(Mystacina tuberculata (Gray))
The short-tailed bat is unique amongst all bats and has consequently been placed as the sole representative of a special family, the Mystacinidae. It is probably the remnant of some ancient, more widespread, fauna and over long periods of isolation in New Zealand has undergone remarkable specialisations. These, being superimposed upon characters shared with the more primitive groups of bats, make family relationships difficult to interpret. It is recognised (diagram 2) by its long and rather pointed ears, by its prominent nostrils, and by its short stumpy tail which projects for about½ in. from the upper surface of the small, leathery, tail membrane. Its total length is usually between 2½ in. and 3 in.The remarkably robust limbs and large feet are also characteristic, and the double talons of the claws are a feature not known in any other bat. The wing span reaches from 10–12 in. and the fur colour may vary from light grey, through brown, to black. Individuals of the short-tailed bat from the Stewart Island region differ quite strikingly from North Island and northern South Island representatives. They are larger and more robust, with relatively short ears which do not reach beyond the nostrils as is the case in the northern form.
At rest a complicated wing-folding process occurs whereby the wing tips are enclosed in small pockets at the sides of the body, just forward of the thighs. The only exposed portions of the wings are thickened and leathery, thus protecting the more delicate regions from possible injury. Similarly, the delicate portion of the tail membrane can be tightly rolled against the body leaving only a thickened basal region exposed. This strange folding process is unique amongst bats. In combination with the robust limbs, large feet, and specialised claws, it permits the short-tailed bat especial freedom upon the ground or in trees. It is likely that this bat may obtain much of its food by hunting in such situations.