2. Elephants begin to copulate at twenty years old. When the female is impregnated, her period of gestation, some persons say, is a year and a half; other people make it three years. The difficulty of seeing their copulation causes this difference of opinion respecting the period of gestation. The female produces her young bending upon her haunches. Her pain is evident. The calf, when it is born, sucks with its mouth, and not with its proboscis. It can walk and see as soon as it is born. 3. Wild swine copulate at the beginning of winter. They produce their young in the spring. For this purpose the female gets away into inaccessible and precipitous places, where there are caves and plenty of shade. The males remain with the females for thirty days. The number of pigs and the period of gestation are the same as in the domesticated herd, and their voices are much alike: the female, however, grunts more and the male less. The castration of the male makes them larger and more fierce, as Homer writes. "He brought up a castrated wild boar, which was not like a beast fed upon food, but resembled a woody mountain peak." Castration takes place from a disease like a swelling in the testicles, which they rub against the trees and so destroy them. CHAPTER XXVI. 1. The female deer usually copulates, as I observed before, from allurement; for she cannot endure the male on account of the hardness of the penis. Some, however, endure copulation as sheep do. When sexual desire is felt, they lie down beside each other. The male is changeable in his disposition, and does not unite himself to a single female, but in a short time leaves one for another. The season for sexual intercourse is in August and September, after Arcturus. The period of gestation is eight months. The female becomes pregnant in a few days, and frequently in one day. 2. She generally produces one fawn, though some have been known to bear twins. She produces her young by the road side, for fear of wild beasts. The growth of the fawns is rapid. The female has no purification at other times, but after parturition her cleansing is sanguineous. The female usually conducts her fawn to some accustomed place, which serves them for a refuge. It is usually an opening in a rock, with but one entrance, where they can defend themselves against those who would attack them. 3. There are fables about their long life. They do not, however, appear to be worthy of credit; and the period of gestation and growth of the young does not agree with the habits of long-lived animals. In the mountain called Elaphoïs, in Arginusa, in Asia, where Alcibiades died, all the deer have their ears divided, so that they can be known if they migrate to another place, and even the fœtus in utero has this distinction. The females have four nipples, like cows.