Fossils of rats as big as dogs found in Southeast Asia

Julien Louys holds the jaw bone of a giant rat species discocvered on East Timor, up against a comparison with the same bone of a modern rat. (Stuart Hay, ANU)

The rats in the New York’s subways may be scary but they would have been no match for their distant relatives who once lived in Southeast Asia.

Those rats, according to archaeologists with The Australian National University (ANU) who discovered fossils of seven giant rat species on East Timor, were up to 10 times the size of modern rats. That would make them the largest rats ever known to have existed.

"They are what you would call mega-fauna. The biggest one is about five kilos, the size of a small dog," said ANU’s Julien Louys, who is helping lead the project, in a statement.

"Just to put that in perspective, a large modern rat would be about half a kilo (2.2 pounds),” he said of the findings that were presented to the Meetings of the Society of Vertebrate Palaeontology in Texas last month.

The work is part of the From Sunda to Sahul project, which is looking at the earliest human movement through Southeast Asia. Researchers are now trying to work out exactly what caused the rats to die out and what role humans might have played in their demise.

Louys said the earliest records of humans on East Timor, a tiny country that became independent in 2002, date to around 46,000 years ago. They lived with the rats for thousands of years, he said.

"We know they're eating the giant rats because we have found bones with cut and burn marks," he said. "The funny thing is that they are co-existing up until about a thousand years ago. The reason we think they became extinct is because that was when metal tools started to be introduced in Timor, people could start to clear forests at a much larger scale."