In this thesis, I investigate the distribution and habitat associations of the Tasmanian spotted-tailed quoll (Dasyurus maculatus maculatus Tasmanian population). Habitat loss, modification and fragmentation have been posited as the greatest threat to the spotted-tailed quoll (Jones et al. 2003; Long and Nelson 2008; Mansergh 1984). The spotted-tailed quoll is the largest extant marsupial carnivore on mainland Australia, and in Tasmania is second in size only to the devil. Males can reach up to 7 kg and females 4 kg (Jones et al. 2001). The species exhibits many of the behavioural and life history traits common to extinction-prone placental predators, including relatively large body size; large home range size (Female 88 – 1, 515 ha; Male 359 – 5, 512 ha (Andrew 2005; Belcher and Darrant 2004; Claridge et al. 2005; Glen and Dickman 2006b; Nelson 2007); female territoriality and natal philopatry (Firestone 1999; Glen
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and dietary specialization (Belcher 1995; Belcher et al. 2007; Dawson et al. 2007; Glen and Dickman 2006a; Jarman et al. 2007; Jones and Barmuta 1998). These attributes theoretically limit the ability of the species to tolerate disturbance to their habitat, or to recolonize
fragmented habitats (Firestone 1999).
The spotted-tailed quoll occurs throughout eastern Australia as two subspecies: D.m
gracilis, in northern Queensland, and D. m. maculatus, found in south-eastern Australia and
Tasmania (Figure 1.1). Two populations of D. maculatus maculatus are recognised: a south- eastern mainland population, which is listed as Endangered and a Tasmanian population, which is listed as Vulnerable (EPBC 1999). A genetic study indicated that D. m.
maculatus (Tasmanian population) should be raised to the subspecies level, and that D. m.
gracilis and D. m. maculatus (south-eastern mainland population) should be treated as separate
management units of the same subspecies (Firestone 1999). To date, this has not occurred. In this thesis, spotted-tailed quoll refers to all subspecies and populations of Dasyurus maculatus; the Tasmanian spotted-tailed quoll refers to Dasyurus maculatus maculatus Tasmanian
population; the south-eastern mainland spotted-tailed quoll refers to Dasyurus maculatus
maculatus south-eastern mainland population; and the northern spotted-tailed quoll refers to
Dasyurus maculatus gracilis.
Most information on the ecology and habitat preferences of the spotted-tailed quoll derives from research on south-eastern mainland populations. At the time of European settlement, the species was distributed continuously throughout its range, including the Victorian coastal forests, and along the length of the Murray River into South Australia (Mansergh 1984).The south-eastern mainland spotted-tailed quoll has suffered an estimated 50% range contraction (Maxwell et al. 1996). The species has become extinct in South
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Australia, is uncommon west of the Great Dividing Range, and remaining populations are disjunct and fragmented. Historically, the south-eastern mainland spotted-tailed quoll has been recorded from a wide range of habitat types, including rainforest, wet and dry sclerophyll forest and woodland, coastal scrub and heath, and grassland or pasture adjacent to forested areas (Long and Nelson 2008), but is now considered to be a primarily forest dependent species that is largely restricted to wet forests (Belcher 2004; Mansergh 1984). Habitat considered critical to the survival of the spotted-tailed quoll includes large patches of forest with a high density of potential den resources and high densities of small- to medium-sized mammalian prey (Belcher and Darrant 2006b; Glen and Dickman 2006b).
Figure 1.1: Current (dark blue) and former (light blue) distribution of spotted-tailed quoll subspecies and populations in eastern Australia. Modified from (Edgar and Belcher 2008)
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At the first-order scale, the distribution of the mainland spotted-tailed quoll appears most strongly associated with extensively forested areas at high elevation on productive soils in regions of high and predictable seasonal rainfall (Burnett 2001; Catling et al. 2002; DNR 1997; Mansergh 1984; Wintle et al. 2005). At the second-order scale, quoll home ranges
preferentially include gullies, flats and escarpments and avoid mid-slopes; factors related to the availability of den sites and prey (Belcher and Darrant 2006a). However, in the same study area, a different study found that adult female spotted-tailed quolls showed no selection for topographic features (Nelson 2007). Within a contiguously forested landscape, a study of use of selectively logged and unlogged forest found that quolls preferred forest more than 50 years of age and avoided young (< 10 year old) forest (Belcher 2008). In the only study conducted in a partially forested and naturally heterogeneous landscape, quoll home range placement in the landscape was associated with forest, woodland and shrub cover and avoids open sedgeland, heathland, grassland, and cleared land (Andrew 2005). Similarly, in the same study area but at the third-order scale, the spotted-tailed quoll showed strong preference for forest and woodland, used shrubs in proportion to availability, and avoided sedgeland, heathland, grassland, and cleared land (Andrew 2005). At the fourth-order scale, the spotted-tailed quoll has been recorded using a variety of den structures including burrows, rock outcrops and piles, and tree hollows (Andrew 2005; Belcher and Darrant 2006a; Glen and Dickman 2006b; Nelson 2007; Ruibal et al. 2011). The type and frequency of den use differs among studies. Similarly, although mammals are always the most frequent prey item in the diet, the size of the prey consumed and the degree of supplementation with other taxa varies among study regions (Belcher 1995; Belcher et al. 2007; Dawson et al. 2007; Glen and Dickman 2006a; Glen et al.
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In contrast to the well-studied south-eastern mainland spotted-tailed quoll, there is little quantitative information on the ecology and habitat preferences of the Tasmanian spotted-tailed quoll. The species is widespread at low abundance across Tasmania. The only known range contractions in Tasmania are the species extirpation from King and Flinders Islands (Bass Strait), where the last confirmed sightings were in 1923 (Green and McGarvie 1971) and 1893 (Gabriel 1984) respectively. Extirpation from these islands has been attributed to land
clearance, human persecution and attacks by domestic dogs (Green and McGarvie 1971). At the first-order scale, the distribution of the Tasmanian spotted-tailed quoll has been
qualitatively associated with wet forest and scrub in the west and north-west of the state (Rounsevell et al. 1991). Similarly, a visual inspection of predicted distribution from a presence-only model indicated that the species’ core distribution occurs in northern Tasmania and coincides with areas of high productivity, as inferred by association with predictable seasonal rainfall, warm annual mean temperature and low altitude, although these relationships have not been quantified (Jones and Rose 1996). There have been few studies of higher-order resource selection by the Tasmanian spotted-tailed quoll. The only detailed study of Tasmanian spotted-tailed quoll habitat use (third-order) investigated niche partitioning and the potential for interspecific competition among the devil, spotted-tailed quoll and eastern quoll (Jones 1997; Jones and Barmuta 1998; Jones and Barmuta 2000). While that study found that the spotted- tailed quoll has higher arboreal activity than the devil and the eastern quoll and made greater use of rainforest and habitats with a structurally complex understory than the other two sympatric marsupial carnivores. However, habitat use was not quantified relative to the availability of habitats in the landscape, making assessment of preference difficult.
The dearth of information on the ecology of the Tasmanian spotted-tailed quoll is hindering its effective conservation management (Jones and Rose 1996). The Tasmanian
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spotted-tailed quoll has been isolated from mainland populations for ~13,000 years (Firestone
et al. 1999; Lambeck and Chappell 2001), and now occurs within a guild of predators and
assemblages of prey that differ significantly from mainland Australia. Most importantly, the south-eastern spotted-tailed quoll co-occurs with and probably experiences competition from the red fox (Glen and Dickman 2005; Glen and Dickman 2008), while the Tasmanian spotted- tailed quoll co-occurs with and probably experiences competition from the devil (Jones 1997; Jones and Barmuta 1998; Jones and Barmuta 2000). These differences in apex predators may result in the Tasmanian and south-eastern mainland spotted-tailed quoll exhibiting divergent habitat associations in the two regions. To date however, management of the Tasmanian spotted-tailed quoll has largely, but unavoidably, been informed by the ecology and habitat associations of the south-eastern mainland subspecies. Given the known differences in habitat use and behavior and co-occurring predators, it seems unlikely that extrapolation of for the management of the Tasmanian subspecies is valid.
The need for information on the ecology and habitat preferences of the Tasmanian spotted-tailed quoll has become more pressing in light of two recent and significant events in the Tasmanian ecosystem. First, the ongoing decline of the Tasmanian devil as a result of DFTD (Hawkins et al. 2006) is expected to result in changes to the distribution and abundance of mesopredators such as the feral cat and the spotted-tailed quoll. Second, the contemporary (~ 1999) introduction of the red fox (Sarre et al. 2013) is expected to adversely impact lower trophic levels and potentially impact directly on spotted-tailed quolls through predation or competition. The fox is currently considered rare but widespread in Tasmania (Sarre et al.
2013). The high rate of conversion of native Tasmanian forest to other land uses (Jones and Rose 1996) also the need for quantitative information on Tasmanian spotted-tailed quoll distribution and habitat preferences to apply to the development of conservation management
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