Mr. Bartlett watched a wild boar quarrelling rather savagely with his sow; and both had their mouths open and their ears drawn backwards. But this does not appear to be a common action with domestic pigs when quarrelling. Boars fight together by striking upwards with their tusks; and Mr. Bartlett doubts whether they then draw back their ears. Elephants, which in like manner fight with their tusks, do not retract their ears, but, on the contrary, erect them when rushing at each other or at an enemy. The rhinoceroses in the Zoological Gardens fight with their nasal horns, and have never been seen to attempt biting each other except in play; and the keepers are convinced that they do not draw back their ears, like horses and dogs, when feeling savage. The following statement, therefore, by Sir S. Baker[434] is inexplicable, namely, that a rhinoceros, which he shot in North Africa, “had no ears; they had been bitten off close to the head by another of the same species while fighting; and this mutilation is by no means uncommon.” Lastly, with respect to monkeys. Some kinds, which have moveable ears, and which fight with their teeth—for instance the _Cereopithecus ruber_—draw back their ears when irritated just like dogs; and they then have a very spiteful appearance. Other kinds, as the _Inuus ecaudatus_, apparently do not thus act. Again, other kinds—and this is a great anomaly in comparison with most other animals—retract their ears, show their teeth, and jabber, when they are pleased by being caressed. I observed this in two or three species of Macacus, and in the _Cynopithecus niger_. This expression, owing to our familiarity with dogs, would never be recognized as one of joy or pleasure by those unacquainted with monkeys. _Erection of the Ears_.—This movement requires hardly any notice. All animals which have the power of freely moving their ears, when they are startled, or when they closely observe any object, direct their ears to the point towards which they are looking, in order to hear any sound from this quarter. At the same time they generally raise their heads, as all their organs of sense are there situated, and some of the smaller animals rise on their hind-legs. Even those kinds which squat on the ground or instantly flee away to avoid danger, generally act momentarily in this manner, in order to ascertain the source and nature of the danger. The head being raised, with erected ears and eyes directed forwards, gives an unmistakable expression of close attention to any animal. CHAPTER V. SPECIAL EXPRESSIONS OF ANIMALS. The Dog, various expressive movements of—Cats—Horses—Ruminants—Monkeys, their expression of joy and affection—Of pain—Anger—Astonishment and Terror.