THE AMERICAN MONKEYS 147 



however, that the species, like the titis, in which the tail is not prehensile, are 

 equally as arboreal in habits as those with prehensile tails, it is quite clear that the 

 latter type of organ can only be regarded as a kind of luxury. Indeed, the whole 

 question as to the reason why some monkeys have long tails, others short tails, and 

 others, again, no tails at all, is involved in great obscurity. 



The headquarters of the American monkeys are the great forest regions of the 

 IvOwer Amazon Valley, known as the Selvas ; although they are also abundant in" 

 many other parts of Brazil, and likewise in the Orinoco Valley in Venezuela. All 

 these animals are truly tropical and subtropical, although they extend to a longer 

 distance on the south of the equator than they do on the north. To the northward, 

 indeed, it appears that monkeys do not extend beyond the Tropic of Cancer in the 

 southern half of Mexico ; whereas in South America they are known to range as 

 far as the Rio Grande do Sul, in latitude 30. 



In the vast forests of South America, monkeys make their presence known by 

 their loud cries much more than in any other part of the world, unless, indeed, 

 it be those parts of the Oriental region inhabited by the gibbons. The best 

 description extant of the nocturnal noises of the American forests is that given 

 by Humboldt. "After eleven o'clock," writes the great German traveler and 

 philosopher, "such a noise began in the contiguous forest, that for the remainder 

 of the night all sleep was impossible. The wild cries of the animals rang through 

 the woods. Among the many voices that resounded together, the Indians could 

 only recognize those which, after short pauses, were heard singly. There was the 

 monotonous, plaintive cry of the aluates [howling monkeys], the whining, flute-like 

 notes of the small sapajous, the grunting murmur of the striped night-monkey 

 {Nyctipithecus trivirgatus} , which I was the first to describe, the fitful roar of the 

 great tiger [jaguar], the cuguar, or maneless American lion [puma], the peccary, 

 the .sloth, and a host of parrots, parraquas, and other pheasant-like birds. When- 

 ever the tiger approached the edge of the forest, our dog, who before had barked 

 incessantly, came howling to seek protection under the hammocks. Sometimes 

 the cry of the tiger resounded from the branches of a tree, and was then always 

 accompanied by the plaintive, piping tones of the monkeys, who were endeavoring 

 to escape from the unwonted pursuit. 



' ' If one asks the Indians why such a continuous noise is heard on certain 

 nights, they answer, with a smile, that ' the animals are rejoicing in the beautiful 

 moonlight, and celebrating the return of the full moon.' To me the scenes appeared 

 rather to be owing to an accidental, long-continued, and gradually increasing con- 

 flict among the animals. Thus, for instance, the jaguar will pursue the peccaries 

 and the tapirs, which, densely crowded together, burst through the barrier of tree- 

 like shrubs which -opposes their flight. Terrified at the confusion, the monkeys 

 on the tops of the trees join their cries with those of the larger animals. This 

 arouses the tribes of birds who build their nests in communities, and suddenly the 

 whole animal world is in a state of commotion. Further experience taught us that 

 it was by no means always the festival of moonlight that disturbed the stillness of 

 the forest ; for we observed that the voices were loudest during the violent storms 

 of rain, or when the thunder echoed and the lightning flashed through the depths 



