Popular Science Monthly/Volume 44/March 1894/Industries of Animals
By FRÉDÉRIC HOUSSAY.
WE find among animals not only hunting and fishing but the art of storing in barns, of domesticating various species, of harvesting and reaping—the rudiments of the chief human industries. Certain animals in order to shelter themselves take advantage of natural caverns in the same way as many races of primitive men. Others, like the fox and the rodents, dig out dwellings in the earth; even to-day there are regions where man does not act otherwise, preparing himself a lodging by excavations in the chalk or the tufa. Woven dwellings, constructed with materials entangled in one another, like the nests of birds, proceed from the same method of manufacture as the woolen stuffs of which nomad tribes make their tents. The termites who construct vast dwellings of clay, the beavers who build huts of wood and of mud, have in this industry reached the same point as man. They do not build so well, no doubt, nor in so complex a fashion as modern architects and engineers, but they work in the same way. All these ingenious artisans operate without organs specially adapted to accomplish the effect which they reach. It is with such genuine industries that we have to deal, for the most part neglecting other productions, more marvelous in certain ways, which are formed by particular organs, or are elaborated within the organism, and are not the result of the intelligent effort of the individual. To this category belong the threads which the spider stretches, and the cocoon with which the caterpillar surrounds himself to shelter his metamorphosis.
Struggles of the Chase.—It is not always sufficient for the hunter to find game and to reach it. If the game is of large size it may be able to hold its own, and the pursuit may end in a violent struggle, in which both skill and cunning are necessary to obtain conquest.
The bird which displays the most remarkable qualities in this struggle which terminates the chase, exhibiting indeed a real fencing match, is the secretary bird (Gypogeranus reptilivorus. Fig. 1). He is the more interested in striking without being himself struck, since the fangs with which his prey, the snake, is generally armed might at the first blow give him a mortal wound. In South Africa he pursues every snake, even the most venomous. Warned by instinct of the terrible enemy he has met, the reptile at first seeks safety in flight; the secretary follows him on foot, and the ardor of the chase does not prevent him from being constantly on guard. This is because the snake, finding himself nearly overtaken, suddenly turns round, ready to use his defensive weapons. The bird stops, and turns in one of his wings to protect the lower parts of his body. A real duel then begins. The snake throws himself on his enemy, who at each stroke parries with the end of his wing; the fangs are buried in the great feathers which terminate it, and there leave their poison without producing any effect. All this time with the other wing the secretary repeatedly strikes the reptile, who is at last stunned, and
Fig. 1.—Fight between the Secretary Bird and a Snake.
rolls over on the earth. The conqueror rapidly thrusts his beak into his skull, throws his victim into the air, and swallows him.
Hunting with Projectiles.—It has often been repeated that man is the only creature sufficiently intelligent to utilize as weapons exterior objects like a stone or a stick; in a much greater degree, therefore, it was said, was he the only creature capable of striking from afar with a projectile. Nevertheless, creatures so inferior as fish exhibit extreme skill in the art of reaching their prey at a distance. Several act in this way. There is first the Toxotes jaculator, which lives in the rivers of India. His principal food is formed by the insects who wander over the leaves of aquatic plants. To wait until they fell into the water would naturally result in but meager fare. To leap at them with one bound is difficult, not to mention that the noise would cause them to flee. The Toxotes knows a better trick than that. He draws in some drops of water, and, contracting his mouth, projects them with so much force and certainty that they rarely fail to reach the chosen aim, and to bring into the water all the insects he desires (Fig. 2). Other animals also squirt various liquids, sometimes in Fig. 2.—The Toxotes throwing Water at Insects. attack, but more especially in defense. The cephalopods, for example, emit their ink, which darkens the water and allows them to flee. Certain insects exude bitter or fetid liquids; but in all these cases, and in others that are similar, the animal finds in his own organism a secretion which happens to be more or less useful to his conservation. The method of the Toxotes is different. It is a foreign body which he takes up, and it is an intended victim at which he takes aim and which he strikes; his movements are admirably coordinated to obtain a precise effect.
Another fish, the Chelinous of Java, also acts in this manner. He generally lives in estuaries. It is therefore a brackish water which he takes up and projects by closing his gills and contracting his mouth; he can thus strike a fly at a distance of several feet. Usually he aims sufficiently well to strike it at the first blow, but sometimes he fails. Then he begins again until he has succeeded, which shows that his movements are not those of a machine.
Methods of Utilizing the Captured Game.—Frequently it is not enough for the animal to obtain possession of his prey. Before making his meal it is still necessary to find a method of making use of it, either because the eatable parts are buried in a thick shell which he is unable to break, or because he has captured a creature which rolls itself into a ball and bristles its plumes. Here are some of the more curious practices followed in such cases.
Sometimes it is a question of carrying off a round fruit which offers no prominence to take hold of. The red-headed woodpecker (Melanerpes erythrocephalus) of North America is very greedy with regard to apples, and feeds on them as well as on cherries. It takes him a considerable time to consume an apple, and as he is well aware of the danger he runs by prolonging his stay in an orchard, he wishes to carry away his booty to a safe and sheltered spot. He vigorously plunges his open beak into the apple; the two mandibles enter separately, and the fruit is well fixed; he detaches it and flies away to the chosen retreat.
The combination is complicated, and approaches more nearly the methods employed by man, when the animal makes use of a foreign body, as a tool or as a fulcrum, to achieve his objects. A snake is very embarrassed when he has swallowed an entire egg with the shell; he can not digest it in that condition, and the muscles of his stomach are not strong enough to break it. The snake often finds himself in this condition, and is then accustomed either
Fig. 3.—The Lanius stocking its Larder.
to strike his body against hard objects or to coil himself around them until he has broken the envelope of the egg he contains.
Neither the beak nor the claws of the shrike or butcher bird (Lanius excubitor) are strong enough to enable him to tear his prey easily. When he is not too driven by hunger he installs himself in a comfortable fashion for this carving process, places on a thorn or on a pointed branch the victim he has made, and when it is thus fixed easily devours it in threads.
The Lanius collurio, an allied bird, uses this method still more frequently. He even prepares a small larder before feasting. One may thus see on a thorny branch spitted side by side Coleoptera, crickets, grasshoppers, frogs, and even young birds, which he has seized when they were in flight. (Fig. 3.)
Of all these well-attested facts that which perhaps best shows how animals in certain circumstances may take advantage of a foreign body to utilize the product of the chase is the following, the observation of which is due to Parseval-Deschênes. He followed during several hours an ant bearing a heavy burden. On arriving at the foot of a little hillock the animal was unable to mount with his load, and abandoned it—a very extraordinary fact for one who knows the inconceivable tenacity of insects. The abandonment, therefore, left hope of return. The ant at last met one of his companions, who was also carrying a burden. They stopped, took counsel for an instant, bringing their antennae together, and started for the hillock. The second ant then left his burden, and both together seized a twig and introduced its end beneath the first load which had been abandoned because of its weight. By acting on the free extremity of the twig they were able to use it exactly as a lever, and succeeded almost without trouble in passing their booty on to the other side of the little hillock. It seems to me that these ants who invented the lever are worthy of admiration, and that their ingenuity does not yield to our own.
Animals construct dwellings either to protect themselves from the cold, heat, rain, and other chances of the weather, or to retire to at moments when the search for food does not compel them to be outside and exposed to the attacks of enemies. Some inhabit these refuges permanently; others only remain there during the winter; others, again, who live during the rest of the year in the open air, set up dwellings to bring forth their young, or to lay their eggs and rear the offspring. Whatever the object may be for which these retreats are built, they constitute altogether various manifestations of the same industry, and I will class them, not according to the uses which they are to serve, but according to the amount of art displayed by the architect.
Dwellings formed of Coarsely Entangled Materials.—Diurnal birds of prey are the first animals who practice skillfully the twining of materials. Their nests, which have received the name of eyries, are not yet masterpieces of architecture, and reveal the beginning of the industry which is pushed so far by other birds. Usually situated in wild and inaccessible spots, the young are there in safety when their parents are away on distant expeditions. The abrupt summits of cliffs and the tops of the highest forest trees are the favorite spots chosen by the great birds of prey. The eyrie generally consists of a mass of dry branches which cross and mutually support one another, constituting a whole which is fairly resistant.
Even these primitive nests are not, however, without more complicated details of interest. Thus Mr. Denis Gale wrote to
Fig. 4.—The Stickleback and its Nest.
Bendire concerning the golden eagle in America: "Here in Colorado, in the numerous glades running from the valleys into the foothills, high, inaccessible ledges are quite frequently met with which afford the eagles secure sites for their enormous nests. I know of one nest that must contain two wagon-loads of material. It is over seven feet high, and quite six feet wide on its upper surface. In most cases the cliff above overhangs the site. At the end of February or the beginning of March the needful repairs to the nest are attended to, and the universal branch of evergreen is laid upon the nest, seemingly for any purpose save that of utility. This feature has been present in all the nests I have examined myself, or have had examined by others; it would seem to be employed as a badge of occupancy."
It is scarcely necessary to recall the skillful art with which the stickleback, which inhabits all our streams, plaits its nest and remains sentinel near it. (Fig. 4.) This fish has indeed monopolized our admiration, and is considered as the most skillful if not the only aquatic architect. Yet, besides those which I have already mentioned, there is one which equals the stickleback in the skill it displays in constructing a shelter for its spawn. This is the Gobius niger, met on our coasts, especially in the estuaries of rivers. The male interlaces and weaves the leaves of algæ, etc., and when he has finished his preparations he goes to seek females, and leads them one by one to lay in the retreat he has built. Then he remains in the neighborhood until the young come out, ready to throw himself furiously with his spines on any imprudent intruders.
Dwellings Woven with Greater Art.—Without doubt the class of birds furnishes the most expert artisans in the industry of the woven dwelling. In our own country we may see them seeking every day to right and left, carrying a morsel of straw, a pinch of moss, a hair from a horse's tail, or a tuft of wool caught in a bush. They intermingle these materials, making the framework of the construction with the coarser pieces, keeping those that are warmer and more delicate for the interior. These nests, attached to a fork in a branch or in a shrub, hidden in the depth of a thicket, are little masterpieces of skill and patience. To describe every form and every method would fill a volume. But I can not pass in silence those which reveal a science sure of itself, and which are not very inferior to what man can do in this line. The Lithuanian titmouse (Ægithalus pendulinus), whose works have been well described by Baldamus, lives in the marshes in the midst of reeds and willows in Poland, Galicia, and Hungary. Its nest, which resembles none met in our own country, is always suspended above the water, two or three metres above the surface, fixed to a willow branch. All individuals do not exhibit the same skill in fabricating their dwelling; some are more careful and clever than others who are less experienced. Some, also, are obliged by circumstances to hasten their work. It frequently happens that magpies spoil, or even altogether destroy with blows of their beaks, one of these pretty nests. The unfortunate couple are obliged to recommence their task, and if this accident happens two or three times to the same household, it can easily be imagined that, discouraged and depressed by the advancing season, they hasten to build a shelter anyhow, only doing what is indispensable, and neglecting perfection.
The Art of Sewing among Birds.—There are birds which have succeeded in solving a remarkable difficulty. Sewing seems
Fig. 5.—The Tailor Bird and its Nest.
so ingenious an art that it must be reserved for the human species alone. Yet the tailor bird, the Orthotomus longicauda, and other species possess the elements of it. They place their nests in a large leaf which they prepare to this end. With their beaks they pierce two rows of holes along the two edges of the leaf; they then pass a stout thread from one side to the other alternately. With this leaf, at first flat, they form a horn in which they weave their nest with cotton or hair. (Fig. 5.) These labors of weaving and sewing are preceded by the spinning of the thread. The bird makes it itself by twisting in its beak spiders' webs, bits of cotton, and little ends of wool. Sykes found that the threads used for sewing were knotted at the ends. It is impossible not to admire
Fig. 6.—An Edible Birds' Nest and the Swallow that makes it.
animals who have skillfully triumphed over all the obstacles met with in the course of these complicated operations.
Gelatin Nests.—These are made by certain swallows who nest in grottoes or cliffs on the edge of the sea. After having collected from the water a gelatinous substance formed either of the spawn of fish or the eggs of mollusca, they carry this substance on to a perpendicular wall, and apply it to form an arc of a circle. This first deposit being dry, they increase it by sticking on to its edge a new deposit. Gradually the dwelling takes on the appearance of a cup, and receives the workers' eggs. (Fig. 6.) These dwellings are the famous swallows' nests so appreciated by the epicures of the extreme East, which are edible in the same way as, for example, caviare.
Constructions built of Earth—Solitary Masons. —Certain animals, whose dwelling participates in the nature of a hollow cavern, make additions to it which claim a place among the constructions with which we are now occupied.
The Anthiophora parietina is in this group: it is a small bee which lives in liberty in our climate. As its name indicates, it prefers to frequent the walls of old buildings, and finds a refuge in the interstices, hollowing out the mortar half disintegrated by time. The entrance to the dwelling is protected by a tube curved toward the bottom, and making an external prominence. (Fig. 7.) The owner comes and goes by this passage, and as it is curved towards the earth the interior is protected against a flow of rain, while at the same time the entry is rendered more difficult for Melectes and Anthrax. These insects, in fact, watch the departure of the Anthophora to endeavor to penetrate into their nests and lay their eggs there. The gallery of entry and exit has been built with grains of sand, the débris produced by the insect in working. These grains of sand glued together form, on drying, a very resistant wall.
The other animals of which I have to speak are genuine masons, who prepare their mortar by tempering moistened earth.
Fig. 7.—Homes of Mason Bees.
Every one has seen the swallow in spring working at its nest in the corner of a window. It usually establishes its dwelling in an angle, so that the three existing walls can be utilized, and to have an inclosed space there is need only to add the face. It usually gives to this the form of a quarter of a sphere, and begins it by applying earth more or less mixed with chopped hay against the walls which are to support the edifice. At the summit of the construction a hole is left for entry and exit. During the whole of its sojourn in our country the swallow uses this dwelling, and even returns to it for many years in succession, as long as its work will support the attacks of time. The faithful return of these birds to their old nest has been many times proved by attaching ribbons to their claws; they have always returned with the distinctive mark.
Masons Working in Association.—Ants have already furnished us with numerous proofs of their intelligence and their prodigious industry. So remote from man from the anatomical point of view, they are of all animals those whose psychic faculties bring them nearest to him. Sociable like him, they have undergone an evolution parallel to his which has placed them at the head of insects in the same way as he has become superior to all other mammals. The brain in ants, as in man, has undergone a disproportionate development. Like man, they possess a language which enables them to combine their efforts, and there is no human industry in which these insects have not arrived at a high degree of perfection. If in certain parts of the earth human societies are superior to those of ants, in many others the civilization of ants is notably superior. No village of Kaffirs can becompared to a palace of the Termites. The classifications separate these insects (sometimes called "white ants") from the ants, since the latter are Hymenoptera, while the former are ranked among the Neuroptera, but their constructions are almost alike, and may be described together. These small animals, relatively to their size, build on a colossal scale compared to man; even our most exceptional monuments can not be placed beside their ordinary buildings. (Fig. 8.) The domes of triturated and plastered clay which cover their nests may rise to a height of five metres; that is to say, to dimensions equal to one thousand times the length of the worker. The Eiffel Tower, the most elevated monument of which human industry can boast, is only one hundred and eighty-seven times the average height of the worker. It is three hundred metres high, but to equal the Termites' audacity it would have to attain a height of sixteen hundred metres.
The lofty nest, or Termitarium, constitutes a hillock in the form of a cupola. The interior arrangement is very complicated, and at the same time very well adapted to the life of the inhabitants. There are four stories in all, covered by the general exterior walls. The walls of the dome are very thick; at the base they measure from sixty to eighty centimetres. The clay, in drying, attains the hardness of brick, and the whole is very coherent. The sentinels of herds of wild cattle choose these tumuli as observatories, and do not break them down. The walls of this exterior enceinte are hollowed by galleries of two kinds: some horizontal and giving access from outside to all the stories, the others mounting spirally in the thickness of the wall to the summit of the dome. When the colony is in full activity, after the construction is completed, these little passages have no further use. They served for the passage of the masons when building
Fig. 8.—Section of a Palace of the Termites.
the cupola, and they could be utilized again if a breach should be made in the wall. At the lower part these galleries in the wall are very wide, and they sink into the earth beneath the palace to a depth of more than 1·50 metre.
These subterranean passages are the catacombs of the Termites, and have a very close analogy with those of old and populous human cities. Their origin is similar; they are ancient quarries. The insects hollowed them in obtaining the necessary clay for their labors. Later, when the rains come, they serve as drains to carry off the water which might threaten to invade the dwelling.
Comparative anatomy has long since removed the barriers, once thought impassable, raised by human pride between man and the other animals. Our bodies do not differ from theirs; and, moreover, such glimpses as we are able to obtain allow us to conclude that their psychic faculties are of the same nature as our own. Man in his evolution introduces no new factor.
The industries in which the talents of animals are exercised demonstrate that, under the influence of the same environment, animals have reacted in the same manner as man, and have formed the same combinations to protect themselves from cold or heat, to defend themselves against the attacks of enemies, and to insure sufficient provision of food during those hard seasons of the year when the earth does not yield in abundance.
It must only be added, to avoid falling into exaggeration, that man excels in all the arts, of which only scattered rudiments are found among the other animals; and we may safeguard our pride by affirming that we need not fear comparison. If our intelligence is not essentially different from that of animals, we have the satisfaction of knowing that it is much superior to theirs.