ignorant - it's not that they have bad intentions or they don't care.

"They don't know because we have been terribly educated."

Ms Simmonds supported the rise in cat curfews that are implemented by some local councils around the country.

But it's about more than simply fining people, she said.

"People need to be given an understanding of why," Ms Simmonds said.

"When people are educated and we explain and we show them the consequences, it's much easier to have that community support."