A Book of Natural History Part 13
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This increase of the value of the slaves as active factors in the ant community might at length proceed to such extremes as we see exemplified in the _Polyergus_, already referred to--a race which has become literally unable to feed itself, and to discharge the simplest duties of ant existence, and whose actual life is entirely spent in marauding expeditions on the nests of its neighbors.
The subject of the general intelligence of ants, and of their ability to adapt themselves to awkward and unusual circ.u.mstances, may be briefly touched upon by way of conclusion.
Between the reason and intelligence of higher animals and the "instinct" of ants there is unquestionably a great gulf fixed. I make this statement unhesitatingly, notwithstanding that I should no more willingly attempt to define "instinct" than to give an exact definition of "insanity." In the latter case one may make the definition so limited as practically to exclude all save one cla.s.s of cases, or so wide as to include even the judge on the bench. In the case of instinct, the rigid definition of one authority might cause us to regard it as the exclusive property of lower forms and as having no relations.h.i.+p whatever with the mental powers of higher beings; or, on the other hand, as being but a modified form of, or in some respects identical with, these very powers. We know too little respecting the so-called "automatic" powers and ways, even of higher animals, to dogmatize regarding the acts of lower animals, but we may safely a.s.sume that one apparent ground or distinction between instinct and reason may be found in the common incompetence of instinct to move out of the beaten track of existence, and in the adaptation of reason, through the teachings of experience, to new and unwonted circ.u.mstances. Let Dr. Carpenter speak as an authority on such a subject. "The whole nervous system of invertebrated animals, then, may be regarded as ministering entirely to _automatic_ action; and its highest development, as in the cla.s.s of insects, is coincident with the highest manifestations of the 'instinctive' powers, which, when carefully examined, are found to consist entirely in movements of the excito-motor and sensori-motor kinds. (The terms '_excito-motor_' and '_sensori-motor_' are applied to nervous actions resulting in movements of varying kinds, and produced by impressions made on nervous centres, but without any necessary emotion, reason, or consciousness.) When we attentively consider the habits of these animals, we find that their actions, though evidently adapted to the attainment of certain ends, are very far from evincing a _designed_ adaptation on the part of the beings that perform them.... For, in the first place, these actions are invariably performed in the same manner by all the individuals of a species, when the conditions are the same; and thus are obviously to be attributed rather to a uniform impulse than to a free choice, the most remarkable example of this being furnished by the economy of bees, wasps, and other 'social' insects, in which every individual of the community performs its appropriated part with the exact.i.tude and method of a perfect machine. The very perfection of the adaptation, again, is often of itself a sufficient evidence of the unreasoning character of the beings which perform the work; for if we attribute it to their own intelligence, we must admit that this intelligence frequently equals, if it does not surpa.s.s, that of the most accomplished Human Reasoner."
Appealing to the most recent observations on ants, we may find evidence of the truth of Dr. Carpenter's statements, whilst at the same time we may also detect instances of the development of higher powers which are hardly to be cla.s.sed as "automatic," and which, in certain species (as in the _Ecitons_, charmingly described by Mr. Belt in "The Naturalist in Nicaragua"), may be said to be elevated above the common instincts of the race. Dr. Henry Maudsley has also well summed up the relations.h.i.+p of the acts of these insects to the acts of higher forms, and to new adaptations when he says: "I do not say that the ant and the bee are entirely dest.i.tute of any power of adaptation to new experiences in their lives--that they are, in fact, purely organized machines, acting always with unvarying regularity; it would appear, indeed, from close observation, that these creatures do sometimes discover in their actions traces of a sensibility to strange experiences, and of corresponding adaptations of movements. We cannot, moreover, conceive how the remarkable instincts which they manifest can have been acquired originally, except by virtue of some such power. But the power in them now is evidently of a rudimentary kind, and must remain so while they have not those higher nerve-centres in which the sensations are combined into ideas, and perceptions of the relations of things are acquired. Granting, however, that the bee or ant has these traces of adaptive action, it must be allowed that they are truly rudiments of functions, which in the supreme nerve-centres we designate as reason and volition. Such a confession might be a trouble to a metaphysical physiologist, who would thereupon find it necessary to place a metaphysical ent.i.ty behind the so-called instincts of the bee, but can be no trouble to the inductive physiologist--he simply recognizes an ill.u.s.tration of a physiological diffusion of properties, and of the physical conditions of primitive volition, and traces in the evolution of mind and its organs, as in the evolution of other functions and their organs, a progressive specialization and increasing complexity."
The recently published experiments of Sir John Lubbock show that ants under certain circ.u.mstances are both stupid and devoid of any intelligent comprehension in the way of surmounting difficulties; but this distinguished observer has also shown that as regards communication between ants, and in the regulation of the ordinary circ.u.mstances of their lives, these insects evince a high degree of intelligence, and exhibit instincts of a very highly developed kind.
Still, making every allowance for the development of extraordinary mental power in some species of ants, there can be little doubt of the purely automatic beginnings and nature of most, if not all, of the acts of ordinary ant existence. The young ant, wasp, or bee, will begin its labors and discharge them as perfectly at the beginning of its existence as a perfect insect, as at the close of life. Here there is no experience, no tuition, no consciousness, no reason, and no powers save such as have been transferred to the insect as a mere matter of heredity and derivation from its ancestors, who lived by an unconscious rule of thumb, so to speak. It is very hard at first to convince one's self, when watching an ant's nest, that intelligence and consciousness play little or no part in the apparently intelligent operation of these insects. But to a.s.sume the contrary would be to maintain that the insect stands on an equal footing to man himself, and for such a supposition there is neither lawful ground nor sympathy. The marvellous instinct of lower life stands on a platform of its own, has its own phases of development, and probably its own unconscious way of progress. The higher reason and intellect of humanity similarly possesses its own peculiar standard, rate, and method of culture. A man may seek and find in the ways of lower existence not merely a lesson in the ordering of his existence, but some comfort, also, in the thought that the progress of lower nature is not unknown in the domain of human hopes and aspirations.
[Ill.u.s.tration: RETURN OF ANTS AFTER A BATTLE.]
THE WILD LLAMA
(FROM A JOURNAL OF RESEARCHES, ETC.)
BY CHARLES DARWIN.
[Ill.u.s.tration: HEAD OF GUANACO.]
The guanaco, or wild Llama, is the characteristic quadruped of the plains of Patagonia; it is the South American representative of the camel in the East. It is an elegant animal in a state of nature, with a long slender neck and fine legs. It is very common over the whole of the temperate parts of the continent, as far south as the islands near Cape Horn. It generally lives in small herds of from half a dozen to thirty in each; but on the banks of the St. Cruz we saw one herd which must have contained at least five hundred.
They are generally wild and extremely wary. Mr. Stokes told me, that he one day saw through a gla.s.s a herd of these animals which evidently had been frightened, and were running away at full speed, although their distance was so great that he could not distinguish them with his naked eye. The sportsman frequently receives the first notice of their presence, by hearing from a long distance their peculiar shrill neighing note of alarm. If he then looks attentively, he will probably see the herd standing in a line on the side of some distant hill. On approaching nearer, a few more squeals are given, and off they set at an apparently slow, but really quick canter, along some narrow beaten track to a neighboring hill. If, however, by chance, he abruptly meets a single animal, or several together, they will generally stand motionless and intently gaze at him; then perhaps move on a few yards, turn round, and look again. What is the cause of this difference in their shyness? Do they mistake a man in the distance for their chief enemy the puma? Or does curiosity overcome their timidity? That they are curious is certain; for if a person lies on the ground, and plays strange antics, such as throwing up his feet in the air, they will almost always approach by degrees to reconnoitre him. It was an artifice that was repeatedly practised by our sportsmen with success, and it had moreover the advantage of allowing several shots to be fired, which were all taken as parts of the performance. On the mountains of the Tierra del Fuego, I have more than once seen a guanaco, on being approached, not only neigh and squeal, but prance and leap about in the most ridiculous manner, apparently in defiance as a challenge. These animals are very easily domesticated, and I have seen some thus kept in northern Patagonia near a house, though not under any restraint. They are in this state very bold, and readily attack a man by striking him from behind with both knees. It is a.s.serted that the motive for these attacks is jealousy on account of their females. The wild guanacos, however, have no idea of defence; even a single dog will secure one of these large animals, till the huntsman can come up. In many of their habits they are like sheep in a flock. Thus when they see men approaching in several directions on horseback, they soon become bewildered, and know not which way to run.
This greatly facilitates the Indian method of hunting, for they are thus easily driven to a central point, and are encompa.s.sed.
[Ill.u.s.tration: THE GUANACO.]
The guanacos readily take to the water: several times at Port Valdes they were seen swimming from island to island. Byron, in his voyage, says he saw them drinking salt water. Some of our officers likewise saw a herd apparently drinking the briny fluid from a salina near Cape Blanco.
I imagine in several parts of the country, if they do not drink salt water, they drink none at all. In the middle of the day they frequently roll in the dust, in saucer-shaped hollows. The males fight together; two one day pa.s.sed quite close to me, squealing and trying to bite each other; and several were shot with their hides deeply scarred. Herds sometimes appear to set out on exploring parties; at Bahia Blanca, where, within thirty miles of the coast, these animals are extremely unfrequent, I one day saw the tracks of thirty or forty, which had come in a direct line to a muddy salt-water creek. They then must have perceived that they were approaching the sea, for they had wheeled with the regularity of cavalry, and had returned back in as straight a line as they had advanced. The guanacos have one singular habit, which is to me quite inexplicable; namely, that on successive days they drop their dung in the same defined heap. I saw one of these heaps which was eight feet in diameter, and was composed of a large quant.i.ty. This habit, according to M. A. d'Orbigny, is common to all the species of the genus; it is very useful to the Peruvian Indians, who use the dung for fuel, and are thus saved the trouble of collecting it.
The guanacos appear to have favorite spots for lying down to die. On the banks of the St. Cruz, in certain circ.u.mscribed s.p.a.ces, which were generally bushy and all near the river, the ground was actually white with bones. On one such spot I counted between ten and twenty heads. I particularly examined the bones; they did not appear, as some scattered ones which I have seen, gnawed or broken, as if dragged together by beasts of prey. The animals in most cases must have crawled, before dying, beneath and amongst the bushes. Mr. Byron informs me that during a former voyage he observed the same circ.u.mstances on the banks of the Rio Gallegos. I do not at all understand the reason of this, but I may observe, that the wounded guanacos at the St. Cruz invariably walked towards the river. At St.
Jago in the Cape de Verd islands, I remember having seen in a ravine a retired corner covered with bones of the goat; we at the time exclaimed that it was the burial-ground of all the goats in the island.
(FROM STUDIES OF ANIMATED NATURE.)
BY W. S. DALLAS, F.L.S.
[Ill.u.s.tration: SLEEPING BAT.]
Among the sounds which greet the ear of the wayfarer as the shades of evening deepen into night, one of the commonest is a rather faint chirping noise which comes mysteriously from overhead. On looking up in search of the source of this peculiar sound, we may see a small, dark, shadow-like creature sweeping to and fro with great rapidity. It is one of the curious groups of animals called Bats, representatives of which are to be met with in in all countries, always active at night or in the twilight, and presenting a remarkable general similarity of structure, although in some respects they may differ considerably in habits. In the British Islands some fourteen species have been distinguished.
Like the owls, with which they share the dominion of the evening air, the Bats have a perfectly noiseless flight; their activity is chiefly during the twilight, although some species are later, and in fact seem to keep up throughout the whole night. As they rest during the day, concealed usually in the most inaccessible places they can find, and are seen only upon the wing, their power of flight is their most striking peculiarity in the popular mind, and it is perhaps no great wonder that by many people, both in ancient and modern times they have been regarded as birds. Nevertheless, their hairy bodies and leathery wings are so unlike anything that we ordinarily understand as pertaining to a bird, that opinion was apparently always divided, as to the true nature of these creatures--"a mouse with wings," as Goldsmith called it once, according to James Boswell, is certainly a curious animal, and very difficult to cla.s.sify so long as the would-be systematist has no particularly definite ideas to guide him. The likeness of the Bat to a winged mouse has made itself felt in the name given to the creature in many languages, such as the "Chauvesouris" of the French and the "Flitter-mouse" of some parts of England, the latter being reproduced almost literally in German, Dutch, and Swedish, while the Danes called the Bat a "Flogenmues," which has about the same meaning, and the Swedes have a second name, "Ladermus,"
evidently referring to the texture of the wings, as well as to the mouse-like character of the body.
But so soon as we have definite characters to appeal to in cla.s.sification, we find no difficulty in a.s.signing these puzzling creatures to their proper place in the system. Bats produce their young alive, and suckle them; the milk being produced by special glands. Now, these are characters which are peculiar among all animals to the vertebrate cla.s.s Mammalia. They possess also other characters that are unmistakably mammalian. Leaving out of consideration the structure of the internal organs, they have teeth implanted in sockets in the jaws, four limbs, and a hairy covering to the skin, so that they possess more decidedly mammalian characters than some other members of the cla.s.s, such as the marine whales and dolphins (_Cetacea_) and manatees (_Sirenia_), which are still often spoken of as fishes. In point of fact, although organized for flight, the Bat may, without any violence to language, be spoken of as a _quadruped_, for its fore-limbs contain all the parts found in those of other mammals fully developed, and they come into use when the creature is walking on the ground.
Perhaps the special characteristics of the Bats will be brought out most distinctly by a comparison of their structure with that of a bird, seeing that the modification of the fore-limbs into wings is their most striking distinction from other Mammalia; for, although some other members of the cla.s.s are spoken of as "flying," such as the Flying Squirrels, Flying Lemurs, and Flying Phalangers, these creatures do not really fly, but merely glide through the air to considerable distances by the action of a broad fold of skin which runs down each side of the body, and which, when stretched between the extended limbs, buoys the creatures up in the air after the fas.h.i.+on of a parachute.
Most of us must have had occasion to pick the bones of a bird's wing, a piece of practical anatomy which may serve us in good stead at present. They consist of a long bone, which may be called the arm-bone (_humerus_), jointed to the shoulder-bones (the so-called "side-bones"
of a fowl or turkey), followed by a pair of parallel bones const.i.tuting the fore-arm, at the end of which we find two or three small bones, then two parallel bones united at their extremities, and some smaller joints terminating the whole.
We need say nothing about the arm-bone and the two bones of the fore-arm, the peculiarity of bird-structure lying chiefly in the terminal portion of the limb, or the hand. Here we find, after two little bones forming the wrist, a pair of long bones as above described, firmly united both at base and apex, and on the outside of the base of these, close to the wrist, a small bone, which may be either free or soldered to the others, and which represents the thumb in the human hand. At the other end of the piece formed by the two united bones, the limb is continued by two joints, forming a second finger, inside of which there is usually a single small bone, representing a third finger. But all these parts are stiffly attached to one another, admitting of very little motion, so that the whole hand forms as it were a single piece. The bony structure of the bird's wing is in point of fact a rod hinged in two places, at the elbow and the wrist, for the convenience of being folded into a small compa.s.s.
The flight of the bird is effected by the agency of a number of stiff feathers implanted in the skin covering the bones and muscles of the arm and hand; these fold together like the sticks of a fan when the wing is folded, and are spread into an elastic instrument for striking the air when the different sections of the bony framework are extended by the action of their respective muscles.
In the Bat the structure is very different. Of course, as in the Vertebrata generally, we find in the Bat's fore-limb the same three main sections as in birds; and as the function of the limb is the same, and a certain stiffness is necessary in the extended organ, the movements of the joints at the elbow and wrists are hinge-like. But the bones of the arm and fore-arm are longer and more slender, especially the latter; and in this part, in place of the two parallel bones of the bird's wing, we find in the Bat only a single long bone representing the smaller bone of the bird, the larger one being usually reduced to very small dimensions, and firmly united with the other into a single piece, although it still forms the elbow-joint. At the other end of this long fore-arm we find some small wrist-bones and to these the fingers are articulated. In birds, as we have seen, only two or three fingers are represented, and these are more or less reduced in size, and the most important of them soldered together; Bats, on the contrary, show the whole five fingers as distinctly as in the hand of man or any other mammals. The first of them, or the _thumb_, is short, slender, and flexible, and composed of three joints; the other four are very long and slender, but chiefly composed of the metacarpal bones, corresponding to those of the palm of the human hand. The first, or index finger, indeed, in many Bats, consists of this bone alone; but in the others it is followed by two or three slender joints, gradually tapering to the extremity, the second finger, corresponding to our middle finger, being always the longest of all.
Just as is the bird's wing, these various parts can be folded together or extended by the action of the muscles, but in the Bat the long fingers become separated when the wing is stretched out, and by this action they at the same time stretch a thin leathery double membrane in which they are enclosed, which is thus converted into a broad surface for striking the air in flight. This membrane is continued from the fingers to the sides of the body, and even to the hind limbs, which are often included in it to the ankle-joints; while in the great majority of Bats there is even a further portion of membrane between the hind legs, enclosing the whole or a portion of the tail. There is usually also a narrow strip of the same membrane in front of each arm, so that the skin of the animal is extended as much as possible, in order to give it support in its aerial evolution. It is to be noted that the long second finger extends to the extreme point of the wing and that the first finger runs close beside it and thus a.s.sists in stiffening that part of the organ. The thumb is left free, and is furnished with a rather strong hooked claw.
Supported by the action of these great leathery wings, the Bat flies about almost incessantly during the twilight, and often late into the night. In full career its flight is swift, though perfectly noiseless, and it has the power of executing rapid turns and changes of direction with the greatest facility, as required for the capture of its prey, which, in the great majority of cases, consists of the insects of various kinds that in most places fly by night. In pursuit of these, the Bats flit rapidly about trees, houses, and other buildings, now and then resting by clinging for a moment to the rough surfaces of the walls or the trunks and branches of trees. Old country church-yards, which are usually full of trees, are naturally favorite haunts of these nocturnal insect-hunters, offering them an excellent field for the chase of their prey, while at the same time, the church itself, with its architectural peculiarities, usually affords them a safe retirement during the day in the dark and secluded corners of its structure. Hence in the popular mind the Bat has long been a.s.sociated with the church-yard, that spot so dreaded that few can pa.s.s through it after nightfall without experiencing certain peculiar feelings, so that it is no great wonder if a portion of the superst.i.tious fear thus engendered has transferred itself to these frail and harmless creatures, and given them and their companions, the owls, something of an evil reputation. And it must be confessed that when seen against the light, flitting silently overhead, there is something weird in the Bat's form, and this is no doubt the reason why, while angels of all kinds are represented with birds' wings, those of Bats have, by universal consent, always been conferred upon demons, dragons, and similar uncanny creatures.
When it descends from its flight upon the ground or any solid body, the Bat becomes to all intents and purposes a genuine quadruped. The fingers being drawn together, with the membranes of the wings thrown into folds between them, the whole hand of the creature is brought up parallel to the fore-arm, and so got out of the way, and the animal can then walk more or less easily, its hind legs, though short and rather feeble, being perfectly formed, and the fore limbs, from which the thumbs with their sharp claws now project freely, becoming available for terrestrial progression. Nevertheless, this progression is generally rather clumsy, as indeed might be expected from creatures so curiously constructed.
While on the wing, our Bats are constantly engaged in the pursuit of the numerous insects of various kinds which, like themselves, are active in the evening and after dark, and of these they must destroy immense quant.i.ties. The swarms of delicate gnats and midges which disport themselves in the most complicated aerial dances, moths of all kinds, and even the hard-sh.e.l.led beetles, many of which fly about in the evening or at night, fall a prey to these leathern-winged rovers of the night air, and weak as the latter would seem to be, some of them are able to seize and devour beetles which appear to be far beyond their powers. Thus, the largest of our British species, the Great Bat, or Noctule (_Scotophilus noctula_), which, however, is only about three inches in length, preys freely upon such large and hard-sh.e.l.led insects as c.o.c.kchafers; these, in fact, appear to be its favorite food, and for their consumption its broad and comparatively strong jaws would seem to be specially fitted, while its large and powerful wings, measuring fourteen or fifteen inches from tip to tip when expanded, enable it to fly with the rapidity necessary for the pursuit and capture of such powerful prey. When thus engaged, the Noctule haunts the neighborhood of trees, and generally flies at a considerable elevation, from which, however, his shrill cry easily reaches the ear of the pa.s.ser-by. His addiction to large prey gives rise to a curious movement, thus noticed by Professor Bell in his valuable book on "British Quadrupeds." "An observer will not watch his movements long," says the Professor, "without noticing a manuvre which at first looks--like the falling of a tumbler-pigeon, but on closer examination proves to be simply a closing of the wings, and a consequent drop of about a foot. Sometimes, this is repeated every few yards, as long as in sight. It is occasioned by some large and intractable insect having been captured, and the anterior joint of the wing, with its well-armed thumb, is required in retaining it until masticated." Notwithstanding this little difficulty, however, the Noctule is pretty rapid in disposing even of his most recusant prey, as he has been known to consume as many as thirteen c.o.c.kchafers one after another.
The foregoing statements apply to all our British Bats, and indeed, in the matter of food and general habits, to the great majority of the species of the order, in whatever country they may occur. But in the tropical and sub-tropical regions of the eastern hemisphere, we find a great and important group of Bats, which, although agreeing in general structure and habits with our European species, differ from them altogether in their diet. These Bats, distinguished generally, among other things, by their larger size and more robust construction, and by certain characters of the molar teeth (grinders), from the ordinary Bats, are almost exclusively confined to a fruit diet, in search of which they fly vigorously, often in flocks, like birds, at the commencement of the night. From this peculiarity of their food they are commonly known as Fruit Bats, while the larger species, such as the Indian Fruit Bat and the Kalong of the Eastern Archipelago, which are respectively eleven and fourteen inches in length, are sometimes called Flying Foxes, in allusion to the prevalence of a reddish tint in their fur, and their more or less lengthened and dog-like muzzles.
In many parts of the Eastern world, in India, the Malayan Archipelago, Australia, Africa, and even in outlying islands at some distance from their main range, these Fruit Bats occur in great numbers. Swarms of them roost together during the day, hanging from the branches of the trees which they select as their regular resting-place, and taking wing at sunset, fly off frequently to great distances in search of their favorite articles of food; for they by no means devour indiscriminately any kind of fruit, but show a distinct preference for particular sorts, generally selecting such as are also prized by their human compet.i.tors. Hence they often do considerable damage in plantations of fruit trees, as when they meet with articles that suit taste, they seem, like some human gourmands, not to know when to leave off eating. Of one of the smaller Indian species, the Margined Fruit Bat, Mr. Dobson obtained a living specimen in Calcutta, and he gives the following account of its voracious appet.i.te:--He gave it "a ripe banana, which, with the skin removed, weighed exactly two ounces. The animal immediately, as if famished with hunger, fell upon the fruit, seized it between the thumbs and the index fingers, and took large mouthfuls out of it, opening the mouth to the fullest extent with extreme voracity. In the s.p.a.ce of three hours the whole fruit was consumed. Next morning the Bat was killed, and found to weigh one ounce, half the weight of the food eaten in three hours! Indeed, the animal when eating seemed to be a kind of living mill"--so continuously does its food pa.s.s through it.
From the statements of some writers, it would appear that although these Bats live chiefly upon fruits, they occasionally, like many other frugivorous animals, diversify their diet with animal food, devouring insects of various kinds, caterpillars, birds' eggs, and even young birds, while there seems to be some reason to believe that one species even feeds upon sh.e.l.l-fish which it picks up upon the seash.o.r.e.
The fruit-eating Bats of this group are not found in the warmer parts of America, but some American Bats feed chiefly upon fruits, while many of the large essentially insectivorous species which occur there vary their diet more or less with fruits, and also occasionally attack and devour other vertebrate animals. Some of them--but it is still very doubtful how many--have another habit connected with their feeding, which renders them very decidedly objectionable, namely, that of inflicting wounds upon birds and mammals, even including man himself, and sucking up the blood that flows from them. This charge has been brought against many Bats of South and Central America, some of which have been commonly named Vampires in consequence, after the ghostly blood-suckers, which were formerly the objects of so much superst.i.tious terror in Hungary and other parts of Eastern Europe; but so far as can be made out from a consideration of the evidence, a verdict of "not proven," at all events, must be arrived at in the case of all but two species, which const.i.tute a little group distinguished by what is apparently a special organization adapting them to this peculiar diet. These wretched little beasts, which only measure two and a half or three inches in length, are furnished in the upper jaw with a single pair of incisor or front teeth, but these are of great size and strength, triangular in form, and so excessively sharp that when the creatures are seized they can draw blood from the hand of their captor by what seems a mere touch. This extreme sharpness of their weapons enables them, when attacking sleeping men or animals, to slice off a small portion of skin almost without causing any pain, and the little oval wounds thus produced, like the similar surface-cuts which a careless shaver sometimes inflicts upon his chin, bleed with particular freedom. The Desmodonts, as these true Vampires are called, will attack horses, mules, and cattle, which they generally wound on the back, near the spine, often in the region of the withers; and they also bite the combs of domestic fowls, and any part of the human body that they can get at. In the case of man, however, according to most authorities, the extremity of the great toe is the favorite part; and some writers, perhaps possessed of a strong poetical vein, have given wonderful descriptions of the artfulness with which these little blood-suckers make their approaches, and keep their victim comfortably asleep during the operation by fanning him with their wings. In fact, the Vampire Bats had so bad a reputation from the accounts given by travellers, that they seemed to be veritable scourges of the countries in which they live, but so far as can be made out from the most trustworthy reports, the mischief they cause may be summed up under two heads, namely, weakness produced by loss of blood, which continues to flow from the wounds long after the Bats have drunk their fill and gone quietly home to rest, and inflammatory affections, caused either by the irritation of the bite in the case of people of a bad habit of body, or by the friction of the saddle or collar upon the part bitten in the case of horses and mules, or of the shoe in the human patient.
That the Desmodonts do really feed on blood is proved by evidence of various kinds. They have been captured in the act of blood-sucking, when their stomachs, which are peculiarly constructed and very long, are found filled with a black paste, which is evidently half-digested blood; and their teeth, which are in part so well adapted for producing the necessary wounds in other animals, are totally unfit for the mastication of an insect prey, such as const.i.tutes the diet of their nearest allies.
[Ill.u.s.tration: THE VAMPIRE BAT.]
After all this feeding, Bats, whatever the nature of their diet, not unnaturally find themselves inclined for repose, and as they are active during the night or in the twilight, of course their rest has to be taken in the daytime. To pa.s.s the period of repose in security they seek shelter of various kinds, not only for protection against the weather, but also for the sake of concealment from other predaceous animals, some of which would no doubt be perfectly willing to make a meal of them. The great Eastern Fruit Bats, trusting perhaps to their size and strength, are content to resort to the branches of trees, from which, after the manner of Bats in general, they suspend themselves by the hind feet with the head downwards. From the statements of various writers it appears that after being out all night in search of food, the Flying Foxes and other allied Bats fly back to their regular resting-places, where they begin to arrive about or soon after dawn. The number resorting to the same retreat is usually so great that the whole of the branches are loaded with them, and in fact they are so crowded together that the settling down of the flock into their repose is preceded by a scene of squabbling and quarrelling of the most noisy description. Mr. Tickell, speaking of the common Indian Flying Fox, says:--"From the arrival of the first comer, until the sun is high above the horizon, a scene of incessant wrangling and contention is enacted among them, as each endeavors to secure a higher and better place, or to eject a neighbor from too close vicinage. In these struggles the Bats hook themselves along the branches, scrambling about hand over hand with some speed, biting each other severely, striking out with the long claw of the thumb, shrieking and cackling without intermission. Each new arrival is compelled to fly several times round the tree, being threatened from all points; and when he eventually hooks on, he has to go through a series of combats, and be probably ejected two or three times, before he makes good his tenure." This scene of selfish contention over, the Fruit Bats pa.s.s some hours in profound sleep, during which they remain suspended in rows along the branches, to which they cling by one foot only, the other with all the lower surface of the body being comfortably wrapped in the leathery mantle formed by the contracted wings. In this condition, as Dr. Horsfield says of the Great Kalong, "ranged in succession with the head downwards ... and often in close contact, they have little resemblance to living beings, and by a person not accustomed to their economy are easily mistaken for a part of the tree, or for a fruit of uncommon size suspended from its branches." In this position the head is folded down upon the breast.
Dr. Bennett and Mr. Gould ascribed very similar habits to a large Fruit Bat common in the northern parts of New South Wales and in Queensland, which is said to be often exceedingly destructive to the peach and other fruit crops of the settlers in those colonies.
The European Bats, and indeed all the Bats except these Flying Foxes and their immediate allies, seek a different kind of shelter. Their chief natural dormitories consist of hollow trees and the caves and fissures of rocks, to which they often resort in great numbers; but in populous countries they also find an abundance of convenient places of retirement in and about buildings of various kinds. Roofs, especially when covered with tiles, or otherwise provided with apertures through which the s.p.a.ce immediately under the roofing is easily accessible, outbuildings of all kinds, church towers and other similar structures, disused chimneys, the s.p.a.ces behind weather-boards and shutters which are not often moved, in fact any dark and sheltered places about our buildings, are readily resorted to by many species, although some few retain their taste for unadulterated nature so strongly that no artificial harbor will serve their turn. Thus among the British species the Great Bat or Noctule, a generally distributed though not abundant species throughout the southern and middle counties of England, seems generally to retreat for its diurnal sleep to the holes or cavities in the trunks of trees, and only to visit buildings when there is a scarcity of such accommodation; and the Horseshoe Bats show a decided preference for caverns and deserted quarries; but the great majority appear to be indifferent in the matter, and to resort to any shelter that seems convenient to them. Some, such as the Barbastelle of the southern parts of England, are solitary in their habits, generally retiring alone for their day's rest; others are more sociable, reposing in larger or smaller parties in their dormitories, whether natural or artificial, and sometimes, like the Fruit Bats, collecting in immense numbers.
The common Bats, like the Fruit Bats, sleep in what we should consider an exceedingly uncomfortable position, namely, with their heads downwards, but they cling by the claws of _both_ hind feet to the small irregularities of the stone or wood forming the walls and other parts of the structure of their retreat. They frequent the same places year after year, so that, where they are numerous, the ground is often completely covered and discolored with their excrements, which in some cases acc.u.mulate in course of time to such an amount as to have given rise to the notion of carrying it away to be used as guano. The little blood-sucking Vampire Bats already mentioned take up their abode in caverns, and, according to Dr. Hensel, who observed their habits, they discharge their excrements, which are black and pasty, near the entrance of the cave just before starting on their evening flight, and this substance by degrees forms quite a thick layer (one foot or more) on the floor of the cavern. The Doctor says that a large dog which had paid a visit of curiosity to one of these caves came out again looking as if he had got long black boots on.
In the warmer regions of the earth's surface, where their supply of food is constant, the activity of the Bats is not known to have any intermission, but in cold and temperate countries they pa.s.s the winter season in a state of torpidity. The period of this hibernation, as it is called, varies somewhat in the different species, but few of them are to be seen flying about, except when the weather is decidedly mild. The commonest of all our British species, the Pipistrelle, has a shorter winter sleep than any of its companions, it usually makes its appearance on the wing by the middle of March, and continues active until quite late in the year; in fact Mr. Gould has recorded the fact of his having shot a specimen of it on a warm sunny day just before Christmas. For the purpose of hibernation the Bats retire to their usual resting-places, but frequently, instead of suspending themselves by their hind feet, as when sleeping, pack themselves away in small parties in holes and crevices, an arrangement which probably furnishes a better protection against the inclemency of the season.
It is probably in the dormitory that the birth of the young bats takes place--at least, so far as we know, the process is affected in a manner which must preclude active exertions on the part of the mother for some little time. The best account of the operation with which we are acquainted is that given fifty years ago by Mr. George Daniell, in a paper read before the Zoological Society, in which he described the habits of some Noctules kept by him in captivity. Four out of five died, and the survivor, a female, was observed on 23d June to become very restless, and to continue so for about an hour, although still suspended by the hind limbs in the att.i.tude of repose. "Suddenly," to use Mr. Daniell's words, "she reversed her position, and attached herself by her anterior limbs to a cross wire of the cage, stretching her hind limbs to their utmost extent, curving the tail upwards, and expanding the interfemoral membrane, so as to form a perfect nestlike cavity for the reception of the young ... which was born on its back, perfectly dest.i.tute of hair, and blind. The mother then cleaned it, turning it over in its nest; and afterwards, resuming her usual position, placed the young in the membrane of her wing. She next cleaned herself, and wrapped up the young one so closely as to prevent any observation of the process of suckling. At the time of birth the young was larger than a new-born mouse, and its hind legs and claws were remarkably strong and serviceable, enabling it not only to cling to its dam, but also to the deal sides of the cage. On the 24th the animal took her food in the morning, and appeared very careful of her young, s.h.i.+fting it from side to side to suckle it, and folding it in the membranes of the tail and wings." Unfortunately, these interesting observations were cut short by the death of the mother, and the young animal, which was with some difficulty removed from the nipple, survived only eight days, during which it was fed with milk from a sponge, and made but little progress, its eyes being still unopened, and its body almost hairless.
There can be no doubt that this process, varied in minor points in accordance with differences of structure, reveals to us what takes place in Bats generally in immediate connection with the birth of the young. From all the observations that have been made it appears certain that the female Bats produce only a single young one at a birth; that this is at first blind, naked, and helpless; and that the female nurses it carefully--a process which must be greatly facilitated by the power of clinging to its parent possessed by the young Bat from the first moment of its appearance in the world. The two nipples possessed by the female are situated upon the breast, sometimes quite at the sides under the arm-pits, a position which renders it particularly easy for the careful mother to tend her offspring, while she is also enabled to carry it about with her in her evening flights, the young creature clinging firmly to its mother's fur, and being quite out of the way of the movements of the wings.
This part of the business, of course, could not be exemplified in Mr.
Daniell's case, as the female was imprisoned in a cage, but it is a well-known fact in the natural history of these creatures that the mother does carry her young about with her so long as it continues helpless. Apparently, indeed, even after the young animal becomes capable of flying about, its mother still retains some interest in its well-being--at least, if we may apply generally a case recorded by Dr.
Allen in his account of the Bats of North America. It relates to a small species, the Red Bat, very common throughout the United States, a young individual of which having been captured by a lad, "three hours afterwards, in the evening, as he was conveying it to the museum in his hand, while pa.s.sing near the place where it was caught, the mother made her appearance, and followed the boy for two squares, flying around him, and finally alighted on his breast, such was her anxiety to save her offspring. Both were brought to the museum, the young one firmly adhering to its mother's teat. This faithful creature lived two days in the museum, and then died of injuries received from her captor. The young one being but half grown was still too young to take care of itself, and died shortly after."
A Book of Natural History Part 13
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A Book of Natural History Part 13 summary
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