Macroderma gigas is the second-largest echolocating species of bat in the world, and the largest in Australia, weighing up to 150 g and having a wingspan of 60 cm. They are present in a wide variety of habitats, from the arid, rocky landscapes of the Pilbara region in Western Australia, to tropical savanna woodlands and rainforests further north and east. They rely on underground roosts with warm, humid microclimates to maintain their heat and water balance (they do not enter torpor, Leitner and Nelson 1967, Baudinette et al. 2000), especially in the more arid regions or at drier times of the year and during breeding (Pettigrew et al. 1986, Churchill and Helman 1990, Churchill 1991, Armstrong and Anstee 2000). As a result, roost availability is restricted to relatively few subterranean structures, though individuals are sometimes found in old mines and caves with cooler and drier conditions. Roosts in natural caves are found commonly in the deeper limestone caves, tower karst and sinkholes, sandstone formations, granite boulder piles and ironstone landscapes (Toop 1985, Armstrong and Anstee 2000, K.N. Armstrong unpublished data).

This species is carnivorous–their diet consists of small mammals (including other bats), birds, reptiles, frogs and large insects, though it can vary according to region and the seasonal availability of some prey types, and the proportion of larger invertebrates can be high (Pettigrew et al. 1986, Schulz 1986, Boles 1999, Claramunt et al. 2019). They forage either by perching in vegetation and ambushing passing prey in the air or on the ground, or by gleaning surfaces, including the ground. Echolocation calls are short and strongly multi-harmonic, as is typical of the family. They also make several social calls that are audible to humans (‘chirps’, ‘squabbles’ and ‘twitters’, Kulzer et al. 1984, Guppy et al. 1985, Pettigrew et al. 1986), though there is an unresolved issue over whether some ultrasonic non-echolocation calls attributed to them in the Pilbara (McKenzie and Bullen 2009) are derived exclusively from other cave-roosting bats (K.N. Armstrong unpublished data). Previous studies in Queensland have shown that foraging areas were an average of 1.9 km from roosts and 62 ha in size (Tidemann et al. 1985), though their wing morphology and the size of some colonies suggests they are capable of a much greater nightly range (Bullen and McKenzie 2002). Most prey is taken to a feeding perch in trees, rock overhangs, or cave entrances to be consumed, and feeding sites can be relatively common compared to diurnal roost sites.

Females mostly give birth to a single young, although pregnant females with twins in utero have been trapped in the Northern Territory (Hanrahan et al. unpublished), and most females breed by two years of age (Hoyle et al. 2001). Parturition occurs over a month commencing in mid-October, and young can be shifted to other caves as caves became warmer as summer progresses. Juvenile bats commence flying at seven weeks with all young capable of flight by the end of January (Toop 1985). Females have high fidelity to their natal roosts, with males having a greater tendency to disperse (Worthington Wilmer et al. 1999). Relatively few breeding sites are known, and most are not explicitly protected or managed (Hall et al. 1997, Armstrong and Anstee 2000, Richards et al. 2008, Worthington Wilmer 2012). Generation time is estimated at 8 years (Woinarski et al. 2014).

Macroderma gigas is endemic to Australia, though there is an unverified record in Papua New Guinea (Filewood 1983). It ranges across northern Australia, from the Pilbara and Kimberley regions of Western Australia, the Top End of the Northern Territory, with scattered colonies in the Gulf Coastal and Mount Isa Inlier bioregions, the eastern side of Cape York Peninsula, and a few localities in central-eastern Queensland (Woinarski et al. 2014). There are many sites in central Australia where the species has declined since European arrival, as is evident from historical sightings and subfossil remains, plus numerous other sites containing fossils (reviews in Molnar et al. 1984, Churchill and Helman 1990, Armstrong and Anstee 2000).

Macroderma gigas occurs on numerous conservation reserves, but there are also many known colonies that do not occur on lands that are managed for wildlife or that are subject to scrutiny, including both pastoral stations and small-scale mining or exploration leases. There is good potential for effective conservation of this species and ameliorating declines if efforts can be coordinated under a national recovery and management plan, and with resource allocation and partnership amongst government, industry and researchers. A programme of standardised non-invasive monitoring at key roost sites would be helpful for informing regional and local management approaches (Armstrong and Anstee 2000; Armstrong 2010, 2011; Woinarski et al. 2014). There is a need for priority attention on colonies in old, disused mine adits-requiring scrutiny, protection and repair of sites and solutions to allow sharing of underground structures between the interest of both mining and bats. The encroachment of iron ore mining on roost habitat in Western Australia is well regulated but would benefit from further information about the effectiveness of buffer zones, the potential for artificial roost habitat creation (as a measure of last resort), the size, seasonal occupancy and breeding status of local occurrences in project areas, and regional context to aid risk assessment and management. There is also good awareness of the need for unbarbed top strands of wire on livestock fences in the Pilbara, and mining companies consider the risk of entanglements for fences on their leases, particularly around new infrastructure. The outcomes from population genetic studies need to be part of management and conservation responses, in particular information about female site fidelity and the distinctiveness of the population isolates. Postgraduate research into acoustic ecology is underway and will resolve issues regarding their acoustic identification. There are several captive colonies in zoos and wildlife parks, which are bred and managed for genetic diversity. M. gigas was only recently specially protected under national environmental legislation in Australia, reversing a previous delisting that has diverted attention away from this species that is deserving of better consideration.