Among certain species of gallinaceæ the male leaves to the female the care of incubation and of rearing the young. During this time he is running after adventures, but returns when the young are old enough to follow him and form a docile band under his government.[48] It is important to notice that, amongst birds, the fathers devoid of affection generally belong to the less intelligent species, and are most often polygamous. It seems, therefore, that polygamy is not very favourable to the development of paternal love.[49]
But bad fathers are rare amongst birds. Often, on the contrary, the male rivals the female in love for the young; he guards and feeds her during incubation, and sometimes even sits on the eggs with her. The carrier pigeon feeds his female while she is sitting;[50] the Canadian goose[51] and the crow do the same; more than that, the latter takes his companion’s place at times, to give her some relaxation. The blue marten behaves in the same manner.[52] Among many species, male and female combine their efforts without distinction of sex; they sit in turn, and the one who is free takes the duty of feeding the one who is occupied. This is the custom of the black-coated gull,[53] the booby of Bassan,[54] the great blue heron,[55] and of the black vulture.[56] According to Audubon, the blue bird of America works so ardently at the propagation of its species that a single brood does not satisfy him; each couple, therefore, exerts itself zealously, rearing two or three broods at the same time, the female sitting on one, while the male feeds the little ones of the preceding brood.[57]
But however violent the love of birds for their progeny may be, it lasts only a short time, and is suddenly extinguished when the young can manage for themselves. It is then quite surprising to see the parents drive away by strokes of the beak the little ones they had been nursing with such devoted tenderness a few days before. The birds of several species, however, teach their young to fly before separating from them. The white-headed sea-eagle carries them on its back to give them lessons in flying; grebes, swans, and eiders teach their young to swim, etc. But the family is only of short duration among birds and animals generally, unless, as is the case with some gallinaceæ, the male keeps a few of his daughters to enrich his harem. As a matter of fact, both with birds and other animals, the paternal or maternal sentiment hardly lasts longer than the rearing time. When once the young are full grown, the parents no longer distinguish them from strangers of their species, and it is thus even with monogamic species when the conjugal tie is lifelong; the marriage alone endures, but the family is intermittent and renewed with every brood. We may remark that it is almost the same with certain human races of low development. But, before speaking of man, it will be well to investigate conjugal union and the family amongst the animals nearest to man—the mammals.
From the point of view of duration and strength of the affections, or that which we as men should call their morality, the mammals are far from occupying the first rank in the animal hierarchy; many birds are very superior to them. We find, however, great differences in the morals, according to the species. Many mammals have stopped at the most brutal promiscuity; males and females unite and separate at chance meetings, without any care for the family arising in the mind of the male. The females of mammals being always weaker than the males, no sexual association comparable to polyandry is possible in this class, since, even if she wished it, the female could not succeed in collecting a seraglio of males. But as to polygamy, it is quite different, and this is very common with mammals, especially with the sociable kinds, living in flocks. It is even a necessity of the struggle for existence. Sociability generally proceeds from weakness. The species that are badly armed for fierce combats, and that have besides some difficulty in finding food, are glad to live in association. Union is strength. The ruminants, for example, do this. Certain carnivorous animals, ill-furnished with teeth and claws, dogs also, and jackals, live in troops for the same reason—that of opposing a respectable front to the enemy. This life in common is certainly favourable to the development of social virtues; it cannot but soften primitive cruelty, and develop altruistic qualities; but it is little conducive to sexual restraint and monogamy. Thus the greater number of sociable mammals are polygamous. The ruminants live in hordes composed of females and young, grouped around a male who protects them, but who expels his rivals and becomes a veritable chief of a band. Very various species compose familial societies in the same manner, and strongly resembling each other.
When the Indian adult elephant renounces the solitary life which strong animals generally adopt, it is in order to found a little polygamous society, from which he expels all the males weaker than himself.[58]
The moufflons of Europe and of the Atlas also form little societies of the same kind in the breeding season.[59]
Among the walrus, says Brehm, the male, who is of very jealous temperament, collects around him from thirty to forty females, without counting young, making altogether a polygamous family sometimes amounting to a hundred and twenty individuals.
The male of the Asiatic antilope saiga is inordinately polygamous; he expels all his rivals, and forms a harem numbering sometimes a hundred females.[60]
The polygamic régime of animals is far from extinguishing affectionate sentiments in the females towards their husband and master. The females of the guanaco lamas, for example, are very faithful to their male. If the latter happens to be wounded or killed, instead of running away, they hasten to his side, bleating and offering themselves to the shots of the hunter in order to shield him, while, on the contrary, if a female is killed, the male makes off with all his troop; he only thinks of himself.
In regard to mammals, there is no strict relation between the degree of intellectual development and the form of sexual union. The carnivorous animals often live in couples for the reason previously given; but this is not an absolute rule, for the South African lion is frequently accompanied by four or five females.[61] Bears, weasels, whales, etc., on the contrary, generally go in couples. Sometimes species that are very nearly allied have different conjugal customs; thus the white-cheeked peccary lives in troops, whilst the white-ringed peccary lives in couples.[62]