Australian archaeologists have found fossils of seven giant rat species in East Timor, which they say are the largest known rats to have ever existed.

The team from the Australian National University (ANU) made the discovery as part of the From Sunda to Sahul project, which is looking at the earliest human movement through Southeast Asia. Researchers are attempting to uncover the reason why the rats died.

What the ANU archaeologists found were called mega-fauna, according to Dr Julien Louys of the ANU School of Culture, History and Language, who is helping lead the project. While a large modern rat would be about half a kilo, the biggest rat that the team reported is about five kilos, which is the size of a small dog.

Louys said the earliest records of humans on East Timor date to around 46,000 years ago, and they lived with the rats for thousands of years. “We know they're eating the giant rats because we have found bones with cut and burn marks,” he said.

According to Louys, those humans and rats co-existed up until about a thousand years ago. They believe that the rats became extinct because that was when metal tools started to be introduced in Timor, and people could start to clear forests at a much larger scale.

He said the project team is hoping to get an idea of when humans first moved through the islands of Southeast Asia, how they were doing it and what impact they had on the ecosystems. The information can then be used for modern conservation efforts.

"We're trying to find the earliest human records as well as what was there before humans arrived. Once we know what was there before humans got there, we see what type of impact they had,” Louys said.

In October 2015, a new genus and species of rat has been discovered in Sulawesi Island in Indonesia. The new rodent, with features never seen by the scientific community before, was found by scientists at Museum Victoria in Australia and Louisiana State University (LSU), in partnership with Indonesian researchers.

The animal was dubbed hog-nosed rat because of its large, flat, pink nose and forward-facing nostrils. It reportedly has extremely large ears, long hind legs that may be used for hopping and very long urogenital hairs. The animal is considered genetically different from any other species, because for one, it has especially long incisors compared with other shrew rats. It is among the three new rat species discovered by the research team in the region since 2012.

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