Smoky mouse (Pseudomys fumeus) - critically endangered species listing
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Smoky Mouse Pseudomys fumeus Brazenor, 1934 as a critically endangered species in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to the Smoky Mouse Pseudomys fumeus Brazenor, 1934 from Part 1 of Schedule 1 (Endangered species) of the Act. Listing of Critically Endangered species is provided for by Part 2 of the Act.
NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Smoky Mouse Pseudomys fumeus Brazenor, 1934 is a small native rodent about 2-3 times the size of the introduced House Mouse, Mus musculus. The total length of the species ranges from 180 mm to 250 mm, with the tail accounting for more than half of this. The ears are 18-22 mm long and the hind feet 25-29 mm long. Adult weight varies from 25 g to 86 g. The species’ fur is pale smoky grey or black above and whitish or grey below. The tail is narrow, flexible, sparsely furred and distinctively bicoloured; white to pale pinkish grey below with a dark narrow stripe above. The ears and feet are pinkish, with sparse white hair (Menkhorst & Broome 2007; Ford 2008).
2. The Smoky Mouse is endemic to mainland south-eastern Australia, where it occurs in Victoria, NSW and the ACT. Recent records of the Smoky Mouse in NSW come from the far south coast hinterland and the Australian Alps. Specimens have been recorded from three locations; the Nullica area, which includes Nullica State Forest and South East Forest National Park (Jurskis et al. 1997; Ford 1998b; Ford et al. 2003; FNSW & DECC 2008), Yarrangobilly Caves, in Kosciuszko National Park (Ford 1998b) and Bondo State Forest, north of Kosciuszko National Park (S. Banks unpub. data). Hair samples have been collected from a further four sites; Mt Poole in Nungatta State Forest (Broome & McDonald 1997); Ingebyra State Forest (Menkhorst & Broome 2008) and two other sites in Kosciuszko National Park (Broome & McDonald 1997; Broome unpub. data).
3. Despite considerable survey effort across the known NSW range for the species, the Nullica area is the only site where the Smoky Mouse is currently found (L. Broome pers. comm. September 2009).
4. Sub-fossil remains of the Smoky Mouse indicate that the species was once more widespread in Australia, with several cave deposits in far western Victoria, eastern Victoria, south-eastern NSW and as far north as Jenolan and Wombeyan Caves (Drummond 1963; Hall 1975; Menkhorst & Seebeck 1981; Hope 1982). This broader distribution of sub-fossil records indicates that the range of the Smoky Mouse has contracted significantly (ACT Government 1999).
5. Across its current range, the Smoky Mouse occurs in a variety of vegetation communities, ranging from coastal heath to dry ridgeline forest, sub-alpine heath and, occasionally, wetter gullies (Menkhorst & Seebeck 1981). Surveys undertaken in eastern Victoria and south-eastern NSW (e.g. Broome & McDonald 1997; Jurskis et al. 1997; Ford 1998a, b) indicate that the species prefers ridge-top sclerophyll forest (Cockburn 1995) with a floristically diverse shrub layer dominated by species from the Ericaceae and Fabaceae families (Menkhorst & Seebeck 1981; Cockburn 1981a; Ford 1998a, b; Ford et al. 2003). Ground cover is also likely to be important for the Smoky Mouse and can be dense low vegetation or grass tussocks, rocks and logs which provide potential shelter sites. Soil conditions also need to be suitable for burrowing and growth of hypogeal (underground, truffle-like) fungi (Menkhorst & Broome 2007). The vegetation at capture sites of the Smoky Mouse varies widely in age post-fire and specimens have been trapped in recently disturbed sites (FNSW & DECC 2008).
6. The Smoky Mouse exists in small discrete colonies based around patches of heath (Cockburn 1981a; 1981b; Ford 1998a; Ford et al. 2003). They shelter in small groups, sometimes consisting of one male and up to five breeding females, in a large, complex burrow system that can be up to 10 m2 and more than 25 m in length, with multiple nesting chambers (Woods & Ford 2000; Ford et al. 2003; Menkhorst & Broome 2008). Numbers can decline rapidly during autumn mainly due to the loss of young recruits as food resources decrease. Cockburn (1981b) found that only those individuals in optimal habitat were likely to survive the winter.
7. Breeding in Smoky Mouse has been recorded from late August to April with an average gestation length of 30 days (Woods & Ford 2000; Ford et al. 2003; Menkhorst & Broome 2007). Litter size is usually three to four and females have been observed to produce one or two litters in a season (Cockburn 1981b; Woods & Ford 2000; Menkhorst & Broome 2007). The Smoky Mouse breeds at age one (Cockburn 1981b), and only females occupying the best quality habitat survive to breed in a second year (Cockburn 1981b). 'Generation Length' (IUCN 2008) is estimated to be 1.5 years.
8. Although primarily herbivorous, the diet of the Smoky Mouse varies seasonally according to food availability and energy demands (Menkhorst & Broome 2007). In winter and early spring the main diet consists of hypogeal fungi, with some seed and soil invertebrates, including arthropods (Cockburn 1981a). In late spring-early summer the species forages for flowers, seeds and Bogong Moths (Agrostis infusa) and from summer to autumn, seeds predominate in the diet (Cockburn 1981a; Ford 1998b).
9. A characteristic of Smoky Mouse colonies is their ephemeral nature, both spatially and temporally. There are numerous examples of unsuccessful attempts to locate the species at sites where it had been found only a few months previously (e.g. Lawrence 1986; Lintermans 1988; Ford et al. 2003; Menkhorst & Broome 2007). It is not understood why populations disappear so rapidly from trapping sites, but as several populations have been confirmed as breeding simultaneously, migration away from and movement between trapping sites is considered unlikely (Ford & Broome 2005).
10. Of the seven sites in NSW where the Smoky Mouse has either been sighted alive or where evidence of the species has been recorded, live specimens have only been caught from one area (Nullica) since 2001. The population of Smoky Mouse around Nullica appears to have declined in recent years (Ford 1998b; Ford et al. 2003). During a six month study conducted during 1997/98, 32 individuals were captured and the Smoky Mouse was considered one of the most commonly trapped rodents in the area (Ford et al. 2003). Since then, numbers have apparently declined with no individuals being caught from 2005-2007. Since 2007, numbers have increased slightly, but still less than 10 individuals have been recorded in each year. The recent captures are likely to reflect an increase in rainfall, which probably leads to an increase in hypogeal fungi (L. Broome pers. comm., September 2009).
11. It is difficult to estimate the population size of the Smoky Mouse due to its ephemeral nature, however, based on current trapping surveys, the total number of mature individuals in NSW may be less than 50 (L. Broome pers. comm., Sept 2009). However further survey of suitable habitat may uncover additional populations.
12. Predation by Feral Cats Felis catus and the European Red Fox Vulpes vulpes have been implicated in the decline of the Smoky Mouse throughout its range (Menkhorst & Broome 2007). Feral Cats were thought responsible for three dead specimens of the Smoky Mouse discovered in Kosciuszko National Park (Ford 1998b) and predation by cats was directly linked to a population crash at a site in the Nullica area in 1997 (Ford et al. 2003). Smoky Mouse remains have also been detected in fox and wild dog scats (May & Norton 1995; Broome & McDonald 1997; DECCW Atlas records). 'Predation by the Feral Cat Felis catus' and 'Predation by the European Red Fox Vulpes vulpes' are listed as Key Threatening Processes under the NSW Threatened Species Conservation Act 1995.
13. Inappropriate fire regimes may affect the quality and viability of Smoky Mouse habitat. High fire frequency could potentially simplify heath understorey in dry forests towards early successional species, depleting floristic diversity, encouraging predators (Catling 1986; 1991) and potentially decreasing the abundance and diversity of hypogeal fungi (Claridge & Cork 1997; FNSW & DECC 2008). Yarrangobilly Caves and much of the known distribution of the Smoky Mouse in the New South Wales Alps was severely burnt by wildfires in 2003 (Ford & Broome 2005). Surveys in this area conducted after the fire failed to locate the species (L. Broome pers. comm. September 2009). 'High frequency fire resulting in the disruption of life cycle processes in plants and animals and loss of vegetation structure and composition' is listed as a Key Threatening Process under the NSW Threatened Species Conservation Act 1995.
14. Approximately 25% of the Smoky Mouse habitat in the Nullica State Forest has been logged, including 33% of what is considered to be key habitat for the species. In total, 20% of the total area of occurrence of the Smoky Mouse within National Parks and State Forests in NSW has been logged since 1990. Although the species may be able to tolerate and survive some logging disturbance in the short-term (Jurskis et al. 1997; Ford et al. 2003; Ford & Broome 2005), the degree of logging disturbance that will permit long-term survival is unknown.
15. Roads and tracks associated with timber harvesting or fire control may also impact on Smoky Mouse populations by fragmenting patches of suitable habitat and by interrupting movement patterns (Andrews 1990; Goosem 2001). Roads and tracks are also likely to facilitate movement of foxes (Catling & Burt 1995) and Feral Cats, creating further predator pressure on local populations of the Smoky Mouse. Local populations of the Smoky Mouse are also inherently at risk of extinction due to their small size.
16. The plant pathogen Phytophthora cinnamomi has the potential to have a very large impact on populations of the Smoky Mouse (Menkhorst & Broome 2007). Many of the plant families and genera characteristic of Smoky Mouse habitat are particularly susceptible to P. cinnamomi, including Ericaceae, Fabaceae, Dilleniaceae, Tremandraceae and Xanthorrhoeaceae (McDougall & Summerell 2003). In the Nullica area P. cinnamomi is present and there is evidence that it is causing the death of Xanthorrhoea species and heathy shrubs in Smoky Mouse habitat, including some key monitoring sites (FNSW & DECC 2008). 'Infection of native plants by Phytophthora cinnamomi' is listed as a Key Threatening Process under the NSW Threatened Species Conservation Act 1995.
17. Although there is only one site where live specimens of the Smoky Mouse have been caught in recent years, it is difficult to say with certainty that the species does not persist at other previously known areas, albeit in very small numbers. The Area of Occupancy (IUCN 2008) for the Smoky Mouse across NSW is therefore conservatively estimated as less than 92 km2, based on the total number of occupied 2 x 2 km grid squares across all sites from which live specimens, or evidence of the species have been collected. This is the spatial scale recommended by the IUCN (2008) for calculating geographical distributions. These occurrences are scattered over a wide range, giving an estimated Extent of Occurrence (IUCN 2008) of less than 13 550 km2 (based on the distance between the most widely separated occurrences and the linear alignment of locations; the method recommended by IUCN 2008).
18. Extant populations of the Smoky Mouse are considered to be severely fragmented, with limited opportunity for gene flow between sites of confirmed or previously known occurrence. For example, Nullica and Mt Poole are approximately 40 km apart and other sites within NSW to the north and the west are between 120 and 200 km from Nullica.
19. The Smoky Mouse Pseudomys fumeus Brazenor, 1934 is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future as determined in accordance with the following criteria as prescribed by the Threatened Species Conservation Regulation 2002:
Clause 16
The estimated total number of mature individuals of the species is:
(a) | very low, |
and either:
(d) | a projected or continuing decline is observed, estimated or inferred in: | |
(i) | an index of abundance appropriate to the taxon, or | |
(ii) | geographic distribution, habitat quality or diversity, or genetic diversity; or | |
(e) | the following conditions apply: | |
(i) | the population or habitat is observed or inferred to be severely fragmented; | |
(ii) | all or nearly all mature individuals are observed or inferred to occur within a small number of populations or locations. | |
Dr Richard Major
Chairperson
Scientific Committee
Proposed Gazettal Date: 24/09/10
Exhibition Period: 24/09/10 - 19/11/10
References:
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