Technology & Science

Australian rodent named the 1st mammal to go extinct due to human-caused climate change

An Australian rodent found only on a tiny island on the Great Barrier Reef has been declared extinct. Scientists say it's the first mammal known to be wiped out by human-caused climate change.

Bramble Cay melomys was found only on a tiny island on the Great Barrier Reef

The Bramble Cay melomys, which looked like a small brown rat, lived on Bramble Cay, a hump of coral just 340 metres long and 150 metres wide that juts out three metres or less above the water between Queensland in Australia and Papua New Guinea. (University of Queensland)

An Australian rodent found only on a tiny island on the Great Barrier Reef has been declared extinct. Scientists say it's the first mammal known to be wiped out by human-caused climate change.

The Bramble Cay melomys, which looked like a small brown rat, lived on Bramble Cay, a hump of coral just 340 metres long and 150 metres wide that juts out three metres or less above the water between Queensland in Australia and Papua New Guinea.

But a thorough survey using small animal traps, camera traps and daytime searches from August and September 2014 failed to turn up any of the animals, says a new report written by Ian Gynther from Queensland's Department of Environment of Heritage Protection and Natalie Waller and Luke Leung at the University of Queensland and released today.

Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic climate change.- Queensland Government and University of Queensland report

The report said the "key factor" responsible for killing off the animals was flooding of their island on multiple occasions during the last decade, "causing dramatic habitat loss" and possibly killing some individuals directly.

"Available information about sea-level rise and the increased frequency and intensity of weather events producing extreme high water levels and damaging storm surges in the Torres Strait region over this period point to human-induced climate change being the root cause of the loss of the Bramble Cay melomys," the researchers added. "Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic climate change."

Scientists have predicted that climate change will cause some species to go extinct, because many can't evolve or migrate fast enough to cope with effects of climate change such as habitat loss. Species restricted to cold climate habitats, such as the Earth's poles or mountain tops, as well as habitats that can only tolerate a narrow range of temperatures, such as tropical coral reefs, are considered most at risk.

30% of mammals at risk

A new study led by Luca Santini at Sapienza University in Rome estimates that about 30 per cent of the mammal species would likely not be able to spread fast enough to keep up with the average rate of climate change, boosting their risk of extinction. He notes that mammals are better at dispersing themselves than other groups of animals, suggesting that the risk for other kinds of organisms could be higher.

The Bramble Cay melomys is a type of mosaic-tailed rat — a group that has a mosaic pattern on scales on its tail instead of the parallel rings found on the tails of most rats and mice. The animals grew to be about 14- to 16-centimetres long, with a tail of about the same length as its body. They were thought to eat mostly plants, especially a succulent herb called Portulaca oleracea that's common on Bramble Cay, and possibly turtle eggs.

The animal was first described in 1845 by Lieut. Yule, commander of the British ship HMS Bramble, and his crew, according to Gynther, Waller and Leung's report.  At that time, there were so many of them that his crew shot them with bows and arrows for fun. In 1978, the population was estimated at several hundred, but it had dropped to less than a hundred by 1998, and a census in 2004 captured just 12 animals.

The last known sighting of the Bramble Cay melomys was made by a professional fisherman in 2009.

However, the report raised the possibility that the species might not be completely extinct. Though it was thought to live only on Bramble Cay and is no longer found there, it or a closely related species might still exist in the Fly River delta of Papua New Gunea, which is thought be where the ancestors of the Bramble Cay population originated.