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Bats (Chiroptera).

With the exception of the great class of Birds, the Bats are the only surviving backboned animals that possess the organs of true flight. Apart from this specialisation for a life in the air the Bats are very similar in their organisation to the Insectivora, and long ago Huxley pointed out that they were exceedingly modified Insectivora; but this modification marks them off sharply from their nearest allies, and the authorities have agreed that it constitutes a reason for setting them apart in a special order—the Chiroptera or wing-handed animals.

So complete has been the adaptation to an aerial life, involving both pairs of limbs, that they are no longer fitted for progression on the earth. The fingers of the hand have been so drawn out that they are longer than the forearm, and the middle finger is at least equal in length to the head and body, whilst the thumb has been converted into a hook by means of which the Bat can hang from any rough surface. Over these exaggerated finger-bones a broad web of skin has been stretched, and connected not only to the sides of the body but also to the hind legs as far as the ankle, and then nearly or quite to the tip of the slender tail. The effect of this great modification, whilst it creates a pair of great wings, is to render the hind limbs unfitted for ordinary locomotion, for these are so twisted out of the position assumed in quadrupeds that the knees are turned backwards. This is the cause of the awkward, shuffling movements of a Bat on the ground which make it quickly rise into the air or at least to climb some vertical surface.

Looking at the skeleton of a Bat, we shall find the vertebral column short, the neck short-boned but broad, the spinal cord being of great thickness at this part though reduced to a mere thread at the hips. The ribs are usually flattened and connected to a strong breastbone, which has a prominent keel for the attachment of powerful muscles controlling the wings. The tail controls the web connecting the hind legs, which acts as a rudder in flight and as a net helping to capture and retain the larger insects upon which the Bat lives.

Pl. 12.][C 30. Lesser or Pigmy Shrew. Sorex minutus.

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Pl. 13.][C 31. Great Bat or Noctule. Nyctalus noctula.

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The permanent teeth—which are quite different from the milk-teeth—vary in the different species, but they always have distinct roots, and in the British species the upper surface always runs into points or cusps, suited for cracking the chitinous shells of beetles.

The Bat's brain is considered to be of a low order; yet its senses are very acute. Spallanzani, in the latter part of the 18th century made a number of experiments on Bats, depriving them of sight, smell, and hearing, and observing their behaviour under such conditions. He found that when released in a room across which he had stretched numerous threads to block their flight, they in every case avoided these, even when directly in their course. They appear to be helped in this matter by the sensitive whiskers around the muzzle, as well as by the delicate membranes constituting the wings and the outer ears. In the Horse-shoe Bats there is also a great development of the appendages to the nose, known as the nose-leaf, which act as delicate organs of special perception.

Skeleton of Bat (Vespertilio).

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In most of the genera there is considerable development of the ear as compared with other mammals. The little lobe that guards the entrance to the ear in the human subject, and is known as the tragus, is much elongated in the Bats so that it becomes a conspicuous feature, and its variation affords one of the characters for identification of the species. Our two Horse-shoe Bats alone are without any prominent tragus.

It is considered that the Bat's powers of flight are superior even to those of the birds. This is especially evident if we watch the rapidity with which it can change its speed, suddenly stopping when in full flight, then making sudden swoops and turning somersaults in a way that would evoke the admiration of the stunt-loving airman. The females as a rule have larger wings and heavier bodies than the males.

Perhaps to the majority of people the Bat appears to be a creature without a voice. It does, however, utter a shrill squeak which is so highly pitched that many human ears are incapable of perceiving it. On the other hand, the Bat has similar deficiencies; and it has been proved that low notes, however loud, make no impression on the Bat, though a sharp clicking sound or the tearing of paper will alarm him at once.

Our Bats are all nocturnal in their habits, though a few indulge in occasional flights by day. Most of them have definite hours for flight, the time depending upon the flight period of the insects they prey upon particularly. They retire for the day into dark situations, such as hollow trees, caves, outhouses, or under roofs. In these sleeping places great numbers often congregate, and several species may be represented. During bad weather—when, of course, their insect prey also remains under cover—they do not leave their daytime shelter. When asleep their body temperature falls considerably. In harmony with this nocturnal habit we find that our Bats are usually dull coloured—some tint of brown with the underside lighter than the upper.

All the British species hibernate, and before the beginning of this period they develop a good deal of fat to carry them through it. On any day in the winter when there is any considerable rise of temperature they wake at once and look around for insects that have been aroused by the same means. The larger kinds usually eat their food as they fly, but the smaller Bats rest for a few moments for this purpose. The web between the legs and tail ("interfemoral pouch") is mostly used to hold their prey whilst it is being eaten. It also serves to receive the newly born young.

Pl. 14.][C 32. Greater Horse-shoe Bat (Rhinolophus ferrum-equinum). Asleep in cave.

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Pl. 15.] Greater Horse-shoe Bat. Head enlarged, to show remarkable nose-leaf.

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Pl. 16.] Whiskered Bat. Myotis mystacinus.

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Pl. 17.][D 33. Lesser Horse-shoe Bat. Rhinolophus hipposideros.

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The young Bat is born blind, but not quite naked. It at once clings to its mother's fur by means of its claws, and by its teeth to her nipple. Nursing mothers appear to form colonies apart from the others. The growth of the young Bat is rapid and it is soon fully covered with fur. Before it is a fortnight old it is able to leave its mother temporarily, but it does not lead an independent life until it is about two months old. Nothing certain is known about the age to which a Bat attains, but it appears to be about four years.

Until the present century there was an astonishing lack of knowledge of the life-histories of our native species; but a small but enthusiastic band of observers have in recent years done much to make good the deficiency. In this connection the work of Messrs. Alcock, Coward, Moffat, Oldham, Tomes and Whitaker calls for acknowledgment. They have hunted far and wide, exploring the sleeping places and hibernacula, in woods, caves, roofs and belfries, and have established—among other facts—that our Bats are more numerous in the south, becoming scarcer as we go west, and that there are few species represented in the fauna of Scotland. Most of the species appear to be common in some one or more localities, even if rare elsewhere; and the physical features of a district have a striking influence on their local abundance or scarcity, certain species being more discriminative in this respect than others. The presence of woods, water, and caves appears to be the most favourable condition governing their comparative plentifulness or scarcity.

The Bats were known generically in Anglo-Saxon times as Flittermouse and Reremouse, and these names may be met with still in certain localities; but to the general public the Bat is still a Bat without distinction of species. Although there are twelve distinct kinds that breed in the British Isles, for each of which the naturalist has had to invent an English as well as an international name, not one of these has got into ordinary use; so that it is impossible to get any precise information from those whose occupation gives them opportunities for observation.

Larger Horse-shoe Bat (Rhinolophus ferrum-equinum, Schreber).

We have two Horse-shoe Bats, distinguished as Larger and Lesser, and they are regarded as the lowest organised of our Bats. Their distinguishing feature as a genus is the absence of the tragus from the ear, and the presence of a leaf-like outgrowth of naked skin on the muzzle around the nostrils. The broad forepart of this forms the horse-shoe, a protruding central portion behind the nostrils is known as the sella, and behind it an erect tapering portion is the lancet. There can be little doubt that this extraordinary expansion is no mere ornament, but a sense organ which enables these Bats to execute their marvellous flight through narrow passages. They are able even to distinguish invisible obstacles like glass, and they fly low down among bushes and herbage where they are far more likely to collide than in the upper air. In these respects their motions are different from those of the other Bats.

The Larger Horse-shoe Bat is a large and rather heavily built Bat whose proportions are only slightly exceeded by the Noctule (page 46), our largest species. The combined length of head and body is about two and a half inches, and of the tail an inch and a quarter. The forearm is two inches or more, and the expansion of the wings covers more than thirteen inches. The large ears are about half an inch broad, narrowing abruptly to the sharp recurved tip; when laid forward over the face they reach slightly beyond the tip of the muzzle. The lower portion of the broad wing membrane is attached to the ankle and the tail almost to the tip of the latter. The colour of the fur above is reddish-grey; on the underside pale grey. Its cry is a sparrow-like chirp.

Pl. 18.][D 34. Whiskered Bat. Asleep on roof timbers.

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Pl. 19.][D 35. Red-grey Bat. Myotis nattereri.

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The mouth has a straight broad opening below the swollen muzzle with its stiff moustache. The large canine teeth are very conspicuous in contrast with the small incisors. The dental formula for this and the next species is: i 1/2, c 1/1, p 2/3, m 3/3 = 32.

As already indicated, the flight of this Bat is usually low, and it alights to consume its prey, which it presses against the wing membrane, the interfemoral pouch not being large enough for the purpose. Its food consists chiefly of the larger beetles, such as cockchafers and dor-beetles, the quick-running ground-beetle Pterostichus, moths, flies, bees, and caddis-flies. It appears to be a thirsty creature, and may be seen lapping water. It takes its daytime sleep in caves, dark buildings, lofts and roofs. It may hang singly or crowd into crevices. Mr. Coward found it in the Cheddar caves hanging in bunches. Their overhead resorts are revealed by heaps of excrement below. Their natural resting attitude is hanging by the feet head downwards. They cannot walk on a flat surface, and before alighting on a vertical one they turn a somersault in the air to get the proper position. Their senses are so acute that Mr. Chas. Oldham says: "Even when sunk in winter sleep they appreciate a man's approach. The eyes are, of course, then shrouded by the wings, and the sense of danger must be conveyed to them either by hearing, smell, or, as seems to be most probable, by the exercise of their extraordinary tactile sense, which enables them to actually feel the approaching danger."

There is but one young at a birth, which occurs at the end of June or in July. Its eyes are closed, and the underside is quite naked and the skin purple. The eyes open about the tenth day.

The Larger Horse-shoe Bat has an extensive distribution. From England it is found through Central Europe and the Mediterranean region, through the Himalayas to China and southern Japan. In our own country it is found chiefly in the South-west of England, South and West Wales, but does not occur in either Scotland or Ireland. The presence or absence of caves suitable for a winter retreat appears to have some bearing upon its distribution.

Lesser Horse-shoe Bat (Rhinolophus hipposideros, Bechstein).

The Lesser Horse-shoe Bat is much smaller and more delicately built than the species last described. The nose-leaf has a narrower outline and its sella is more wedge-shaped; the lancet slender with a wedge-shaped tip. The expanse of wings is less than ten inches, and the length of the forearm is only an inch and a half. The colour is much the same as in the larger species, but somewhat darker above and more yellow below. Its habits are similar also, but, naturally, it does not hunt such large beetles, nor does it fly so low. It has a more fluttering flight with intervals of gliding. Its "tchek-tchek" cry is of lower pitch than in most Bats, and Oldham compares it to a diminutive of the alarm-note of the Greater Spotted Woodpecker.

The single young one is born somewhat later than in the last species: it is born like the other with a thin coat of downy hair on the upper side only.

Males, apparently, are more numerous than females.

The species appears to be more abundant in localities where there are caves which provide it with the equable temperature it requires in hibernation. It is most susceptible to wind, and will frequently remain inactive in its shelter because there is wind outside. Even tame individuals exhibit a strong desire to get into the most retired corners and crevices. The first recorded British example was taken in a cavity over a baker's oven to which it had obtained access through a small fissure.

Pl. 20.][D 36. Red-grey Bat. Emerging from retreat in hollow tree.

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Pl. 21.][D 37. Daubenton's Bat. Myotis daubentonii.

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It may be considered a common species in the South of England from Kent to Cornwall, and more sparingly to Wales. It is unknown in East Anglia, rare in the Midlands, and its northward range terminates at Ripon. In Ireland it occurs in the West only, in some parts of which it is the commonest species. Its wider distribution includes Central Europe, Mediterranean, to Gilgit; northward in Europe to the Baltic.

Whiskered Bat (Myotis mystacinus, Kuhl).

The small and usually solitary Whiskered Bat was formerly considered to be a rare species, but it turns out that the naturalists of last century frequently confused it with the Common Bat—the Pipistrelle—which, however, is smaller and has a broader muzzle. The head and body measure about an inch and a half, and the tail the same length. The wings are narrow, but long, and have an expanse of nine inches.

The soft, long fur of the upper parts is light yellowish-brown in colour; lighter, almost dirty white below. It extends but slightly on the wing membrane, and there is little of it on the long, slender ear, whose outer margin is deeply notched, and the straight, tapering tragus half the length of the shell of the ear. The hinder margin of the brownish black wing membrane is continued to the base of the toes, and the spur (calcar) reaches halfway from the ankle to the long tail. Owing to the length of the fur on the face the small eyes are almost hidden and the face appears to be very short. There is a bristly moustache on the upper lip which has suggested its trivial and scientific names.

Though reputed to be of solitary disposition—and it usually enjoys its daytime rest apart from its kin—it has been taken in numbers on several occasions. It makes its appearance early in the evening, flying low along hedgerows, plantations, and cliffs, its method of hunting being not to chase flying insects in the air but to pick off such as have settled on leaves and twigs. It may also be seen at times flying in the daytime. It has a fondness for the neighbourhood of woods and water, where it finds many flies, beetles, and moths in flight. It is quite silent on the wing.

Mr. Oldham describes the flight of the Whiskered Bat as "slow, steady, and silent—I have never heard this species squeak on the wing. Individuals did not appear to wander far, but confined their attentions to single pools or short stretches of the stream, where they flitted about the alder-bushes or threaded their way with marvellous precision through the lower branches of the sycamore trees. I never saw one rise to a greater height than twenty feet, and often they flew within a few inches of the ground or skimmed the surface of a pool for a yard or two, only to rise again to resume their flight around the alders."

It is not very particular where it takes its daytime sleep. Any sort of shelter will do, whether it be a hollow tree or under a piece of loose bark, a hole in the wall, a roof, or behind window shutters. Its hibernation is passed by preference in a cave, whence it emerges for a flight whenever the weather is fine. In spite of its customary silence, it can produce a feeble squeak.

On the wing it is not easily distinguished from the Pipistrelle, which is so similar in size; but the noisiness of the Pipistrelle compared with the silence of the Whiskered Bat is the best guide.

The solitary young one is born in June or July.

It is widely distributed throughout England, with the exception of East Anglia. In Yorkshire it has been found at an elevation of 1400 feet. It appears to be common in Wales and Ireland, but rare in Scotland. It occurs all over Europe where there are trees, and extends eastwards to Asia. It is the smallest member of its genus.