Babirusa ("pig-deer"), the Malay name of the wild swine of Celebes and Buru, which has been adopted in zoology as the scientific designation of this remarkable animal (the only representative of its genus), in the form of Babirusa alfurus. The skin is nearly naked, and very rough and rugged. The total number of teeth is 34, with the formula i.2/3. c.1/1. p.2/3. m.3/3. The molars, and more especially the last, are smaller and simpler than in the pigs of the genus Sus, but the peculiarity of this genus is the extraordinary development of the canines, or tusks, of the male. These teeth are ever-growing, long, slender and curved, and without enamel. Those of the upper jaw are directed upwards from their bases, so that they never enter the mouth, but pierce the skin of the face, thus resembling horns rather than teeth; they curve backwards, downwards, and finally often forwards again, almost or quite touching the forehead. Dr A. R. Wallace remarks that "it is difficult to understand what can be the use of these horn-like teeth. Some of the old writers supposed that they served as hooks by which the creature could rest its head on a branch.
But the way in which they usually diverge just over and in front of the eye has suggested the more probable idea, that they serve to guard these organs from thorns and spines while hunting for fallen fruits among the tangled thickets of rattans and other spiny plants. Even this, however, is not satisfactory, for the female, who must seek her food in the same way, does not possess them. I should be inclined to believe rather that these tusks were once useful, and were then worn down as fast as they grew, but that changed conditions of life have rendered them unnecessary, and they now develop into a monstrous form, just as the incisors of the beaver and rabbit will go on growing if the opposite teeth do not wear them away. In old animals they reach an enormous size, and are generally broken off as if by fighting." On this latter view we may regard the tusks of the male babirusa as examples of redundant development, analogous to that of the single pair of lower teeth in some of the beaked whales. Unlike ordinary wild pigs, the babirusa produces uniformly coloured young. (See Swine.)