Ghost bat
Macroderma gigas | |
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Captive specimen hanging at roost | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Chiroptera |
Family: | Megadermatidae |
Genus: | Macroderma |
Species: | M. gigas
|
Binomial name | |
Macroderma gigas | |
Ghost bat range | |
Synonyms | |
Megaderma gigas |
The ghost bat (Macroderma gigas) is a species of bat found in northern Australia. The species is the only Australian bat that preys on large vertebrates – birds, reptiles and other mammals – which they detect using acute sight and hearing, combined with echolocation, while waiting in ambush at a perch. The wing membrane and bare skin is pale in colour, their fur is light or dark grey over the back and paler at the front. The species has a prominent and simple nose-leaf, their large ears are elongated and joined at lower half, and the eyes are also large and dark in colour. The first description of the species was published in 1880, its recorded range has significantly contracted since that time.
Taxonomy
A species of
The specimen had previously been described by
Studies of brain structures indicate that Macroderma gigas is an intermediate and divergent species of the insectivorous microchiropterans and the
Common names that refer to Macroderma gigas have included ghost bat, false vampire, false vampire bat, and Australian false vampire bat.[10][7] The name ghost bat derives from its distinct colouring, the predominant colour of its fur may be near white or pale grey.[6]
Description
A larger species of
Other measurements of the species are a 96 to 112 mm (3.8 to 4.4 in) range for the forearm length, 98 to 120 mm (3.9 to 4.7 in) for the combined length of the head and body, and a weight range of 75 to 145 g (2.6 to 5.1 oz).[12]
The eyes are comparatively large and well developed for nocturnal vision, a feature shared with the long-eared genera Nyctophilus. The nose-leaf is also large and prominent, and simple in form.[16] The nasal appendage is presumably similar in usage to the elaborate forms of the horse-shoe and leaf-nosed bat genera, manipulating, directing and receiving echolocation signals to detect prey. The lack of a tail, effectively absent, is a characteristic of the species. The membrane at the rear is, however, supported by a calcar at the ankle.[17] The teeth and short robust jaw allow the consumption of a wide variety of animals, either the flesh and bones of other vertebrate species or hard shells of larger invertebrates.[18] A pregnant bat possesses two sets of teats, one pair beneath the armpits provide milk from the mammary glands and another pair at the pubic area. The pubic teats do not have a lactational function, rather they act as purchase points for the new-born to be carried in flight by the mother.[19]
The voice is audible to humans, one sound resembles the avian species
Behaviour and diet
Although Macroderma gigas is inactive during daylight hours, they do not hibernate. The colony size reduces in the austral winter, increasing when they gather to breed or females form maternity groups.[20]
They leave the roost several hours after sunset, alone, in pairs, or as small groups. Hunting occurs via a 'sit and wait' technique while suspended from a tree or as low surveys over vegetation.
Prey may be taken at or to the ground, where it is enveloped with the wings and killed with bites to the neck. The sharp teeth and strong jaws are able to subdue animals as large as the bar-shouldered dove, species
The family Megadermatidae is carnivorous, feeding on animals that includes vertebrate species, and this species commonly feeds on arthropod, mammalian, amphibian and reptilian prey.[7][12] These include large insects and small mice, other bats, small birds, frogs, Pygopodidae (legless lizards), geckos and snakes.[6][12][7] Macroderma gigas is formally referred to as a specialised carnivore, but they have been known to feed on insects if prey is scarce. Vertebrate prey is eaten much more frequently, and is usually consumed at the site of capture.[6] Other species of microbats are taken in flight, these include species of Taphozous (sheathtails), Saccolaimus (bentwings), horseshoe bats and the little cave eptesicus.[7][25] The microbat species consumed by M. gigas feed at a variety of habitat and altitudes, and includes those known to cohabit with this species at cave roosts.[25]
A study of the avian prey of the bat revealed that over fifty species of birds are targeted, in a range of sizes but a preference for those weighing less than 35 grams. Birds that roost in flocks make up a large part of the diet, and a quarter of the species are non-passerines. One nocturnal species of bird is recorded at their middens, the Australian owlet-nightjar
Field workers report that the species is remarkably passive when handled.[14] Other workers have recorded and confirmed reports of Macroderma gigas preying on rodents caught in their pitfall traps.[27]
Distribution and habitat
The ghost bat is endemic to Australia. Three population centres are identified, the Northern
The southernmost record is Austin's 1854 note at Mt Kenneth. The species is well represented at Litchfield National Park, which provides important caves and habitat for a number of bat species in the northern regions near Darwin.[30] The largest recorded breeding colony of M. gigas is at a gold mine named Kohinoor at the Top End.[31] The mine was dug in the late nineteenth century and later occupied as a creche when it became unprofitable, however, it remains on a lease that may be profitable as an open-cut operation.[32] Another well known breeding site is found at Nourlangie Rock in Kakadu National Park, a region that is protected by conservation.[33] It is also recorded in national parks at Mount Etna Caves NP and at Tunnel Creek where they cohabit with other bat species.[34][11] Small colonies have been recorded along the Victoria River and at Camooweal Caves NP.[11] The range extends in association with rocky cliffs, gorges, or outcrops along watercourses in the Kimberley region of northwest Australia.[34]
Built environments may be used as feeding grounds,[6] but the ghost bat selects daytime roosts in caves, sheltered rock crevices, boulder piles or disused mines; occupation of abandoned buildings is only occasionally reported.[35][11] A preference is given to sites with a complex of shafts or cavities and several openings to the outside.[12] Macroderma gigas favours these caves with multiple entrance ways as they are large enough to accommodate the greater wingspan of the species and allow an alternative exit when sensing a threat.[36] They require several suitable sites for rest, feeding and reproduction, and change locations seasonally.[20] The species is especially sensitive to disturbance by humans, and this contributes to the selection or abandonment of a roost site.[12]
The bat and the caves they occupied were well known to peoples of Australia, often informing field workers of their locations in central Australia; some sites were part of 'men's business' that imparted a story of the being to young initiates.[9]
Macroderma gigas is present in the fossil record of Australia and found at the
Range decline
The ghost bat was once widely distributed throughout Australia, and became restricted to a sparser population across northern regions.
Researchers have noted the lack evidence for the species in former range, and the contraction to the north both before and after European settlement has been investigated. There are isolated congregations of bats in specified maternity sites in which the alleles expressed by the females are distinguishable; this implies that the separation of such populations extends through evolutionary time. This scattering into small sets of populations greatly raises the threat of extinction to the species.[40]
It is estimated that several thousand ghost bats remain in existence today.
Reproduction
During the breeding season, late October to early November, female bats congregate in groups and give birth to a single young.[6] The generation length is estimated at four years.[1] According to a study conducted on range of ghost bats in Australia, “female bats gave birth to a single young in late spring, but only 40% of females bred in their second year, increasing to 93% for females greater than 2 years old”.[citation needed]
Maternity colonies are founded in large and open caves and occupied until the young are reared.
Ecology
The associated species include the black flying fox
Macroderma gigas has few predators, and most competition of their nocturnal hunts is from medium-sized owls (
The bat will often take prey to a feeding roost, where a midden is formed from the discarded remains.[11] The range of a species of skink, found in the Northern Territory, was extended to Queensland by a record at a feeding roost of M. gigas.[24]
The species is vulnerable to several anthropogenic hazards, one is barbed wire fencing that accounts for many deaths when they are snagged through the easily torn wing membrane while in flight. The damage caused by the barbed wire strands, often left littering their environment, is greatly increased as the individual become entangled as it attempts to dislodge itself.[46] A study in the Pilbara region identified this as an especial concern, with indications that barbed wire was significantly impacting local populations when erected. The foraging height of M. gigas is around that of the dominant Triodia (spinifex) vegetation and the species is unable to visually detect the wire strand, and is not thought to use echolocation to forage in flight.[47] The thorny and tangled introduced plant lantana also presents a similar hazard to bats.[1] They are especially sensitive to disturbance in wintering roosts, and a single fleeting visit will see the site deserted for several weeks or altogether if human activity continues.[48] Most bat species are vulnerable to human disturbance, but attempts to view M. gigas at their roosts are especially discouraged due to the rapid decline in range and population.[11] New or reopened mining operations may have an impact on local colonies, although they may provide diurnal roosts when complete; they are vulnerable to dilapidation in former mines such as the collapse of ceilings.[14]
The
Gallery
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This image and following:Ghost bats at Featherdale Wildlife Park
References
- Richards, G.C.; Hall, L.S.; Parish, S. (photography) (2012). A natural history of Australian bats : working the night shift. CSIRO Pub. ISBN 9780643103740.
- ^ . Retrieved 20 December 2023.
- ^ ISSN 0370-2774.
- ^ OCLC 62265494.
- ^ Miller, G.S. (1906). "Twelve new genera of bats". Proceedings of the Biological Society of Washington. 19: 83–85.
- ^ Richards 2012, p. 56.
- ^ JSTOR 3503920. Archived from the original(PDF) on 2016-03-16.
- ^ ISBN 0207144540.
- ^ Krefft, Gerard (1879). "Communications". Proceedings of the Zoological Society of London. 1879. Academic Press, [etc.]: 386.
- ^ doi:10.1071/AM90015.
- ^ Richards 2012, p. 140.
- ^ ISBN 9780643098145.
- ^ ISBN 9780195573954.
- ^ a b Richards 2012, p. 163.
- ^ a b c d "Ghost bat". Department of Environment and Science. Queensland government. 18 August 2006. Retrieved 31 January 2019.
- ^ a b Richards 2012, pp. 55–56.
- ^ Richards 2012, p. 60.
- ^ Richards 2012, pp. 57, 58, 163.
- ^ Richards 2012, pp. 54, 163.
- ^ Richards 2012, pp. 66.
- ^ a b c d e Richards 2012, p. 10.
- ^ Richards 2012, p. 55.
- ^ Richards 2012, p. 64.
- ^ Richards 2012, p. 62.
- ^ a b c Richards 2012, p. 77.
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- ^ Richards 2012, p. 43.
- ^ Richards 2012, p. 13.
- ^ Richards 2012, p. 93.
- ^ a b Richards 2012, p. 12.
- ^ a b Richards 2012, p. 16.
- ^ Richards 2012, p. 153.
- ^ Richards 2012, p. 89.
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- ^ Richards 2012, p. 121.
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- ^ a b Richards 2012, pp. 66–67.
- ^ Richards 2012, p. 17.
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- ^ Richards 2012, p. 94.
- ^ Richards 2012, p. 106.
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- ^ Richards 2012, p. 109.
- ^ a b "Macroderma gigas — Ghost Bat". Species Profile and Threats Database. Department of the Environment. Retrieved 31 January 2019.