Smithsonian Report/1898/The Laws of Orientation Among Animals
THE LAWS OF ORIENTATION AMONG ANIMALS.[1]
By Capt. G. Reynaud.
It would seem that wild animals are devoted to a wandering life, and yet a careful observation of their habits shows that the fields, the woods, the plains, and the air are quite equitably divided among them, as separate districts. Each one of them lives within a domain whose resources he uses to the best advantage, and where, fearing the competition of his kind, he permits only a limited number of them to range. Thus among animals property is communal.
The extent of the domain varies, moreover, with the resources which it presents, the protection which it offers against every kind of danger, and especially according to the animal's power of locomotion.
This division of domain is in some measure a necessity of existence. Every animal that, by reason of defective instinct or for any other reason, attempts to escape from it is quickly exterminated by natural selection; driven off by his comrades with whom he strives for daily food, wandering haphazard in a unknown territory full of snares, he becomes an easy prey for the enemies of his species.
The instinct of orientation, which guides an animal back to his home, and consequently his habits, his food, his protection against danger, plays a prominent part in his life. To it he owes his individuality, the memory which attaches him to the past, and, up to a certain point, the satisfaction of his needs in the present.
We propose to study the mechanism of this orientation among animals. As the principal object of our study, we have chosen the carrier pigeon. A great number of facts observed by us for the first time have been grouped and classified. We have deduced, if not the law that controls, at least a theory that accounts for them. This theory we will now explain. All of its propositions are founded upon facts rigorously and scrupulously established or on experiments easy to reproduce.
I.
Just as occurrences seemingly casual, such as the distribution of bullets in a target, are subject to laws of which science has given us the secret, so in the capricious flight of a bird or the wandering course of a wild animal chance has, as we believe, no part.
The motive which determines the actions of the animal is the instinct of preservation of the individual and of the species. The animal is capable of a spontaneous activity when he is roused by necessity; it is very seldom that he performs an act that has no immediately useful end. Initiative[2] is not within his power, and when, in ants or bees, we think we have observed forethought for the future, we soon see that this supposed provision is nothing more than obedience to the momentary call of instinct: the animal accomplishes an action without foreseeing the result.
The search for food and sleep are the two poles between which the existence of an animal constantly gravitates. If, to utilize the resources of his domain, he is obliged to vary his course daily, the periodic need for rest yet brings him back to the same quarters. The lack of initiative leads him to always follow the same road to return to the same point. This is why the animal on his domain makes a number of trails which are interwoven in every direction; he acquires in this way a very complete knowledge of the locality; in the region where every little irregularity is familiar to him he is ready to move in every direction.
Necessity may force the inhabitant of one region to overstep its limits, in time of drought or famine, for example. Then he makes a rapid incursion into the neighboring territory, delays not a moment, but as soon as he has quenched his thirst or appeased his hunger returns in all haste to his home. In this second region, seldom fully explored, the animal knows but a limited number of trails, usually straight ones. If he is surprised there by a danger of any kind, he is much more exposed than in his own territory.
One example will show plainly the essential difference existing between these two zones. When a stag is attacked in his own domain by hunters, he begins by doubling, makes a thousand turns, and for a time throws his adversaries off the track. Soon again discovered, he sets out anew; pursued from shelter to shelter he finally "gets away" and plunges into the second zone, where the trails are straight. The chase then changes its character, and takes on a rapid pace which it did not have in its first phase.
The stag soon reaches the limits of the known territory and tries to return on his tracks and regain his own domain. Constantly driven back, pressed closely by the dogs, he again sets out, crosses the second zone, and then, entering the unknown territory, he is "off," running straight forward until he falls.
It is interesting to see how a stag acts who has been carried some distance in a cage and then set at liberty before a hunting party to be chased. The animal, cast on an unknown ground, does not try to double, but springs before the dogs and is off immediately. The chase presents none of the evolutions which we described above; it is nothing but a race between the herbivorous animal, who has on his side speed, and the carnivorous animal, who has endurance. From the condition of the animal and the speed of the hunting party one can determine beforehand the duration of the chase. We will not dwell longer on these facts so well known to hunters. It is, in fact, sufficient to go through a wood in Sologne, or in any other country abounding in game, to be convinced that the ground is traversed in every direction by trails which do not escape the experienced eyes of the poacher.
Birds also follow through the air roads invisible to our eyes, but which can be revealed by observation. The bird, like the quadruped, contracts the habit of always returning to the same point by the same route. We have watched for some time a group of pigeons that returned every day to the fields at the same time. In going, as in coming, they undeviatingly followed a line which we had marked out on the neighboring ground. We have observed the same regularity of route in the coming and going of two birds of prey.
The peasants know very exactly the points which mark the course of the migrations of birds, and turn this knowledge to account by hunting during certain seasons.
Similar observations have been made on fishes in the sea as well as in rivers, and the very exact information obtained is put to a daily use by fishermen.
We will not put further stress on an array of facts long since observed and known. We will limit ourselves to deducing from them a primary conclusion. In the air, on land, or in the water all animals follow routes definitely determined; their movements seem, therefore, to be subject to other laws than those of caprice or chance.
II.
The actions of animals are all dictated by a single law, which each one of them obeys in a different way. The animal is controlled by his environment. If he finds around his home an abundauce of the necessities of life, he moves about but little and his existence is passed in a very restricted domain. In the opposite case he lives a very active life, traversing his domain unceasingly, extending its limits as far as possible and sometimes going beyond them. Each animal is thus led to contract habits which become peculiar to him and which constitute his individuality. He obeys the call of instinct, but he seems to have the choice of the means of execution, a certain liberty, while he is simply under the influence of his surroundings. It is necessary to bear this in mind before fixing those general laws to which the movements of the individuals of each species are subject.
It is a fact known by experiment for some time that an animal moving about in a territory familiar to him is guided in finding his way back to his home by all five senses working together. Always, in every species, one of the senses is more developed than the rest, and therefore plays a more prominent part in the act of orientation—sight for the bird, scent for the dog, etc.
If orientation within restricted limits is easily explained by the combined play of the five senses, it is not so as regards orientation in an unknown and distant territory. Let us cite an examine: In order to lose a cat you put him in a bag and carry him by railroad a distance of 80 kilometers. Set at liberty he returns to his home. Though his sight and his local knowledge guided him constantly back to his home after his daily wanderings, he yet will not know how to make the same use of them on this occasion. His sight, were it excellent, could not be a great help to him, as the slightest obstacle, the most insignificant rise in the ground, would be sufficient to hide the familiar landscape. Is it, then, his sense of smell that guides him? In this case precautions seem to have been carefully taken to put this sense at fault. One fact, however, remains—we are going to try to explain it—the cat has easily returned to his home.
Let us take another example: The pigeon fanciers of Brussels every year let loose pigeons at Bordeaux. In preparation for this they make three successive releases, at increasing distances, between Brussels and Orleans, consequently towards Bordeaux, then after the release effected at Orleans, without further preparation, the pigeons are set at liberty at Bordeaux and they return to Brussels. Can we attribute their return to a memory of the locality, to a piercing vision? Let us admit that in the three preparatory flights the pigeons may have remarked certain prominent landmarks between Brussels and Orleans. At the time when they were let loose at Bordeaux, the elevation of the land, the rotundity of the earth, set limits to their vision, however piercing it might be. To see Orleans from Bordeaux the pigeon would have to rise several kilometers above the earth, which would be physically impossible.[3]
Let us cite another case: Some pigeons belonging to a pigeon fancier in Orleans had traveled in the direction of Reims. Some one conceived the idea of releasing them 500 kilometers out to sea beyond Nantes, without any preparation, and they almost all returned. In this example, as in those preceding, the return can not be explained by the working of any one of the five senses. It is therefore necessary to acknowledge the intervention of a distinct organ serving for orientation from a distance. Since the function exists, we are not illogical in supposing that there is, corresponding to that function, an organ which we will call the sense of direction.
We therefore admit that orientation near at hand is easily explained as the use of the five senses, and that orientation from a distance rests solely on the working of a sixth sense.
It has been objected that orientation from a distance or near at hand is always the same act, and that it is illogical, contrary to the established order of things, to see the same functions carried on by two distinct organs. But this objection is not well taken. It is quite frequent to see in nature the same function accomplished by very different organs.
The strawberry, for instance, is reproduced by means of the seeds formed by the foundation of the flower. It is also reproduced by means of runners that grow out from the plant, take root in their turn and abandon the fragile thread that holds them to the mother plant.[4] Close observation will enable us to cite many examples of the same sort. The hypothesis that a special sense comes in to take the place of the five original senses, whose range is limited, has in it nothing illogical.
III.
We will now study a number of interesting cases, seeking to deduce from them the mechanism of orientation from a distance.
First. During a hunt with greyhounds that took place in the forest of Orleans, a stag, not the animal hunted, was followed by some dogs; cornered in an angle of the forest he "went away;" the master of the hunt, seeing the mistake made, recalled his dogs and set them on the right track. But a poacher who had seen the stag leave the forest noted exactly the place where he passed out and lay in wait for him, feeling certain that the animal when he no longer thought himself threatened would return, by the next morning at the latest, and over exactly the same path by which he had made his exit. The result proved him right. The poacher had made use of the fact well known to the charcoal burners who live in the forest of Orleans. The stags and roebuck, finding almost everything they need for food in the forest, almost never leave it. When for any reason whatever they go out into the adjoining land they follow in return the same road they used in going.
The art of setting snares is founded on this observation. The snare prepared in the woods at a point presumably on the track of an animal, or even exactly at the spot where the animal has passed, does not necessarily entrap him. He wanders throughout the whole extent of his domain, often leaving one track to try new ones; while an animal which has ventured into strange territory will surely return shortly and pass at the same point at which he went out. If the snare be set at a point where his departure was observed he will surely be taken.
Second. The horse which passes twenty-two or twenty hours every day in the stable in semi obscurity, his nose against the wall, can not be endowed with much instinct. All voluntary action is forbidden him, since he can only act in obedience to his master. His instinct is, if not atrophied, at least exceedingly diminished.
The stable is a permanent center of attraction to the horse, who finds there food and rest. When set at liberty he finds his way back to it with the constancy of the magnetic needle turning to the pole.
The horse knows perfectly the road back to his home. If in the course of a drive the reins are let to fall loose on his neck he will take this opportunity of returning to his stable. With the help of an excel- lent memory he knows the comparative length of the roads to be fol- lowed, and chooses without hesitation the shortest.
Suppose that the same horse is taken into a country of which he is ignorant. After a stay of some hours in a stable he develops the same attachment for his new home which he showed for the former. If in the first drive he is left to his instinct to find his way back it has been ascertained that he will follow the same road, reversed, by which he came, even if it is not the shortest.
Third. The carrier pigeon when set loose within a short radius of its home will return to its cote by the shortest way. If it is set at liberty some hundreds of miles from its home it follows in its return very exactly the line of the railroad by which it came. We need no further proof of this than the following fact.
In the season of the conventions of pigeon fanciers the inhabitants of Bapaume remarked the flight every Sunday of numerous bands of pigeons returning to their homes in the north of France, or in Belgium. We can not claim that Bapaume is exactly on the straight line that connects the different points from which the pigeons were let loose to their dovecotes scattered throughout the region of the north, from Dunkerque to Mézières. It was not merely choice that thousands of pigeons should pass every Sunday over the little city. Bapaume is only an insignificant point in the very extended zone which separates Belgium from the center of France. Moreover, from similar observations made at Amiens, at Arras, and all along the line of the route from Paris to Brussels, it was proven that the pigeons retraced in a contrary direction the road by which they had been taken to the place of release.
We might cite any number of observations of the same sort. For example, the employees of the Orleans railway have often told us of the passage to Arthenay, to Étampes, or to Juvisy of Belgian pigeons released at Poitiers, Angouléme, and Bordeaux.
We have deduced from these facts the following hypothesis, which we will call the "law of retracement." The instinct of orientation from a distance is a faculty which all animals possess in different degrees, of retracing a route over which they have once passed.
IV.
In the study of mathematics the method is often employed of considering a proposition as demonstrated, then stating it in the form of a problem and studying out the consequences. We will use this method here. Let us admit that the hypothetical law stated above has been sufficiently proven and let us make use of it to explain certain facts, inexplicable by any other means. Let us imagine that we are present at a release of pigeons. Many hundreds of birds coming from cotes in the same region are set at liberty at the same time. They set out together, separate to travel in two or three groups. Then as soon as they reach the horizon to which they are accustomed each flies straight to its own home.
A certain number of pigeons do not return, others come in on the following days. The owner merely registers the losses and notes the tardy ones without trying to discover the cause of the failure in instinct. In truth, how can we ask for the secret of a bird which, with one stroke of its wing disappears from our view. Its instinct is at fault; the bird must then wander at will, counting on chance to find its way home.
We can not agree to this proposition for the following reasons: The bird that has gone astray through a defect of instinct is still, nevertheless, not beyond the control of that general law of self-preservation which guides all its actions. On the contrary, it feels strongly the call of instinct which incites it to return to its own cote. It sees clearly the end, but the means of attaining it are for the moment at fault. It displays then all the voluntary activity of which it is capable, trying path after path successively. The law of retracement will permit us to follow it in its wandering course and to retrace its journey. When we have found out the secret of the lost pigeon we shall realize again that chance plays a very small part in the decisions of animals.
In 1896 we were present at Orleans when a number of pigeons from the cotes at Mons and Charleroi were released. The two bands of pigeons having by chance been set free at the same time, at two different points in the freight station, joined each other in the air and formed at their departure a single group. The weather was extremely unfavorable. Fog, rain, and contrary wind contributed to delay the return of the winged voyagers. One first mistake in instinct, easy to explain, was made at the outset. Two pigeons from Mons were taken in at Charleroi and three from Charleroi were received at Mons. Besides about forty pigeons did not return home on the evening of their release. They had, however, left Orleans together. The birds which first returned had pointed out to their companions the proper road and some of the latter had followed their guides blindly, even so far as to enter strange cotes.
But in Orleans an observer remarked that between 3 o'clock in the afternoon and 7 in the evening about thirty pigeons flew up and rested on the roof of the station. When night came we succeeded in capturing nine; five were from Charleroi and four from Mons. They were again set at liberty. This observation leads us to suppose that the thirty-two pigeons that returned to Orleans had all gone astray from the group released that morning. The next morning between 5 and 7 o'clock they all disappeared one after another toward the north; about thirty late returns were noted at Charleroi and at Mons on the same day. These goings and comings are all naturally explained by the law of retracement. Our winged travelers, although they formed a single band at their departure from Orleans, doubtless soon broke up into several groups; we have already observed that it was necessary for them to battle against rough weather. Now the carrier pigeons are not all in this respect equally provided. The little pigeon of Liège flies with extraordinary swiftness in ordinary weather. The full-plumed pigeons of Antwerp, endowed with considerable muscular strength, while they cannot vie with the Liège pigeons in ordinary weather, can, however, battle with a strong wind. It is then quite natural that our pigeons of different powers starting out together should divide up along the route according to their comparative strength. A pigeon from Mons, finding himself in the midst of a band of birds seeking Charleroi, follows them to their destination; then, having seen them scatter to their different homes he remains alone, lost on the roofs of a strange city. Mons is not far distant from Charleroi and the lost one need only rise into the air to see his own home. But he does not do so, for he has in previous journeys become accustomed to using only the sense of direction to find his way home from a distance; it never occurs to him to use his sense of sight. Retracing the road taken to reach Charleroi, he flies to the point in Orleans where he was set at liberty in the morning. Tired by the long journey he has made he rests for one night. The next morning he gets his bearings, finally finds the reverse of the journey taken two days before by the railroad and returns to Mons. The thirty-two pigeons who returned to Orleans on the evening of their release and the next day disappeared had very probably gone through an experience similar to this.
The example we have just cited is certainly very interesting. We have established our position with facts, and, when facts were lacking, with simple conjectures in order to explain the goings and comings of the pigeons. We have therefore in our conclusion, if not certitude, at least great probability. But we will now give a few cases more conclusive than the first.
A pigeon belonging to a fancier in Grand-Couronne fell into the garden of General M, at Évreux. On the same day we had to go to Rouen. We took the lost pigeon with us and set him free in the station at Grand-Couronne, near his own cote. The pigeon took his bearings and flew off to Évreux, to the house of General M. Again captured he was this time sent back to his owner by post. When released at his cote he no longer tried to return to Évreux. The pigeon, stopping to rest a minute and eat near the house of General M, did not for an instant think of this unknown house as a new home. It meant for him. only a point in the journey previously made and to be therefore the point of departure for his further flight. After some hours of rest he would have left to return again over the aerial path which had brought him to Évreux. He only thought of finding his lost cote.
We carried him to Graud-Couronne and set him free a few steps from his cote. But the sense of orientation from a distance, the sixth sense, was acting almost to the exclusion of the other five. The bird made his way back again, passed, as if hypnotized, in sight of his home—without seeing it,[5] and reached Evreux the point in the itinerary which he sought to reestablish.
His calculation was foiled, when led to the home of his owner and set at liberty he then knew where he was. The five senses, reawakened by stronger stimuli, rose supreme, and the sixth sense, having become useless, refused to act.
There is at Orleans a depot for pigeons where the birds are kept indoors. The pigeons which are shut in here and which come from the cotes of Paris and the north, live in a semi-obscurity and in absolute ignorance of what passes outside. When, after a month or two of confinement, they are to be released, the precaution is taken to carry them some miles from this transitory home, to which, moreover, no pleasant memory can attract them. We have ascertained that very often the pigeons know how to return to this house to which they do not even know the approaches. They come and rest on the roof, then after a very brief stay, take their bearings and disappear on the way back to their own home.
The law of retracement enables us to explain the action. Taken to the station of Aubrais, for instance, and released there, he will retrace his way and come to hover over the depot which represents for him the terminus of the road by which he was brought to Orleans. It is, then, from there that he will depart to reverse that journey whose memory has remained deeply graven on his mind.
We might cite a great many examples of the same sort to show that a lost pigeon always returns to the point where it was released. To convince ourselves of this it is sufficient to glance at the roofs of the stations of Paris, Orleans, Blois, Tours, Poitiers, Bordeaux, etc., where every Sunday, in good weather, hundreds, and sometimes thousands, of pigeons are set free. On Monday numbers of pigeons, lost the day before, return here. Having been unsuccessful in their first attempt to return to their homes, they will make a second and even a third attempt to find the right road.
When set free the day before, the pigeon took his flight, he flew as fast as possible from the place where he was released, a spot to which apparently no memory, no interest attracted him. If strong on the wing, he covered 400 or 500 kilometers, perhaps more, in tbe wrong direction—perceiving his mistake he knew, by some mysterious instinct, how to retrace his path and find again the point of his departure, the spot of his release, which he had hardly noticed in the morning. The combined work of the five senses can not explain such a return.
A lost dog behaves in exactly the same way. When, having been brought by rail to a hunting ground entirely unknown to him, and, having lost his way, he returns to the place where he last saw his master, and stations himself there to wait until someone comes to find him; or, even further retracing his way, he will follow back again the way by which he was brought and return to his home.
Let us cite one of a number of instances of this sort which have been reported to us by a trustworthy witness.
A young dog belonging to Mr. D, a proprietor at Pont-Audemer, was carried to the station at Beaumont-le-Roger, and from there to a hunting ground situated between Goupillières and Fumechon. He disappeared during the hunt and in the evening returned to Pont-Audemer. Since he was by chance observed by certain railroad employees and gate keepers, who saw him pass, it has been possible to trace the road which he took. The dog returned first to the station at Beaumont-le-Roger, and then walked along the railroad to Pont-Audemer, passing Serquigny. To reach the station he had to walk away from home; he then walked along a road which made a considerable detour, several times crossing the Rille, while from Fumechon he could have reached Pont-Audemer directly by a much shorter route.[6]
The migrations of birds have been the subject of observations too well known for us to relate them. We will limit ourselves to explaining, with the aid of our theory, facts which have long been known.
The migratory bird is subject, like those of its kind that remain always in the same region, to the law of the domain. Only it has two domains, a summer and a winter one. It has been ascertained that the same swallows come every year to occupy the same nest, and the same region. The same observation has been made upon storks and upon many other birds.
When the time for departure is come, birds of the same species, inhabiting the same region, come together for the journey. Those that have already made the voyage take the lead and retrace the path by which they came. The younger birds, born since the last journey, con- fine themselves to following their elders, and when, some months later, it becomes time to return, these are able in their turn to follow in a reverse direction the journey previously made.
When the migratory bird, born in our country, who has never made a journey, is for any reason not present at the departure of his companions, he does not go away. This is why woodcocks, wounded, and consequently unfit to undertake a long journey, resign themselves to remaining in our country another year. The same thing has been noticed of plovers, of curlews, of storks, and of swallows held in captivity at the time of the departure of their companions. Some of these birds endure the inclemencies of the winter climate; others, especially the swallows, succumb to them.
Thus, then, it is by means of a sort of tradition that the migratory birds transmit to each other from generation to generation the knowledge of the airy paths they follow. These paths once laid out are unchangeable.
The path of the quail that come to Provence from Africa, or of the woodcocks that alight in Jersey, is well known to the peasants, who capture them by thousands. To baffle their enemies it would be sufficient for the poor birds to change their path only a few kilometers. But they can not do it; they are fatally bound to this aerial route followed in their last journey, and they can not deviate from it or they will be lost.
Like other animals, fish also are districted; certain of them have, like migratory birds, two or three dominions which they successively occupy. To go from one to the other they emigrate en masse, following routes subject to the same rules as those we have explained for the migration of birds. The desperate war waged against them by fishers who know their habits has never decided them to change their route.
Our theory of orientation seems therefore applicable to animals of every species; it enables us to arrange properly and satisfactorily a number of facts observed and known for some time.
V.
We have demonstrated that the combined play of the five senses, whose range is limited, is not sufficient to explain orientation from a distance. This faculty is governed by a distinct organ, which we have called the sense of direction. The sense has its seat in the semicircular canals of the ear. Numerous experiments have, in fact, proved that any lesion which injures this organ results in immediate impairment of the faculty of orientation in the patient.
The semicircular canals of vertebrates are formed of three little membranous passages filled with a fluid called endolymph. They are independent of one another except at one point, where they have a common cavity, and open into a little sac called the utricle. They are situated, generally speaking, in three mutually perpendicular planes.
After the remarkable experiments of Flourens in 1834 and the autopsies of Ménière, their working was studied by Czermak, Harless, Brown-Séquard, Vulpian, Boetticher, Goltz, Cyon, Crum-Brown, Brewer, Mach, Exner, Bazinsky, Munck, Steiner, Ewald, Kreidl, and Pierre Bonnier. To-day it is known that their function is directly connected with the faculty of equilibration and is entirely independent of audition. M. P. Bonnier, after having studied throughout the entire animal series the functions of the labyrinth and those organs which precede it, by comparing the data of comparative anatomy and physiology and verifying them by clinical observations, has been able to show that these organs subserve directly what he calls the "sense of altitudes," which furnishes the images of position, of distribution, and consequently of movement and of displacement in space.[7]
It is not yet exactly known what is the physiological excitant which puts in action the semicircular canals; awaiting further researches for the settlement of this interesting point, we will try to determine the method of action of the sense of direction. This way of procedure is moreover in no way illogical—in natural sciences, as in others, the knowledge of the effect usually precedes the knowledge of the cause.
An animal wandering in a strange territory follows on his return the reverse of the road, more or less winding, by which he came. When he reaches known territory he moves in a straight line to his destination.
The carrier pigeon, set at liberty at a distance of some 500 kilometers from its home, follows, in returning, the railroad which brought it; it is now guided by its sixth sense. Having in this way reached the known horizon, say 80 kilometers from its home, it no longer depends on its sixth sense, but goes by its sight straight homeward.
At other times when it reaches known regions the pigeon does not think of making use of its five senses, but follows its former path back to its cote. Sometimes it goes past it; thus we have seen pigeons returning from a long journey pass within 40 or 50 meters of the cote, go on and only return after an hour or two, having covered in this way, perhaps from 30 to 60 kilometers in the wrong direction.
If a common pigeon, accustomed to using almost exclusively its five senses, and a carrier pigeon broken to long voyages, are carried about 10 kilometers away from the cote, when they are successively released an interesting fact is noticeable—the ordinary pigeon, going by sight, will usually make its way much more rapidly than the carrier pigeon, who will find its way back carefully with the aid of its sense of direction.
From this fact we may conclude that the sense of direction does not combine its action with that of the live others. It begins to act in a zone where the other senses are inactive, and often continues to act in the known region to the exclusion of the other five senses.
It seems that it is not actuated by impressions received from the path followed and that it is in some degree a subjective organ. We have made cm this subject a very curious observation. When a basket of pigeons which have already performed journeys is carried by rail-road, they manifest great agitation when they reach a station whence they have formerly been released, although they remained indifferent whenever they stopped at previous stations. Now, it will certainly be admitted that a pigeon inclosed in a basket, which in turn is shut up in a dark carriage, can not, from the noise alone, distinguish one station from another. Its sight and its other senses are of no use to it, since it is as completely as possible isolated from whatever passes outside, and yet it knows exactly where it is in respect to the point of its departure. We were right, then, in saying that an animal carried to a a distance possesses an entirely subjective idea of his situation independent of the surroundings through which he is for the moment passing.
Mythology relates how Theseus, penetrating the mazes of the labyrinth, held in his hand the thread given him by Ariadne. He could in this way go back on his own track and reach the entrance to the chasm. Does it not seem that the animal possesses likewise the thread of Ariadne, and unrolls it whenever he enters unknown regions?
Before we pass to a new course of thought, let us stop for an instant to consider an objection which naturally occurs to us. We have cited in support of our last deduction some observations made on the carrier pigeon. Since the organ of distant orientation has been developed by a wise selection in this interesting messenger, can we generalize and apply to other animals the remarks which concern it? We do not hesitate to answer such a question affirmatively. By selection man develops a certain faculty abnormally to the detriment of some other; he deforms the primitive type, often destroys the equilibrium of nature for his own profit. He can not, however, develop a new faculty; he must limit himself to only modifying the existing ones. Variation and heredity are, in fact, the only means which he can use to accomplish his purpose. We can not, therefore, discover in the carrier pigeon any trait which did not exist in the germ in its wild ancestor.
If a new example seems, nevertheless, necessary to confirm this theory, we will cite another interesting fact from the history of migratory birds. In 1883, on a dark night during a heavy squall, a flock of wild geese alighted at Clermont-Ferrand on the church of St. Eutrope and the neighboring houses. After a stay of two hours, the wind having lulled, the birds took up their interrupted journey through the air. Some of them, however, who had descended into the gardens or into the courts, did not succeed in taking flight. They struck against the walls or got entangled in the trees. Some were killed and others so badly wounded that they were picked up the next morning by the people.
The wild goose has not an eye formed like that of nocturnal birds. Deprived of sight by exceptional darkness, these birds did not, however, hesitate to set out on their journey, guided only by the organ of distant orientation. The sense of direction, a subjective organ, gave them the direction to be followed, pointed out the reverse of the path of the preceding season. Sight, an objective organ, would have put them on guard against obstacles; in the present instance it was of no use to them. This is why the birds on the church and on the roofs took up their way through the air without difficulty, while their companions, lost in a labyrinth of trees, walls, and houses, did not succeed in freeing themselves from these obstacles.
VI.
We have shown that an animal is restricted to a domain where he finds everything that is demanded for the preservation of himself and of his species. This domain, more or less extensive for the wild beast, is restricted for the pigeon, for example, to the four walls of his cote. In truth does he not find there, to use the apt expression of the fabulist, "good food, a good bed, and everything else?" On the other hand, if it is true that a knowledge of his locality is not absolutely indispensable to insure his return home, and the sense of distant orientation suffices to guide the animal, it will without doubt be admitted that it is possible to make a pigeon house movable and to teach its inhabitants to lead a wandering life.
Let us suppose that a cote is transported into entirely new surroundings without the least disturbance being made in the life of its inhabitants. They, set at liberty on their arrival, will perhaps wander away, but the law of retracement will insure their return. We have remarked above that a lost pigeon knows how to return to the point of his release which he has hardly noticed in the morning and to which apparently no pleasant memory, no interest, attracts him. For still greater reason the dweller in a movable pigeon house would attempt to retrace his journey. If he is taken to some distance and then released, he will go to find his home just where he left it. The movable pigeon house which comes into a new region will therefore render, to some extent, almost immediate service in the locality.
This new way of using the carrier pigeon, impracticable according to the ideas which have hitherto been held with respect to orientation, is only the strict application of our theory.
Interesting experiments have proved conclusively that faithfulness to his native cote can be reconciled with wandering life. A certain number of pigeons were born and raised in a wagon used as a pigeon house. They had no other home than this moving house. It was of little consequence to one of these pigeons whether its house stopped to-day in the bottom of a valley, to-morrow sought shelter in a forest, or stopped for a little while in the maze of houses forming a large city. If it were taken away from its cote to be released, it would not be guided on its return by the necessarily slight knowledge of the region around its carriage, but by the sense of direction, which would give it a subjective idea of its position in respect to its home.
Practice has in every case confirmed our theory. We have had occasions to make some interesting observations, and we will now cite certain facts which relate directly to our discussion.[8]
A pigeon carriage was stationed for twenty-four hours at Épernay. Its inhabitants were not set at liberty, while the pigeons of the neighboring wagons, after remaining quiet for two hours, were taken to some distance to be released.
The next morning the carriages were taken to Chalons, with the exception of the carriage from which the pigeons had not flown at Épernay. Those pigeons were distributed among the other carriages, which were exactly like the first in pattern. At Chalons the cotes were opened and these pigeons set free. Some of those which had made the journey from Épernay to Chalons in a strange wagon left for Épernay, and there found their wandering home. How did they succeed in tracing their way back from Épernay to Chalons, and in finding their carriage in a place of which they could know nothing? Only the law of retracement can explain this action. We have, moreover, repeated this curious experiment many times.
While a pigeon carriage was stationed at the Chateau of Morchies two pigeons went astray. They were found again at Bapatume, the last stopping place of the carriage. One was taken, the other escaped. Its course of flight was reported to us from all the places where its carriage had stopped. It arrived in this way at Houdain. From there it left for Évreux, taking up the reverse of a journey made some days before on the railroad. At Évreux, where the carriage had stopped for some months, we succeeded in capturing it. Is not the retracing of this journey step by step the best proof which could be given in support of our theory? By means of the law of retracement we can almost always determine the exact point at which to find our lost pigeon. We thus succeed in decreasing the number of losses which would otherwise be numerous and difficult to repair.
The return of a pigeon to a moving home is not an exceptional thing; we might cite many examples of the same sort borrowed from the history of birds.
The birds of prey which live in the forests of Argonne and of Ardennes or even in the solitudes of the Alps, find in spring in their native region everything that is necessary to their subsistence—young broods and game in abundance. But when autumn comes, when the game has grown strong and has learned to escape by flight from the pursuer, he finds himself forced to abandon the domain which he has devastated; he emigrates to the plains and leads a wandering life, settling temporarily in such regions as offer abundant game. He picks out in the center of his hunting ground temporary shelters, to which he returns every evening until spring brings him back to the solitudes, where he builds his nest. What guides the bird of prey in this long expedition? Undoubtedly the sense of direction. We can not admit that the bird has a memory sufficiently lasting to retain for many months the recollection of all the irregularities of the ground which mark a course of many thousands of kilometers. All the bird's power of observation is in fact concentrated on one object—the chase. Topography is of no consequence to him. Like a registering machine set going at the moment of departure, the sense of direction notes automatically all the road covered by the bird in his pursuit of prey.
The cormorant and many of the fishing birds sometimes follow for many months the long routes of migrating fishes. Though lost in the midst of the sea, they know well how to return to their homes when their fishing is over.
Naturalists who have studied orientation have very wrongly noticed only one fact—the return to a single home. They have usually attributed this to a knowledge of the locality, founded on long observation. Such a theory gives no explanation of the facts we have just cited. Have we not shown that the law of retracement guides the animal when it wanders away from the known territory, brings him back to a temporary home, and sometimes, after an absence of many months, leads him back to his native region?
VII.
It would be interesting to know whether the theory we have just explained is applicable to man.
An animal's movements are regulated by the law of preservation, which assigns to him an imperative purpose, leaving him a restricted liberty in the choice of means. Man is actuated by the same law, but instinct is not the only determining cause of his action; he is also endowed with reason. While instinct points out to the animal only one course, reason points out to man many solutions; he chooses freely whichever seems best to him. He can even consider the promptings of instinct of no consequence; thus by suicide and Malthusian practices he may set himself in revolt against the law of preservation of himself and his kind.
We have attempted to prove that the action of orientation from a distance depends solely on the function of one organ—the sense of direction—which acts to some extent automatically. If a man who is trying to orient himself calls to his aid both reason and observation, the sense of direction, through lack of exercise, becomes atrophied. This is why a well-informed man, who estimates everything that he does, often finds his direction less accurately than a man whose intellectual culture is limited; he makes an act which should be in some measure mechanical and impulsive an act of reason. As a result of these considerations, savages, deprived of improved instruments and possessed of sharpened senses, can furnish us with more interesting facts than can civilized peoples.
A former military attaché at Pekin told us that when undertaking long hunting expeditions he took with him two Mongolians, who, after many days' journey, would lead him back to the point of departure. The confidence which he reposed in these guides was never deceived; they found again in the return the path followed in going. American Indians also seem to make use of the law of retracement when, after many weeks of absence, hunting in very distant regions, they return to their home. The nomads of Africa and Asia follow in their wanderings laws based to some extent on those which govern the migrations of animals.
These facts are certainly very curious, but one must not draw too strict conclusions from them; the primitive man knows, in spite of his intellectual inferiority, how to reason out what he shall do. It is consequently very difficult in analyzing an act of orientation to discern in it the part played by reason.
VIII.
We have vainly sought in the works of naturalists a theory which might explain satisfactorily the acts of orientation performed by animals. Many very interesting notes have been made on their habits; the life of certain ones has no further secrets for us. But when it becomes necessary to pass from effect to cause the observer usually takes the wrong side. Erroneously taking himself as a term of comparison, he asks what he would do to accomplish such and such an action proved instinctive in an animal. However, if an animal has not reasoning power he possesses senses whose power surpasses anything that we can imagine.
We know the famous experiment of the female peacock moth shut up in a box and set out at night on a balcony in Paris where representatives of its species were very seldom found. The next morning there were four males, doubtless from the neighboring forest, settled on the box. How did they know that 20 kilometers away they would find a female in the midst of Paris, where they had never before ventured?
When in the Pyrenees the hunters run down an ibex, it is useless for them to hide the entrails under a bush or in a hole; vultures appear from every direction, although but a few minutes before not one was visible on the horizon.
Such facts as these are inexplicable from what we know of the senses—of our own especially. The acts of orientation are not less extraordinary; therefore the observers who have remarked these things have tried to explain thein by endowing the beast with the calculation and reasoning powers which we would use if we were in his position.
It is in this way that some pigeon fanciers attribute the return of the pigeons to a wonderful memory of the locality. In his daily sport the bird rising above his home will note the landmarks of the country, study their relative position, and will notice them in relation to his home, thus making a veritable triangulation of the country where he dwells. According to others, the bird does in time acquire a profound knowledge of the local magnetic currents. Such an hypothesis explains a mysterious fact by means of others still more mysterious. It has even been seriously suggested that a pigeon orients himself by the course of the stars.
We think that these fantastic theories should be rejected; an animal can not be a mathematician, a geometrician, an electrician, or an astronomer; and observers have been wrong to attribute any intellectual manifestation to a material action which only puts to use a very perfect organ. The animals most highly gifted in the art of orientation at a distance are not, in fact, the most intelligent, but those which possess the most powerful means of locomotion.
Such is the idea which has inspired us in the study of the mechanism of orientation. We have formulated a series of very simple propositions founded on observation and explaining a number of facts long known. It has been possible to draw from our theory many interesting inferences which experiment has confirmed. In expressing our opinion of this much disputed subject we hope to arouse discussion and incite to new researches which will doubtless lead us to a complete knowledge of the truth.
- ↑ Translated from the Revue des Deux Modnes, Vol. CXLVI, pp. 380-402.
- ↑ An animal is by nature a slave to routine; when surprised by the hunter he does not invent a plan of flight, but makes use of trails over which he formerly passed.
- ↑ Pigeons rarely fly at more than 300 meters above the ground. Set at liberty from a balloon more than 2,000 meters high, they descend with a dizzy rapidity, letting themselves fall, and not resuming their flight until near the earth.
- ↑ The plant-louse has also several methods of reproduction.
- ↑ If sight is the principal means for orientation for the pigeon, those living in the cotes of the Grenelle quarter must be particularly favored since the building of the Eiffel tower. This is a prominent landmark easily seen within a radius of 200 kilometers around Paris. But upon inquiry we find the percentage of losses suffered during the training season from the pigeon farms around the Champ de Mars is exactly the same to-day as before the construction of the tower.
- ↑ When, on market day, peasants lose the dog which they have brought with them to the city, to seek him they go to the different places where their wagon has stopped and always find him again.
- ↑ We can only refer our readers to the researches of M. Bonnier on the Ear (Leauté Collection) and to a recent report to the Biological Society on the Sense of Orientation (December 11, 1897).
- ↑ Our experiments have settled one interesting point. According to M. Daresre, eggs shaken with some violence for a considerable time will not hatch out. We have proved that rolling over roads, over a pavement, or on a railroad, when the eggs are shipped, in no way alters the conditions of hatching. We may say with certainty that in a movable cote the pigeons hatch with the same regularity as their kindred in ordinary cote.