But though animals sleep, many of them are nocturnal in their habits. Humboldt gives a vivid description of night in a Brazilian forest.
"Everything passed tranquilly till eleven at night, and then a noise so terrible arose in the neighbouring forest that it was almost impossible to close our eyes. Amid the cries of so many wild beasts howling at once the Indians discriminated such only as were (at intervals) heard separately. These were the little soft cries of the sapajous, the moans of the alouate apes, the howlings of the jaguar and couguar, the peccary and the sloth, and the cries of (many) birds. When the jaguars approached the skirt of the forest our dog, which till then had never ceased barking, began to howl and seek for shelter beneath our hammocks. Sometimes, after a long silence, the cry of the tiger came from the tops of the trees; and then it was followed by the sharp and long whistling of the monkeys, which appeared to flee from the danger which threatened them. We heard the same noises repeated during the course of whole months whenever the forest approached the bed of the river.
"When the natives are interrogated on the causes of the tremendous noise made by the beasts of the forest at certain hours of the night, the answer is, they are keeping the feast of the full moon. I believe this agitation is most frequently the effect of some conflict that has arisen in the depths of the forest. The jaguars, for instance, pursue the peccaries and the tapirs, which, having no defence, flee in close troops, and break down the bushes they find in their way. Terrified at this struggle, the timid and distrustful monkeys answer, from the tops of the trees, the cries of the large animals. They awaken the birds that live in society, and by degrees the whole assembly is in commotion. It is not always in a fine moonlight, but more particularly at the time of a storm of violent showers, that this tumult takes place among the wild beasts. 'May heaven grant them a quiet night and repose, and us also!' said the monk who accompanied us to the Rio Negro, when, sinking with fatigue, he assisted in arranging our accommodation for the night."
Life is indeed among animals a struggle for existence, and in addition to the more usual weapons—teeth and claws—we find in some animals special and peculiar means of offence and defence.
If we had not been so familiarised with the fact, the possession of poison might well seem a wonderful gift. That a fluid, harmless in one animal itself, should yet prove so deadly when transferred to others, is certainly very remarkable; and though the venom of the Cobra or the Rattlesnake appeal perhaps more effectively to our imagination, we have conclusive evidence of concentrated poison even in the bite of a midge, which may remain for days perceptible. The sting of a Bee or Wasp, though somewhat similar in its effect, is a totally different organ, being a modified ovipositor. Some species of Ants do not sting in the ordinary sense, but eject their acrid poison to a distance of several inches.
Another very remarkable weapon is the electric battery of certain Eels, of the Electric Cat Fish, and the Torpedoes, one of which is said to be able to discharge an amount of electricity sufficient to kill a Man.
Some of the Medusæ and other Zoophytes are armed by millions of minute organs known as "thread cells." Each consists of a cell, within which a firm, elastic thread is tightly coiled. The moment the Medusa touches its prey the cells burst and the threads spring out. Entering the flesh as they do by myriads, they prove very effective weapons.
The ink of the Sepia has passed into a proverb. The animal possesses a store of dark fluid, which, if attacked, it at once ejects, and thus escapes under cover of the cloud thus created.
The so-called Bombardier Beetles, when attacked, discharge at the enemy, from the hinder part of their body, an acrid fluid which, as soon as it comes in contact with air, explodes with a sound resembling a miniature gun. Westwood mentions, on the authority of Burchell, that on one occasion, "whilst resting for the night on the banks of one of the large South American rivers, he went out with a lantern to make an astronomical observation, accompanied by one of his black servant boys; and as they were proceeding, their attention was directed to numerous beetles running about upon the shore, which, when captured, proved to be specimens of a large species of Brachinus. On being seized they immediately began to play off their artillery, burning and staining the flesh to such a degree that only a few specimens could be captured with the naked hand, and leaving a mark which remained a considerable time. Upon observing the whitish vapour with which the explosions were accompanied, the negro exclaimed in his broken English, with evident surprise, 'Ah, massa, they make smoke!'"
Many other remarkable illustrations might be quoted; as for instance the web of the Spider, the pit of the Ant Lion, the mephitic odour of the Skunk.