Ansorge's Free-Tailed Bat (Tadarida ansorgei)
Like all so-called ‘free-tailed’ bats, the distal portion of the tail of the Ansorgi's Free-Tailed Bat is not encased in the interfemoral membrane, and thus presents as a protrusion above the flying membrane. Like its sister species, Ansorgi’s free-tailed bat furthermore has the wrinkled lips and caulie-flower ears, as well as the narrow and elongated wings typical of this genus. This bat is smaller than most free-tailed bats, with a head-to-tail length of 106 mm and a mass of about 10 gr. Apart from dental features, it is externally distinguished from the others by its dark umber brown upper parts, the top of the neck and head almost black, and the under parts are a lighter shade.
Ansorgi's Bat, like other free-tailed bats, are limited to whichever insects are present within the open air spaces where they hunt.
No information of the reproductive behaviour of this species is available.
The Ansorgi's Bat has narrow, elongated wings. The ratio between total wing surface area and body mass give a high wing loading index for this group of bats. As a consequence they are not such adept agile flyers as horseshoe bats or even vesper bats. They are therefore obliged to fly fast in order to remain airborne, and follow straighter flight paths. All free-tailed bats avoid any form of cluttered air space and therefore most often fly in open air space above the tree canopy. Their echolocation tends to be of lower frequencies which allows them to detect insects over a much greater distance, but at lower levels of resolution.
Where they are found
Free tailed bats are a gregarious species. Colonies can be as large as several hundred individuals. During the day they seek out rock crevices in which the colony shelters out of the reach of predators, in densely packed numbers. A precondition of such roosting sites is that the exits must at least be a metre or two above ground level, so that emerging bats can build up sufficient air speed in order to become air borne during the free fall upon emergence. In South Africa, this rare species is known only from a few specimens collected from only a few localities in KwaZulu-Natal. It is furthermore known from scattered localities throughout Africa to as far north as Sudan and Ethiopia. It is likely to have a wider range than is presently known.