Bats are supposed to perceive external objects without coming actually in contact with them, because in their rapid and irregular flight, amidst various surrounding bodies, they never fly against them; yet, to some naturalists, it does not appear that the senses of hearing, seeing, or smelling serve them on these occasions, for they avoid any obstacles with equal certainty when the eye, ear, and nose are closed: hence has been ascribed a sixth sense to these animals. The nerves of the wing are large and numerous, and distributed in a minute network between the integuments. The impulse of the air against this part may possibly be so modified by the objects near which the animal passes as to indicate their situation and nature. The Bat tribe fly by means of the fingers of the fore feet, the thumb excepted, being, in these animals, longer than the whole body; and between them is stretched a thin membrane, or web, for flying. It is probable that, in the action of flight, the air, when struck by this wing, or very sensitive hand, impresses a sensation of heat, cold, mobility, and resistance on that organ, which indicates to the animal the existence or absence of obstacles which would interrupt its progress. In this manner blind men discover by their hands, and even by the skin of their faces, the proximity of a wall, door of a house, or side of a street, even without the assistance of touch, and merely by the sensation which the difference in the resistance of the air occasions. Hence they are as little capable of walking on the ground as apes with their hands, or sloths with their hooked claws, which are calculated for climbing.
In a certain kind of Bat, the Nycteris, there exists a power of inflation to such a degree that, when inflated, the animal looks, according to Geoffroy St. Hilaire, like a little balloon fitted with wings, a head, and feet. It is filled with air through the cheek-pouches, which are perforated at the bottom, so as to communicate with the spaces of the skin to be filled. When the Bat wishes to inflate, it draws in its breath, closes its nostrils, and transmits the air through the perforations of the cheek-pouches to the spaces; and the air is prevented from returning by the action of a muscle which closes those openings, and by valves of considerable size on the neck and back.
There was formerly a vulgar opinion that Bats, when down on a flat surface, could not get on the wing again, by rising with great ease from the floor; but White saw a Bat run, with more dispatch than he was aware of, though in a most ridiculous and grotesque manner. The adroitness with which this Bat sheared off the wings of flies, which were always rejected, was very amusing. He did not refuse raw flesh when offered; so that the notion that Bats go down chimneys, and gnaw men's bacon, seems no improbable story.
Mr. George Daniell describes a female Bat, who took her food with an action similar to that of a dog. The animal took considerable pains in cleaning herself, parting the hair on either side, from head to tail, and forming a straight line along the middle of the back. The membrane of the wings was cleaned by forcing the nose through the folds, and thereby expanding them. This Bat fed freely, and at some times voraciously, the quantity exceeding half an ounce, although the weight of the animal itself was not more than ten drams.
The Kalong Bat of the Javanese is extremely abundant in the lower parts of Java, and uniformly lives in society. The more elevated districts are not visited by it. "Numerous individuals," says Dr. Hornfield, "select a large tree, and, suspending themselves with the claws of their posterior extremities to the naked branches, often in companies of several hundreds, afford to a stranger a very singular spectacle. A species of ficus (fig-tree), resembling the ficus religiosa of India, affords them a very favourite retreat, and the extended branches of one of these are sometimes covered by them. They pass the greater portion of the day in sleep, hanging motionless, ranged in succession, with the head downwards, the membrane contracted about the body, and often in close contact. They have little resemblance to living beings; and, by a person not accustomed to their economy, are readily mistaken for a part of the tree, or for a fruit of uncommon size suspended from its branches."
In general, these societies are silent during the day; but if they are disturbed, or a contention arises among them, they emit sharp, piercing shrieks; and their awkward attempts to extricate themselves, when oppressed by the light of the sun, exhibit a ludicrous spectacle. Soon after sunset they gradually quit their hold, and pursue their nocturnal flight in quest of food. They direct their course by an unerring instinct to the forests, villages, and plantations, attacking and devouring every kind of fruit, from the abundant and useful cocoa-nut, which surrounds the dwellings of the meanest peasantry, to the rare and most delicate productions which are cultivated by princes and chiefs of distinction. Various methods are employed to protect the orchards and gardens. Delicate fruits are secured by a loose net or basket, skilfully constructed of split bamboo, without which precaution little valuable fruit would escape the ravages of the Kalong. There are few situations in the lower part of Java in which this night wanderer is not constantly observed. As soon as the light of the sun has retired, one animal is seen to follow the other at a small but irregular distance, and this accession continues uninterrupted till dark:—
"The night came on apace,
And falling dews bewet around the place;
The bat takes airy rounds, on leathern wings,
And the hoarse owl his woful dirges sings."