Desert mouse (Pseudomys desertor) - critically endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Desert Mouse Pseudomys desertor Troughton, 1932 as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Desert Mouse Pseudomys desertor Troughton, 1932 from Part 4 of Schedule 1 (Species presumed extinct) 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 Desert Mouse Pseudomys desertor Troughton, 1932  is a medium sized rodent with bright chestnut brown fur, overlaid by long, dark guard hairs that produce a spiny, unkempt appearance. Underneath is light grey - brown. The tail is brown above, sparsely furred with a scaly appearance and lighter along the sides and below. The tail is equal to or shorter than the head-body length. The upper lip and chin of the Desert Mouse is greyish-white. The eyes are large, with a distinctive ring of pale orange. The sexes are of similar size, weighing 18-28 g, measuring 75-100 mm (head and body length) with the tail 80-95 mm (Dickman 1993; Kerle  et al. 2008).

2. The Desert Mouse once ranged from the Murray-Darling region in NSW (Krefft 1866) through the Flinders Ranges (Tunbridge 1991) to the Gibson and Great Sandy Deserts, Nullarbor Plain, west coast and Bernier Island of Western Australia (Watts & Aslin 1981). Since the arrival of Europeans, the range of the Desert Mouse  has apparently contracted to the central deserts (Kerle  et al. 2008).

3. Until recently, there had been no confirmed records of the Desert Mouse in NSW since 1857. Early records of the abundance of the species in NSW are limited, although it was previously described as being present in 'large numbers' at a location between Gol Gol Creek and the Darling River (Krefft 1866).

5. The Desert Mouse is generally regarded as a semi-arid or desert-dwelling species (Murray et al. 1999; Read  et al. 1999; Kerle  et al. 2008). Most records of the Desert Mouse come from sand dune or sand plain habitats dominated by Spinifex ( Triodia spp.) (e.g. Finlayson 1941; Burbidge  et al. 1976). Habitat for the species can also include savanna woodland, shrubland, and grassland, mostly within a rainfall zone of 500-750 mm (Kutt  et al. 2004). The presence of dense groundcover of mature hummock ( Triodia spp.), tussock grasses, sedges, or shrubs is very important for the species (Kerle  et al. 2008), which is also known from samphire, chenopod and nitrebush shrublands, and from bore-drain sedgelands (Read  et al. 1999). Suitable habitat for the species appears to extend throughout the Simpson-Strzelecki Dunefields Bioregion; the far north-east corner of which occurs in NSW.

6. In NSW, the habitat along the Murray and Darling Rivers at the time of the original record (1857) would have been riparian scrub and woodland (Krefft 1866) with the closest area of Spinifex habitat located 20-25 km east or west of the Darling, north of Mildura (Dickman 1993).

7. The animal captured in Sturt National Park in 2008 was found in habitat described as: '... parallel, vegetated and thus stabilized sand dunes of up to 15 m in height which alternate with interdunal areas of varying width and character. The interdunes can be rocky plains, clay pans, swamps or a combination of the three. Vegetation is varied and patchy, depending on the substrate. Most sand dunes feature a relatively dense permanent upper shrub cover, the most common species being Acacia ligulata (Sandhill Wattle),  A. aneura (Mulga),  Dodonaea spp. (Hopbushes),  Hakea leucoptera (Needlewood) and  Atalaya hemiglauca (Whitewood). The lower shrub cover consists mainly of species from the genera  Senna,  Eremophila,  Atriplex,  Sida,  Hibiscus,  Enchylaena and  Ptilotus. After sufficient rainfall ephemeral forbs and grasses are abundant. The interdunal areas are in general devoid of trees and shrubs, except for occasional small patches. The soil of the interdunes, which is mainly clay dominated, is often covered with small rocks and supports a diverse range of herbaceous vegetation, grasses, saltbushes ( Atriplex, Rhagodia) and copperburrs ( Sclerolaena). A particular feature of many interdunes is temporary canegrass ( Glyceria ramigera) or lignum ( Muehlenbeckia florulenta) swamp communities with deep cracking clay soil.' (Kloecker, 2009).

8. The Desert Mouse is herbivorous (Watts 1972; Watts & Aslin 1981), predominately folivorous (Morton & Baynes 1985; Morton et al. 1994), although the diet may vary temporally and spatially, with the species feeding opportunistically on whatever is available. In parts of its range some dependence on seed and invertebrates has been observed (Finlayson 1941; Murray  et al. 1999; Sutherland & Dickman 1999; Read  et al. 1999). The Desert Mouse has been observed to be at least partially diurnal (Masters 1993), possibly as a result of the time-consuming and regular foraging requirements of its folivorous diet.

9. The oestrous cycle of the Desert Mouse is seven to nine days and gestation is 27-28 days. Females undergo post-partum oestrus soon after delivering a litter (which averages three). Young are weaned at three weeks and sexual maturity is reached at about 10 weeks. Births in the wild have been recorded in March, June and August to December. This fast reproductive cycle enables populations to increase dramatically. For example, a 24-fold increase in trapping success was recorded at two sites near Uluru in less than two years. Some eruptions, but no plagues, have been recorded (Masters 1993; Dickman et al. 1999: Kerle  et al. 2008).

10.  The Desert Mouse survives in small pockets of preferred habitat and expands into a wider range of habitat after suitable rain and subsequent vegetation growth. In contrast, fire leads to a decrease in Desert Mouse populations as groundcover is lost. Letnic & Dickman (2005) found that the Desert Mouse had a strong preference for vegetation that had not been burnt for a long time (> 25 years post fire), suggesting that the species required dense vegetation.

11. The distance between the original records from the Murray-Darling region and the recent record from Sturt National Park is around 570 km. Based on the only two available records for the species in NSW, the AOO is estimated to be 8 km² (based on two 2x2 km grids cells, the scale recommended for assessing area of occupancy by IUCN (2008)).

12. The early demise of the Desert Mouse in NSW has been attributed to the severe destruction of habitat as a result of overgrazing by sheep and rabbits in the late 1800s (Dickman 1993). 'Competition and grazing by the feral European Rabbit, Oryctolagus cuniculus (L.)' is listed as a Key Threatening Process under the NSW  Threatened Species Conservation Act.

13. Although the degree of threat posed by introduced predators such as European Red Foxes (Vulpes vulpes) and Feral Cats ( Felis catus) is not known, their impact on Desert Mouse populations may be significant. Such threats would exacerbate the inherent threats faced by such an apparently restricted and small population. 'Predation by the European Red Fox  Vulpes vulpes (Linnaeus, 1758)' and 'Predation by the Feral Cat  Felis catus (Linnaeus, 1758)' are listed as a Key Threatening Processes under the NSW  Threatened Species Conservation Act.

13. Populations of native rodents may be reduced by competition from the introduced House Mouse (Mus musculus) (Newsome & Corbett 1975; Morton  et al. 1994). The House Mouse is present throughout Sturt National Park and may compete with the Desert Mouse for limited resources.

14. The Desert Mouse Pseudomys desertor Troughton, 1932  is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing a very high risk of extinction in New South Wales in the near future as determined in accordance with the following criteria as prescribed by the  Threatened Species Conservation Regulation 2002:

Clause 17

The total number of mature individuals of the species is observed, estimated or inferred to be:

(a) extremely low.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 13/08/10
Exhibition period: 13/08/10 - 08/10/10

A notice of determination to provisionally list this species as a critically endangered species was gazetted on 16/10/09.

References:

Burbidge AA, McKenzie NL, Chapman A, Lampert PM (1976) The wildlife of some existing and proposed reserves in the Great Victoria and Gibson Deserts, Western Australia. Wildlife Research Bulletin, W.A. 15, 1-16.

Dickman CR (1993) 'The biology and management of native rodents of the arid zone in NSW.' NSW National Parks and Wildlife Service, Species Management Report No. 12.

Dickman CR, Mahon PS, Masters P, Gibson DF (1999) Long-term dynamics of rodent populations in arid Australia: the influence of rainfall. Wildlife Research 26, 389-403.

Finlayson HH (1941) On central Australian mammals. Part II. The Muridae. Tra nsactions of the Royal Society of South Australia 65, 215-231.

IUCN (2008) 'Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.' (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland).

Kerle JA, Kutt AS, Read JL (2008) Desert Mouse Pseudomys desertor In 'The Mammals of Australia, Third Edition.'(Eds S Van Dyke and R. Strahan) pp. 625-626 (New Holland / Queensland Museum: Brisbane)

Kloecker U (2009) Management of the terrestrial small mammal and lizard communities in the dunes system of Sturt National Park, Australia: historic and contemporary effects of pastoralism and fox predation. Unpublished PhD thesis, University of New South Wales, Australia.

Krefft G (1866) On the vertebrate animals of the lower Murray and Darling, their habits, economy, and geographical distribution. Tra ns. Phil. Soc. NSW. 1862-1865, 1-33

Kutt AS, Thurgate NY, Hannah DS (2004) Distribution and habitat of the desert mouse (Pseudomys desertor) in Queensland.  Wildlife Research 31, 129-142.

Letnic M, Dickman CR (2005) The responses of small mammals to patches regenerating after fire and rainfall in the Simpson Desert, central Australia. Austral Ecology 30, 24-39.

Masters P (1993) The effects of fire-driven succession and rainfall on small mammals in spinifex grassland at Uluru National Park, Northern Territory. Wildlife Research 20, 803-813.

Morton SR, Baynes A (1985) Small mammal assemblages in arid Australia: a reappraisal. Australian Mammalogy 8, 159-169.

Morton SR, Brown JH, Kelt DA, Reid JRW (1994) Comparisons of community structure among small mammals of North American and Australian deserts. Australian Journal of Zoology 42, 501-525.

Murray BR, Dickman CR, Watts CHS, Morton SR (1999) The dietary ecology of Australian desert rodents. Wildlife Research 26, 857-858.

Newsome AE, Corbett LK (1975) Outbreaks of rodents in semi-arid and arid Australia – causes, preventions and evolutionary consideration. In ‘Rodents in Desert Environments’ (Eds I. Prakash & PK Ghosh) pp. 117-151 (Junk: The Hague)

Read J, Copley P, Bird P (1999) The distribution, ecology and current status of Pseudomys desertor in South Australia.  Wildlife Research 26, 453-462.

Sutherland EF, Dickman CR (1999) Mechanisms of recovery after fire by rodents in the Australian environment: a review. Wildlife Research 26, 405-419.

Tunbridge D (1991) 'The Story of the Flinders Ranges Mammals.' (Kangaroo Press: Kenthurst)

Watts CHS (1972) 'Handbook of South Australian Rodents and Small Marsupials.' (Field Naturalists Society of South Australia: Adelaide.)

Watts CHS, Aslin HJ (1981) 'The Rodents of Australia.' (Angus and Robertson: Sydney)