It is owing to their union in large bands that Crows have so little to fear from diurnal birds of prey; if one approaches, they do not hesitate to throw themselves on him altogether. The Great Horn Owl, however, causes many ravages among them; for when asleep at night the Crow is without defence against the ravisher, for whom, on the contrary, obscurity is propitious. Thus they recognise him as a hereditary enemy, and never allow an opportunity of revenge to pass without profiting by it. If by chance an owl appears by day and one of them perceives him, immediately a clamour arises — a veritable cry of war; all those who are in the neighbourhood fly to the spot, and business ceases; the nocturnal bird of prey is assaulted, riddled with blows from beaks, stunned, his feathers torn out, and, notwithstanding his defence, he succumbs to numbers.
In all the preceding examples the social species unite for the common security the forces and effects which they can derive from their own organs.
I have spoken of the Apes and described how they defend themselves with their hands and teeth; but in certain cases they use weapons, employing foreign objects like a club or like projectiles.
Acts of this nature are considered to indicate a high degree of development, and it has often been repeated that they are the appanage of man alone; we have, however, seen the Toxotes, who, like all fishes, is not particularly intelligent, squirt water on to his victims. It is not easy to understand how a greater intellectual effort is required to throw a stone with the hand than to project water with the mouth. This is what the apes do, throwing on their assailants from the heights of trees everything which comes to hand: cocoa-nuts, hard fruits, fragments of wood, etc.
Baboons (Cynocephali) who usually live in the midst of rocks protect their retreat by rolling very heavy blocks on to their aggressors, or by forcibly throwing stones about the size of the fist. As these bands may contain from a hundred to one hundred and fifty individuals, it is a veritable hail of stones of all sizes which they roll down from the heights of the mountains where they find shelter.
Sentinels. — Not only do Apes know how to face danger or to avoid it by a prudent flight, but they also seek to foresee it, and to avoid exposing themselves to it. A troop of Apes, according to Brehm, generally places the leadership in the hands of a robust and experienced male. This primitive royalty is founded partly on the confidence inspired by an old chief, and partly by the fear inspired by his muscular arms and ferocious canine teeth. ([Fig. 9.]) He gives himself a great deal of trouble for the security of his subjects, and does not abuse the authority which he possesses. Always at the head, he leaps from branch to branch, and the band follows him. From time to time he scales a tall tree, and from its heights scrutinises the neighbourhood. If he discovers nothing suspicious a particular guttural grunt gives information to his companions. If, on the contrary, he perceives some danger he warns them by another cry, and all draw in ready to follow him in his retreat, which he directs in the same way as he guided the forward march.
Apes are not alone in relying on the experience of one of their members. Many other animals act in the same way: antelopes, gazelles, elephants, who advance in troops always conducted by an old male or female who knows all the forest paths, all the places favourable to pasture, and all the regions which must be avoided.
