Aluatta senicula, Slack, Proc. Acad. Nat. Sci. Philad., 1862, p. 517.
(Plate XVIII.)
Characters.—Head, neck, limbs and tail, dark chestnut-brown; back and sides golden-yellow; beard in the full-grown male long, the hair golden-yellow at the root, otherwise chestnut-brown; face naked, black; chest naked, the abdomen sparsely covered with long brown hairs.
The hair of the body is soft. The tail varies in colour in individual specimens, being sometimes, at its termination, of the same colour as the back, and sometimes bright golden-yellow. The mammæ are occasionally situated in the axillæ (or arm-pits). Length of body, 19½ inches; tail, 20 inches.
Young.—Of the same colour as the parents, only a little darker, the hair hard and rigid.
Distribution.—Brazil; New Granada; Venezuela; Copataza river, Ecuador; Eastern Peru, along the Ucayali and Huallaga rivers.
Habits.—The Red Howlers always travel in large companies, keeping to the forests of the low lands and shores of the rivers. "We stopped," writes Humboldt, "to observe the Howling Monkeys, which, to the number of thirty or forty, crossed the road by passing in a long file from one tree to another upon the horizontal and intersecting branches." On another occasion the same celebrated naturalist records that "on approaching a group of trees, we perceived numerous bands of Arguatoes going as in a procession from one tree to another with extreme slowness. A male was followed by a great number of females, several of which carried their young on their shoulders. The uniformity with which the Arguatoes execute their movements is extremely striking. Whenever the branches of neighbouring trees do not touch, the male that leads the band suspends himself by the callous and prehensile part of his tail; and letting fall the rest of his body, swings himself till in one of his oscillations he reaches the neighbouring branch. The whole file performs the same action on the same spot. It is almost superfluous to add how dubious is the assertion that the Arguatoes and other Monkeys with prehensile tails form a sort of chain, in order to reach the opposite side of a river. We had opportunities, during five years, of observing thousands of these animals, and for this very reason we place no confidence in these stories."
"The Arguatoes are sometimes accused of abandoning their young, that they may be more free for flight when pursued by Indian hunters. It is said that mothers have been seen taking off their young from their shoulders and throwing them down to the foot of the tree. I am inclined to believe that a movement merely accidental has been mistaken for one that was premeditated. The Arguatoes, on account of their mournful aspect and their uniform howlings, are at once detested and calumniated by the Indians."
Mr. Wallace, in a paper "On the Monkeys of the Amazon," in the "Proceedings of the Zoological Society," says: "Humboldt observes that the tremendous noise which these Howlers make can only be accounted for by the great number of individuals that unite in its production. My own observations, and the unanimous testimony of the Indians, prove this not to be the case, one individual alone making the howling, which is certainly of a remarkable depth and volume and curiously modulated; but on closely remarking the suddenness with which it ceases and again commences, it is evident that it is produced by one animal, which is generally a full-grown male."
The flesh of this species is very good to eat, and furnishes the principal food of the inhabitants of the regions in which it abounds.