British settlers brought domestic cats to Australia in 1788 to control rats and mice around ships, farms, and settlements, but escaped cats now kill billions of native animals every year across the continent

If you've ever seen your own cat pounce on a toy mouse in your living room, you've had a little preview of a much bigger story being played out on the other side of the world. According to the historical study, ‘The spread of the cat, Felis catus, in Australia: re-examination of the current conceptual model with additional information,’ by researcher Ian Abbott, published in Conservation Science Western Australia, cats arrived in Australia with British settlers in 1788 and had spread over more than 90 percent of the continent by 1890.

Abbott found 33 other journals of expeditions or accounts of excursions before 1895, and none of them mentioned cats in country beyond the settled frontier, the paper says. He also found almost 150 new records of cats elsewhere in Australia, which he says still fit the chronology of spread outlined in his earlier model, with only one small revision for northeast Queensland. Research by the Australian National University, Charles Darwin University, and the University of Sydney estimates that cats in Australia kill more than 1.5 billion native animals every year.

It could be a hard number for American readers to picture. Cats are among the most popular pets in the U.S., curled up on couches from one coast to the other. But in Australia the same animal has become a major threat to the continent’s wildlife. The story of how that happened starts more than two centuries ago, with a fleet of British ships and their cargo holds full of rats.


How cats hitched a ride to a new continent
When the First Fleet landed in Australia in 1788 to establish a British penal colony, cats came along for a practical reason. Ships had to have something to keep rats and mice away from the food stores, and so did the earliest farms and settlements, where grain and supplies had to be protected. Nobody probably planned for what happened next.

Abbott pieced together sightings of cats by researching old expedition diaries, farm journals, and 19th-century newspapers. Her research found the spread happened region by region. Cats were feral around Sydney by about 1820 and reached Perth and southeastern Australia by about 1840. They colonized north-west Australia by about 1870 and by 1890 covered over 90 percent of the continent. That’s a very quick takeover for an invasive predator travelling across a landmass the size of the contiguous United States.

Tasmania had a little bit of a different timeline. The same study found that domestic cats were introduced to the island in 1804, the year after the settlement at Hobart was established, and were first recorded as feral animals living there in the 1840s.

Rabbits, rats, and a mistake
Now, here’s the part that most surprises American readers: in several cases, people didn’t simply lose track of their cats by accident. They let them go on purpose.

In the late 1800s, when rabbits exploded into plague numbers across the Australian countryside, officials and settlers looked at cats to fix the problem. Abbott’s research shows that in 1886 the New South Wales government sent 400 cats to a rabbit-infested sheep station on the Paroo River in the hope that they would bring down the rabbit population. A few years later, the Victorian government went to even greater extremes, passing a law in 1885 to prevent the killing of feral cats, which were seen as a natural enemy of the rabbit. Sugar cane growers in northern Queensland adopted a similar tactic when they released cats to control rats, which were destroying their crops.

It didn't work out as anybody wanted. The release programs mostly added a second invasive species to the landscape rather than removing one, as cats found it much easier to hunt native birds, lizards, and small marsupials than to control rabbits.

A predator native wildlife never saw coming
For millions of years Australia’s mammals, birds and reptiles evolved in near-isolation from placental predators. Nothing in their evolutionary past had prepared them for a fast, stealthy, endlessly adaptable hunter like a wild cat.

The results have been severe. In The Conversation, ecologists Sarah Legge, Chris Dickman, John Woinarski and colleagues write that cats have been a factor in most of Australia’s 34 mammal extinctions since European settlement, and still threaten around 120 more native species today. Small and medium-sized marsupials, ground-nesting birds, and native rodents have suffered the most, as they fall smack into a cat's preferred prey-size range.

What stands out is how quickly it happened. Abbott’s research showed that in region after region, feral cats became noticeably larger within 10 to 30 years of a region being settled. Generations of hunting larger native prey favored larger cats. By 1870, reports of remarkably large feral cats were emerging in northwestern New South Wales, between 1873 and 1888 near Radbourne in Western Australia, and by 1909 near Broken Hill.

Why does this still matter for pet owners everywhere
You don’t have to be in the Australian outback for this story to feel relevant. The same research, backed by NESP, found that urban cat densities can be far higher than in the bush, with pet cats allowed to roam freely, even in ordinary cities and suburbs, adding substantially to the wildlife death toll.

For American cat owners, Australia’s experience amounts to a 200-year natural experiment in what happens when a clever, adaptable predator with no natural enemies of its own is dropped into an ecosystem that never evolved to defend itself against it. What researchers keep teaching us is simple: keeping cats contained, whether by a leash, an enclosed “catio” or just by keeping them indoors, protects both local wildlife and the cats themselves from cars, disease and fights.

Australia is still trying to solve a problem that started with a handful of ships’ cats more than two centuries ago. It’s a slow-motion reminder of how even small, well-meaning decisions about animals can reverberate across an entire continent for generations.