National recovery plan for the Golden Bandicoot Isoodon auratus and Golden-backed Tree-rat Mesembriomys macrurus 2004 - 2009
Palmer, C. Taylor, R. and Burbidge, A.
Northern Territory Department of Infrastructure, Planning and Environment, 2003
The Golden Bandicoot is listed nationally as Vulnerable and is known to have disappeared from almost all of its former wide distribution across half of the Australian continent, where it occupied a large range of habitats. The Golden Bandicoot is a small omnivorous marsupial which is now restricted to rocky sandstone spinifex habitats and vine thickets in the north Kimberley region, four Western Australian (WA) islands (two Pilbara, two Kimberley) and one island off the northeast Arnhem Land coast of the Northern Territory (NT). On the Kimberley mainland the Golden Bandicoot appears to have discrete and restricted populations. There are population estimates for three of the islands where the species is recorded. Golden Bandicoot populations have been estimated for Barrow Island (tens of thousands) and Middle Islands (1,000) in WA and Marchinbar Island (1,400) in the NT.
The Golden-backed Tree-rat is listed nationally as Vulnerable as its range has declined substantially in WA and it is known from only three historic records in the NT. The Golden-backed Tree-rat is a large rodent, which has been recorded from a broad range of habitats. There is little information on the ecology of this species and this lack of information provides a poor base for assessing the overall status of this species in WA and NT.
Populations of surviving Golden Bandicoots and Golden-backed Tree-rats are recorded on a range of tenures including Defence Land, Aboriginal Land, Conservation Land and Unallocated Crown Land. In the Kimberley there is no specific on-ground conservation management for either species. Likewise, in the NT, there is no on ground conservation management for the Golden Bandicoot. There are no population estimates for either species from the mainland or Kimberley islands.
No factor has yet been identified as causing the decline of either species or critical weight range (CWR) mammals generally in the Kimberley and Top End of the NT. The most likely causal factors are predation by feral cats and changed fire regimes. These factors may be operating synergistically with increased susceptibility to predation after the undergrowth is destroyed by intense fires. Changed fire regimes and grazing by livestock and feral animals may have altered the availability of tall fruit bearing understorey shrubs for the semi-arboreal Golden-backed Tree-rat. The status of the Golden Bandicoot and Golden-backed Tree-rat is indicative of processes affecting critical weight range mammals associated with the tropical savannas of northern Australia.
Recovery actions detailed in this report include:
- Develop and implement cooperative management arrangements between relevant agencies, land managers and landowners (Commonwealth, State, Territory and at the regional level).
- Convene a multiple species recovery team (collaborating across jurisdictions) to address the issue of faunal decline in northern Australia;
- Monitor both species to determine population trends;
- In the NT translocate Golden Bandicoots from Marchinbar Island to two other suitable islands and follow-up with ongoing monitoring of source and translocated populations. Investigate recent possible sightings/records of Golden-backed Tree-rat;
- Identify key threatening processes affecting critical weight range mammals in the tropical savannas generally and initiate management to ameliorate threats;
- Develop appropriate educational and communication materials targeted at the diverse range of stakeholders; and
- Inform and involve the community and all stakeholders in the recovery process
Surviving populations of Golden Bandicoot and Golden-backed Tree-rat occur in remote areas with poor accessibility. There are thus high costs associated with on-ground management and adaptive research.
This Recovery Plan has been developed as a two-species Recovery Plan. However, recovery actions detailed in this document are likely to benefit a range of other declining species that co-occur with the Golden Bandicoot and Golden-backed Tree-rat. These include Northern Quoll Dasyurus hallucatus, Scaly-tailed Possum Wyulda squamicaudata, Rock Ringtail Possum Petropseudes dahli, Kimberley Rock Rat Zyzomys woodwardi and Pale Field Rat Rattus tunneyi, Partridge Pigeon Geophaps smithii and Black Grasswren Amytornis housei.
Isoodon auratus is a small bandicoot generally weighing up to 670 g (mean adult weight 450 g), though recently two Golden Bandicoots were recorded weighing 820 g (Start unpubl. data). The Golden Bandicoot has golden-brown fur on its back and sides and stiff, quill-like guard hairs that give it a sleek appearance (McKenzie et al. 1995). It is superficially similar to the more common Northern Brown Bandicoot, Isoodon macrourus, though the Golden Bandicoot is smaller and has a flatter and more elongate head. The species are able to be distinguished unequivocally from differences in the morphology of their hair. Both species may have been marginally sympatric (Parker 1973) and have been recorded recently co-occurring in some areas (Palmer et al. in prep; Start unpubl. data). Recently, the Northern Brown Bandicoot has been reported to be prone to sudden declines in abundance, possibly linked to the occurrence of intense fires (Pardon et al. 2003).
The Golden Bandicoot was first described in 1897 from a specimen collected near Derby, Western Australia. Three bandicoot species are recognised in northern Australia; I. obesulus from Queensland, I. auratus from the Northern Territory and Western Australia and I. macrourus which occurs in all three states. For I. auratus two subspecies are recognised, Isoodon auratus barrowensis from Barrow Island and I. auratus auratus from the Kimberley and Northern Territory. However, the taxonomy of the genus Isoodon has recently been reviewed (Pope et al. 2001) based on mitochondrial DNA analysis. Pope et al. (2001) recognises two distinct lineages I. macrourus and an I. obesulus complex. This analysis does not recognise I. auratus as a separate species, but rather identifies it, including the Barrow Island subspecies, as a form of I. obesulus. This concurs with earlier work by Lyne and Mort (1981).
Mesembriomys macrurus is a large rodent (about 200 g), midway in size between two other large semi-arboreal tree-rat species occurring in northern Australia, the smaller Brush-tailed Tree-rat Conilurus penicillatus and the larger Black-footed Tree-rat Mesembriomys gouldii. Distinctive features include a long slightly brush-tipped tail that is white for at least the distal half and white feet. The type specimen was collected in 1875 near Roebourne, WA.