Real marriage is to be found only among birds.[26] For mammals the same cannot be said, for though the mother generally gives much attention to the young, the father does not always have as much concern. He even, in some cases, is the enemy of his own offspring. Yet even in the cases of mammals there are durable associations between the sexes. Very often these last only during the rutting season, but among whales, seals, hippopotami, the _Cervus campestris_,[27] gazelles,[28] the _Neotragus Hemprichii_ and other small antelopes, reindeer, the _Hydromus coypus_, squirrels, moles, the ichneumon, and certain carnivorous animals, among the latter cats, martens, the yaguarundi of South America, and the _Canis Brasiliensis_ and perhaps the wolf, there are durable matings. Association between the sexes is common among all of these animals for periods after the young have been born. And in all cases the male is the family’s protector. What is an exception among the lower mammals is, however, a rule among the Quadrumana. According to the natives of Madagascar some species of Prosimii are nursed by both male and female in common. Among the _Arctopitheci_ the female is always assisted by the male in taking care of the young. Coming to the man-like apes, we are told by Lieutenant de Crespigny that “in the northern part of Borneo they live in families—the male, female, and young one. On one occasion,” he says, “I found a family in which were two young ones, one of them much larger than the other, and I took this as a proof that the family tie had existed for at least two seasons. They build commodious nests in the trees which form their feeding-ground, and, so far as I could observe, the nests, which are well lined with dry leaves, are occupied only by the female and young, the male passing the night in the fork of the same or another tree in the vicinity. The nests are very numerous all over the forest, for they are not occupied above a few nights, the mias (or orang-utan) leading a roving life.” Dr. Savage says that the gorillas live in bands and that but one male is seen in every band. M. du Chaillu says that the male gorilla is always accompanied by the female.