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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Australian Terrestrial Biodiversity Assessment 2002
Paul Sattler and Colin Creighton
National Land and Water Resources Audit, 2002
ISBN 0 642 3713
6. Mammals
Summary
Tammar Wallaby, Macropus eugenii.
Photo: D. Watts
Australia has 305 indigenous terrestrial mammal species (excluding those found in the External Territories) and 26 exotic species. Of the 305 indigenous species, 85% are endemic to Australia.
There has been a massive contraction in the geographical ranges and species composition of Australia's indigenous mammal fauna over the last 100+ years. One third of the world's extinct mammals since 1600 AD are Australian. Such a record is unparalleled in any other component of Australia's biodiversity, or anywhere else in the world.
Significant decline is still occurring. The continuing contraction in the distribution of species means that further extinctions are likely.
Twenty-two species of mammals are extinct in Australia, with eight other species remaining only on islands. A further two, possibly three, species have become extinct on Christmas Island, an Australian External Territory: Rattus macleari, Rattus nativitatis and possibly the shrew Crocidura attenuata.
The key findings are:
- mammals persist best in high rainfall bioregions;
- arid and semi-arid areas have lost a high proportion of their mammals;
- critical weight range mammals are most susceptible to extinction; and
- bats—the only mammals that can fly—demonstrate lower levels of decline and extinction.
Several new insights have also been identified through this study. In particular, the belief that the Top End of the Northern Territory and the North Kimberley are refugia for a range of mammal species appears to be misleading, as these regions are also experiencing declines in mammal numbers.
The study identified which biroregions are most important for the conservation of species that have disappeared from most of their ranges. These are Carnarvon, Avon Wheatbelt, Jarrah Forest and Esperance Plains in Western Australia, Stony Plains in South Australia, and Channel Country, which straddles the South Australia - Queensland border. Some species now rely on a single bioregion for their persistence.
Cape York is a key region as it is relatively undeveloped and still retains a large number of species that have limited distributions.
The recent appearance of the European Red Fox in Tasmania is cause for major concern, as it could precipitate the extinction of species that are already in decline such as the Eastern Quoll, Eastern Barred Bandicoot, and the Tasmanian Bettong. Exotic Polynesian Rats and Ferrets are also considered to be at high risk of increasing their range to the detriment of the indigenous fauna.
While mammal decline is being addressed in some parts of Australia through detailed species and fauna recovery programs, many areas and many species are not the subject of effective recovery programs. Detailed survey data are lacking for several bioregions. Unless Australia provides more resources to mammal conservation and is willing to address the continuing extensive changes to mammal habitat, species will continue to be lost.
Introduction
The purpose of the mammal component of the Biodiversity Assessment was to review the trend in condition of a key part of Australia's biodiversity where dramatic change has occurred within a relatively short time frame. This may provide an insight into the likely future impact of current environmental modification on other taxa where there may be a longer extinction lag.
The project developed a national database showing the original distribution of Australia's terrestrial mammals and their current status by bioregion, and analysed the database to reveal centres of endemism and patterns of decline. An attempt was made to correlate the patterns of mammal decline with environmental changes and with life history and behavioural attributes of mammals.
The database compiled for this study was contributed by State and Territory conservation agencies. It incorporates all information available including Museum data and information gained from extensive sub-fossil research.
The Assessment
The first stage of the assessment was to list all Australian terrestrial mammal species. The list included well-recognised undescribed species but excluded endemic species found on the External Territories and oceanic islands and marine species. A conservation status was allocated to each species for each bioregion based on where it occurred at the time of European settlement and its change in extent and population (Box 6.1). This information was used to calculate a number of indices related to number of endemic species (both past and present) and regional patterns of decline and extinction of terrestrial mammals. Four independent variables were used to analyse the patterns of decline: landscape stress (NLWRA 2001a) which is a measure of environmental change; long-term average rainfall; the mean adult body weight of species and the ability of indigenous mammal species to fly. Detailed information on the methods used can be found in the project report that underpins this chapter and is available on-line from the Australian Natural Resources Atlas.
Box 6.1 Conservation status allocated to each species for each bioregion it occurred in at European settlement
- Persists in greater than 50% of former range within region;
- Declined by 50-90% of former range within region;
- Severe decline: extant within region but declined by greater than 90% of former range within region (range equates to 'extent of occurrence', not 'area of occupancy' (IUCN 2000);
- Extinct in region: when there is no reasonable doubt that the last individual has died;
- Range naturally expanded/ing into region during historical times;
- Persists in greater than 50% of former range within region, translocated population(s) established for greater than 10 years;
- Declined, translocated population(s) established;
- Severe decline, translocated population(s) established;
- Extinct in the past, translocated population(s) established.
A species was shown as translocated if it has been extablished in the wild for more than 10 years and is self-maintaining. (Self-maintaining includes conservation dependent populations where the species may disappear unless conservation management, (e.g. fox control, fencing), is maintained.
Plains Mouse, Pseudomys australis.
Photo: H & J Beste
Squirrel Glider, Petaurus norfolcensis.
Photo: QEPA
Findings
Number of Species
Australia's 331 mammal species includes 305 indigenous and 26 exotic species. Given the ongoing revision of the taxonomy of Australian mammals, it is likely that new species will be identified in the future.
Australian Endemism
Eighty-five per cent of the species in this study (258 of 305) are endemic to Australia. The remaining 47 species also occur in Papua New Guinea and/or nearby islands. Thirty of the species shared between Australia and islands to its north are bats.
Richness of the Original Faunas
Figure 6.1: Species richness of the original mammal fauna in each bioregion.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
Figure 6.1 shows the relative richness of Australia's regional mammal faunas as best we can re-construct them from a combination of modern, historical and recent sub-fossil specimens. The mesic regions of northern and eastern Australia had the faunas with the highest number of species, while the regions with the lowest number of species fell into two classes:
- Cool temperate regions of Tasmania and the south-western tip (Warren bioregion) of Western Australia that are the smallest in area of Australia's bioregions, but also lack the rich array of small dasyurids and rodents found in semiarid, arid and tropical Australia.
- Remote and sparsely-settled regions in which only localised mammal surveys have been undertaken, and from which museums have received relatively few opportunistic records (Gulf Plains, Desert Uplands and Mulga Lands of Queensland and Yalgoo of Western Australia, in particular). Caution is needed in interpreting the analysis outputs related to these four bioregions. For example, current records indicate that the Desert Uplands is at least 30% poorer than similar bioregions around it, with only 25 known species.
Introduced Mammals
Twenty-six exotic species of mammals have established in the wild (Table 6.1). Dingoes (Canis lupus dingo), descendents of Asian wolves, are treated as an exotic species, having been introduced to Australia by humans about 4000 years ago. They have established in all 76 mainland bioregions. Some species are widespread, with Felis catus (Cat) occurring in all 85 bioregions, Mus domesticus (House Mouse) occurring in 76 bioregions, and Vulpes vulpes (European Red Fox) occurring in 60 bioregions. Others are highly restricted, for example Funambulus pennantii (Five-striped Palm Squirrel) occurs only in the Perth Metropolitan area near Perth Zoo. It previously occurred in Sydney suburbs near Taronga Park Zoo. Rattus exulans (Polynesian Rat) has been recorded only on islands of Australia's northern coastline (two bioregions), while Mustela putorius (Polecat; domesticated individuals are known as Ferrets) have established in four bioregions. Polynesian Rats and Polecats are at high risk of increasing their range to the detriment of the indigenous fauna. Vulpes vulpes (European Red Fox) is absent from tropical coastal and near-coastal regions of Australia and until very recently from Tasmania. These regions show the lowest levels of attrition of mammals.
Translocations
Nine species that were either regionally extinct or had very low numbers have been successfully translocated into 12 bioregions (Table 6.2). Many additional translocations have taken place in recent years (eg. Morris 2000) but have been established for less than 10 years.
Golden Bandicoot, Isoodon auratus.
Photo: Pavel German
Expanding Range
The range of three species was found to have naturally expanded into new regions during historical times: Perameles gunnii (Eastern Barred Bandicoot) has expanded into three Tasmanian bioregions (Ben Lomond, King and Tasmanian Southern Ranges), Pteropus poliocephalus (Grey-headed Flying Fox) has expanded into the Victorian South East Coastal Plain and Rhinolophus megaphyllus (Eastern Horseshoe Bat) has established in the Victorian Midlands bioregion. The expansion of the Eastern Barred Bandicoot can be attributed to land clearance opening up previously unsuitable habitat.
Faunal Change
Some species have contracted from more than 90% of the bioregions that they originally occupied (Figure 6.2). Regions whose faunas have been most susceptible to changes include: the arid and semiarid regions of Northern Territory, South and Western Australia, particularly the desert and cereal crop regions.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
| SPECIES | NO. OF BIOREGIONS |
|---|---|
| RODENTIA | |
| Muridae | |
| Mus domesticus (House Mouse) | 76 |
| Rattus exulans (Polynesian Rat) | 2 |
| Rattus norvegicus (Brown Rat) | 32 |
| Rattus rattus (Black Rat, Ship Rat) | 58 |
| Sciuridae | |
| Funambulus pennantii (Five-striped Palm Squirrel) | 1 |
| CARNIVORA | |
| Canidae | |
| Canis lupus dingo (Dingo) | 76 |
| Vulpes vulpes (Red Fox) | 60 |
| Felidae | |
| Felis catus (Cat) | 85 |
| Mustelidae | |
| Mustela putorius furo (Ferret, Polecat) | 4 |
| LAGOMORPHA | |
| Leporidae | |
| Oryctolagus cuniculus (European Rabbit) | 67 |
| Lepus capensis (Brown Hare) | 31 |
| PERISSODACTYLA | |
| Equidae | |
| Equus caballus (Brumby, Horse) | 59 |
| Equus asinus (Donkey) | 40 |
| ARTIODACTYLA | |
| Suidae | |
| Sus scrofa (Pig) | 51 |
| Camelidae | |
| Camelus dromedarius (Dromedary, Camel) | 21 |
| Bovidae | |
| Bubalis bubalis (Water Buffalo) | 13 |
| Bos javanicus (Bali Banteng) | 1 |
| Bos taurus (European Cattle) | 63 |
| Capra hircus (Goat) | 44 |
| Ovis aries (Sheep) | 48 |
| Cervidae | |
| Dama dama (Fallow Deer) | 21 |
| Cervus elaphus (Red Deer) | 16 |
| Cervus timorensis (Rusa Deer) | 15 |
| Cervus unicolor (Sambar) | 19 |
| Axis axis (Chital) | 2 |
| Axis porcinus (Hog Deer) | 3 |
| SPECIES | BIOREGION WHERE TRANSLOCATED POPULATION(S) ESTABLISHED |
FORMER STATUS IN REGION |
|---|---|---|
| Mrymecobius fasciatus (Numbat) | Jarrah Forest | extinct |
| Avon Wheatbelt | declined | |
| Isoodon obesulus (Southern Brown Bandicoot) | Avon Wheatbelt | severe decline |
| Macrotis lagotis (Bilby) Eyre | Yorke Block | extinct |
| Phascolarctos cinereus (Koala) | Naracoorte Coastal Plain | extinct |
| South East Coastal Plain | severe decline | |
| South East Corner severe | decline | |
| Victorian Midlands | extinct | |
| Victorian Volcanic Plain | extinct | |
| Pseudocheirus occidentalis (Western Ringtail Possum) | Swan Coastal Plain severe | decline |
| Bettongia penicillata (Brush-tailed Bettong) | Eyre Yorke Block | extinct |
| Jarrah Forest | persists | |
| Petrogale lateralis (Black-footed Rock-wallaby) | Avon Wheatbelt | severe decline |
| Petrogale rothschildi (Rothschild's Rock-wallaby) | Pilbara | persists |
| Leporillus conditor (Wopilkara, Greater Stick-nest Rat) | Eyre Yorke Block severe | decline |
| Geraldton Sandplains | extinct |
Proserpine Rock Wallaby Petrogale persephone
Photo: P.M. Johnson
The species with major range contractions are hare wallabies, nail-tailed wallabies, rat kangaroos, Numbat, bandicoots and large rodents (Notomys, Leporillus, large Pseudomys and Zyzomys). All species had ranges centred on the continent's arid and semi-arid zone.
In general, bats and small mammals (<35g mean adult body weight) show little range contraction. High range contractions among species from Australia's medium to high rainfall bioregions were confined to Conilurus albipes (Paroo, White-footed Tree-rat), Macropus greyi (Toolache Wallaby), Potorous platyops (Broad-faced Potoroo) and the Basalt Plains Mouse, all of which had geographic ranges confined to regions that are now intensively settled or virtually cleared. Thylacinus cynocephalus (Thylacine) may be a special case, as it was a relatively large animal that became extinct in Tasmania, where it was selectively hunted (Smith 1981).
Figure 6.3 provides a comparison of levels of endemism at the time of European settlement and was derived by assessing the number of species within each region's original mammal fauna that were confined to five or less of Australia's 85 bioregions. The highest number of species in this category were found in Cape York Peninsula and Wet Tropics. Many of these species have distributions that also occur outside of Australia, while other species show little or no range-contraction at region-to-region scales over the last 200 years.
To refine this view of regional values, a map showing bioregions with high relictual fauna value was derived (Figure 6.4). This identifies bioregions that have retained the greatest number of species that now occur in only a few regions (excluding translocated species). The bioregions with extant populations of the greatest number of these species (>5 species) are Carnarvon Basin, Avon Wheatbelt, Jarrah Forest and Esperance Plains in Western Australia, Stony Plains in South Australia, and the Channel Country, which straddles the South Australia - Queensland border. Ignoring translocations, some species rely entirely on a single bioregion for their persistence. These are:
- Carnarvon Basin (Western Australia): Lagostrophus fasciatus, Lagorchestes hirsutus, Bettongia lesueur, Perameles bougainville and Pseudomys fieldi(Barrow, Bernier and Dorre Islands);
- Jarrah Forest (Western Australia): Potorous gilbertii and Myrmecobius fasciatus;
- The Gulf Coastal Plain (Northern Territory) retains Pseudantechinus mimulus (Sir Edward Pellew Islands);
- MacDonnell Ranges (Northern Territory): Zyzomys pedunculatus;
- Eyre Yorke Block (South Australia) Leporillus conditor (Franklin Island).
- Brigalow Belt North (Queensland): Lasiorhinus krefftii and Onychogalea fraenata
- Wet Tropics (Queensland): Bettongia tropica.
Rufous Hare Wallaby, Lagorchestes hirsutus dorreae.
Photo: B. & B.Wells
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
Eastern barred-Bandicoot, Perameles gunnii.
Photo: H. & A.Wapstra
Islands are an important refuge for species that have contracted in their range (Burbidge 1999). The island of Tasmania (comprising nine small bioregions) is an important refuge for several species that have contracted in their range, including Dasyurus viverrinus (Eastern Quoll), Bettongia gaimardi (Tasmanian Bettong) and Perameles gunnii (Eastern Barred Bandicoot). The recent appearance of the European Red Fox in Tasmania is cause for concern as these species are susceptible to predation by the fox because of their body size.
Other species that have shown very significant contractions in their range, such as Parantechinus apicalis (Dibbler), Bettongia penicillata (Brushtailed Bettong), Notomys cervinus (Ooarri, Fawn Hopping-mouse) and Rattus sp. (Central Queensland), now persist in only two bioregions.
The pattern of mammal attrition resembles rainfall patterns with higher levels of mammal decline in bioregions with lower annual rainfall (Figure 6.5). One visible modifier of this pattern is that the cereal-growing regions show higher-than-expected attrition indices.
Rainfall is closely related to the patterns of attrition in Australia's mammal fauna, with body weight, ability to fly and landscape stress (NLWRA 2001a) as significant interacting factors (Figure 6.6). 'Stress' in this context represents the cumulative effect of pastoral-use, changed fire regimes, vegetation clearance for cereal crops and related processes that impact on the soil A-horizon, coverage of indigenous plants, feral herbivores and predators, invasive weeds and salinity.
Bilby, Macrotis lagotis.
Photo: QEPA
Stress explained around 12% of the variation in the data while 15% was explained by the body weights of the species comprising each region's fauna, and a further 15% was explained by the proportion of flying species in each region's fauna. Regional rainfall (herein used as an approximate surrogate of regional productivity) explained 39% of the variation. About 19% of the variation on the data was unexplained by the analyses.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
While body weight is considered to be a fundamental determinant of a species' ecology (e.g. Peters 1983), the inclusion of variables representing other biological characteristics would probably have accounted for more of the variation in the data.
In this study significant variation was accounted for by separating species into flying and non-flying foraging strategies. In an earlier study, significant variation was accounted for by separating species on whether they were confined to the ground's surface or not (e.g. arboreal, burrowing, rockpile-dweller), and whether they were carnivores/insectivores or omnivores/ herbivores (Burbidge & McKenzie 1989).
The patterns of attrition for six different mammal taxa show some similarities (Figure 6.7). All taxa have persisted better on the high-rainfall margin of their former geographical ranges, but grounddwellers such as bandicoots, most macropods, most rodents and most dasyurids show greater attrition than possums (mostly arboreal) and especially bats. The worst affected has been the bandicoots, although, when the large rodents were considered in isolation, similar patterns were evident.
Bats, which are the only mammals that fly, had the least attrition of all the taxa examined. There is a logical mechanism for this related to foraging efficiency in terms of energy cost per unit time (Calder 1984; Burbidge & McKenzie 1989).
That is, in terms of the total area searched, flight is a far more energy efficient form of foraging than running on the ground.
Figure 6.7: Patterns of attrition in different types of Australia's mammals.
Note: Data used are assumed to be correct from the data suppliers.
Map Data Source: National Land and Water Resources Audit,Assessment of Terrestrial Biodiversity 2002 Database. ©Commonwealth of Australia 2002.
| EXTINCT AUSTRALIAN MAMMAL SPECIES | NUMBER OF BIOREGIONS FROM WHICH ORIGINALLY RECORDED |
|---|---|
| Thylacinus cynocephalus (Thylacine) | 9 (Tasmania) |
| Perameles eremiana (Desert Bandicoot) | 8 |
| Chaeropus ecaudatus (Pig-footed Bandicoot) | 21 |
| Macrotis leucura (Lesser Bilby) | 10 |
| Bettongia pusilla (Nullarbor Dwarf Bettong) | 3 |
| Caloprymnus campestris (Desert Rat-kangaroo) | 4 |
| Potorous platyops (Broad-faced Potoroo) | 9 |
| Lagorchestes asomatus (Central Hare-wallaby) | 5 |
| Lagorchestes leporides (Eastern Hare-wallaby) | 7 |
| Macropus greyi (Toolache Wallaby) | 2 |
| Onychogalea lunata (Crescent Nailtail Wallaby) | 19 |
| Pteropus brunneus (Percy Island Flying-fox) | 1 |
| Conilurus albipes (Parroo, White-footed Tree-rat) | 7 |
| Leporillus apicalis (Djooyalpi, Lesser Stick-nest Rat) | 25 |
| Notomys amplus (Yoontoo, Short-tailed Hopping-mouse) | 13 |
| Notomys longicaudatus (Koolawa, Long-tailed Hopping-mouse) | 20 |
| Notomys macrotis (Noompa, Big-eared Hopping-mouse) | 1 |
| Notomys mordax (Payi, Darling Downs Hopping-mouse) | 1 |
| Notomys sp. (Great Hopping-mouse) | 2 |
| Pseudomys glaucus (Blue-grey Mouse) | 1 |
| Pseudomys gouldii v(Koontin, Gould's Mouse) | 6 |
| Pseudomys sp. (Basalt Plains Mouse) | 1 |
Ghost Bat, Macroderma gigas
Photo: QEPA
Four variables explain 81% of the observed patterns in mammal decline and extinction in Australia. Variation in annual average rainfall between bioregions explained 39%, body weight and ability to fly each explained 15% and landscape stress explained 12%.
In general, these analyses confirmed the results of earlier studies (e.g. Burbidge & McKenzie 1989; Johnson, Burbidge & McKenzie 1989; Morton 1990; Short & Smith 1994; Smith & Quinn 1996; McKenzie, Hall & Muir 2000):
- mammals persist best in bioregions that receive high rainfall;
- arid and semi-arid areas have lost a high proportion of their mammals;
- Critical Weight Range mammals are most susceptible to extinction; and
- mammals that are unable to fly show a greater level of attrition than those that can (bats).
| SPECIES NOW PERSISTING ONLY ON ISLANDS | BIOREGIONS IN WHICH ISLANDS OCCUR |
|---|---|
| Pseudantechinus mimulus (Carpentarian Antechinus) | Gulf Coastal |
| Perameles bougainville (Western Barred Bandicoot) | Carnarvon |
| Bettongia gaimardi (Tasmanian Bettong) | All Tasmania except King & Tasmanian West |
| Bettongia lesueur (Burrowing Bettong) | Carnarvon |
| Lagorchestes hirsutus (Rufous Hare-wallaby) | Carnarvon |
| Lagostrophus fasciatus (Banded Hare-wallaby) | Carnarvon |
| Leporillus conditor (Wopikara, Greater Stick-nest Rat) | Eyre Yorke Block |
| Pseudomys fieldi (Djoongari, Shark Bay Mouse) | Carnarvon |
This study extended these hypotheses by demonstrating that landscape stress contributes to mammal decline - this is particularly evident in the cereal-growing, extensively cleared bioregions, such as Avon Wheatbelt (Western Australia) and Victorian Volcanic Plain.
The landscape stress attribute represents a number of distinct types of changes (cumulative effects of landuses, exotic predators and herbivores, weeds, salinity, etc). In relation to mammal decline, more accurately-defined measures of environmental change are needed, in which these various disturbances are examined separately so that their different weightings in different bioregions can be taken into account. The Intensive and Extensive Land-use Zones used by the Landscape Health Assessment (NLWRA 2001a) could also be analysed separately, and the different components of landscape stress assessed individually.
These results also help put into perspective the impact of introduced mammals on indigenous species. Introduced mammals affect indigenous mammals by competing for resources, changing habitats or direct predation. In particular, foxes have been implicated in the decline of Critical Weight Range mammals (e.g. Kinnear, Onus & Bromilow 1988; Kinnear, Onus & Sumner 1998). However, wetter bioregions show lower attrition even if they have been colonised by foxes, and declines have been occurring in bioregions not colonised by foxes (eg. Central Kimberley). Furthermore, mammals were becoming extinct in the Carnarvon Basin of Western Australia's arid zone more than 20 years before foxes colonised that region (McKenzie et al. 2000). From a study in the Flinders Ranges of South Australia, Tunbridge (1991) reached a similar conclusion. This does not mean that foxes have not caused extinctions and that fox control is not necessary in order to conserve today's remnant populations-it means that other factors associated with land use have caused significant mammal declines and extinctions.
More of the variation in patterns of mammal decline and extinction may be accounted for if differences in species' habitats (eg. rock pile versus more fragile alluvial plains habitats) and diets (carnivore/insectivore versus omnivore/herbivore) are taken into account, as these attributes were shown to be significant for Western Australia by Burbidge & McKenzie (1989). Also, soil fertility and rainfall affect environmental resilience and carrying capacity, so a combination of these may provide a better measure of regional productivity than rainfall on its own.
Three key maps can be used to identify where strategic efforts for mammal conservation can be directed most effectively. Figure 6.5 shows the geographical pattern of attrition in terrestrial mammals, while Figure 6.2 shows the regional mammal faunas most affected. Figure 6.4 shows bioregions with the greatest number of relictual populations following range contraction. These figures identify the important bioregions for the conservation of threatened mammals.
Conclusions
Conclusion 1
There has been a significant contraction in the geographical ranges and species composition of Australia's indigenous mammal fauna. This is unparalleled in any other component of Australia's biodiversity, or anywhere else in the world.
This study confirms that Australia's terrestrial mammal fauna is particularly susceptible to declines and extinction. One third of the world's extinct mammals since 1600 AD are Australian (Baillie 1996). Twenty-two species of mammals are extinct in Australia (excluding External Territories) (Table 6.3), with eight other species remaining only on islands (Table 6.4). A further two, possibly three, species have become extinct on Christmas Island (Indian Ocean): Rattus macleari, Rattus nativitatis and possibly the shrew Crocidura attenuata.
Conclusion 2
Spot-tailed Quoll, Dasyurus maculatus
Photo: QEPA
Evidence suggests that the wave of mammal extinctions in Australia is continuing.
During the last two decades, all ground-dwelling Critical Weight Range mammal records in the North Kimberley have come from only the northwestern fringe of the region, less than 20 km from its coast. Over the last 30 years this region has suffered significant changes in vegetation composition and structure due to increased fire frequency and the recent arrival of large exotic herbivores that have now penetrated to the coast. Recent trends indicate that with current land use some of the region's mammals will become extinct, while others will persist only on islands. Similar recent declines are evident elsewhere in Australia, for example Myrmecobius fasciatus (Numbat) and Dasyurus geoffroii (Western Quoll) have disappeared from the Avon Wheatbelt during the last 25 years.
The Top End of the Northern Territory and the North Kimberley have been considered to be refugia for a range of mammal species- based on this and other studies, this belief appears to be misleading. Woinarski et al. (2001) documented recent major declines in abundance of a variety of mammal species in the mesic regions of the Northern Territory and equivalent changes have been observed in the North Kimberley.
Addressing some of the threats in these regions could be more cost effective than for more intensively utilised bioregions, many of which require considerable human and financial resources. While mammal decline is being addressed in some parts of Australia through detailed species and fauna recovery programs, many areas and many species are not the subject of effective recovery programs. Detailed survey data are also lacking for several bioregions. Unless Australia provides more resources to mammal conservation and is willing to address the ongoing massive changes to mammal habitat, species will continue to be lost.
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