The white-striped free-tailed bat (Austronomus australis ) is a species of bat in the family Molossidae. Its echolocation calls are audible to humans, which is a characteristic found in only a few microbat species.The species was formerly classified as Tadarida australis.
The white-striped free-tailed bat is robust in build and the largest of the eleven Australian Molossids. The colour of the pelage is a deep chocolate brown, with well defined white stripes beneath the wing; occasional patches of white may appear at the upper ventral side.Individuals have a mass of 33 to 41 grams, and average of 37 g, and a head and body length of 85 to 100 millimetres. The free tail extends 40 to 55 mm from the body and can be folded during high speed flight to reduce drag.The forearm length range is 57-63.It has a condylobasal length of 23–24 mm.The skull is dorso-ventrally flattened. The baculum is divided into three lobes.
This species has a wingtip shaped similarly to the crescent form found on fast-flying birds and on the caudal fins of fast-swimming fish.These tips have leading edges that curve around to chordwise orientation and have trailing edges with aft-sweep or zero-sweep over the outer half of the tip. This bat's wings are considered as having low camber sections with faired humerus and radius bones, typical leading-edge flaps and surface disjunctions and protuberances. This allows this interceptor species to optimise for least drag generation at the expense of maximum lift ability at high speeds.The white-striped free-tailed bat can reach speeds of up to 17 m/s.
The large, forward pointed ears are 20 to 25 mm in length and assist in their aerodynamic lift. The ears are exceptionally broad and noticeably ribbed.A short hairless tragus is present and also points forward. The inner margins of the ears touch, but are not joined where they meet on the head. The upper lip is deeply wrinkled, and this species have single incisor teeth on each of the frontal cranial bones of the upper jaw. Both sexes have a throat pouch. The colour of the skin is very dark, blackish, with a slight pink hue.Fur colour varies with dark brown dorsally and lighter ventrally. A distinctive pattern of white fur on each side of the body progresses from the front to the back where the wings fold against the body, giving this species its common name, white-striped free-tailed bat. This species displays sexual dimorphism with the male being larger.
An endemic species to Australia, the white-striped free-tailed bat is wide spread and common. They are seasonally migratory but not recorded in the northern third of the continent or previously known at the southern island of Tasmania.However, surveys conducted in Tasmania between 2009 and 2013 indicated the species is present and maybe a periodic visitor or vagrant in Tasmania.In Western Australia this species is restricted south of the 20°S latitude during the breeding season, the austral spring and summer, then extending north in the winter.This species can be found in most habitats from closed forest to open flood plain, and occurs in urban areas, in regions across temperate and subtropical Australia.
This free-tailed bat is a specialized high altitude, fast flying interceptor insectivore. Their diet consists principally of moths, beetles and bugs.
Although single bats spend a majority of their daytime in separate day-roosts, they spent an average of 1 day in every 11 within the communal roost.The bats also visited the communal roost for periods of time during their nocturnal activity, some individuals were recorded twice as often frequenting the communal roost during the night compared with the day.
Males do not have the ability to store sperm in their vesicular follicles during the winter period, therefore breeding commences late in August.Females give birth to one young between mid-December and mid-January, this indicates a gestation period of about 14 weeks.
