Threatened Species and threatened ecological communities
Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
Scientific name: Dasyurus maculatus maculatus
Common name: Spot-tailed Quoll, Spotted-tailed Quoll, Tiger Quoll
To date D. maculatus maculatus has comprised the southeastern mainland population and Tasmanian population. Recent genetic research is expected to result in a formal taxonomic 'split' of the Tasmanian population from the southeastern mainland population, each being attributed subspecific status. This research, utilising mtDNA and microsatellite analyses, indicates that the mainland and Tasmanian Tiger Quolls are two distinct evolutionary significant units.
The north Queensland subspecies, D. maculatus gracilis, is indicated to be genetically distinct from the southeastern mainland population using microsatellite but not mtDNA analyses and hence is not considered to be a separate evolutionary significant unit. However, the combination of microsatellite data, distinct morphology (smaller body size) and geographic isolation, is considered sufficient evidence to retain D. maculatus gracilis at the subspecies level, particularly for management purposes.
Experts consulted during the assessment process accepted this recent genetic research and the likely taxonomic outcome of three distinct subspecies. That is, D. maculatus maculatus comprising the southeastern mainland population, D. maculatus subsp. nov. comprising the Tasmanian population and D. maculatus gracilis comprising the North Queensland population.
D. maculatus maculatus southeastern mainland population (Spot-tailed Quoll, Spotted-tailed Quoll, Tiger Quoll) extends from southeastern Queensland through New South Wales to Victoria (and formerly into South Australia). D. maculatus maculatus Tasmanian population (Spot-tailed Quoll, Spotted-tailed Quoll, Tiger Quoll) is restricted to Tasmania.
D. maculatus maculatus (comprising both the southeastern mainland and Tasmanian populations) is currently listed as vulnerable under the EPBC Act. D. maculatus maculatus is considered by State authorities to be extinct in South Australia (though listed as endangered in the absence of an extinct category), threatened in Victoria and the ACT, and vulnerable in NSW and Queensland.
D. maculatus gracilis (Spotted-tailed Quoll, Yarri) is a geographically isolated population from the Wet Tropics of North Queensland. This subspecies is currently listed as endangered under the EPBC Act.
TSSC judges the species, D. maculatus maculatus southeastern mainland population (Spot-tailed Quoll, Spotted-tailed Quoll, Tiger Quoll), to be eligible for listing as endangered under the EPBC Act. When using the term 'Tiger Quoll' below, this refers only to D. maculatus maculatus southeastern mainland population (Spot-tailed Quoll, Spotted-tailed Quoll, Tiger Quoll) The justification against the criteria is as follows:
There is limited quantitative data available from which the extent or rates of decline can be determined for the Tiger Quoll across its range due to the lack of systematic and comprehensive broadscale survey data. In the absence of comprehensive broadscale surveys and long term record keeping, historical records and anecdotal information can be used to assess the extent and rates of declines experienced by the Tiger Quoll.
The historical records of former distribution and abundance, along with other anecdotal information, indicates widespread decline in population numbers of up to 50% since European settlement. Where previously the Tiger Quoll was considered common in a wide range of habitats including rainforest, open forest, woodland, coastal heathland and inland riparian forests extending from the coast to the snowline throughout southeastern Australia it is now generally regarded as rare to uncommon in most of these habitats.
The Tiger Quoll was last collected in SA in 1958 near Barmera and is considered by the relevant government authorities to be locally extinct. Its range in South Australia previously extended from the far south-east of the state along the Murray River.
In Victoria one expert describes the decline as dramatic and demonstrable, the taxon occupying barely half of its former range. Another expert provided similar information, indicating the decline in size of the Victorian population to be at least 50%.
An expert advised that surveys undertaken in southeastern Queensland during the early 1990's indicated significant range contraction within the preceding 20 years. Three areas in southeastern Queensland appear to have stable populations, however, densities are very low and the populations are highly fragmented.
Whilst some recent data from northern New South Wales indicates there is a significant population within at least one northern New South Wales National Park, elsewhere there have been declines in the extent of occurrence, area of occupancy, number of locations or subpopulations and number of mature individuals.
The area, extent and quality of habitat for Tiger Quoll continues to decline throughout all areas of the current range, with the exception of some reserves in northern New South Wales. This trend is expected to continue throughout the entire range of the southeastern mainland population. The major cause of habitat loss is land clearing. Reduction in the quality of habitat may result from logging of forests in a manner that does not provide for protection of prime Tiger Quoll habitat such as den sites. Inappropriate fire regimes that remove protective cover and food resources also degrade suitable habitat. The presence of competitive predators, particularly foxes, and probably to a lesser extent wild dogs, may also result in a significant decline in the quality of habitat.
Whilst there is little indication that foxes prey on Tiger Quolls, they are known to compete for the same prey. The regions of northern New South Wales where Tiger Quoll populations are highest have relatively low numbers of foxes in comparison to the southern regions of New South Wales and Victoria where fox numbers are higher and Tiger Quoll numbers lowest.
The susceptibility of Tiger Quoll to 1080 poison baiting has been inferred for some years from a knowledge of the animals relative susceptibility to 1080 and its role as a scavenger and consumer of carrion. Research at two study sites in southern New South Wales and one in Victoria indicated local declines in the order of 60 - 100% over the past five years, the researcher suggesting aerial baiting for wild dogs with 1080 poison to be the primary cause of these localised population declines and extinctions.
The impact of 1080 poison baiting programs on non-target animals is debated by experts and particularly the vulnerability of Tiger Quoll to 1080 poisoning.
A number of factors are known to affect the longevity of 1080 in baits and the environment generally, including temperature, moisture and bacteria, which have not been consistently or fully considered in studies addressing the potential impact of 1080 on non-target animals. In addition, 1080 poison can be deployed using several methods (surface or buried meat, vegetable or proprietary baits) depending on the target animal (dog, fox, pig, rabbit) and State government controls and this may affect the impact of the poison on non-target animals. There are several ongoing research project specifically aimed at acquiring further information on the susceptibility of Tiger Quolls to 1080 poisoning as a result of various methods utilised to control feral pest animals.
The threats to the southeastern mainland Tiger Quoll population continue to operate at varied intensities throughout its range and both the historic and future impact of the identified threats is difficult to quantify. Habitat loss and degradation, competition with introduced predators and inappropriate 1080 poison baiting programs may all play a significant role in localised population declines to the extent that local populations may decline rapidly to extinction. This is particularly the case where populations are fragmented and numbers already low. The magnitude of the declines has resulted in population numbers that are low throughout all areas of the current range with the exception of northern NSW and there are no indications of the observed declines being slowed or reversed.
Therefore, the species is eligible for listing as endangered under this criterion.
The geographic distribution of the southeastern mainland Tiger Quoll population is contracting and populations are becoming increasingly fragmented. Declines in the extent of occurrence, area of occupancy, number of locations or subpopulations, number of mature individuals and the area, extent and quality of habitat have been observed and are projected to continue. The major factors in observed and projected declines are habitat loss and degradation and competition with introduced predators. Inappropriate 1080 poison baiting programs may also be contributing to the decline in numbers. The southeastern mainland population is, however, widely distributed in southeastern Queensland, eastern New South Wales and Victoria. Consequently neither the extent of occurrence nor area of occupancy are so limited as to be considered precarious (ie. less than 20,000 km2 or less than 2000 km2 respectively) for its survival.
Therefore, the species is not eligible for listing under this criterion.
Quantitative data on the total population size is unavailable due to the cryptic nature of the animal and lack of broadscale surveys.
Estimates of population density (including juveniles) have been obtained from several study sites, in most cases selected for the relatively high frequency of occurrence of Tiger Quolls. In Werrikimbe National Park (northern New South Wales), 40 individual Tiger Quoll have been trapped along a 40 km stretch of road, thought to represent an area of approximately 240 km2, over 12 months during 2000-2001. In Tallaganda State Forest (southern New South Wales), in an area of 43 km2, six individuals were recorded in 1997, seven in 1998, eight in 1999 and one in 2000. In Badja State Forest (southern New South Wales), in an area of 60 km2, 11 individuals were recorded in 1996 and zero in 2000 and 2001. A transect survey encompassing parts of both Tallaganda and Badja State Forests, with an estimated catchment area of 240 km2, recorded 23 individuals in 1999. At Suggan Buggan (north-eastern Victoria) in an area of 43 km2 six individuals were recorded in 1994, four in 1995 and two in 1996. At Mt Eccles (south-western Victoria) a hairtube survey obtained 4 records from three adjoining 1 km2 survey blocks in a total survey area of 33 km2. At the Otway Ranges (southern Victoria) a survey in 1999 obtained four records from an area of 1200 km2. A survey in south-eastern Qld at eight sites recorded six Tiger Quoll from a single site over an eight month period during 1993. At study sites in southern New South Wales and Victoria where Tiger Quolls were frequently encountered, estimates of the population density ranged from one per 5 km2 to one per 10 km2. In northern NSW the density appears to be higher at approximately one per 4.5 km2.
Whilst historically, the Tiger Quoll was considered common, it is now considered rare or uncommon throughout the southeast mainland, except in South Australia where it is considered extinct and in some reserves in northeastern New South Wales where it is considered common. Noting the reductions in range and quality of habitat through all areas of its range (with the exception of northeast New South Wales) and the naturally low density of top-order predators, the total population size is considered low. Expert advice supports this assessment and while expert estimates of the total population size vary it is likely that the total number of mature adults is greater than 2,000 and less than 10,000.
Declines in the extent of occurrence, area of occupancy, number of locations or subpopulations, number of mature individuals and the area, extent and quality of habitat have been observed and are projected to continue. The major factors in observed and projected declines are habitat loss and degradation and competition with introduced predators inappropriate application of 1080 poison baits may also be contributing to declines
One or more of the identified threats have been observed at localised sites to significantly reduce population numbers, in some cases resulting in localised extinction. The threats continue to operate at varied intensities, throughout the range of the southeastern mainland population. Consequently, it is likely that there could be declines in numbers, area and extent of occupancy in the vicinity of 20% in the immediate future.
Therefore, the species is eligible for listing as vulnerable under this criterion.
The total population size is unknown due to the cryptic nature of the animal and lack of broadscale surveys.
Therefore, the species is not eligible for listing under this criterion.
There is no quantitative data available against this criterion.
Therefore, the species is not eligible for listing as under this criterion.
Despite the lack of systematic and comprehensive broadscale survey data and hence quantitative data for rates or extent of decline across the range of the D. maculatus maculatus southeastern mainland population, contemporary research data indicates significant declines, including localised extinction, continue to threaten its survival. The key threats to the D. maculatus maculatus southeastern mainland population have been identified as habitat loss and degradation and competition with introduced predators. In addition, inappropriate application of 1080 poison baits may also be contributing to declines. In conjunction with significant historic declines, low population numbers and ongoing threats, the available evidence suggests that numbers will continue to decline at a high rate along with the number of locations or subpopulations, extent of occurrence, area of occupancy and quality of habitat.
The species is eligible for listing as endangered under criterion 1.
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