Bramble cay melomys
Common name: Bramble Cay melomys
Scientific name: Melomys rubicola
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 Resource Management 'Back on Track' species prioritisation framework.
Description
Bramble Cay melomys 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 about the size of a small rat (body length: 14-16cm; tail length: 14.5-18cm) with light-brown to orange-brown fur.
Habitat and distribution
This species is only found on Bramble Cay, a small vegetated coral cay (a type of island) 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. Speculation exists 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 Bramble Cay melomys biology and ecology. They have been observed foraging at night among vegetation. They appear to eat plant material including Portulaca oleracea.
The reproduction of the Bramble Cay melomys is not known.
Threatening processes
The shrinking or disappearance of Bramble Cay due to erosion is the major threat to this species (Latch 2008). The size of the island is in a state of flux determined by both normal weather patterns and wave action, and more extreme winds and storm surges associated with cyclones. Historical records indicate that the island is shrinking. If this continues, both the Bramble Cay melomys and its habitat will disappear into the Coral Sea. However, more recent measurements suggest the cay might be growing in size (Latch 2008).
The introduction of exotic animals or plants to the island also threatens the melomys. This includes predation by dogs that come ashore from boats landing at the island.
Genetic analysis of this species reveals a level of inbreeding which theoretically could lead to inbreeding depression and ultimately extinction (Latch 2008).
Recovery actions
It is important to find out how many Bramble Cay melomys exist and if the species is declining in numbers. It is also necessary to establish that the Bramble Cay melomys is a true species by obtaining genetic material and comparing it with the closely related Cape York melomys Melomys capensis.
Last reviewed 23 February 2011
Last updated 23 July 2010