It would even appear that mere novelty, or change for the sake of change, has sometimes acted like a charm on female birds, in the same manner as changes of fashion with us. The Duke of Argyll says,[284]-and I am glad to have the unusual satisfaction of following for even a short distance in his footsteps-"I am more and more convinced that variety, mere variety, must be admitted to be an object and an aim in Nature." I wish the Duke had explained what he here means by Nature. Is it meant that the Creator of the universe ordained diversified results for His own satisfaction, or for that of man? The former notion seems to me as much wanting in due reverence as the latter in probability.
Capriciousness of taste in the birds themselves appears a more fitting explanation. For example; the males of some parrots can hardly be said to be more beautiful, at least according to our taste, than the females, but they differ from them in such points, as the male having a rose-coloured collar instead of, as in the female, "a bright emeraldine narrow green collar;" or in the male having a black collar instead of "a yellow demi-collar in front," with a pale roseate instead of a plum-blue head.[285] As so many male birds have for their chief ornament elongated tail-feathers or elongated crests, the shortened tail, formerly described in the male of a humming-bird, and the shortened crest of the male goosander almost seem like one of the many opposite changes of fashion which we admire in our own dresses.
Some members of the heron family offer a still more curious case of novelty in colouring having apparently been appreciated for the sake of novelty. The young of the _Ardea asha_ are white, the adults being dark slate-coloured; and not only the young, but the adults of the allied _Buphus coromandus_ in their winter plumage are white, this colour changing into a rich golden-buff during the breeding-season. It is incredible that the young of these two species, as well as of some other members of the same family,[286] should have been specially rendered pure white and thus made conspicuous to their enemies; or that the adults of one of these two species should have been specially rendered white during the winter in a country which is never covered with snow.
On the other hand we have reason to believe that whiteness has been gained by many birds as a s.e.xual ornament. We may therefore conclude that an early progenitor of the _Ardea asha_ and the _Buphus_ acquired a white plumage for nuptial purposes, and transmitted this colour to their young; so that the young and the old became white like certain existing egrets; the whiteness having afterwards been retained by the young whilst exchanged by the adults for more strongly p.r.o.nounced tints. But if we could look still further backwards in time to the still earlier progenitors of these two species, we should probably see the adults dark-coloured. I infer that this would be the case, from the a.n.a.logy of many other birds, which are dark whilst young, and when adult are white; and more especially from the case of the _Ardea gularis_, the colours of which are the reverse of those of _A. asha_, for the young are dark-coloured and the adults white, the young having retained a former state of plumage. It appears therefore that the progenitors in their adult condition of the _Ardea asha_, the _Buphus_, and of some allies, have undergone, during a long line of descent, the following changes of colour: firstly a dark shade, secondly pure white, and thirdly, owing to another change of fashion (if I may so express myself), their present slaty, reddish, or golden-buff tints. These successive changes are intelligible only on the principle of novelty having been admired by birds for the sake of novelty.
_Summary of the Four Chapters on Birds._-Most male birds are highly pugnacious during the breeding-season, and some possess weapons especially adapted for fighting with their rivals. But the most pugnacious and the best-armed males rarely or never depend for success solely on their power to drive away or kill their rivals, but have special means for charming the female. With some it is the power of song, or of emitting strange cries, or of producing instrumental music, and the males in consequence differ from the females in their vocal organs, or in the structure of certain feathers. From the curiously diversified means for producing various sounds we gain a high idea of the importance of this means of courtship. Many birds endeavour to charm the females by love-dances or antics, performed on the ground or in the air, and sometimes at prepared places. But ornaments of many kinds, the most brilliant tints, combs and wattles, beautiful plumes, elongated feathers, top-knots, and so forth, are by far the commonest means. In some cases mere novelty appears to have acted as a charm. The ornaments of the males must be highly important to them, for they have been acquired in not a few cases at the cost of increased danger from enemies, and even at some loss of power in fighting with their rivals.
The males of very many species do not a.s.sume their ornamental dress until they arrive at maturity, or they a.s.sume it only during the breeding-season, or the tints then become more vivid. Certain ornamental appendages become enlarged, turgid, and brightly-coloured during the very act of courtship. The males display their charms with elaborate care and to the best effect; and this is done in the presence of the females. The courtship is sometimes a prolonged affair, and many males and females congregate at an appointed place. To suppose that the females do not appreciate the beauty of the males is to admit that their splendid decorations, all their pomp and display, are useless; and this is incredible. Birds have fine powers of discrimination, and in some few instances it can be shewn that they have a taste for the beautiful. The females, moreover, are known occasionally to exhibit a marked preference or antipathy for certain individual males.
If it be admitted that the females prefer, or are unconsciously excited by the more beautiful males, then the males would slowly but surely be rendered more and more attractive through s.e.xual selection. That it is this s.e.x which has been chiefly modified we may infer from the fact that in almost every genus in which the s.e.xes differ, the males differ much more from each other than do the females; this is well shewn in certain closely-allied representative species in which the females can hardly be distinguished, whilst the males are quite distinct. Birds in a state of nature offer individual differences which would amply suffice for the work of s.e.xual selection; but we have seen that they occasionally present more strongly-marked variations which recur so frequently that they would immediately be fixed, if they served to allure the female.
The laws of variation will have determined the nature of the initial changes, and largely influenced the final result. The gradations, which may be observed between the males of allied species, indicate the nature of the steps which have been pa.s.sed through, and explain in the most interesting manner certain characters, such as the indented ocelli of the tail-feathers of the peac.o.c.k, and the wonderfully-shaded ocelli of the wing-feathers of the Argus pheasant. It is evident that the brilliant colours, top-knots, fine plumes, &c., of many male birds cannot have been acquired as a protection; indeed they sometimes lead to danger. That they are not due to the direct and definite action of the conditions of life, we may feel a.s.sured, because the females have been exposed to the same conditions, and yet often differ from the males to an extreme degree. Although it is probable that changed conditions acting during a lengthened period have produced some definite effect on both s.e.xes, the more important result will have been an increased tendency to fluctuating variability or to augmented individual differences; and such differences will have afforded an excellent groundwork for the action of s.e.xual selection.
The laws of inheritance, irrespectively of selection, appear to have determined whether the characters acquired by the males for the sake of ornament, for producing various sounds, and for fighting together, have been transmitted to the males alone or to both s.e.xes, either permanently or periodically during certain seasons of the year. Why various characters should sometimes have been transmitted in one way and sometimes in another is, in most cases, not known; but the period of variability seems often to have been the determining cause. When the two s.e.xes have inherited all characters in common they necessarily resemble each other; but as the successive variations may be differently transmitted, every possible gradation may be found, even within the same genus, from the closest similarity to the widest dissimilarity between the s.e.xes. With many closely-allied species, following nearly the same habits of life, the males have come to differ from each other chiefly through the action of s.e.xual selection; whilst the females have come to differ chiefly from partaking in a greater or lesser degree of the characters thus acquired by the males. The effects, moreover, of the definite action of the conditions of life, will not have been masked in the females, as in the case of the males, by the acc.u.mulation through s.e.xual selection of strongly-p.r.o.nounced colours and other ornaments. The individuals of both s.e.xes, however affected, will have been kept at each successive period nearly uniform by the free intercrossing of many individuals.
With the species, in which the s.e.xes differ in colour, it is possible that at first there existed a tendency to transmit the successive variations equally to both s.e.xes; and that the females were prevented from acquiring the bright colours of the males, on account of the danger to which they would have been exposed during incubation. But it would be, as far as I can see, an extremely difficult process to convert, by means of natural selection, one form of transmission into another. On the other hand there would not be the least difficulty in rendering a female dull-coloured, the male being still kept bright-coloured, by the selection of successive variations, which were from the first limited in their transmission to the same s.e.x. Whether the females of many species have actually been thus modified, must at present remain doubtful. When, through the law of the equal transmission of characters to both s.e.xes, the females have been rendered as conspicuously coloured as the males, their instincts have often been modified, and they have been led to build domed or concealed nests.
In one small and curious cla.s.s of cases the characters and habits of the two s.e.xes have been completely transposed, for the females are larger, stronger, more vociferous and brightly-coloured than their males. They have, also, become so quarrelsome that they often fight together like the males of the most pugnacious species. If, as seems probable, they habitually drive away rival females, and by the display of their bright colours or other charms endeavour to attract the males, we can understand how it is that they have gradually been rendered, by means of s.e.xual selection and s.e.xually-limited transmission, more beautiful than the males-the latter being left unmodified or only slightly modified.
Whenever the law of inheritance at corresponding ages prevails, but not that of s.e.xually-limited transmission, then if the parents vary late in life-and we know that this constantly occurs with our poultry, and occasionally with other birds-the young will be left unaffected, whilst the adults of both s.e.xes will be modified. If both these laws of inheritance prevail and either s.e.x varies late in life, that s.e.x alone will be modified, the other s.e.x and the young being left unaffected.
When variations in brightness or in other conspicuous characters occur early in life, as no doubt often happens, they will not be acted on through s.e.xual selection until the period of reproduction arrives; consequently they will be liable to be lost by the accidental deaths of the young, and if dangerous will be eliminated through natural selection. Thus we can understand how it is that variations arising late in life have chiefly been preserved for the ornamentation and arming of the males, the females and the young being left almost unaffected, and therefore like each other. With species having a distinct summer and winter plumage, the males of which either resemble or differ from the females during both seasons or during the summer alone, the degrees and kinds of resemblance between the young and the old are exceedingly complex; and this complexity apparently depends on characters, first acquired by the males, being transmitted in various ways and degrees, as limited by age, s.e.x, and season.
As the young of so many species have been but little modified in colour and in other ornaments, we are enabled to form some judgment with respect to the plumage of their early progenitors; and we may infer that the beauty of our existing species, if we look to the whole cla.s.s, has been largely increased since that period of which the immature plumage gives us an indirect record. Many birds, especially those which live much on the ground, have undoubtedly been obscurely coloured for the sake of protection. In some instances the upper exposed surface of the plumage has been thus coloured in both s.e.xes, whilst the lower surface in the males alone has been variously ornamented through s.e.xual selection. Finally, from the facts given in these four chapters, we may conclude that weapons for battle, organs for producing sound, ornaments of many kinds, bright and conspicuous colours, have generally been acquired by the males through variation and s.e.xual selection, and have been transmitted in various ways according to the several laws of inheritance-the females and the young being left comparatively but little modified.[287]
CHAPTER XVII.
SECONDARY s.e.xUAL CHARACTERS OF MAMMALS.
The law of battle-Special weapons, confined to the males-Cause of absence of weapons in the female-Weapons common to both s.e.xes, yet primarily acquired by the male-Other uses of such weapons-Their high importance-Greater size of the male-Means of defence-On the preference shewn by either s.e.x in the pairing of quadrupeds.
With mammals the male appears to win the female much more through the law of battle than through the display of his charms. The most timid animals, not provided with any special weapons for fighting, engage in desperate conflicts during the season of love. Two male hares have been seen to fight together until one was killed; male moles often fight, and sometimes with fatal results; male squirrels "engage in frequent contests, and often wound each other severely;" as do male beavers, so that "hardly a skin is without scars."[288] I observed the same fact with the hides of the guanacoes in Patagonia; and on one occasion several were so absorbed in fighting that they fearlessly rushed close by me. Livingstone speaks of the males of the many animals in Southern Africa as almost invariably shewing the scars received in former contests.
The law of battle prevails with aquatic as with terrestrial mammals. It is notorious how desperately male seals fight, both with their teeth and claws, during the breeding-season; and their hides are likewise often covered with scars. Male sperm-whales are very jealous at this season; and in their battles "they often lock their jaws together, and turn on their sides and twist about;" so that it is believed by some naturalists that the frequently deformed state of their lower jaws is caused by these struggles.[289]
All male animals which are furnished with special weapons for fighting, are well known to engage in fierce battles. The courage and the desperate conflicts of stags have often been described; their skeletons have been found in various parts of the world, with the horns inextricably locked together, shewing how miserably the victor and vanquished had perished.[290] No animal in the world is so dangerous as an elephant in must. Lord Tankerville has given me a graphic description of the battles between the wild bulls in Chillingham Park, the descendants, degenerated in size but not in courage, of the gigantic _Bos primigenius_. In 1861 several contended for mastery; and it was observed that two of the younger bulls attacked in concert the old leader of the herd, overthrew and disabled him, so that he was believed by the keepers to be lying mortally wounded in a neighbouring wood. But a few days afterwards one of the young bulls singly approached the wood; and then the "monarch of the chase," who had been lashing himself up for vengeance, came out and, in a short time killed his antagonist. He then quietly joined the herd, and long held undisputed sway. Admiral Sir B. J. Sulivan informs me that when he resided in the Falkland Islands he imported a young English stallion, which, with eight mares, frequented the hills near Port William. On these hills there were two wild stallions, each with a small troop of mares; "and it is certain that these stallions would never have approached each other without fighting.
Both had tried singly to fight the English horse and drive away his mares, but had failed. One day they came in _together_ and attacked him.
This was seen by the capitan who had charge of the horses, and who, on riding to the spot, found one of the two stallions engaged with the English horse, whilst the other was driving away the mares, and had already separated four from the rest. The capitan settled the matter by driving the whole party into the corral, for the wild stallions would not leave the mares."
Male animals already provided with efficient cutting or tearing teeth for the ordinary purposes of life, as in the carnivora, insectivora, and rodents, are seldom furnished with weapons especially adapted for fighting with their rivals. The case is very different with the males of many other animals. We see this in the horns of stags and of certain kinds of antelopes in which the females are hornless. With many animals the canine teeth in the upper or lower jaw, or in both, are much larger in the males than in the females; or are absent in the latter, with the exception sometimes of a hidden rudiment. Certain antelopes, the musk-deer, camel, horse, boar, various apes, seals, and the walrus, offer instances of these several cases. In the females of the walrus the tusks are sometimes quite absent.[291] In the male elephant of India and in the male dugong[292] the upper incisors form offensive weapons.
In the male narwhal one alone of the upper teeth is developed into the well-known, spirally-twisted, so called horn, which is sometimes from nine to ten feet in length. It is believed that the males use these horns for fighting together; for "an unbroken one can rarely be got, and occasionally one may be found with the point of another jammed into the broken place."[293] The tooth on the opposite side of the head in the male consists of a rudiment about ten inches in length, which is embedded in the jaw. It is not, however, very uncommon to find double-horned male narwhals in which both teeth are well developed. In the females both teeth are rudimentary. The male cachalot has a larger head than that of the female, and it no doubt aids these animals in their aquatic battles. Lastly, the adult male ornithorhynchus is provided with a remarkable apparatus, namely a spur on the fore-leg, closely resembling the poison-fang of a venomous snake; its use is not known, but we may suspect that it serves as a weapon of offence.[294] It is represented by a mere rudiment in the female.
When the males are provided with weapons which the females do not possess, there can hardly be a doubt that they are used for fighting with other males, and that they have been acquired through s.e.xual selection.
It is not probable, at least in most cases, that the females have actually been saved from acquiring such weapons, owing to their being useless and superfluous, or in some way injurious. On the contrary, as they are often used by the males of many animals for various purposes, more especially as a defence against their enemies, it is a surprising fact that they are so poorly developed or quite absent in the females.
No doubt with female deer the development during each recurrent season of great branching horns, and with female elephants the development of immense tusks, would have been a great waste of vital power, on the admission that they were of no use to the females. Consequently variations in the size of these organs, leading to their suppression, would have come under the control of natural selection, and if limited in their transmission to the female offspring would not have interfered with their development through s.e.xual selection in the males. But how on this view can we explain the presence of horns in the females of certain antelopes, and of tusks in the females of many animals, which are only of slightly less size than in the males? The explanation in almost all cases must, I believe, be sought in the laws of transmission.
As the reindeer is the single species in the whole family of Deer in which the female is furnished with horns, though somewhat smaller, thinner, and less branched than in the male, it might naturally be thought that they must be of some special use to her. There is, however, some evidence opposed to this view. The female retains her horns from the time when they are fully developed, namely in September, throughout the winter, until May, when she brings forth her young; whilst the male casts his horns much earlier, towards the end of November. As both s.e.xes have the same requirements and follow the same habits of life, and as the male sheds his horns during the winter, it is very improbable that they can be of any special service to the female at this season, which includes the larger proportion of the time during which she bears horns.
Nor is it probable that she can have inherited horns from some ancient progenitor of the whole family of deer, for, from the fact of the males alone of so many species in all quarters of the globe possessing horns, we may conclude that this was the primordial character of the group.
Hence it appears that horns must have been transferred from the male to the female at a period subsequent to the divergence of the various species from a common stock; but that this was not effected for the sake of giving her any special advantage.[295]
We know that the horns are developed at a most unusually early age in the reindeer; but what the cause of this may have been is not known. The effect, however, has apparently been the transference of the horns to both s.e.xes. It is intelligible on the hypothesis of pangenesis, that a very slight change in the const.i.tution of the male, either in the tissues of the forehead or in the gemmules of the horns, might lead to their early development; and as the young of both s.e.xes have nearly the same const.i.tution before the period of reproduction, the horns, if developed at an early age in the male, would tend to be developed equally in both s.e.xes. In support of this view, we should bear in mind that the horns are always transmitted through the female, and that she has a latent capacity for their development, as we see in old or diseased females.[296] Moreover the females of some other species of deer either normally or occasionally exhibit rudiments of horns; thus the female of _Cervulus moschatus_ has "bristly tufts, ending in a k.n.o.b, instead of a horn;" and "in most specimens of the female Wapiti (_Cervus Canadensis_) there is a sharp bony protuberance in the place of the horn."[297] From these several considerations we may conclude that the possession of fairly well-developed horns by the female reindeer, is due to the males having first acquired them as weapons for fighting with other males; and secondarily to their development from some unknown cause at an unusually early age in the males, and their consequent transmission to both s.e.xes.
Turning to the sheath-horned ruminants: with antelopes a graduated series can be formed, beginning with the species, the females of which are completely dest.i.tute of horns-pa.s.sing to those which have horns so small as to be almost rudimentary, as in _Antilocapra Americana_-to those which have fairly well-developed horns, but manifestly smaller and thinner than in the male, and sometimes of a different shape,[298] and ending with those in which both s.e.xes have horns of equal size. As with the reindeer, so with antelopes there exists a relation between the period of the development of the horns and their transmission to one or both s.e.xes; it is therefore probable that their presence or absence in the females of some species, and their more or less perfect condition in the females of other species, depend, not on their being of some special use, but simply on the form of inheritance which has prevailed. It accords with this view that even in the same restricted genus both s.e.xes of some species, and the males alone of other species, are thus provided. It is a remarkable fact that, although the females of _Antilope bezoartica_ are normally dest.i.tute of horns, Mr. Blyth has seen no less than three females thus furnished; and there was no reason to suppose that they were old or diseased. The males of this species have long straight spirated horns, nearly parallel to each other, and directed backwards. Those of the female, when present, are very different in shape, for they are not spirated, and spreading widely bend round, so that their points are directed forwards. It is a still more remarkable fact that in the castrated male, as Mr. Blyth informs me, the horns are of the same peculiar shape as in the female, but longer and thicker. In all cases the differences between the horns of the males and females, and of castrated and entire males, probably depend on various causes,-on the more or less complete transference of male characters to the females,-on the former state of the progenitors of the species,-and partly perhaps on the horns being differently nourished, in nearly the same manner as the spurs of the domestic c.o.c.k, when inserted into the comb or other parts of the body, a.s.sume various abnormal forms from being differently nourished.
In all the wild species of goats and sheep the horns are larger in the male than in the female, and are sometimes quite absent in the latter.[299] In several domestic breeds of the sheep and goat, the males alone are furnished with horns; and it is a significant fact, that in one such breed of sheep on the Guinea coast, the horns are not developed, as Mr. Winwood Reade informs me, in the castrated male; so that they are affected in this respect like the horns of stags. In some breeds, as in that of N. Wales, in which both s.e.xes are properly horned, the ewes are very liable to be hornless. In these same sheep, as I have been informed by a trustworthy witness who purposely inspected a flock during the lambing-season, the horns at birth are generally more fully developed in the male than in the female. With the adult musk-ox (_Ovibos moschatus_) the horns of the male are larger than those of the female, and in the latter the bases do not touch.[300] In regard to ordinary cattle Mr. Blyth remarks: "In most of the wild bovine animals the horns are both longer and thicker in the bull than in the cow, and in the cow-banteng (_Bos sondaicus_) the horns are remarkably small, and inclined much backwards. In the domestic races of cattle, both of the humped and humpless types, the horns are short and thick in the bull, longer and more slender in the cow and ox; and in the Indian buffalo, they are shorter and thicker in the bull, longer and more slender in the cow. In the wild gaour (_B. gaurus_) the horns are mostly both longer and thicker in the bull than in the cow."[301] Hence with most sheath-horned ruminants the horns of the male are either longer or stronger than those of the female. With the _Rhinoceros simus_, as I may here add, the horns of the female are generally longer but less powerful than in the male; and in some other species of rhinoceros they are said to be shorter in the female.[302] From these various facts we may conclude that horns of all kinds, even when they are equally developed in both s.e.xes, were primarily acquired by the males in order to conquer other males, and have been transferred more or less completely to the female, in relation to the force of the equal form of inheritance.
The tusks of the elephant, in the different species or races, differ according to s.e.x, in nearly the same manner as the horns of ruminants.
In India and Malacca the males alone are provided with well-developed tusks. The elephant of Ceylon is considered by most naturalists as a distinct race, but by some as a distinct species, and here "not one in a hundred is found with tusks, the few that possess them being exclusively males."[303] The African elephant is undoubtedly distinct, and the female has large, well-developed tusks, though not so large as those of the male. These differences in the tusks of the several races and species of elephants-the great variability of the horns of deer, as notably in the wild reindeer-the occasional presence of horns in the female _Antilope bezoartica_-the presence of two tusks in some few male narwhals-the complete absence of tusks in some female walruses;-are all instances of the extreme variability of secondary s.e.xual characters, and of their extreme liability to differ in closely-allied forms.
Although tusks and horns appear in all cases to have been primarily developed as s.e.xual weapons, they often serve for other purposes. The elephant uses his tusks in attacking the tiger; according to Bruce, he scores the trunks of trees until they can be easily thrown down, and he likewise thus extracts the farinaceous cores of palms; in Africa he often uses one tusk, this being always the same, to probe the ground and thus to ascertain whether it will bear his weight. The common bull defends the herd with his horns; and the elk in Sweden has been known, according to Lloyd, to strike a wolf dead with a single blow of his great horns. Many similar facts could be given. One of the most curious secondary uses to which the horns of any animal are occasionally put, is that observed by Captain Hutton[304] with the wild goat (_Capra aegagrus_) of the Himalayas, and as it is said with the ibex, namely, that when the male accidentally falls from a height he bends inwards his head, and, by alighting on his ma.s.sive horns, breaks the shock. The female cannot thus use her horns, which are smaller, but from her more quiet disposition she does not so much need this strange kind of shield.
Each male animal uses his weapons in his own peculiar fashion. The common ram makes a charge and b.u.t.ts with such force with the bases of his horns, that I have seen a powerful man knocked over as easily as a child. Goats and certain species of sheep, for instance the _Ovis cycloceros_ of Afghanistan,[305] rear on their hind legs, and then not only b.u.t.t, but "make a cut down and a jerk up, with the ribbed front of their scimitar-shaped horn, as with a sabre. When the _O. cycloceros_ attacked a large domestic ram, who was a noted bruiser, he conquered him by the sheer novelty of his mode of fighting, always closing at once with his adversary, and catching him across the face and nose with a sharp drawing jerk of his head, and then bounding out of the way before the blow could be returned." In Pembrokeshire a male goat, the master of a flock which during several generations had run wild, was known to have killed several other males in single combat; this goat possessed enormous horns, measuring 39 inches in a straight line from tip to tip.
The common bull, as every one knows, gores and tosses his opponent; but the Italian buffalo is said never to use his horns, he gives a tremendous blow with his convex forehead, and then tramples on his fallen enemy with his knees-an instinct which the common bull does not possess.[306] Hence a dog who pins a buffalo by the nose is immediately crushed. We must, however, remember that the Italian buffalo has long been domesticated, and it is by no means certain that the wild parent-form had similarly shaped horns. Mr. Bartlett informs me that when a female Cape buffalo (_Bubalus caffer_) was turned into an enclosure with a bull of the same species, she attacked him, and he in return pushed her about with great violence. But it was manifest to Mr.
Bartlett that had not the bull shewn dignified forbearance, he could easily have killed her by a single lateral thrust with his immense horns. The giraffe uses his short hair-covered horns, which are rather longer in the male than in the female, in a curious manner; for with his long neck he swings his head to either side, almost upside down, with such force, that I have seen a hard plank deeply indented by a single blow.
[Ill.u.s.tration: Fig. 61. Oryx leucoryx, male (from the Knowsley Menagerie).]
With antelopes it is sometimes difficult to imagine how they can possibly use their curiously-shaped horns; thus the spring-boc (_Ant.
euch.o.r.e_) has rather short upright horns, with the sharp points bent inwards almost at a right angle, so as to face each other; Mr. Bartlett does not know how they are used, but suggests that they would inflict a fearful wound down each side of the face of an antagonist. The slightly-curved horns of the _Oryx leucoryx_ (fig. 61) are directed backwards, and are of such length that their points reach beyond the middle of the back, over which they stand in an almost parallel line.
Thus they seem singularly ill-fitted for fighting; but Mr. Bartlett informs me that when two of these animals prepare for battle, they kneel down, with their heads between their front legs, and in this att.i.tude the horns stand nearly parallel and close to the ground, with the points directed forwards and a little upwards. The combatants then gradually approach each other and endeavour to get the upturned points under each other"s bodies; if one succeeds in doing this, he suddenly springs up, throwing up his head at the same time, and can thus wound or perhaps even transfix his antagonist. Both animals always kneel down so as to guard as far as possible against this manuvre. It has been recorded that one of these antelopes has used his horns with effect even against a lion; yet from being forced to place his head between the forelegs in order to bring the points of the horns forward, he would generally be under a great disadvantage when attacked by any other animal. It is, therefore, not probable that the horns have been modified into their present great length and peculiar position, as a protection against beasts of prey. We can, however, see that as soon as some ancient male progenitor of the Oryx acquired moderately long horns, directed a little backwards, he would be compelled in his battles with rival males to bend his head somewhat inwards or downwards, as is now done by certain stags; and it is not improbable that he might have acquired the habit of at first occasionally and afterwards of regularly kneeling down. In this case it is almost certain that the males which possessed the longest horns would have had a great advantage over others with shorter horns; and then the horns would gradually have been rendered longer and longer, through s.e.xual selection, until they acquired their present extraordinary length and position.
With stags of many kinds the branching of the horns offers a curious case of difficulty; for certainly a single straight point would inflict a much more serious wound than several diverging points. In Sir Philip Egerton"s museum there is a horn of the red-deer (_Cervus elaphus_) thirty inches in length, with "not fewer than fifteen snags or branches;" and at Moritzburg there is still preserved a pair of antlers of a red-deer, shot in 1699 by Frederick I., each of which bears the astonishing number of thirty-three branches. Richardson figures a pair of antlers of the wild reindeer with twenty-nine points.[307] From the manner in which the horns are branched, and more especially from deer being known occasionally to fight together by kicking with their fore-feet,[308] M. Bailly actually came to the conclusion that their horns were more injurious than useful to them! But this author overlooks the pitched battles between rival males. As I felt much perplexed about the use or advantage of the branches, I applied to Mr. McNeill of Colinsay, who has long and carefully observed the habits of red-deer, and he informs me that he has never seen some of the branches brought into action, but that the brow-antlers, from inclining downwards, are a great protection to the forehead, and their points are likewise used in attack. Sir Philip Egerton also informs me in regard both to red-deer and fallow-deer, that when they fight they suddenly dash together, and getting their horns fixed against each other"s bodies a desperate struggle ensues. When one is at last forced to yield and turn round, the victor endeavours to plunge his brow-antlers into his defeated foe. It thus appears that the upper branches are used chiefly or exclusively for pushing and fencing. Nevertheless with some species the upper branches are used as weapons of offence; when a man was attacked by a Wapiti deer (_Cervus Canadensis_) in Judge Caton"s park in Ottawa, and several men tried to rescue him, the stag "never raised his head from the ground; in fact he kept his face almost flat on the ground, with his nose nearly between his fore-feet, except when he rolled his head to one side to take a new observation preparatory to a plunge." In this position the terminal points of the horns were directed against his adversaries. "In rolling his head he necessarily raised it somewhat, because his antlers were so long that he could not roll his head without raising them on one side, while on the other side they touched the ground." The stag by this procedure gradually drove the party of rescuers backwards, to a distance of 150 or 200 feet; and the attacked man was killed.[309]
Although the horns of stags are efficient weapons, there can, I think, be no doubt that a single point would have been much more dangerous than a branched antler; and Judge Caton, who has had large experience with deer, fully concurs in this conclusion. Nor do the branching horns, though highly important as a means of defence against rival stags, appear perfectly well adapted for this purpose, as they are liable to become interlocked. The suspicion has therefore crossed my mind that they may serve partly as ornaments. That the branched antlers of stags, as well as the elegant lyrated horns of certain antelopes, with their graceful double curvature, (fig. 62), are ornamental in our eyes, no one will dispute. If, then, the horns, like the splendid accoutrements of the knights of old, add to the n.o.ble appearance of stags and antelopes, they may have been partly modified for this purpose, though mainly for actual service in battle; but I have no evidence in favour of this belief.
[Ill.u.s.tration: Fig. 62. Strepsiceros Kudu (from Andrew Smith"s "Zoology of South Africa").]
An interesting case has lately been published, from which it appears that the horns of a deer in one district in the United States are now being modified through s.e.xual and natural selection. A writer in an excellent American Journal[310] says, that he has hunted for the last twenty-one years in the Adirondacks, where the _Cervus Virginia.n.u.s_ abounds. About fourteen years ago he first heard of _spike-horn bucks_.
These became from year to year more common; about five years ago he shot one, and subsequently another, and now they are frequently killed. "The spike-horn differs greatly from the common antler of the _C.
Virginia.n.u.s_. It consists of a single spike, more slender than the antler, and scarcely half so long, projecting forward from the brow, and terminating in a very sharp point. It gives a considerable advantage to its possessor over the common buck. Besides enabling him to run more swiftly through the thick woods and underbrush (every hunter knows that does and yearling bucks run much more rapidly than the large bucks when armed with their c.u.mbrous antlers), the spike-horn is a more effective weapon than the common antler. With this advantage the spike-horn bucks are gaining upon the common bucks, and may, in time, entirely supersede them in the Adirondacks. Undoubtedly the first spike-horn buck was merely an accidental freak of nature. But his spike-horns gave him an advantage, and enabled him to propagate his peculiarity. His descendants, having a like advantage, have propagated the peculiarity in a constantly increasing ratio, till they are slowly crowding the antlered deer from the region they inhabit."
Male quadrupeds which are furnished with tusks use them in various ways, as in the case of horns. The boar strikes laterally and upwards; the musk-deer with serious effect downwards.[311] The walrus, though having so short a neck and so unwieldy a body, "can strike either upwards, or downwards, or sideways, with equal dexterity."[312] The Indian elephant fights, as I was informed by the late Dr. Falconer, in a different manner according to the position and curvature of his tusks. When they are directed forwards and upwards he is able to fling a tiger to a great distance-it is said to even thirty feet; when they are short and turned downwards he endeavours suddenly to pin the tiger to the ground, and in consequence is dangerous to the rider, who is liable to be jerked off the hoodah.[313]
Very few male quadrupeds possess weapons of two distinct kinds specially adapted for fighting with rival males. The male muntjac-deer (_Cervulus_), however, offers an exception, as he is provided with horns and exserted canine teeth. But one form of weapon, has often been replaced in the course of ages by another form, as we may infer from what follows. With ruminants the development of horns generally stands in an inverse relation with that of even moderately well-developed canine teeth. Thus camels, guanacoes, chevrotains and musk-deer, are hornless, and they have efficient canines; these teeth being "always of smaller size in the females than in the males." The Camelidae have in their upper jaws, in addition to their true canines, a pair of canine-shaped incisors.[314] Male deer and antelopes, on the other hand, possess horns, and they rarely have canine teeth; and these when present are always of small size, so that it is doubtful whether they are of any service in their battles. With _Antilope montana_ they exist only as rudiments in the young male, disappearing as he grows old; and they are absent in the female at all ages; but the females of certain other antelopes and deer have been known occasionally to exhibit rudiments of these teeth.[315] Stallions have small canine teeth, which are either quite absent or rudimentary in the mare; but they do not appear to be used in fighting, for stallions bite with their incisors, and do not open their mouths widely like camels and guanacoes. Whenever the adult male possesses canines now in an inefficient state, whilst the female has either none or mere rudiments, we may conclude that the early male progenitor of the species was provided with efficient canines, which had been partially transferred to the females. The reduction of these teeth in the males seems to have followed from some change in their manner of fighting, often caused (but not in the case of the horse) by the development of new weapons.
Tusks and horns are manifestly of high importance to their possessors, for their development consumes much organised matter. A single tusk of the Asiatic elephant,-one of the extinct woolly species,-and of the African elephant, have been known to weigh respectively 150, 160, and 180 pounds; and even greater weights have been a.s.signed by some authors.[316] With deer, in which the horns are periodically renewed, the drain on the const.i.tution must be greater; the horns, for instance, of the moose weigh from fifty to sixty pounds, and those of the extinct Irish elk from sixty to seventy pounds,-the skull of the latter weighing on an average only five and a quarter pounds. With sheep, although the horns are not periodically renewed, yet their development, in the opinion of many agriculturists, entails a sensible loss to the breeder. Stags, moreover, in escaping from beasts of prey are loaded with an additional weight for the race, and are greatly r.e.t.a.r.ded in pa.s.sing through a woody country. The moose, for instance, with horns extending five and a half feet from tip to tip, although so skilful in their use that he will not touch or break a dead twig when walking quietly, cannot act so dexterously whilst rushing away from a pack of wolves. "During his progress he holds his nose up, so as to lay the horns horizontally back; and in this att.i.tude cannot see the ground distinctly."[317] The tips of the horns of the great Irish elk were actually eight feet apart! Whilst the horns are covered with velvet, which lasts with the red-deer for about twelve weeks, they are extremely sensitive to a blow; so that in Germany the stags at this time change their habits to a certain extent, and avoid dense forests, frequenting young woods and low thickets.[318] These facts remind us, that male birds have acquired ornamental plumes at the cost of r.e.t.a.r.ded flight, and other ornaments at the cost of some loss of power in their battles with rival males.
With quadrupeds, when, as is often the case, the s.e.xes differ in size, the males are, I believe, always larger and stronger. This holds good in a marked manner, as I am informed by Mr. Gould, with the marsupials of Australia, the males of which appear to continue growing until an unusually late age. But the most extraordinary case is that of one of the seals (_Callorhinus ursinus_), a full-grown female weighing less than one-sixth of a full-grown male.[319] The greater strength of the male is invariably displayed, as Hunter long ago remarked,[320] in those parts of the body which are brought into action in fighting with rival males,-for instance, in the ma.s.sive neck of the bull. Male quadrupeds are also more courageous and pugnacious than the females. There can be little doubt that these characters have been gained, partly through s.e.xual selection, owing to a long series of victories by the stronger and more courageous males over the weaker, and partly through the inherited effects of use. It is probable that the successive variations in strength, size, and courage, whether due to so-called spontaneous variability or to the effects of use, by the acc.u.mulation of which male quadrupeds have acquired these characteristic qualities, occurred rather late in life, and were consequently to a large extent limited in their transmission to the same s.e.x.
Under this point of view I was anxious to obtain information in regard to the Scotch deerhound, the s.e.xes of which differ more in size than those of any other breed (though blood-hounds differ considerably), or than in any wild canine species known to me.
Accordingly, I applied to Mr. Cupples, a well-known breeder of these dogs, who has weighed and measured many of his own dogs, and who, with great kindness, has collected for me the following facts from various sources. Superior male dogs, measured at the shoulder, range from twenty-eight inches, which is low, to thirty-three, or even thirty-four inches in height; and in weight from eighty pounds, which is low, to 120, or even more pounds. The females range in height from twenty-three to twenty-seven, or even to twenty-eight inches; and in weight from fifty to seventy, or even eighty pounds.[321] Mr. Cupples concludes that from ninety-five to one hundred pounds for the male, and seventy for the female, would be a safe average; but there is reason to believe that formerly both s.e.xes attained a greater weight. Mr. Cupples has weighed puppies when a fortnight old; in one litter the average weight of four males exceeded that of two females by six and a half ounces; in another litter the average weight of four males exceeded that of one female by less than one ounce; the same males, when three weeks old, exceeded the female by seven and a half ounces, and at the age of six weeks by nearly fourteen ounces. Mr. Wright of Yeldersley House, in a letter to Mr.
Cupples, says: "I have taken notes on the sizes and weights of puppies of many litters, and as far as my experience goes, dog-puppies as a rule differ very little from b.i.t.c.hes till they arrive at about five or six months old; and then the dogs begin to increase, gaining upon the b.i.t.c.hes both in weight and size. At birth, and for several weeks afterwards, a b.i.t.c.h-puppy will occasionally be larger than any of the dogs, but they are invariably beaten by them later." Mr. McNeill, of Colinsay, concludes that "the males do not attain their full growth till over two years old, though the females attain it sooner." According to Mr. Cupples" experience, male dogs go on growing in stature till they are from twelve to eighteen months old, and in weight till from eighteen to twenty-four months old; whilst the females cease increasing in stature at the age of from nine to fourteen or fifteen months, and in weight at the age of from twelve to fifteen months. From these various statements it is clear that the full difference in size between the male and female Scotch deerhound is not acquired until rather late in life.
The males are almost exclusively used for coursing, for, as Mr. McNeill informs me, the females have not sufficient strength and weight to pull down a full-grown deer. From the names used in old legends, it appears, as I hear from Mr. Cupples, that at a very ancient period the males were the most celebrated, the females being mentioned only as the mothers of famous dogs. Hence during many generations, it is the male which has been chiefly tested for strength, size, speed, and courage, and the best will have been bred from. As, however, the males do not attain their full dimensions until a rather late period in life, they will have tended, in accordance with the law often indicated, to transmit their characters to their male offspring alone; and thus the great inequality in size between the s.e.xes of the Scotch deerhound may probably be accounted for.