National Multi-species Recovery Plan for the Carpentarian Antechinus Pseudantechinus mimulus, Butlers Dunnart Sminthopsis butleri, and Northern Hopping-mouse Notomys aquilo 2004-2008
Australian Government Department of the Environment and Heritage, 2004
Part B: Distribution and habitat
- Habitat critical to the survival of the species
- Mapping of habitat critical to the survival of the species
- Important populations
The core range of all three species appears to be in the “Top End” (the northern monsoonal tropics) of the Northern Territory, with disjunct populations in either Queensland or Western Australia. However, available information on all three species is remarkably limited, and the distributions cannot be tightly circumscribed.
The known range of all three species is largely unreserved. Butlers dunnart is known from no conservation reserve; and the northern hopping-mouse and carpentarian antechinus are each represented in only one conservation reserve (Nanaydjaka IPA and Barranyi NP respectively).
The carpentarian antechinus is known from three broadly-defined sites - Alexandria (Barkly Tablelands, NT), the Pellew Islands, and north-western Queensland (Fig. 1). The Alexandria record (from 1905) is particularly imprecise, and somewhat anomalous. As now defined, Alexandria station comprises almost entirely mitchell grasslands, with scattered bluebush swamps - environments highly unlikely to be suitable for this rock-dwelling (saxicoline) species. However, around the beginning of the twentieth century, the name Alexandria was loosely applied to a far greater area of north-eastern Northern Territory, and probably encompassed some rocky ranges, such as the Mittiebah Ranges and other rugged country in the Gulf Falls and Uplands bioregion. It is probable that the type specimen was collected in such ranges.
Figure 1. Known distribution of carpentarian antechinus. Note that the record from Alexandria (the southernmost of the NT records) has little geographic precision.
On the Pellew Islands, the carpentarian antechinus was recorded from rocky habitats on North Island (58 km2: now Barranyi National Park) in 1967 (3 individuals: Kitchener 1991); subsequently on North Island (2 specimens) and also on Centre (84 km2: 4 individuals) and South-west (95 km2: 2 individuals) Islands in 1988 by Johnson and Kerle (1991); and on North and Vanderlin (262 km2) Islands in 2003 (two captures of one individual on North Island, and four captures of three individuals on Vanderlin Island: Taylor et al. 2004). The only large island of the Pellew group on which the species has not been recorded is West Island, which has far smaller areas of rugged sandstone, which have not been adequately sampled. The species has not been recorded on several smaller sampled islands in the Pellew group (e.g. Skull (6 km2), Watson (13 km2), Black Craggy (4 km2)), but the extent of this sampling has been limited (total of 500 Elliott trap-nights: Johnson and Kerle 1991).
In Queensland, the carpentarian antechinus is known from only four recent specimens. Three of these were collected near Mt Isa in 1997 (Griffiths 1998), and one at Selwyn mine site about 140 km SE of Mt Isa in 2000 (S. Van Dyck pers. comm.). These records have not been documented. Despite recent fauna survey, it has not been recorded in apparently suitable habitat on Lawn Hill (Boodjamulla) National Park, to the north of these isolated records.
Given the uncertainties about the distribution of this species, it is difficult to estimate the extent of occurrence or area of occupancy. A minimum area of occupancy can be calculated from the size of the islands from which the species is known (taking also into account the extent of suitable habitat on these islands), plus an estimate of the extent of suitable habitat around the two known Queensland locations.
This provides a very approximate lower estimate of about 400 km2. Spanning the distance from the southernmost Queensland record to the northwest most Pellew Island record, the extent of occurrence can be estimated at approximately 16000 km2.
Knowledge of the distribution of Butlers dunnart is similarly frustratingly limited (Fig. 2). Its sole records from Western Australia are three individuals collected (hand-caught under logs and other shelter) near Kalumburu in the north Kimberley in 1965-66. It has not been recorded from the Kimberley since, despite substantial general wildlife survey effort.
Figure 2. Known distribution of Butlers dunnart.
Butlers dunnart has not been recorded from the Northern Territory mainland, again despite considerable general wildlife survey effort over the last two to three decades. However, a total of six individuals have been collected from widely-scattered locations on Bathurst Island (1693 km2) and the nearby Melville Island (5788 km2) (together, the Tiwi Islands). One of these records was from 1913, two from 1991, and three between 1999 and 2002 (Woinarski et al. 2003). Building up information on the distribution of this species is hampered by its apparently low trappability, at least using conventional trapping techniques. The five records from the Tiwi Islands since 1990 came from a wildlife survey effort there that included over 33,000 Elliott trap-nights and 3,200 pitfall trap-nights, and one of these records was of an individual hand caught under a fallen log rather than trapped.
Knowledge of the distribution of northern hopping-mouse is also limited (Fig. 3), and constrained by its apparent low trappability using conventional techniques (Woinarski et al. 1999). There has been no confirmed record from Queensland since the very imprecise “Cape York” record of the 1870s, despite some limited searches in possibly suitable sites.
Figure 3. Known distribution of northern hopping-mouse. Note that the record from Queensland cannot be attributed to any more specific location than “Cape York”.
In the Northern Territory, with one exception, the only specimen records of northern hopping-mouse are from Groote Eylandt (2260 km2). The single exception is a specimen from the Upper Caddell River area of central Arnhem Land, in 1973 (Calaby 1983). Nonetheless, there are sight records and plausible records based on the species distinctive tracks and burrow systems, from a number of other locations in and around the Arnhem Land mainland, especially in coastal sand dunes at Nanydjaka (Cape Arnhem) IPA (Woinarski et al. 1999). Records from Groote Eylandt have been widespread, but concentrated particularly on coastal dunes and sandsheets (Woinarski et al. 1999).
There is circumstantial but not substantial evidence suggesting that the current distribution of each of these three species is reduced from that of 200 years ago. For the northern hopping-mouse, there have been no records from Cape York Peninsula since the single original record more than 120 years ago, notwithstanding some extensive wildlife surveys in the general area. Likewise, for the carpentarian antechinus, there have been no records from the region around the type locality since the original collection (nearly 100 years ago), nor from elsewhere on the mainland of the Northern Territory, again despite some extensive wildlife surveys in apparently suitable habitat. Similarly, for Butlers dunnart, there have been no subsequent records from the region around the type locality (Kalumburu) since the original collections nearly 40 years ago, again despite some extensive wildlife surveys in the general area.
The reality and extent of such apparent regional loss is clouded by some possible doubts about the type localities for northern hopping-mouse and carpentarian antechinus, and the difficulty of sampling northern hopping-mouse and Butlers dunnart using conventional wildlife survey techniques.
Again, given the limited information base, it is difficult to describe habitat preferences for any of the three species with any confidence.
The habitat of the carpentarian antechinus is probably the most readily determined. All but one of the 19 known records of this species are from rocky areas. On the Pellew Islands, these comprise mostly sandstone boulders, pavements and outcrops, typically supporting a ground layer of hummock grasses Triodia spp., with a scattered low woodland or shrubland including such species as Eucalyptus aspera, E. kombolgiensis, Acacia latifolia, A. multisiliqua, Bossiaea bossiaeoides and Calytrix spp.
The historic Alexandria record of Carpentarian Antechinus may, on face value, represent a very dissimilar habitat, but there were no habitat details given for this record (Thomas 1906), and the provenance of the record is at best imprecise.
The habitat of three of the four records from north-west Queensland was described briefly by Grifffiths (1998) as comprising rocky (sandstone) ridges supporting open woodland (of Eucalyptus leucophloia, E. normantonensis, Corymbia terminalis, Atalaya hemiglauca and Acacia spp.) over hummock grassland.
The total of nine records of Butlers dunnart show no consistent tightly-defined habitat (Woinarski et al. 1996, 2003). Most are from eucalypt open forest (typically dominated by Darwin stringybark Eucalyptus tetrodonta and Darwin woollybutt E. miniata) on sandy substrates, but the records also include Melaleuca woodlands, coastal shrublands and “blacksoil sandplain ... heavily vegetated with eucalypt and grass” (Archer 1979a).
The habitat for northern hopping-mouse comprises a broad range of grassland, shrubland and open forest habitats, typically in sandy substrates in coastal or near-coastal areas (Woinarski et al. 1999). From an extensive search on Groote Eylandt (Woinarski et al. 1999), it was recorded most frequently in open shrubland dominated by either Acacia spp., Hakea arborescens or Banksia dentata, especially where these overtopped hummock grasses Triodia stenostachya and where there was high species richness of native peas (including Tephrosia, Cajanus, Boassiaea and Jacksonia species).
Given the apparently relatively broad habitat range used by each species, it is not possible to tightly define any habitat that is “critical” for the survival of any of the species.
All species are characterised by highly disjunct populations and, given the limited known occurrence of each species, it could be argued that each of these disjunct populations is important for the maintenance of these species. However, some populations may be more substantial than others, and some may be more likely to be managed successfully.
For the carpentarian antechinus, the populations on the Pellew Islands (Centre, North, South-west and Vanderlin) may be recognised as most important, because their isolation provides them some - fragile - protection against processes that may affect much of their mainland populations. The thinness of this protection is evident from the advent of cane toads and feral cats to each of these islands over the last two to three decades.
Similar arguments may be made for the special importance of island populations of Butlers dunnart (Bathurst and Melville Islands) and northern hopping-mouse (Groote Eylandt), again with the same caveats about the weakness of the assumed quarantining.