Bramble Cay melomys
Common name: Bramble Cay melomys
Scientific name: Melomys rubicola (Melo = Melanesian, mys = mouse; rubicola = Bramble (Cay)
Family: Muridae (native rats and mice)
Conservation status: This species is listed as Endangered in Queensland (Nature Conservation Act 1992) and nationally (Environment Protection and Biodiversity Conservation Act 1999). It is considered a high priority for conservation under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
The Bramble Cay melomy is one of the mosaic-tailed rats (distinguished by the mosaic pattern of scales on its tail rather than the concentric rows of scales running along the length of the tail found in most other types of rats and mice). It is larger than the three other Australian species of melomy and about the size of a small rat (body length: 148-165 mm; tail length: 145-185 mm). It has reddish-brown fur with a paler underbelly, relatively small ears and a long tail with a prehensile tip.
Habitat and distribution
This species is only found on Bramble Cay, a small vegetated coral cay (an island composed of coral rubble and sand) 340 m long by 150 m wide, located at the northern tip of the Great Barrier Reef. This makes it Australia's most isolated species of mammal. There has been speculation that the species may also occur in Papua New Guinea (PNG) given the close proximity of the cay to the Fly River region, or on other islands in the Torres Strait. Further survey work on these islands and PNG along with clarification of its taxonomic status in relation to PNG species is required (Latch 2008).
Life history and behaviour
Little is known about the biology and ecology of the Bramble Cay melomys. They have been observed foraging at night among vegetation and appear to eat plant material including Portulaca oleracea.
Trap data has demonstrated that the Bramble Cay Melomy has a strong female-biased sex ration. Pregnant and lactating females, juveniles and subadults have, in the past all been trapped in July, suggesting an extended winter breeding season.
The Bramble Cay melomys coexists with large numbers of shore birds and nesting green turtles which can contribute to variable trapping success. The Bramble Cay melomys have been noted to avoid shore birds but may eat turtle eggs.
Threats to the species centre on three areas. Firstly there is only the single known population of the species and searches on other cays and in adjacent areas of New Guinea have failed to discover other populations. Secondly the cay is prone to inundation from storm surge and other disturbances. Further compounding risk to the species is that the species appears to be inbred. Therefore resilience of the species to catastrophic events such as cyclones, introductions of weeds or introduced predators, or the arrival of a novel disease is very low (Curtis et al 2012).
The most recent survey for the species in 2012 resulted in no animals being recorded. The most recent verified record of the species is from a trapping effort in 2004. It is possible that a catastrophic inundation of the island has already occurred.
It is important to find out if the Bramble Cay melomys still occur on the cay and if the species is declining in numbers. It is also necessary to establish whether the Bramble Cay melomys is a true species by obtaining genetic material and comparing it with the closely related Cape York melomys Melomys capensis.
Other recommended recovery actions include (Curtis et al 2012):
- educating visitors about the cay and the melomys and threats to its survival
- enforcing strict quarantine measures on visitors by restricting visitation to the cay and possibly using engineering techniques to stabilise the cay
- establish one or more other populations either in captivity or on another carefully selected island as a safeguard.
If the species has become extinct it is a highly undesirable outcome. However this species is also a case study in how the role of natural and largely unpreventable processes and the high cost of undertaking any recovery actions in such an isolated location are important considerations when weighing up how and where conservation actions are directed.
Curtis LK, Dennis AJ, McDonald KR, Kyne PM and Debus SJ. 2012. Queensland’s Threatened Animals, CSIRO Publishing, Victoria, Australia
Latch P. 2008. Recovery Plan for the Bramble Cay Melomys Melomys rubicola. Report to Department of the Environment, Water, Heritage and the Arts, Canberra. Environmental Protection Agency, Brisbane.
Watts CHS. 2002. Bramble Cay Melomys in Strahan, R. (ed.),The Mammals of Australia. Reed New Holland, Sydney.