Extinct Rodents Of Unusual Size Discovered In Timor

Dr Julien Louys compares the jawbone of one of the giant extinct rats he has discovered with one from a modern rat. Stuart Hay, ANU

For tens of thousands of years, Timor was populated by giant rats, with seven extinct species recently discovered. Among these is the largest rat species every known, which only became extinct about a thousand years ago.

It's not quite the fireswamp, but the islands of southeast Asia are home to some impressively large rats. The Bosavi woolly rat of Papua New Guinea, for example, can weigh three kilograms (seven pounds), a terrifying six times the size of the largest Rattus norvegicus you're likely to find scuttling through the sewers of major cities. Other disturbingly large rats exist on Flores and the giant rat of Sumatra even got a sufficiently tantalizing reference in a Sherlock Holmes story to spark numerous books and films

However, the Australian National University's Dr Julien Louys has topped them all, with one still unnamed species identified from Timor that grew to five kilograms (11 pounds), which Louys compared in a statement to, “the size of a small dog.” While we may recoil in horror, the first people to arrive on Timor 46,000 years ago just saw dinner. "We know they're eating the giant rats because we have found bones with cut and burn marks," Louys said of the remnants left at human campsites around East Timor.

Humans and rats survived together until about a 1,000 years ago, at which point all the Timor giant rat species disappeared roughly simultaneously. This was not the consequence of a Timorese pied piper, but a more frequent form of overreach. “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," Louys said.

It's not just the rats' jaws that dwarfed those of their modern relatives. Credit: Stuart Hay, ANU

Deforestation proved far more devastating on Timor than nearby islands, Louys told IFLScience, because the Timorese soils are not as rich as those of volcanic islands, and rainfall is not as heavy. Consequently, while forests swiftly regrew nearby as soon as humans stopped cutting them, on Timor changes proved more permanent, giving the rats nowhere to live.

Louys' work has yet to be published, but was presented at last month's Society of Vertebrate Paleontology conference in Texas, as part of a discussion of what we could learn from past extinctions about preventing future ones. The dire consequences of forest destruction might be the most immediate lesson in a region currently choking on smoke.

The discovery of the rats came from Louys' work on the From Sunda to Sahul project tracing the movement of humans through those islands of Indonesia and neighboring countries that, even at the height of the last Ice Age, were not attached to either the Asian mainland or Australia. Part of the project involves studying the impact human arrival had on the ecosystems of the islands, and why some responded differently to others.

Although two of the rat species Louys identified have already been scientifically described, most have not. Louys promised to consider Princess Bride references when the time comes.

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