WAYS OF THE WILD.

Auckland Star, Volume LXVI, Issue 236, 5 October 1935, Page 1 (Supplement)

WAYS OF THE WILD.

EARS OF ANIMALS. MANY VARIED FORMS. (By A. T. PYCROFT.) Many forms of ears in animal life are described by E. G. Boulenger, director of the London Zoological Society’s aquarium, who states that where quick reception is a life and death matter the ears are of large size and highly mobile. The deer, sheep, cattle, kangaroo, rhinoceros, pig, hare and rabbit are but a few cases that at once suggest themselves. The elephant may hold the record as regards “acreage,” but th© largest ears, relatively speaking, belong to the little galago that haunts tho great African forests. The immense and very delicate ears of this halfmonkey have the unique peculiarity that they are collapsible and can be folded up at their owner’s will. In detecting sounds the ears may be augmented by strange fleshy outgrowths as in the bat. Spallanzoni found that temporarily blinded bats when liberated in a room traversed by a complete network of cotton threads never once collided with the threads though flying at a rate of some 20 miles an hour. The threads were stretched in such a manner as to leave just sufficient space for them to pass between with outstretched wings. The bats not only succeeded in passing between these threads without contact, likewise avoiding the walls and ceiling of the room, but when the threads were placed still nearer together they contracted thei*? wings in order to be able to pass without contact. It is possible that the ability to do this is due to the extreme development of a sense akin to hearing and touch. The sense of touch was evolved long before the simplest form of ear, which is a structure enjoyed only by the vertebrate animals. Even amongst insects which are without ears there is a very fair appreciation of rhythm. This is obvious when we consider Hie day and night-long concerts of grasshoppers and crickets, it being only reasonable to suppose that no creature would put up an eight-hour non-stop instrumental effort unless confident of some sort of audience. The Wireless in Insect Life. The vibrations are picked up in the insect world by an apparatus that, when first conceived, foreshadowed one of the greatest forces of our complex life to-day—the wireless —and the reception is believed to be achieved by most insects through the antennae, or feelers, which are at once aerial and receiving •

sets. Recently it has been ascertained that the groups of hairs upon the limbs of crabs and lobsters are furnished with nerves connected with the main nervous system and so-called brain, and experiments have proved that without these hairs the creatures are oblivious to the activities of an under-water buzzer, but that with them they readily respond to the stimulus. The’ crayfish may even have an insect-like appreciation of music, being provided with a species of stridulatory apparatus that when in action is capable of imitating some of the deeper notes of a double bass. Our own highlyrefined ears are scarcely consistent with our capacity for enjoying sounds, since the actual sounding-board or outer ear is of medium size and of simple workmanship. Through disuse many of the surrounding muscles have ceased to function at all, and as a result the whole head must be turned to gather sounds not projected directly upon the tympanum. There is great uniformity in the ears of semi-aquatic mammals. Thus in the sea lion, the otter and the hippopotamus the organ is reduced to a minimum. In the seals, dugongs and whales there is no external ear at all, the presence of the seat of hearing being represented by a tiny orifice. Birds’ ears are seldom detected by a noticeable external feature, although it is readily apparent in bare-headed birds such as ostriches and ground hornbills. Usually it is covered by feathers, and is relatively uniform in size and structure throughout the class. The* night-flying owls are exceptions, since their ears are of immense size and covered by feathery flaps which can be slightly raised. With these the bird is able to appreciate the slightest sounds. The ears of birds and reptiles have much in common. Snakes are, however, without external ears of any kind whatever, their internal auditory bones and nerves being in a state of degeneracy. Experiments have failed to arouse the slightest interest amongst serpents in any kind of music, and the droning pipe play of the professional charmer is merely a piece of showmanship which impresses the audience whilst leaving the reptile angry but unappreciative. So far as a snake can be said to hear at all it hears with its tongue, which is remarkably sensitive to the slightest vibration, quite apart from its more general use as a feeler. Can Fishes Hear? All the bony fishes have a very well defined structure known as the auditory apparatus, but just how far this is a receiving set and not a species of spirit level enabling the fish to keep its correct balance is still a debatable point. Fish do not respond readily to vibrations, only reacting to violent shocks, the ear being concerned merely with a sense of equilibrium and direction, which is one of its functions in ourselves. In some aquaria an attendant blows a whistle at feeding time, and. the fisn immediately evince the liveliest expectation. The real cause of the sudden liveliness, however, is the food pail visible to the fish gazing upwards at the usual feeding place. It would have been remarkable if the fish had really heard, for aerial sound waves are almost completely deflected on striking a liquid' surface. In such experiments it is necessary to produce the sound in the water. Thus, a man while swimming under water cannot hear a pistol shot discharged in the air immediately above him, though he can readily detect the sound of a submerged bell. One observer has stated that if a stone is thrown into the water the fish hury to the spot where the water is disturbed. It is thought that fishes respond, not to the sound of a stone striking the water, but only to the shock to the water caused by the blow. What is even more interesting, however, is the fact that they are said to react to similar shocks when the ear sacs and auditory nerves have been removed. On the whole, it seems most probable that sense of hearing, if developed at all, is far from acute, and may be largely confined to the perception of disturbances in the water.