Feral cats are present on 99.8 percent of Australia's land area, according to more than three-dozen Australian researchers who examined the continent's long-running problem with wild felines.
Writing in a study published recently in the journal Biological Conservation, the scientists collated the findings of 91 other studies on the country's wild cats to derive the tally. What's more, they found, nearly 80 percent of Australia's island land area shows the presence of feral cats.
"Our study highlights the scale and impacts of feral cats and the urgent need to develop effective control methods, and to target our efforts in areas where that control will produce the biggest gains," said the study's lead author, Sarah Legge, of the University of Queensland, in a statement.
Controlling the problem will be a daunting task. Legge and her colleagues determined that Australia's overall feral cat population fluctuated between 2.1 million and 6.3 million cats, with population densities higher in areas that received greater rainfall.
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Feral cats dine on, and wreak havoc with, native fauna in the country. In such numbers they contribute greatly to the extinction risk of species close to the brink, and the wild felines have already been linked to the disappearance of more than 20 mammals in Australia.
Measures such as fencing off predator-free zones on islands and the mainland to keep the cats out are at best small bandages on a large wound, Legge suggested.
"These projects are essential for preventing extinctions," she said, "but they are not enough. They protect only a tiny fraction of Australia's land area, leaving feral cats to wreak havoc over the remaining 99.8 percent of the country."
The scientists say their research will help inform new approaches to getting control of all the cats. Indeed, the study was backed by the Australian government.
"This new science shows that the density of feral cats in Australia is lower than it is in North America and Europe, and yet feral cats have been devastating for our wildlife," said Australia's Threatened Species Commissioner Gregory Andrews.
Feral cats were likely introduced to Australia by 19th-century Europeans, according to a 2015 study – new predators on the landscape.
"Australia is the only continent on Earth other than Antarctica where the animals evolved without cats, which is a reason our wildlife is so vulnerable to them," Andrews noted. "This reinforces the need to cull feral cats humanely and effectively."
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Andrews backs a plan announced in 2015 to cull some 2 million feral cats by 2020.
It's unclear whether the new study, which reduces considerably earlier countrywide estimates of 15-20 million ferals, would possibly have any impact on the 2-million-cat goal.
Legge told Australian Associated Press that while the 2 million goal is a good one "it's going to be very important to target cat culling to achieve the greatest benefit for wildlife. If you get rid of cats on larger islands, you can then stop their reintroduction with biosecurity measures, and then you have a big area that's safe for wildlife."
"We also need to address the issue of feral cats living in heavily urbanized areas, where their densities can be 30 times greater than in natural environments," Legge said. "As well as preying on the threatened species that occur in and near urban areas, these urban feral cats may provide a source of feral cats to bushland areas."
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