Wildlife

The little Bramble Cay melomy is likely first mammal species claimed by man-made climate change

At first glance, the Australian island of Bramble Cay is unremarkable except for the steel lighthouse at one end. Otherwise, the small isle is dotted with a few grass clumps, shorebirds and nesting sea turtles.

Years ago, however, fishers who visited the island in the Great Barrier Reef could also spot little, rat-like rodents scurrying over the sand and coral rubble.

As mackerel fishermen Egon Stewart told Queensland scientists in a new report, around 2009 there had been “a heap of sticks and a smashed up dug-out canoe at the north-western end of the island.” When Stewart flipped over the pile, a few of the furry critters took flight across the island.

This was the last time, the researchers believe, anyone saw a living Bramble Cay melomy, a rodent round in body, long in whisker and lumpy in tail. The creatures are likely the first mammal casualty of man-made, or anthropogenic, climate change, University of Queensland researcher and study author Luke Leung said in a statement. Despite subsequent search efforts, there is no evidence the animals remain on the island, the only place they were known to live on the planet.

The first recorded Bramble Cay melomy sightings date back to the 1800s. In 1978, researchers estimated several hundred rodents lived on the island, but the numbers dropped to the double-digits by 1998. Twelve melomys were caught in November 2004; in December 2011, scientists looking for the rodents turned up empty-handed. For this report, that utilized survey methods consisting of nocturnal traps as well as daytime searches, no sign of a melomy was to be found — no critter, paw print or pellet.

It was, in all likelihood, death from lack of resources. In the decade between 2004 and 2014, the amount of leafy plants on Bramble Cay shrunk by 97 percent, the authors say. Without plants providing food and shelter, the scientists believe rodents succumbed to local extinction. And the lack of plants, in turn, was likely caused by a rising sea that swept over the island during storms and high tides — ocean inundation.

Bramble Cay is quite flat, rising no more than 9 feet above sea level at its highest point. Based on observations of erosion, scattered driftwood and dead plants, the authors concluded, “Bramble Cay has been subjected to repeated episodes of seawater inundation.” The scientists also note that data from tides and satellites indicate the average sea level in the area has risen a quarter inch per year.