Buffon says: 'A number of beavers are employed together at the foot of the tree in gnawing it down; and when this part of the labor is accomplished, it becomes the business of others to sever the branches, while a third party are engaged along the borders of the river in cutting other trees, which though smaller than the first tree, are yet as thick as the leg, if not the thigh, of a common-sized man. These they carry with them by land to the brink of the river, and then by water to the place allotted for their building; where sharpening them at one end, and forming them into stakes, they fix them in the ground, at a small distance from each other, and fill up the vacant spaces with pliant branches. While some are thus employed in fixing the stakes, others go in quest of clay, which they prepare for their purpose with their tails and their feet. At the top of their dyke, or mole, they form two or three openings. These they occasionally enlarge or contract, as the river rises or falls. Note.—Should the current be very gentle, the dam is carried nearly straight across; but when the stream is swiftly flowing, it is uniformly made with a considerable curve, having the convex part opposed to the current.
'Ac veluti ingentem formicæ farris acervum
Cum populant, hyemis memores, tectoque reponunt:
It nigrum campis agmen, prædamque per herbas
Convectant calle augusto: pars grandia trudunt
Obnixæ frumenta humeris: pars agmina cogunt,
Castigant que moras: opere omnis semita fervet.'
Æneid, IV., 402.
'In formicâ non modo sensus sed etiam mens, ratio, memoria.'—Cic.
'Si quis comparet onera corporibus earum (formicarum) fateatur nullis portione. Vires esse majores. Gerunt ea morsu; majora aversæ postremio pedibus moliuntur, humeris obnoxæ. Est iis Reip ratio memoria cura. Semima arrosa condunt vie rursus in fruges exeant e terra. Majora ad introitum (cavernæ) dividunt Madefacta imbre proferunt atque siccant.'—Pliny: lib. XI., cap. 30.
Many birds and other animals, Buffon informs us, station a watch, while they are feeding in the fields. Whenever marmots venture abroad, one is placed as a sentinel, sitting on an elevated rock, while the others amuse themselves in the fields below, or are engaged in cutting grass and making it into hay for their future convenience; and no sooner does their trusty sentinel perceive a man, an eagle, a dog, or any other enemy approaching, than he gives notice to the rest by a kind of whistle, and is himself the last that takes refuge in the cell. It is asserted that when their hay is made, one of them lies upon its back, permits the hay to be heaped between its paws, keeping them upright to make greater room, and in this manner remaining still upon its back, is dragged by the tail, hay and all, to their common retreat.
These instances could be multiplied indefinitely; but more than sufficient have been cited. They prove in the first place, without need of argument, that animals have a language by which they apprehend each other. Concert of action and division of labor would be impossible without it. They also exhibit the exercise of memory and abstraction; and it now remains to ascertain whether their conduct was the result of reason.
If a person should take a friend whose arm had been fractured to a skilful surgeon who had before cured him of a similar wound, we should infer the following course of reasoning: First, a comparison of facts, to discover whether the injury in question was like the one he had received; the ability of this surgeon over others in such cases; and the presumption that the same skill and remedies will again produce the same effects. These are the most obvious points. The dog, in the cited case, had once been healed of a broken limb by a surgeon; and having found a mate in a like situation, took him also to the same surgeon. It is evident that his conduct was as wise as the man's. The facts and actions in the two cases are parallel; and having seen that animals obtain a perception of objects by the same agencies that man does, it only remains to ascertain whether the intermediate reasoning process between perception and action were essentially the same. Now, we cannot prove directly that the mind of another passes through any process whatever; because the proof of any process of our own mind is consciousness, which cannot go beyond us; but we can infer the train of reasoning in a given case with great correctness, taking self-knowledge as a basis; and the similarity of conduct in another, in view of premises, with what our own would have been. This is the chief criterion by which much of our daily conduct is regulated, and is the most substantial proof that can be reached. Hence, we can infer with just as much certainty that the instinct of the dog passed through the process mentioned, as that the mind of the man did in the case supposed. We can also infer it with as much truth as that instinct is susceptible of the process of memory, since the proof in both cases is drawn from facts, and on the same principles.
Again: The beaver's dam is constructed at the very place a skilful engineer would have selected for a similar purpose. This choice of one place before another is necessarily founded on comparison, which is a deliberative reasoning process. It is therefore inconsistent with an impulse, which seems to be the action suggested, by instantaneous perception and reasoning; a single, inflexible propulsion in one direction; without a careful choice, and without deliberation: hence the term impulsive cannot be applied to a large proportion of the actions of animals; and having no reason for supposing the impulses of animals supernatural, or unlike human impulses, the term itself should be abandoned as vague and unmeaning. Gnawing the large tree upon the inner side, that it might fall directly across the stream, also rises above the utmost that we can understand by an inward persuasion; for it is the incipient step, and has full relation to the subsequent work of erecting a pier. We have seen that while one part are cutting down the tree, another part go up the stream, cut smaller trees for stakes, and draw them to the water's edge; while still a third division go in quest of clay to prepare as a mortar. This completeness of plan, and combination of means to execute it, is wholly inconsistent with the common explanation of instinctive operations. Such exhibitions, as we have already remarked, are simply the workings of a certain principle they possess; performing for them the same office that mind does for man; and the true direction of inquiry is to the nature of its qualities. The actions themselves exhibit comparison, a knowledge of the adaptation of means to an end, the combination of these means in regular detail to effect the end, and the still higher intelligence of future cause and effect, as evinced by the enlargement of the water passage with the rise of the stream. These actions, then, being ascertained to be uniformly the same in a great variety of cases, and manifesting the operation of an intelligent principle in every act; and being such as in man would have been in pursuance of the processes of reason mentioned; we are clearly directed to the inference (indeed no other rational one can be made) that they compared the advantages of different places, to enable them to select the best, having reference to the construction of a dam; that they reasoned out the plan of this dam and the adaptation of certain materials to its erection; that they reflected upon the need of its convexity, the better to resist the pressure of the stream, should it be rapid; that they considered the advantages of a division of labor to expedite the work; that they understood from experience, or arrived at the conclusion by reason, that it was safer to discharge the surplus water at one opening well guarded, than over the continuous edge of the dam; and finally they had in view the uses and purpose of this dam from the beginning; and the reasoning preparatory to each successive step was as exact and efficient, with reference to the end designed and the means to be employed, as man's could have been; and was conducted in much, if not exactly, the same manner; because we can conceive of but one way in which an intelligent principle thinks.
To learn, we must derive an impression of the object or event by the senses; and then interpret its meaning by a process of the understanding. The domestic animals may be taught a variety of performances, which if done by man we should not hesitate to pronounce the result of reasoning. Ravens have been taught to sing a regular piece, involving to a certain extent the same kind of apprehension, as in instructing a child in music.[1] The parrot may be taught to speak. Falcons have been learned to hunt, under the influence of motives; a favorite dish being the reward of skilful services. The elephant, the camel, and the horse, in adapting themselves to the wants of man as beasts of burden, give constant proofs of intelligence and deliberation. Some of the most stupid animals apparently, have been taught a variety of feats under the stimulus of rewards, which raise our astonishment at their shrewdness and ingenuity. Imitation, if carefully considered, will be found impossible without the aid of a thinking principle. We know, indeed, very little of any species but our own. Their language is as vague to us as the guttural tongue of the Indian; their movements are usually unmeaning, and all but their general necessities, unknown; we are profoundly ignorant of every thing but the most general manifestations of animal life; and at the same time it must be admitted that they exhibit more intelligence in adapting themselves to, and understanding us, than we do in suiting our conduct to their apprehension.