Isoodon obesulus obesulus (Southern Brown Bandicoot)
Advice to the Minister
1. Scientific name, common name (where appropriate), major taxon group
Isoodon obesulus obesulus (Southern Brown Bandicoot)
2. International/National Context
The Southern Brown Bandicoot only occurs in Australia - in New South Wales, Victoria and South Australia.
The sub-species is listed as endangered in NSW and has recently been listed as vulnerable in South Australia. It is not listed in Victoria.
3. How judged by TSSC in relation to the Environment Protection and Biodiversity Conservation Act 1999 criteria.
The Threatened Species Scientific Committee (TSSC) has assessed the Southern Brown Bandicoot to be eligible for listing as endangered under the Act. Justification for this is provided below.
Criterion 1: It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a severe reduction in numbers.
The evidence provided by the nominator and experts meet the for this criterion. The evidence provided for this criterion is based on field surveys and historical anecdotal accounts of the sub-species abundance. The evidence presented indicates that the abundance of the Southern Brown Bandicoot has severely declined and is continuing to decline. However, TSSC notes that the historical evidence is anecdotal and not verifiable, and thus introduces some uncertainty to the assessment.
The information provided by the nominator indicates that the abundance of this sub-species has suffered a severe reduction in numbers since European settlement. In the mid-1800s this sub-species was reported as being extremely common being reported as one of the 'very commonest' Australian mammals. By the 1920s the Southern Brown Bandicoot was considered to be rare. Although current numbers are difficult to estimate, compared to historical indications that this sub-species was very common (the nominator suggests that they may have numbered in the millions), today its abundance appears to be a fraction of what it was. This indicates that this sub-species has undergone a severe reduction in numbers. Further, the sub-species appears to be continuing to decline - a number of local extinctions are known to have occurred during the last decade. This is particularly evident in NSW. In addition, recent surveys provide evidence that that the sub-species has declined in distribution and abundance in south-west Victoria.
Evidence has been provided that the threats to this sub-species are continuing to operate over much of its range. These are changed fire regimes (especially frequent fuel reduction burning), predation by the Red Fox and feral Cat (both listed as Key Threatening Processes), and habitat clearing and fragmentation. The TSSC considers that unless specific actions are undertaken to ameliorate these threats where the sub-species occurs, it will continue to be threatened.
The TSSC concludes that the nomination meets this criterion for Endangered.
Criterion 2: Its geographic distribution is precarious for the survival of the species and is restricted.
The evidence is based on field surveys and historical accounts of the sub-species distribution and abundance. Historical records (including sub-fossil remains) indicate that the Southern Brown Bandicoot was widely distributed in south-east Australia. It has been recorded from the Eyre Peninsula in SA to the Hawkesbury River in NSW, on Kangaroo Island and possibly in the Murray-Darling Basin.
Concomitant with its reduction in numbers has been a contraction in its geographic distribution. It is estimated that the current extent of occurrence/area of occupancy of the Southern Brown Bandicoot is approximately 5000 km2 across seven regions. Evidence provided by the nominator and several of the experts indicate that the most severe contractions in its distribution have been in SA and NSW. In SA, it has disappeared from a number of localities/regions and remnant populations are highly fragmented. This makes these populations vulnerable to catastrophic disturbance - particularly fire - with little potential for natural recolonisation. In NSW, the sub-species is rare or extinct in most parts of its former range (it has declined over 50% or more of its previous range) and is continuing to decline.
Although a number of the experts suggested that the Southern Brown Bandicoot is not threatened in Victoria, recent surveys in the south-west of the State - where the sub-species was previously thought to be abundant - show that large amounts of suitable habitat are now unoccupied. This suggests that this sub-species is continuing to decline in Victoria.
The evidence provided by the nominator clearly indicates that the sub-species range is contracting. Estimates of the extent of occurrence of the Southern Brown Bandicoot is approximately 5000 km2 and the results from field survey etc indicate that its range is continuing to contract. The TSSC guidelines for listing as Endangered indicate the extent of occurrence must be estimated to be less than 5000 km2 and additionally, it must also be demonstrated that populations are severely fragmented or known to exist at no more than five locations, or the species/sub-species is subject to extreme fluctuations in extent of occurrence, area of occupancy, number of locations or subpopulations, or number of mature individuals. The evidence provided does not satisfy the guidelines for listing as endangered, however, TSSC considers that the Southern Brown Bandicoot is eligible for listing as vulnerable under this criterion.
The evidence presented by the nominator is assessed to meet Criterion 1 of the EPBC Regulations for listing a species/sub-species as endangered (and Criterion 2 for listing as vulnerable). Only one criterion needs to be met for a species/sub-species to be eligible for listing under a nominated category.
The threats to this sub-species are continuing to operate which casts some doubt as to its persistence in the long-term without appropriate targeted management action and conservation strategies.
The submissions from experts generally did not provide information on the conservation status of the Southern Brown Bandicoot nationally. Generally, where experts rejected the nomination it was on the basis of their understanding that Victorian populations of the sub-species are secure. However, recent results from research in Victoria challenge this assumption.
TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by,
including in the list in the Endangered category:
- Isoodon obesulus obesulus (Southern Brown Bandicoot)