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
Most information on the ecology of the Golden Bandicoot comes from a single short-term study on Marchinbar Island (Southgate et al. 1996). Like other peramelids, the Golden Bandicoot is omnivorous. From scat analyses, Southgate et al. (1996) concluded the diet on Marchinbar Island was comprised mainly of beetles and ants but included cockroaches, spiders, centipedes and plant material. On the Western Australia mainland the diet includes insects, arachnids and plant material (McKenzie et al. 1995). On Barrow Island Golden Bandicoots have been observed eating turtle eggs and reptiles (McKenzie et al. 1995)
The Golden Bandicoot appears to be a solitary species (McKenzie et al. 1995) although home ranges have some overlap (Southgate et al. 1996). On Marchinbar Island, male home ranges vary from 4.4 ha to 35 ha while female ranges varied from 1.7 ha to 12.7 ha. Sample sizes were small in the NT study and home ranges of males and females did not differ statistically. Home ranges also tended to be larger in the dry season, although again the difference between seasons was not significant. A preliminary radio tracking study by Graham (1996) in the north Kimberley indicated that Golden Bandicoots have defined areas of activity centred on nest sites.
On Marchinbar Island, Golden Bandicoots tend to be associated with low heath vegetation or shrubland comprising Grevillea sp., Asteromyrtus sp. and Acacia sp. on sand or sandstone, with ground cover vegetation dominated by Triodia spp. Similarly, on Barrow Island Golden Bandicoots were observed to seek shelter primarily in hummock grasses but also in limestone caves. On the Kimberley mainland, Golden Bandicoots have been recorded in King Leopold Sandstone with an understorey comprising Triodia sp., Cymbopogon sp., Eragrotis sp., Eriachne sp. and perennial Sorghum sp. (Palmer et al. in prep).
Some differences have been recorded between Golden Bandicoot populations at different sites. Marchinbar Island Golden Bandicoots are sexually dimorphic and larger than Golden Bandicoots on Barrow Island (Bradshaw et al.1994; Southgate et al. 1996;), but smaller than those in the Kimberley (McKenzie et al. 1975; Friend et al. 1991). Golden Bandicoots on Marchinbar Island appear to breed all year round (Southgate et al. 1996), whereas the Golden Bandicoot population on Barrow Island shows a strong seasonality with a summer peak. In the Kimberley, Golden Bandicoots have been recorded with two pouch young in May (Tony Start unpubl. data) and September (Carol Palmer unpubl. data).
There have been three published estimates for the Golden Bandicoot population on Barrow Island: 1000+ (Butler 1970), 4,000 (Short et al. 1988) and 60,000 to 80,000 (McKenzie et al. 1995). Ongoing trapping and radio tracking data for Barrow Island suggest a population of some tens of thousands (Burbidge pers comm.). On Middle Island the population has been estimated around 1,000 (Burbidge pers comm.) and Marchinbar Island 1400 (Southgate et al. 1996). Apart from Barrow Island and occasionally Middle Island there is currently no monitoring of any of the surviving Golden Bandicoot populations and no explicit conservation management undertaken.
Most information on the Golden-backed Tree-rat comes from a 10-day study at Mitchell Plateau and a short-term diet analysis study (Morton 1992). Hence, ecological information on Golden-backed Tree-rat is based on limited data. The species has never been recorded commonly in any habitat (Kerle 1987). Rather has been recorded around the ecotone between monsoon forest patches and some savanna woodland types, some distance from monsoon forest, mangroves and the boulder edges of a plateau (Kerle 1987). Friend et al. (1991) described the habitat of Golden-backed tree-rats as rainforest patches, some woodlands with fan palms (Livistona spp.) or screw palms (Pandanus spp.) and, occasionally, rugged sandstone scree. McKenzie and Kerle (1995) describe the habitats used in the Kimberley as:
- Rainforest patches on volcanic, lateritic
- Sandstone and floodplain surfaces
- Eucalypt-dominated woodlands over tussock
- Hummock grasslands on volcanic hill country
- Lateritic uplands (with Livistona palms)
- Blacksoil plains (with Pandanus trees)
- Rugged sandstone screes
- Coastal beaches adjacent to the above communities
During a fauna survey of Yampi Sound Training Area in 2002 (Palmer et al. in prep), Golden-backed Tree-rats were recorded in King Leopold Sandstone comprising a shrub layer of Erythrophleum chlorostachys, Acacia stigmatophylla, Cycas furfuracea, Petalostigma pubescens, Buchanania obovata. At this site they co-existed with the Golden Bandicoot Isoodon auratus. Presence and absence data collected during a mammal survey in the north Kimberley during 2003 suggest that Golden-backed Tree-rats were common in open woodland (Tony Start unpubl. data).
In the NT, the specimen from Deaf Adder Gorge collected in 1969 was found among Pandanus along a watercourse in sandstone country. There is no habitat information for the other two NT sites.
Diet of the Golden-backed tree-rat was assessed via scat analysis from five individuals collected during the dry season from a site that encompasses escarpment, vine thicket and savanna woodland in the Mitchell Plateau area of WA. They were found to eat predominantly fruit, flowers (Persoonia falcata, Hypoestes floribunda, Canarium australianum, Eucalyptus tetrodonta), and termites with small amounts of some grass, dicotyledon leaves, ants and beetles (Morton 1992).
The species roosts in tree hollows or occasionally in loose woven nests under the spiky crown of pandanus. In the wild, pregnant females and immatures have been found from August through to October (Kitchener et al. 1981). In captivity animals breed readily and all year round (S. Templeton pers. comm.) and it is possible that this also occurs in the wild (McKenzie and Kerle 1995) as occurs with black-footed tree-rats (B. Rankmore pers. comm.). Females have four teats and usually have two, but sometimes one or three, young.
Young are weaned at six or seven weeks and are fully-grown at four months and mature at around 12 months. A female and young have been found in a nest of woven strips of leaves in the foliage of a Pandanus tree (McKenzie and Kerle 1995).
Radio tracking of Golden-backed tree-rats at Mitchell Plateau found them to be relatively solitary with large home ranges (500 m in length) (Kerle 1992). The larger black-footed tree-rat has a home range of around 30-50 ha in open forest near Darwin (B. Rankmore pers. comm.) and the smaller brush-tailed tree-rat ranged from 0.1 to 4.4 ha in open forest on Cobourg Peninsula (Firth 2003). The patchy nature of the occurrence of fruit probably requires individuals to be reasonably mobile and the need for a large home area indicates that a patch of suitable habitat cannot support many individuals. One pair of adults and, probably, some juveniles occupy a home range (McKenzie and Kerle 1995).