Taphozous georgianus Thomas 1915

12. Common Sheath-tailed Bat

Taphozous georgianus

French: Taphien de King George / German: Gewöhnliche Grabfledermaus / Spanish: Tafozo australiano

Other common names: Sharp-nosed Tomb Bat

Taxonomy. Taphozous australis georgianus Thomas, 1915,

“ King George’s Sound,” Western Australia, Australia.

Taphozous georgianus is in the subgenus Taphozous. Monotypic.

Distribution. NW & N Australia, in Western Australia (Pilbara and Kimberley bioregions), Northern Territory in the Top End, S of Gulf of Carpentaria, and Gulf Fall and Uplands bioregion, and Queensland E to N Mount Isa Inlier and W Gulf Plains bioregions; also on Hook I off coast of Queensland and several small offshore islands off coasts of Western Australia and Northern Territory.

Descriptive notes. Head-body 61-6-80 mm, tail 21-39-4 mm, ear 16-5-24-1 mm, hindfoot 8-1-9-5 mm, forearm 65-75 mm; weight 30-51 g in April (when laden with fat deposits) and 19-31 g in September. There is no sexual dimorphism in body size. Dorsal fur of the Common Sheath-tailed Bat is dark olive-brown above base of creamy brown and speckled with buff-brown guard hairs. Venter is lighter brownish olive, with base of deep neutral gray. There are fine grizzled gray hairs along undersurface of forearm. Sparse yellow-brown hairs cover undersurface of base of tail. Skin of flight membranes is sepia. There are no throat pouches, typical of adult males in Taphozous-, both sexes have radio-metacarpal wing pouches.

Habitat. Rocky escarpments and cliffs with outcrops that forms caves among dry and wet sclerophyll forests and woodlands.

Food and Feeding. Common Sheath-tailed Bats forage for aerial insects, including beetles, while flying high and fest, usually eating insects in flight. Although they live in semiarid zones throughout much ofthe distribution, they apparently do not to need to drink.

Breeding. Female Common Sheath-tailed Bats are thought to be monoestrous, giving birth to one young each year, although at lower latitudes in its distribution, it is possible that they give birth twice a year. Mating occurs in August-September, and births occur in October—February. At birth, young are one-quarter their mothers’ weights, and eyes are open. Mothers carry young while foraging for 3-4 weeks by which time young are one-halftheir mothers’ weight. Adult size is reached at c.3 months ofage, and sexual maturity at C.9 months for females. Males do not breed until 21 months ofage. Testis remain abdominal for much of the year and then descend to scrotal position in summer and early autumn during which time sperm is produced and stored in tail ofepididymis over winter until mating in the following spring. Tail of epididymis is permanently located in an exposed region of the scrotum that maintains cooler temperatures than found in deeper body regions. Females have one functional ovary on the right, and fetuses only develop in the right horn of the uterus. Life expectancy is less than four years for most individuals, and only c.10% of females and c.3% of males survive longer.

Activity patterns. The Common Sheath-tailed Bat is crepuscular and roosts in twilight zones of rock crevices, caves, and mine adits. While roosting, it clings to vertical walls and props itselfup to avoid contact with much of the substrate, using its wrists and feet in typical emballonurid posture. It emerges around dusk to forage. Individuals remain in roosts in deep torpor during mid-winter cold periods. Peak echolocation call used to search for prey is 25 kHz.

Movements, Home range and Social organization. Common Sheath-tailed Bats exhibit strong roost fidelity even after capture and release during reproductive season, but at other times ofyear, they might move among several roosts. They frequently roost singly or in groups of 20 or less, but colonies of up to 100 individuals are recorded. Individuals maintain separated individual spacing and will defend roost space. Except during winter torpor, they remain alert in roosts, and when disturbed by humans, they scurry crabwise to secluded crevices or fly away. Substantial fat reserves are accumulated in autumn and supply energy during periods of winter torpor. Small groups cluster during torpor. In Central Queensland, body weight can drop from average peak of 41 g in autumn to an average of 26 g in spring. During non-winter periods of insect scarcity, Common Sheath-tailed Bats can enter shallow torpor to conserve energy.

Status and Conservation. Classified as Least Concern on The IUCNRed List. The Common Sheath-tailed Bat has a large distribution and presumably large and stable overall population, uses a wide variety ofhabitats, occurs in protected areas, and does not face significant threats. Nevertheless, mining interests in ironstone terrains of the Pilbara coincide frequently with roosting habitat. Larger colonies in caves and unused mines should be protected from mining interests.

Bibliography. Chimimba & Kitchener (1991), Jolly et al. (2008), Kitchener (1973, 1976a, 1983), Milne (2002), Strahan (1995), Troughton (1925).