The Minds and Manners of Wild Animals: A Book of Personal Observations

In its Bornean jungle home, the orang-utan is nearly as silent as the grave. Never save once did I hear one utter a vocal sound. That was a deep bass roar emitted by an old male that I disturbed while he was sleeping on the comfortable nest of green branches that he had built for himself. Concerning the chimpanzee, the late Mr. Richard L. Garner testified as follows: "Not only does the chimpanzee often break the silence of the forest when all other voices are hushed, but he frequently answers the sounds of other animals, as if in mockery or defiance. ... Although diurnal in habit, the chimpanzees often make the night reverberate with the sounds of their terrific screaming, which I have known them to continue at times for more than an hour, with scarcely a moment's pause,--not one voice but many, and within the area of a square mile or so I have distinguished as many as seven alternating adult male voices. "The gorilla is more silent and stoical than the chimpanzee, but he is far from being mute. He appears to be devoid of all risibility, but he is often very noisy. Although diurnal in habit, he talks less frequently during the day than at night, but his silence is a natural consequence of his stealth and cunning. There are times, however, when he ignores all danger of betraying his whereabouts or his movements, and gives vent to a deluge of speech. At night his screams and shouts are terrific."