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AUSTRALIAN CONSERVATION STATUS (EPBC Act)
Only on Bramble Cay, a small coral island in the Torres Strait
Coral, sand and marine island
THE BRAMBLE CAY melomys, or mosaic-tailed rat, is quite the most isolated of Australia's mammals. It lives only on a small coral cay just 340m long and 150m wide that's closer to PNG than the Australian mainland.
The cay is under the traditional ownership of the Erub islanders who call it 'Maizab Kaur' and is the most northerly island in the Great Barrier Reef.
It's thought the endemic rodent, first described in 1924, could extend into other islands in the Torres Islands or even Papua New Guinea, but none have been recorded anywhere but on Bramble Cay.
Brambe Cay is also used by green turtles and sea birds for nesting. (Credit: Queensland Government)
THe melomys is larger than the three other Australian species in the genus, with its body measuring 15-16.5cm long and tail 14.5-18.5cm long.
Because of its isolation and low population, little is known about its behaviour. Scientists have noted it eating vegetation at night.
In the late 1970s, visitors to the cay noted there were hundreds of the rats, but a 2004 survey estimate only 93 were left. A survey from 2004 found it likely that fewer than 50 individuals remained. Unfortunately, the most recent survey in 2012 found no evidence of the rodents, so it's possible the Bramble Cay melomys has been wiped out.
Since the melomys lives on an isolated island, it's one of the few species not directly affected by humans, though sea-level rise from climate change is a future issue. Erosion of the island and storm surges are other threats, and introduced species could potentially quickly wipe out the rodent.
But the biggest threat is the population size itself. With just a single population of fewer than 50 individuals, genetic inbreeding is likely and could lead (or has already led) to extinction.