Climate Change Effects: Australian Rodent First Documented Case Of Extinction By Climate Change

Researchers in Australia believe rising sea levels caused by man-made climate change killed off a tiny rodent that lived on an isolated atoll in the Great Barrier Reef. Now considered extinct, the small animal was the only known mammal to inhabit Bramble Cay, an island roughly the size of a football field.

Known as the Bramble Cay melomys, the mouse-like, long-tailed creature once thrived on the remote island in the northeast Torres Strait between the Cape York Peninsula and the coast of Papua New Guinea. However, despite ground searches, strategically placed motion-sensitive cameras as well as animal traps, one has not been seen in several years.

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Luke Leung, a scientist from the University of Queensland, is convinced climate change effects created the environmental factors that killed off the rodents.

“The key factor responsible for the death of the Bramble Cay melomys is almost certainly high tides and surging seawater, which has traveled inland across the island. The seawater has destroyed the animal’s habitat and food source. This is the first documented extinction of a mammal because of climate change.”

Scientists have been predicting that climate change will ultimately lead to some animal species dying off as many are unable to evolve or migrate fast enough to cope with the aftereffects. Experts believe animals that live in cold climates or species that cannot adapt to temperature extremes are the most at risk.

One study conducted by researchers with Sapienza University in Rome estimated nearly 30 percent of warm-blooded species would likely not survive long enough to adjust to the effects of climate change. The study noted that other groups of organisms, like certain insect species, may have an even higher risk of extinction.

Leung is urging the Australian government officially declare the species extinct.

“The assertion that Australia has lost another mammal species can be made with considerable confidence,” he wrote.

The Bramble Cay melomys was easily distinguished from other rats and mice by the unique mosaic pattern of scales on its tail. Generally growing up to six inches in body length, they had a tail equally long. Their diet consisted mainly of local vegetation, particularly a common herb called Portulaca oleracea, as well as turtle eggs.

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Lieutenant Yule of the British ship HMS Bramble wrote the first official documentation of the Bramble Cay melomys in 1845. According to the ship’s log, there were so many of the rat-like mammals, the crew would shoot them for sport.

Once listed as an endangered species, their numbers dropped from a few hundred in 1978 to less than a hundred by 1998. A 2004 census found only 12 in the wild and the last one ever seen was by a professional fisherman in 2009.

By spring 2014, the island’s livable habitat had shrunk considerably and many of the rock caves and crevices where the melonmys would seek shelter had all but disappeared.

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Data collected over several years indicate climate change must have accelerated the end of the already threatened mammal population.

“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.”

According to Leung, flooding of the island would not have to be severe or even very frequent for the rodents to be wiped out, just enough to kill the plants they eat and destroy fresh water sources. Some flooding could have downed the melonmys as well.

While there have been no documented sightings of the rodent on Bramble Cay in nearly seven years, some experts are not convinced that the Bramble Cay melomys is completely extinct. Either another population of the species or one very close to it is thought to inhabit the area around the Fly River delta of Papua New Guinea.

[Photo by Ian Waldie/Getty Images]