With no sightings since 2009, experts have officially recommended that the Bramble Cay melomys (Melomys rubicola, also known as the mosaic-tailed rat) be declared extinct. Researchers from the University of Queensland have concluded that the main cause of the extinction is human-induced climate change.  In the decade between 2004 and 2014, the amount of leafy plants on Bramble Cay shrunk by 97 percent.  The lack of plants, in turn, was probably caused by a rising sea that swept over the island during storms and high tides — ocean inundation, as the scientists call it.

Bramble Cay is part of the Shire of Torres, specifically of the Eastern Islands Region.

Had it been something like a fuzzy koala or panda instead of a rat, the world might have taken more notice, but maybe not.  The animal’s demise could be dismissed as nothing more than a lost “rat”!  It’s one more piece in the avalanche of the world’s Sixth Extinction process.

It was larger than the three other Australian species of melomys and about the size of a small rat (head and body length: 148-165 mm; tail length: 145-185 mm). In 1978, the population on Bramble Cay was estimated to comprise at most several hundred individuals. A formal population census of the Bramble Cay melomys conducted in 1998 estimated the cay’s population size was 93, based on the capture of 42 individuals. Surveys conducted for the species in 2002 and 2004 detected only 10 and 12 individuals, respectively.

Certainly, anecdotal reports indicate at least some individuals were killed by domestic dogs that were released onto the island from visiting boats, but also that the species was hunted by indigenous people who visited from PNG on a sporadic basis.

Temperature changes are likely the main driver, not sea level rise. The trend towards a strengthening in the intensity of La Niña conditions until at least 2012 has been linked to climate change, specifically the increase in global mean temperature (L’Heureux et al.2013), with the frequency of extreme La Niña events predicted to increase (almost doubling) with greenhouse warming during this century (Cai et al. 2015).

Dr Luke Leung of UQ’s School of Agriculture and Food Sciences said “anecdotal information obtained from a professional fisherman who visited Bramble Cay annually for the past 10 years suggested that the last known sighting of the Bramble Cay melomys was made in late 2009.”

There is a slim chance, Leung said, the Bramble Cay melomys still exists — perhaps on nearby Papua New Guinea — though there is no confirmation of the animals having lived anywhere except the coral island.