|Scientific Name:||Macroderma gigas|
|Species Authority:||(Dobson, 1880)|
|Red List Category & Criteria:||Vulnerable C1 ver 3.1|
|Assessor/s:||McKenzie, N. & Hall, L.|
|Reviewer/s:||Lamoreux, J. (Global Mammal Assessment Team), Racey, P.A., Medellín, R. & Hutson, A.M. (Chiroptera Red List Authority)|
Listed as Vulnerable because this species has a small population (less than 10,000 mature individuals), the inferred decline in the last three generations has been greater than 10%, and there is the potential for the population to decline even faster within the next three generations. Populations of the species are fragmented, but not considered to be severely fragmented - other than within the Queensland part of the range - as there is likely to be interchange among colonies within, though not between, other parts of the range.
|Range Description:||This species is endemic to Australia. Its current range is discontinuous with geographically disjunct colonies distributed across northern tropical and subtropical coastal and inland regions (J. Worthington-Wilmer pers. comm.). There are scattered historical records through arid Western Australia, southern Northern Territory, northern South Australia, and western and south-western Queensland.|
Native:Australia (Northern Territory, Queensland, Western Australia)
|Range Map:||Click here to open the map viewer and explore range.|
Current total population estimates are between 7,000 and 9,000 individuals, and varies in each of the three range states. The population in Queensland is located in only 4-5 highly disjunct localities and is estimated at less than 1,000 animals, with its major colony at Mount Etna having declined in the last 10 years. The Northern Territory population is thought to be more or less stable at 2,500-3,500 individuals and is distributed among at least 6-7 main population centres, but the largest colony (at Kohinoor Mine, Pine Creek) is potentially threatened by mine collapse. In Western Australia Ghost Bats occur in two separate regions: in the Pilbara, there are c.600 individuals (N. McKenzie pers. comm.), whereas the Kimberley population is inferred to be about 3,000-4,000 individuals (N. McKenzie pers. comm.).
The species has undergone a major population genetic analysis, with nearly all major known localities included with the exception of the Kimberley, Western Australia and some Northern Territory populations. These studies have shown that Macroderma gigas populations are highly structured, being genetically distinct at both regional and local scales (Worthington-Wilmer et al. 1994, 1999; Armstrong et al. in prep). Populations at the southern limits of the species range are geographically isolated separated by a minimum distance of 300 km. This geographic isolation is reflected in the genetic data with populations at Mt Etna, Cape Hillsborough, and Camooweal in Queensland and the Pilbara in Western Australia being highly divergent genetically and implies virtually no movement of individuals among these sites (Worthington-Wilmer et al. 1999). Recently expanded studies within the Pilbara have revealed strong structure between eastern and western populations (Armstrong et al. in prep). Populations within the Northern Territory and far north Queensland are also highly distinct from each other and other population centres, however, there is less structure among populations within these regions with the data implying greater connectivity occurring via male mediated gene flow (Worthington-Wilmer et al. 1999). While only two samples were obtained from the Kimberley region, one caught in the far west (Tunnel Creek) the other in the east (Cave Springs near Kununurra), sequence data showed the Kimberley bats were distinct not only from all other Australian populations but also from each other (Worthington-Wilmer 1996).
|Habitat and Ecology:||
Although it occurs in rainforest areas, the Ghost Bat is mainly found in the arid zone near rock outcrops, and roosts in caves, mines, and rock clefts. The species also occurs throughout the tropical savanna, in savanna woodlands, and in mangroves (N. McKenzie pers. comm.). It generally forages within 1-2 km of the roost site. Most of the prey are large invertebrates such as beetles, but it is also known to take small vertebrates including other bats, birds, lizards, and snakes (Tidemann et al. 1985). In captive feeding experiments some fruit will be eaten only when no animal food is available (Douglas 1967). Most prey is taken to a feeding perch in trees, rock overhangs, or cave entrances (Hutson et al. 2001).
Ghost bats move between a number of caves seasonally or as dictated by weather conditions. Thus they require a range of cave sites (Hutson et al. 2001). Most maternity sites appear to require multiple entranced caves (L. Hall pers. comm.). Maternity colonies are limited within the range of this species, and include mines, especially in the Pilbara. Generation length is probably around four years and recruitment is very low (L. Hall pers. comm.).
|Major Threat(s):||This species is very vulnerable to disturbance in its roost sites. Cave tourism has been identified as a problem, but the most serious threat is from quarrying and reworking of old mine areas. In some cases, the collapse of disused mines may also be a threat. Habitat modifications for livestock may be a problem in some areas, as may competition for prey with introduced foxes and feral cats (Hutson et al. 2001). Barbed wire fences on cattle stations and lantana cause some direct mortality (Armstrong and Anstee 2000). For the populations at the southern limits of the species' range, the general paucity of suitable roost sites, the geographic distance between existing colonies, and the evident complete lack of gene flow indicates that these populations are totally isolated and will not be rescued by immigration or recolonised should local extinctions occur (J. Worthington-Wilmer pers. comm.).|
The majority of known colonies occur in protected areas (e.g., national parks or heritage listed mine sites), however, there are a number of notable exceptions. The mine roosts the species relies on for breeding in the Pilbara region of Western Australia are not protected and no formal monitoring plan has been implemented (Armstrong and Anstee 2000; K. Armstrong pers. comm). The breeding populations at Claravale Station, Northern Territory and Kings Plains Station, north Queensland occur on private pastoral property with no conservation status (J. Worthington-Wilmer pers. comm.).
Current management activities take into account the results of population genetic studies, which have shown that colonies constitute separate metapopulations (Worthington-Wilmer et al. 1994, 1999). Activities include a captive breeding programme, long-term population studies and monitoring in Queensland, and population studies in Western Australia. In the late 1980s, a massive international campaign to prevent destruction of caves used by this bat at Mount Etna failed and this population has subsequently declined.
The species was evaluated in a Recovery Outline published in "The Action Plan for Australian Bats" (Duncan et al. 1999). That Action Plan downgraded the category of threat from Vulnerable to Lower Risk (near threatened) due to supposed uncertainty regarding the genetic boundaries for many of the known maternity sites and the inability to match Macroderma gigas to IUCN criteria. In 2001, apparently in response to the comments in the Action Plan, the species was delisted from the category of Vulnerable by the Australian federal government Threatened Species Scientific Committee, and no longer falls under the protection of the Commonwealth Government’s endangered species legislation. Legislation, however, in at least two of the three range states (Western Australia and Queensland) maintains Macroderma gigas in threatened or vulnerable categories (J. Worthington-Wilmer pers. comm.).
There is a need for increased regulation of cave tourism and visitation (B. Thomson pers. comm.). Mining companies are increasingly inserting non-barbed wire fences in crucial sections to avoid mortality (N. McKenzie pers. comm.). Identification and direct protection of unprotected maternity colonies is a priority. More ecological research and particularly identification of maternity sites is necessary (L. Lumsden pers. comm.).
|Citation:||McKenzie, N. & Hall, L. 2008. Macroderma gigas. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 24 May 2013.|
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