How Did Cats Get to Australia?

CC BY 2.0. Kristian Thøgersen/flickr

A new study aims to settle the debate about how and when this invasive species was introduced to the island country.

Sorry cat lovers, please don’t lambaste the messenger here ... but in some places cats are officially considered an invasive species. Like Australia, where the government website notes on its invasive species fact sheet: “The feral cat is found in most habitats across Australia. It has caused the extinction of some species on islands and is thought to have contributed to the disappearance of many ground-dwelling birds and mammals on the mainland.”

Of the 22 invasive mammalian species found in Australia, two of them are predators – the European red fox and the domestic cat. Feral cats threaten over 100 native species of Australia and efforts to reintroduce threatened species in some areas have failed due to predation by cats.

Feral cats – wild cats that live independently of humans, but are descended from domestic ones – have established invasive populations over large swaths of Australia, but there has long been debate about just where in fact they came from, Australia being an island and all. There have been several theories. One is that they hitched a ride on 19th century sailing vessels, where they served as resident mousers or companion animals. Another theory suggests that cats came there with European explorers in the late 18th century. And yet another postulates that cats accompanied Malaysian fisherman in the 17th century.

Knowing when cat populations were founded would increase the understanding of how the species has affected Australia, and thus researchers from the Senckenberg Biodiversity and Climate Research Centre and the University of Koblenz-Landau in Germany set out to get some answers. They analyzed genetic samples from 269 Australian feral cats from six mainland and seven island locations to explore their evolutionary history and dispersal patterns.

What they determined is that Australia’s feral cats likely came along with Europeans in the 19th century. While there was some evidence of a secondary influx from Southeast Asia, there was no indication of a stable feral cat population coming entirely from Asia.

"The analysis of genetic structure and diversity of Australian feral cat populations answered the question of the time of feral cat introduction to Australia and revealed that remnants of the historically introduced cat genotypes are still discernable on isolated islands,” says Katrin Koch, lead author from the BiK-F. “These findings have implications for invasive species management, since our study determined a specific time frame for the arrival of cats to Australia, allowing us to link the time of introduction with the decline and extinction of several native species."

See the full study in BMC Evolutionary Biology.