All the larger Ungulates, and many of the smaller species, are polygamous. The Rhinoceros, and all of the swine-group save the Hippopotamus, among the larger species are exceptions to the rule. The preponderance of females which this implies is generally supposed to be due to the losses sustained among the males by fighting during the struggle for mates. The case of horses, however, seems to militate against this view, for though they undoubtedly fight furiously, no evidence is forthcoming to show that such conflicts terminate fatally.
Were it possible to secure the necessary data it would probably be found that polygamy, and polyandry, are determined solely by the numerical proportions of the sexes: the excess of males or females being due neither to “Natural” nor “Sexual” Selection, but to inherent peculiarities of the germ-plasm tending to produce an excess of males, or females, as the case may be.
Finally, all the evidence goes to show that it is a mistake to suppose that polygamy is due to the excessive sexual avidness of the males, which impels them to first essay the overthrow of all possible rivals, and then to appropriate every female within their sphere of influence, holding them by force. On the contrary, this plurality of mates is thrust upon them. And this because the females, impelled by “mate-hunger,” attach themselves to the nearest male within call: the size of the harem depending on the number of available males. The battles which are fought between rival males are no more sanguinary than in the case of monogamous species. This contention is well illustrated by the African Wydah-birds (Vidua), which are markedly polygamous, though they have no special weapons of offence. In districts where males are numerous the harem will not exceed eight, or ten, females; where males are scarce this number may be increased to fifty. In like manner the varying number of hinds accompanying a stag are to be regarded, not as an index of his prowess, but of the scarcity or abundance of males in the neighbourhood.
CHAPTER V
THE LION AND HIS KIN
A Surprising Relationship—The Lion’s Mane—The Sabre-toothed Tiger—Some Theories about Origins—Sea-lions in Love—Some Strange Ornaments—Whales and Weapons.
That the Lion and the Lamb could possibly have been derived from the same stock seems incredible: yet such is the case, though the pedigree is now well-nigh lost in the mists of a hoary antiquity. It is not surprising, then, that in their present-day garb they should show so little in common. Nor is it strange that among their many points of divergence the one should differ so conspicuously from the other in the matter of secondary sexual characters. For when these are conspicuous among the Ungulates they usually take the form of horns, of which the Carnivores have no need, for the teeth and claws whereby they win their daily portion of meat make equally serviceable weapons of offence when turned against their own kind.
Among the larger Carnivora, the Lion alone displays any obvious distinction between the sexes in the matter of ornament, and this in the form of the well-known mane. Darwin, and later authorities, have regarded this as a shield to protect the great blood-vessels from injury during battles between rivals. But it is not very clear that this alone is sufficient to explain its presence, inasmuch as the Tiger in this respect is defenceless. Mr. F. C. Selous long ago pointed out that the varying abundance of the mane is due to climatic causes. Lions which live in districts where the nights are very cold, as in high table-lands, have large manes; those which occupy lower ground, where the nights are relatively warm, have but a scanty mane. It is clear, however, that the abundance of the mane is not determined by the need for warmth, otherwise it would have been as well developed in the female. Rather we must regard a low temperature as conducive to the growth of long hair when a natural tendency to produce this is present.
There are few men who can claim to have so great a first-hand acquaintance with Lions as Mr. Selous, and he has pointed out to me one significant fact which seems to show not only that the mane has not been developed to serve as a shield when fighting, but that fights between rival males must be rare. And this because of the absence of any evidence in the shape of scars on the skin. With claws so formidable as those of the lion, ugly wounds would certainly be made in any prolonged conflicts, for the skin of this animal is very thin.