WAYS OF THE WILD.

Auckland Star, Volume LXVI, Issue 70, 23 March 1935, Page 1 (Supplement)

WAYS OF THE WILD.

BATS. HAND-WINGED MAMMALS. (By A. T. PYCROFT.) ■ A recent paragraph in the "Star" that two bats had been seen flying over a Nortli Island homestead, has caused a correspondent to ask if these bats are natives of New Zealand, and if they are like the English flitter-mouse. New Zealand possesses two species of bats, the only land mammal. Both are insect eaters like the English flitter-mouse, but they are distinct from the English species. New Zealand's two species are known as the long-tailed and shorttailed bats. The long-tailed bat is the commoner of the two species and is also found in Australia. The short-tailed bat, known as the New Zealand bat, is peculiar to this country. It is now rare, and particular interest attaches to it because it has no living allies. It differs from other members of the family to which it belongs in that the third or middle finger of the wing is provided with three distinct bony joints, of which the first, when at rest, is folded back beneath, instead of above, its supporting metacarpal bone. Moreover, while the greater part of the wing membranes is very thin, the portion along the sides of the body and the lower parts of the limb is much thickened. Beneath this thickened portion the remaining parts of the wings lie folded away as if in a case, and in that condition this species is better adapted to indulge in a crawling or climbing life than any other member of the order. There are other peculiarities that are adapted to aid in climbing, and these are connected with the thumb, feet and legs. The length of the head and body is two and a half inches, and the general colour of the upper parts is brown, though beneath it is paler. Even the fur of this bat can, under the microscope, bo distinguished from that of all other species, the iridividnal hairs being very thick, and with only faint traces of the projecting scales characteristic of other bats. The tail is extremely short. From its structural peculiarities it is surmised that this bat hunts for its insect food, not only in the air, but also on the branches and leaves of trees, among which it is able to creep with ease.

Life Spent in the Air. So thoroughly are bats adapted to a life in the air that most of them seldom resort to the ground, and even when they do so they generally endeavour to leave it as soon as possible by ascending a tree, rock or wall, whence they either again take to flight, or settle themselves in their favourite position of repose. In some cases, bats when at rest suspend themselves head downwards by the feet, but others hang by the claws of their thumbs in the normal position. It is often stated that bats are unable to take flight from a level surface, but this is an error. Most bats feed and drink while on the wing. Their most obvious and important characteristic is their faculty of flight. The apparatus for this being mainly furnished by the v fore limb, the order to which they belong has been appropriately named chiropteray or hood-winged, from the Greek cheir-hand and pteronwing. In the great majority of mam' mals the hind limbs are as large as, or larger than, the .front pair, but in bats the latter vastly exceed the former in length. In a bat's wing the humerus, or bone, of the upper arm is only moderately elongated, but the single complete bone in the forearm, corresponding the radius in man, has a far greater length, and this extraordinary elongation is carried still further in the bones of the hand, all of which, with the exception of those of the thumb, form long, slender rods. The thumb is free, and terminates in a hooked claw, which can be used for the purposes of climbing or suspension, but the fingers, of which the third is the longest, are connected by the delicate membrane constituting the soft part of the wing. This wing membrane is continued along the arm and the sides of the body, and thence to the hind legs. There is also a similar membrane connecting the two hind limbs with the generally long tail, this membrane being usually supported by a peculiar spur of bone projecting from the foot. The toes, however, are quite free. In consequence of the connection of the hind limb with the wing membrane, the knee-joint in bats is directed backwards instead of forwards in the usual manner, and this peculiar arrangement renders a bat's movement on the ground an awkward kind of shuffle. In order to afford space for the attachment of the powerful muscles necessary to move the wings, the chest of bats, like that of birds of flight, is remarkably large, but as these animals are poor walkers, the haunch bones are relatively small and weak.

Bats' Food. The great majority of bats feed solely on insects, and have their cheek teeth furnished with a number of sharp cusps, adapted for holding and piercing the tough covering of beetles and many other insects. A few bats, however, are blood suckers, and these have the front teeth specially modified for piercing the skin of the animals they select as their victims. Others, and among them the largest representatives of the order, are fruit eaters, and these accordingly have a quite different kind of cheek teeth in which the crowns are nearly smooth and without cusps, but marked by a midian longitudinal groove. In their active life bats are mostly nocturnal, while their eyes are relatively small, and it is obvious that they must be provided with some special means of avoiding contact with objects during flight. This is effected by the extreme development of a sense more or less akin to the ordinary sense of touch, by which the neighbourhood of objects is perceived without actual contact. In the great majority of bats this sense of touch is situated in the wing membranes and in the delicate and frequently enormous!v elongated ears, which are often provided with a kind of secondary inner ear, known as the tragus. Certain bats, however, have an additional organ of perception, which takes the form oi expansions of skin from the nose and adjacent parts of the face, forming what is generally known as the "nose leaf," which is specially developed in the horse shoe bats and vampires. These folds of skin may be either comparatively small and simple, or so large as to form a kind of mask, communicating a really extraordinary physiognomy to the bats in which they occur. Tho various membranes forming these nose leaves are always fringed with long and fine hairs, which evidently correspond to the whiskers of tho cat, and these nose leaves may be regarded mere y as an excessive development of the cat» whiskers accompanied by leaf-hke growths from the skin of the noae,-