Neither the conditions of absolute monogamy, nor those of absolute promiscuity seem to be found at present in humanity, nor among animals; but one sees the couple, in several animal and human species, either in state of tendency, or in state of habit. More often, especially among insects, the father, even if he survives it a little while, remains indifferent, to the consequences of the genital act. At other times, the fights between males so reduce their number that a sole male remains the master and servant of a great number of females. So one must distinguish between true, and successive polygamy; between the monogamy of one season, and that of an entire lifetime; and finally one must set apart those animals who make love only once, or during one season which is followed by death. These different varieties and nuances demand methodic classification. It would be a long work, and would perhaps not attain true exactitude, for in animals, as in man, one must count with caprice in sexual matters: when a faithful dove is tired of her lover, she takes flight, and soon forms a new couple with an adulterous male. The couple is natural, but the permanent couple is not. Man has never bent to it, save with difficulty, even though it be one of the principal conditions of his superiority.
The breasts of the male do not seem to prove the primordiality of the couple in mammals. Although there are veridic examples of the male's having given suck, it is difficult to consider the male udder as destined for a real rôle, or for an emergency milking.[2] This replacement has been too rarely observed for one to use it as a basis of argument. Embryology gives a good explanation of the existence of this useless organ. An useless instrument is, moreover, quite as frequent in nature as the absence of a useful instrument. Perfect concordance of organ and act is rare. In the case of insects who live but for one love-season, sometimes for two real seasons if they can benumb themselves for the winter, polygamy is nearly always the consequence of the rarity of males, or the superabundance of females. Space is too vast, their food too abundant for there to be truly deadly combats between males. Moreover, their love accomplished, the minuscule folk ask only to die, the couple is formed only for the actual time of fecundation, the two animals at once resume their liberty, that is for the female to deliver her eggs, and for the male to languish, and sometimes to cast a final song to the winds. There are exceptions to this rule, but if one looks upon the exceptions with the same gaze as on the rule, one would see in nature only what one sees on the surface of a river, vague movements and passing shadows. To conceive some reality, one must conceive a rule, first, as an instrument of vision and of measure. With most insects the male does nothing but live; he deposits his seed in the female receptacle, flies on, vanishes. He does not share any of the labours preparatory to laying. Alone the female sphex engages in her terrible and clever strife with the cricket, whom she paralyzes with three stabs of her dagger in his three moto-nervous centres; alone she hollows the oblique burrow at the bottom of which live her larvæ; alone she adorns it, fills it with provisions, closes it. Alone the female cerceris heaps up in the deep gallery the stunned weevils and burn-cows, fruit of her excavations, larder for her progeny. Alone the she-osmie, she-wasp, she-philanthe—one would have to cite nearly all the hymenoptera. One understands better, when the insect deposits her eggs by chance, without prefatory manœuvres, or by special instruments, that the male co-operation is lacking; only the female cicada can sink her clever burrow in the olive bark.
There are however couples among insects. Among coleoptera there are the "purse-maker," the necrophore. Stercorian geotrupes, lunar copris, onitis bison, sisyphus, work soberly side by side preparing the larder for their coming families. In these cases, the male seems master, he directs the manœuvres in the complicated operations of the necrophores. A couple get busy about a corpse, say of a field mouse; nearly always one or two isolated males join them, the troop is organized, one sees the chief engineer explore the territory and give orders. The female awaits them, motionless, ready to obey, to follow the movement. As soon as there is a couple the male necrophore commands. The male assists the female during the work of arranging the cell and the laying. Most purse-makers, sisyphus or copris make and transport together the pill which serves as food for the larvæ; their couple is just like that of birds. One might believe that in this case monogamy is necessitated by the nature of the work; not at all: the male in other quite closely related species, sacred scarab, for example, leaves the female alone to build the excremental ball in which she encloses her eggs.
Coming up to vertebrata one finds also certain examples of a sort of monogamy: when the male fish serves as hatcher for his own eggs, either carrying them in a special pouch, or heroicly sheltering them in his mouth. This is rare, since, usually, the two sexes of fish do not approach each other, do not even know each other. Batrachians, on the contrary, are monogamous; the female does not lay save under male pressure, and it is so slow an operation, preceded by such long manœuvres that the whole season is filled with it. The male of the common land toad rolls the long chaplet of eggs about his feet as soon as it is divided, and goes in the evening to place it in the neighbouring pool. Nearly all saurians seem also to be monogamous. The he and she lizard form a couple said to last several years. Their amours are ardent, they clasp each other closely belly to belly.
Birds are generally considered monogamous, save gallinaceæ and web-footed birds; but exceptions appear so numerous that one would have to name the species one by one. The fidelity of pigeons is legendary, and is perhaps only a legend. The male pigeon certainly has tendencies to infidelity and even to polygamy. He deceives his companion; he goes so far as to inflict upon her the shame of having a concubine under the conjugal roof! And these two spouses, he tyrannizes over them, he enslaves them by beating. The female, it is true, is not always of an easy disposition. She has her caprices. Sometimes, refusing her mate, she deserts him and gives herself to the first comer. One will not find here any of the zoölogical anecdotes on the industry of birds, their union in devotion to the specie. The habits of these new-comers in the world, are very unstable; yet among certain gallinaceæ, monogamous for exception, like the partridge, the males seem pulled by contrary desires, they undergo the couple rather than choose it, and their share in the rearing of young is often very slight. One has seen the male red partridge, after mating, abandon his female and rejoin a troop of male vagabonds. The nightingales, perfect pair, sit on the eggs turn by turn. The male, when the female comes to relieve him, remains near by and sings until she is comfortably settled on the eggs. Still more devoted is the male talegalle, a sort of Australian turkey. He makes the nest, an enormous heap of dead leaves; when the female has laid, he watches the eggs, comes from time to time to uncover them for exposure to the sun. He takes his share of watching the young, sheltering them under leaves until they are able to fly.
Of mammals, the carnivora and rodents often practice a certain, at least temporary, monogamy. Foxes live in couples, and educate the young foxes. One finds their real habits in the old "Roman du Renart": Renard the fox goes vagabond, hunting for prey and windfalls, while Madame Hermaline, his wife, waits at home, in her bower at Maupertuis. The vixen teaches her children the art of killing and dividing; their apprenticeship is made on the still living game which the male purveyor has brought to the house. The rabbit is very rough in love; the hamster, another rodent, often becomes carnivorous during the rutting season; they say that he is quite ready to eat his young, and that the female, fearing his ferocity, leaves him before delivery. These aberrations are exaggerated in captivity, and affect even the female. One knows that the she-rabbit sometimes eats her young; this happens especially when one has the imprudence to touch or even to look too closely at the young rabbits. This is enough to bring on a violent disturbance of maternal sentiment. The same dementia has been observed in a vixen who had kittened in a cage; one day someone passed, and looked steadily at the young foxes, a quarter of an hour later they were throttled.
Various explanations are given for this practice among she-rabbits, the simplest being that they are driven by thirst to kill the young in order to drink the blood. This is rather Dantescan for she-rabbits. They say also, regarding both wild and tame rabbits, that the female when surprised kills the young because she has not industry like the doe-hare, cat, or bitch, to transport them to some other place or to save at least one, by the scruff of its neck. The third explanation is that, devouring the afterbirth, like nearly all mammals, and this from physiological motive, the doe-rabbit acquires a taste, and continues the meal, absorbing the young as well. Without rejecting any of these explanations one may present several others. First, it is not only the females who eat the young, the males are equally given to it. Being very lascivious, the male rabbit tries to get rid of his young, in order to stop suckling, and have his female again. On the other hand, it is a regular fact, that as soon as she has retaken the habit of having the male, the mother rabbit, even if she is still giving suck, at once ceases to recognize her offspring, her brief ideas already turned toward her new, coming family. Different causes may engender identical acts, and different lines of reasoning bring the same conclusions. There is reasoning in this case of the rabbit; there is no reasoning save in case of initial error, when there is trouble in the intellect. This trouble and the final massacre is all that one can state definitely: the reasoning escapes our analysis.
Is the rabbit really monogamous? Perhaps, with a monogamy for the season, or from necessity. The male, in any case pays no attention to the young, unless it be to throttle them; thus the female as soon as she is gravid, takes refuge in an isolated burrow. Their coupling, which occurs especially toward evening, is repeated as often as five or six times an hour, the female crouching in a particular manner; the break away is very sudden, the male throwing himself back, sidewise and uttering a short cry. What really makes one doubt the monogamy of the rabbit is that one male is enough for eight or ten females, that he is a great runner, that the males have murderous fights among themselves. Doubtless one must take each specie separately. Buffon pretends that in a warren the oldest buck rabbits have authority over the young. An observer of rabbit habits, M. Mariot-Didieux, admits this trait of superior sociability in angoras, which is just the specie Buffon had studied.
Buck rabbits have still other aberrations, hunters pretend that they pursue doe-hares, tire them and wear them out by their lustiness; it is certain that these couplings give no result.
The Egyptian ichneumon lives in families. It seems that it is very interesting to see them on a hunting expedition, first the male, then the female, then the young in Indian file. Female and young do not take their eyes off father, and imitate all his gestures with care: one might think the train was a large serpent moving in reeds. The wolf who like the fox lives in pairs, helps his female and feeds her, but he does not know his young and will eat them if they come to hand. Certain great apes, gibbon and orang are temporarily monogamous.