Popular Science Monthly/Volume 79/July 1911/Concealing Coloration
By ABBOTT H. THAYER
MONADNOCK, N. H.
At the last meeting of the American Ornithologists' Union, in Washington, some forty naturalists looked in broad daylight straight at a small stuffed deer that wore from its dorsal line down its sides two white stripes in imitation of those of certain African antelopes. These stripes were in every respect such as Theodore Roosevelt says have no concealing virtue of any kind whatsoever. Yet they so completely concealed this deer in an almost clean-shorn public park that although for each of the forty spectators I pointed straight at the deer only ten yards away, not one of them detected it. The animal was placed just above the eye-level of the spectator, exactly as African antelopes would be above that of the creeping lions or leopards. And, exactly as would commonly be the case with the antelopes, the white stripes absolutely counterfeited the glimpses of the sky-background seen through the thin half leafless bush that intervened. When the white stripes were removed the spectators exclaimed at how clearly one could now see the deer, and all agreed that it was these white stripes that had fooled them. Dr. C. Hart Merriam said it was a most conclusive demonstration (though he still believed that such marks exist also for purposes of display, under other conditions).
The way this deer demonstration brings to instant ridicule the extraordinarily positive statements of Theodore Roosevelt must set the reader wondering about the value of the remainder of his attack. The simple fact is that Roosevelt, like most of the rest of the world, is totally ignorant of a great optical principle which has lain right under people's noses, and to which I have at last called attention, and which can not possibly remain ignored. All the various objections and doubts about our book, including this extraordinary tirade of Roosevelt's, have been possible only because of people's not seeing this principle.
The principle is, basally, merely this: that if you lie on the floor you will have not the floor but the ceiling to look at, while if you were fastened to the ceiling you would see not the ceiling but the floor. All over this planet, and all over every other planet that receives light-vibrations and possesses detached objects of any sort, either on or above its surface, this law rules the aspect of every object in its appearance from the view-point of each other object. All such detached objects are forever
between the overhead light which is their ceiling, and the underfoot earth which is their floor. The higher you mount from the earth, and consequently the nearer you get to the outside of this zone of detached objects, the more do all things that you have to look at come between you and the brown earth—and the more these things resemble the earth in color the less you notice them. Contrariwise (let the world for the first time notice this Contrariwise, which would have saved Roosevelt and others so much erroneous writing), contrariwise, the nearer you get to the bottom of this layer of inhabitants of the atmosphere, i. e., close to the earth's surface, the more you have only things above you to look at; and the more these things are bright like the sky the less you see them, and the darker they are the more you see them. This means that the nearer to earth's surface an animal lives, the larger will be the proportion of neighbors he detects by seeing them dark against the sky. Only such neighbors as are no taller than he will escape coming between him and his sky.
After years of trying to bring home to naturalists this great fact, which wholly suffices to account for white top-patterns in general, I know to my sorrow that nothing short of seizing them all and binding them to the ground, so that their eyes will be as low as a mouse's, will ever cause the truth to spring into vital existence for them! I have demonstrated to many audiences on both sides of the Atlantic where scarcely one man would consent actually to go down on the turf and let this immense fact rush upon his consciousness.
Everywhere, in every situation, it is the rule that animals are colored like the background that most concerns their feeding and escaping attack. Sea-birds, in general, are either all ocean-and sky-colored, or this with the addition of the color of the rocks they breed and roost on. Animals living between bare snow and sky are white. (I have shown by ocular demonstration the wonderful aid that this white background-matching gets from the small black marks commonly worn by these white species.) Sand-dwellers, on land or in the sea, are sand-colored. One can find pictured on a locust the peculiarities of the special type of ground he lives on, be it rock, or sand, or meadow. Everywhere, in every case where the animal's background is most unvarying, as in the above-cited instances, the animal's colors are at least amply accounted for by their matching of this background.Now why is it that even after people intellectually perceive that a terrestrial mouse or lizard sees almost all sizable neighbors against the light, and detects them least when they look lightest—why is it that these people go on failing to undersand that white upper slopes on all species which need to avoid the sight of these mice and lizards are just as necessary to their wearers as is the brownness of the mouse or lizard, whose enemy looks at him from above downward and consequently sees
An imitation oryx head, looked up at, simulating branches against the sky—as at a reedy drinking-place it would simulate reeds.
The same oryx head and also a brown (counter-shaded) one, the former inconspicuous, the latter less so.
him against the ground? In each case, the animal's colors comprise all the background's typical color-notes. Under foliage, the lizard, looking up, sees things against a tapestry of dark twigs and the shadow-side of leaves-—the whole mass sharply patterned by bright glimpses through it of the sky above it all. And this ensemble, is precisely what is worn by dusky-coated white-top-striped animals that come between the lizard and this background.
What bewitchment of the student's mind thus holds him from discovering the truth that there is evidently just one universal need of minimized visibility from the point of view which most concerns the creature looked at, and that nature inevitably grants this minimized visibility to all creatures that can use it?
Here is the explanation of the misunderstanding. The basic use of men's brains is one which they share with the lower animals. Like all these animals, man lives, primarily, not by speculative reason, but by what for convenience we may call mere sensation-memory. The aborigines differ from white hunters by their still greater propensity to hunt always where they have once killed.' And a horse that has once been scared by a factory whistle going off too near him on the road always afterward shows alarm when he passes that factory. Man is, we feel sure, one story higher than the other animals, and on top of what he shares with them adds a more or less vigorous layer of "reason." But let anything make the least bit of a run on this reason-bank, and he is bankrupt indeed, and falls back on his sensation-memory.Let us examine a few of the limitations governing the vast accumulation of man's sense records. Here, for instance, is a thing seldom thought of: Man is, mainly, a looker-down—perhaps as much so as a cow. He tills the soil, he hunts, he fishes—largely or wholly looking downward in all these occupations. And the men of towns look still more predominantly down on desks, tables, tool-benches, etc. This habitual down-looking of men is well attested just now in New England by the difficulty the hunters for the brown-tail moth nests have in accustoming their eyes to day-long searching of the tree-tops. A few weeks of this looking up strains their eyes. Another proof of all this is that men say white is the color that shows by night. This is the idea of a race that mainly looks downward. A mouse, on the contrary, because almost everything comes between him and the sky, would consider black the color that showed best in the night. Now when some one asks us to form a clear idea of the mouse's (and the creeping lion's and leopard's) view of the animal kingdom, our thinking-power balks, and we fall back on our sensation-memory, which vouchsafes us, generally, not a single instance of view from this low level, while it deluges us with memories of the bird's-eye view that we habitually get of these same species. If we are forced for a moment into the realm of thought, in the next
The same two heads seen against sky and branches.
The same effect as in the preceding.
moment this relatively scant faculty is fatigued, and we fall back into the hands of the old animal instinct, sensation-memory, which we share with the horse and woodchuck, and we proceed to rattle off the list of the hundreds of times we have seen one of these white patterns, the skunk's or deer's (bright against the ground as man's height makes to be the case). But these white tops are white evidently because concealment from a lower level, for one purpose or another, is the thing most important to the animals so patterned.
Eoosevelt carried into Africa the regulation down-looker's misconception of the subject. And nowhere on all his pages (or in fact on any other man's pages) is to be found the faintest perception that all these white patterns on zebras and antelopes were playing a diametrically opposite part to the eyes of the creeping enemies of these plains-haunting animals.
Colonel Roosevelt, with the best intentions, was fated to put himself on record in the most unfortunate of attacks on our book—an attack which forces us, if we answer it at all, to expose its extraordinary weaknesses. It is the nearest to one hundred per cent, of error that I have ever read, on any subject that I understood.
First, he shows fatal ignorance of the laws of optics on which the whole thing rests, and consequently absolutely misconceives what concealing-coloration is or could be. Secondly, he does not see the joke against all who try to prove that nothing has escaped their sight by telling what they saw. He would be too sagacious to apply such reasoning to practical affiairs—why does he take science less seriously? When I announce to the world the discovery of an almost universal concealing-power, under certain conditions, in animals' costumes, what has it to do with the case to tell of the animals one has seen? Let us apply Roosevelt's method to some practical case. If the police announce the discovery in the garret of some respected citizen of a complete counterfeiting apparatus, with every sign of daily use, what does it avail to testify that you have seen the citizen hundreds of times not counterfeiting? The discovery of the evidence compels an investigation. If the owner of a game preserve discovers in the cellar of some neighbor a supply of freshly used game traps, what does it avail that this neighbor is daily seen not trapping? Again only an investigation will do. What I have discovered is that all these patterns of an animal's costume are potential counterfeiters, of the most perfect kind, ready for action (action in some cases almost constant, in others only at rare, but vital, moments)—each one a most exquisite reproduction of some background typical of the wearer's habitat. An artist is of course the judge of such copies; and it is therefore as an expert that I pronounce on them.No amount of reiterating that you have seen the poacher not poaching, or the bank-note counterfeiter not counterfeiting, or this new
The same two heads against the sky; the black-and-white one hard to distinguish, though (as in most of these pictures) wholly uneclipsed, the brown one, though masked by many branches, very conspicuous.
discovered animals'-costume-scenery-counterfeiter not counterfeiting scenery, is any step at all toward finding out whether they all three do at certain times perform their tricks. Forty years of daily meeting the poacher at the post office does not strengthen his credit. And forty years of Roosevelt's seeing zebras not hidden by their costume, and failing to guess what the animal's stripes are for, are just as little to the point.
This effacing machinery is not the only highly specialized mechanism that animals carry always with them merely to have ready for occasional need. It is just the same with many of their other members and adaptations. The tiger's tremendous claws, if we estimate that he kills only once in two days, and that it takes perhaps four seconds for him to do it, are in operation only a 44,700-th of his life. Would Colonel Roosevelt for want of seeing them at their work decide that it was only a theory that they are for pulling down game? (I, by the way, do not even stop at the evidence that animals' costumes are for concealment. I point to the actual concealment in full operation.) The tiger's whole massive steely build serves him scarcely more constantly than do his claws. It, with the claws, does the pulling-down, and adds the bearing-away. The rattlesnake has a heavy rear body, growing slender and agile toward the head end, evidently in order that his terrible poison-apparatus may have a strong base to spring from. All this mechanism serves him only for occasional instants—days, weeks or months apart. Yet, there he always is, a heavy slow snake good only for lying in wait and for these rare murderous lunges, and totally incapable of the arboreal feats and racing of the black-snake's life. Would Roosevelt, because he so often sees rattlers not biting, hoot at the idea that this snake's fangs and build are made for biting? The generative organs of every monogamous species that breeds only once a year are carried through life for a few moments' function once a year—and so on and so forth. With costumes it is just as with all other adaptations. They may, according to their wearer's habits, play in his life a long part or a short one.
The particular herds and individuals of plains game that stood out so visible to Colonel Roosevelt were commonly those that happened to have the light behind them; and wherever any form of tree, shrub or very tall grass constituted an element of the scene, there were sure to be other herds and individuals in directions in which the illumination favored their counter-shading, wholly invisible amidst the haze of scrub and grass. A spectator in such a scene is surrounded with vast reaches of all-engulfing distance into which the haze of interposed scrub growth merges on every side. In these spaces a counter-shaded animal, when the direction of the daylight favors the working of his counter-shading, is already wonderfully matched to the scrub's color, and the further off he is the more of this scrub actually comes between him and the spectator. There is therefore obviously some distance at which he is wholly covered by the scrub. Now from the very nose of the beholder all the way to the point where the animal is actually hidden by accumulated twiggery there is a scale of diminishing visibility, and, while the light favors the animal's background-matching, he becomes utterly indistinguishable from the scrub and grass long before he is at the point of actual eclipse. Yet Roosevelt is able to say: "There is never any difficulty in seeing them "! Compare Stewart Edward White's description of the evanescence of deer in similar situations, written before he ever heard of concealing-coloration.
It is when the light gets behind an animal that its main power to upset concealing coloration comes into play. Except in the middle of the day, there is always one direction which is toward the light, and looked at in this direction the sheltering ambiguities of these thin coverts have to give up many of their secrets. An hour earlier the antelope's imitation twig-haze passed all right, but now that the sun is low and streams through the whole gauzy growth, behold, the opaque antelope becomes a black silhouette on a light gray ground. He is not really a gauzy growth!
It is hardly worth while to say that all these laws of light and its relation to vegetation are practically identical the world over. Though I have been through most of Europe, from Norway and England to Italy and Sardinia, and through most of eastern North America, from Quebec to Florida, and in many of the Lesser Antilles and Trinidad (finding everywhere, what I knew before I went, that the laws of illumination of animals and vegetation are the same over the whole planet), I have not been in Africa. But—and this is more to the point—my critics have evidently not been in the land of the inexorable optics which govern this entire matter.
One of Roosevelt's most fundamental errors is his complete gap of perception about the effect of motion on concealing-coloration. In our book's introduction I say: "Thus at these crucial moments in the lives of animals, when they are on the verge of catching or being caught, sight is commonly the indispensable sense. It is for these moments that their coloration is best adapted, and, when looked at from the point of view of enemy or prey, as the case may be, proves to be obliterative." Had our critics studied this sentence, it would have saved them much misapprehension of what the book is about. But here let it suffice to remind them that the tennis-player's need of bright, clean, white balls, to be seen against the green turf, entirely refutes their ideas. The tennis-player calls for clean balls when the grass-stained ones are beginning to spoil his play; and well might a hawk, if his call would avail, demand a "clean chipmunk"—i. e., an un-counter-shaded and un-dead-leaf-colored one—when the little beast dodges him. Note, too, that a grass-stained ball against the grass is, at its worst, far more conspicuous than an average chipmunk against the leaves, because the ball turns over, and therefore could not be counter-shaded. (Note also that predators in general are believed to miss far oftener than they succeed.)
Many familiar experiences prove this fact, that one's power to catch or hit a moving object depends on the distinctness with which one sees it. The more brilliantly a dodging object shows against the background, the more promptly can the brain of the pursuer command the corresponding movement. Those who have tried to catch butterflies, houseflies or mosquitoes, on the wing, or shoot a flying bird, either know this by heart or will realize it the moment they try it again. When a dark fly passes a dark space, to make sure of him you wait till he gets against a light space, and a shooter does the same with a bird. Throughout all nature animals' coloration proves to be such as minimizes, in the most wonderful way, to the eyes of their pursuers, their visibility when in motion. And in missing this fact" Colonel Roosevelt has missed a vast part of the whole wonderful subject. So true is it that, as he says, motion almost ensures detection, that it is no wonder we find concealing-coloration by far most constantly needed and at work—making the wearer as hard as possible to catch—where there is pursuit and flight. This matter would come home clearly to Colonel Roosevelt if he would try to hit a concealingly counter-shaded moving target against a background that it matched, and see what kind of a score he could make compared to what he could do with an un-countershaded one.
As soon as the public have been shown the astounding concealing-power of those African animals' reed-and-sky counterfeits, such as the zebra's and oryx's—which make it as hard as possible, by night as well as by day, for the springing feline to distinguish between starting zebra and jostled reeds—they will begin to see how complete has been their misconception of this matter. And the moment they see a demonstration of the magical working of facsimiles of these animals amidst reeds and branches, out-of-doors, they will see at a glance that it would be just so anywhere in the world. Colonel Roosevelt has confounded detection with catching. There is a vast difference. Every animal that has lived a year or two has been detected—how many thousand times—by other animals that would gladly have caught him; yet there he still is! Detection means, in some cases, much; but in far more case it means little. As Roosevelt evidently thought about the plains game, out in the open detection is nothing to them. He is also right when he says that these animals, zebras for instance, are sure to be observed by the ambushed lion as they nervously troop down to drink. The reader shall see how wonderfully their case bears out the hypothesis that all available adaptations of an animal's body will be found ranged against his life-and-death danger.
Out in the open, the zebra's watchful eye and ear, backed by his agility, ensure his safety. But if he pass too near any cover as ample as the lion must have for his operations, his stripes begin to be a safeguard, because cover enough to conceal the lion means reeds or tranches silhouetted across the lion's view of the zebra. The zebra is inevitably against the crouching feline's sky, and his own sky-and-reed counterfeit begins to have the advantage of confusion with the real vegetation through which the lion is condemned to look. A chain is no stronger than its weakest link. What is, obviously, the weakest link in the zebra's life chain? It is when he must risk the lion's ambush and drink. All available powers of getting through this tightest place in his life are sure to be found in operation. This need to drink is as much the crux of the zebra's life as the need to be able to swim would be the crux of a foot-passenger's journey from New York to California, if there were neither boats nor bridges. There will arrive in California no foot-passengers that can not swim, because there is the Mississippi. And there will survive no race of zebras that were not the watchfulest, the agilest and the hardest to see when they had to go through this greatest danger of their lives. It is their Mississippi. When a zebra comes to a drinking-place, the faintest sound that could mean an ambushed lion must not pass undetected by him, and he starts away from the faintest rustle. The crouching lion sees him come into the reeds—sees him all the time—and if the zebra comes within range, springs upon him, but even in his first spring has inevitable difficulty in distinguishing the zebra's outlines because of the absolute similarity of the zebra's imitation of reeds and sky to the real ones. The zebra's uneasiness keeps both the real and the counterfeit in motion together. Very often, doubtless, as the best naturalists seem to agree, the zebra's automatic start comes in time to save him, and the lion's instantaneous now-or-never second spring, such as probably all felines make, must be guided by a lightning-swift perception which of the violently agitated sky- and reed-stripes are the zebra and which are not! Any one who saw my deer at Washington will understand this (and better still will any one who will come to Monadnock and see the wonders of my artificial zebra and oryx). Plainly, then, since the zebra must at this necessary moment be terribly near the lion, his race could not have continued except by having every counter-balancing advantage; and it is demonstrably here that the full magic of his coloration comes into play. These sky-counterfeits are as plainly addressed to the lion's sight, and most of all at the night drinking-place, as the thickness of a grizzly's frontal bone is addressed to the teeth of his enemies.
Colonel Roosevelt has done himself a wrong by not studying our plates of counter-shaded "vanished" models. He does not seem to take in at all the marvelous power of this counter-shading, which can actually efface the thing on which it is painted. And he has an idea that it chiefly affects the lower part of an object—as if it were merely a juxtaposition of dark top to white bottom, instead of a continuous gradation over the animal's entire surface. He says: "But as a matter of fact, the great majority of these mammals, when they seek to escape observation, crouch on the ground, and in that posture the light belly escapes observation, and the animal's color pattern loses very much of, and sometimes all of, the 'full obliterative shading of surface colors' of which Mr. Thayer speaks." Let Colonel Eoosevelt cover the lower half of one of our "vanished" models, in our book, and see if this cause the upper half to appear! Or let him cover the lower half of the visible monochrome model, and see if this cause the upper half to disappear.
Two more particularly flagrant errors of Roosevelt's must be mentioned. First, his speaking as if an animal's not trying to hide disproved his being concealingly-colored. He will in time discover that in a vast majority of instances, the very reverse is the case: that the more an animal doesn't hide, the more nature has to help him by coloring, precisely as in the case of the zebra at the drinking-place, or the humming-bird with his head stuck into a flower, or the flamingo at dawn with his head in the mud. Second, his much-insisted-on idea that if one coloration is a concealer, a different one on an animal of the same general habits isn't. He might just as well apply this objection to the mixed herds of diverse-shaped African game, of which so many species have closely resemblant habits, saying, for instance: "If the zebra is built right for this life, then it is a physical impossibility that the oryx is." Or to the innumerable forest plants, each with its own shape, but with, to the casual eye, identical circumstances. Or, concerning such a company of birds as feed together on the marshes, he should say: "These curlews, plover, and sandpipers live together and eat the same things; but if the curlew's bill is the right shape for his life, the very differently shaped bills of the other species are accidents and not adaptations." This is an old, obsolete method in natural history, henceforth to be succeeded by pure experimentalism. And I am presenting simply the experimentally established facts of these marvelous background-matchings. Amid sunlit snow and blue shadows the blue jay is exquisitely 'effaced' by its most perfect matching of each color-note. Likewise the peacock up in a tree, or the wood duck among sunlit water-plants, etc. Each of these facts is here to stay, no matter where it leads us. Our book was written only after all its facts were verified. It contains essentially nothing but facts, and might have been called an expert's presentation of examples of consummate resemblances between animals' costumes and certain of their backgrounds. It has greatly surprised us that so many people have so slightly noticed the facts revealed as to take them for illustrations of a supposed "theory." The facts, themselves, are what we present.
From now on I shall be delighted to show to all comers to Monadnock the perfect background-counterfeiting powers of all sorts of gorgeous birds and butterflies. I have already prepared good facsimiles of a zebra and the head of an oryx, to show the truly wonderful way in which when looked at from a creeping lion's or leopard's eye-level these animals pass for mere sky-vistas through the reeds or branches. My Washington deer was merely a crude beginning of the exhibitions that I can already give of this type of concealing-costume.
Any child who has access to a wide, open field away from lights can prove for himself that white does not show against a starlit night sky. And it is only fair to point out that any one so ignorant of the simplest laws of optics as to share the popular notion that it does, is not competent to testify in this matter. Let the experimenter hold up between his eye and a clear, moonless night sky, a white card so inclined as to permit him to see its upper side. Even in a wide, open field he can at most make it come as bright as the sky beyond it, and consequently vanish; but it can not of course get brighter than the sky. How could it, since it owes all its light to this very sky! Yet Roosevelt says: "At night, in the darkness, . . . the white rump-mark of the antelope is almost always the first thing about them that is seen, . . . and at night it does not fade into the sky, even if the animal is on the sky-line."
Many persons who hear of the vanishing-power I show in the brilliant bird-skins and butterflies and these white-topped animals suggest that in the animals' homes all might be different. I need only answer that when they see the vast range and astounding precision of what I show, this fear will vanish. The evidence is literally overwhelming. It is in every case only against a background notably like that of the animal's home that he will vanish.
Like John Burroughs in his Atlantic Monthly paper called "Gay Plumes and Dull," Colonel Roosevelt does not even take pains enough with his data. Burroughs said: "Why does only one of our four weasels turn white in winter?" The answer is that all of the four turn white in winter! Roosevelt says: "Bears. . . have no white on them." The fact is that seven species, without counting the two all-white kinds, wear more or less white, especially in breast-crescents, collars, and foreshoulder stripes.
About war-paints and appendages, too, I tell only optical, invincible facts. On this subject I shall soon have more to say.
The possibility of wonderful demonstrations of the effacing-power even of stuffed skins of gorgeous or powerfully marked species such as a peacock, or an oryx or zebra, is unfolding itself to me at a rate that almost takes my breath away, and which can not fail to astonish all who witness my experiments.
Not yet understanding that this matter is unequivocally the artist's business, Colonel Roosevelt, like some of our other reviewers, proposes a "scientific" tribunal for our book. Science means simply knowing. What does science teach any scientific man more imperatively than that he must employ specialists in every direction? Does astronomy fit a man to practise medicine? Yet the astronomer and the doctor are both men of science. Do naturalists imagine that the arts can stand as they do, illuminating beacons through the ages, without having adamantine, crystal truth at their core? The laws of color-correlation are of course the very axis of the art of coloring, and any intellectual painter inevitably is the scientist of all that is knowable in this matter. While all painters perceive spontaneously that shadows on the snow in a sunny open field have exactly the color of the aggregate overhead sky, very few persons who are not artists can discover that they are more than "bluish." As our book's introduction explains, a colorless mirror laid in such a snow-shadow and facing upward reflects of course the overhead sky, and this reflection proves absolutely to match the snow-shadow. This knowledge of the actual color of things, and especially of transitory aspects, rests, then, wholly with painters; and, if scio means I know, it is science.
My critics say it is my theory that this or that bird's patterns pass for the background; yet every time I show them this bird against such a background, they either fail or nearly fail to detect it, and invariably admit that it was its patterns' resemblance to background-details that fooled them. Is it my theory that they are thus deceived?
Will not my critics wisely adjourn for the present the question of the validity of any deductions I may have made, and contemplate instead the array of actual facts? Whenever naturalists will take the trouble to lie down on the ground beside a stuffed flamingo, or a li one in a zoo, with horizontal sunlight bathing it, they will see that it looks wonderfully like a pink cloud (which is, strange to say, just what Roosevelt remarks about a flying flock of the African species), and all discussion as to whether this is so or not will be at an end. In connection with a long chain of similar phenomena, hitherto unknown, is this fact worthy only of derision? If inhabitants of the world's floor prove to see the more aerial species against the sky, the flamingo's aquatic enemies, dwelling below this floor, see denizens of the upper air always against the sky. The flamingo question, then, has come down to why he is colored for dawn and sunset sky more or less at the expense of his all-day matching. The answer would seem to be connected with his nocturnal habits. According to Audubon the red flamingo is nocturnal (as, apparently, all the other red and rosy waders are); and in that case his feeding wouldn't extend further into daytime than merely, at both ends of the night, to overlap into the rose and salmon light of dawn and evening. His feeding is especially unfavorable to. his keeping watch against enemies, since he buries his face in the mud and muddy water in his search for the worms and other animals he lives on; and we find his coloration fitting this emergency.
This matter of sky-matching has come very clear in my demonstration with the oryx head, reproduced herein, which shows the inevitable effect of all the other branch- and sky-patterns, such as abound on birds, beasts and butterflies that are looked up at. I have been studying for years to find out the exact scene that each costume best represents; and I now beg my readers to come to Monadnock and let me show them the results.
- ↑ These wholly unretouched illustrations absolutely demonstrate the wonderful concealing effect of the white patterns that Roosevelt and others say have no concealing effect whatsoever. These play, as Roosevelt truly asserts, little or no part when the wearer is out on the safe open plain, but seem designed for making him the very worst of targets when he tries to dodge the spring of an ambushed lion or leopard, especially at night, just as the night hawk's colors, dark and conspicuous to terrestrial eyes through all his safe aerial hunting, prove to be an unmistakable picture of his background when at last he squats on the bare rock in danger from predatory birds and mammals. No one can study these oryx head pictures without perceiving that, against the ground, the brown (of course countershaded) head is hard to distinguish, while the black and-white one is very conspicuous. On the other hand, when the same two heads are looked at from below, i. e., against the sky, it is the brown one that shows, and the brilliant black-and-white one that is now hard to detect. It is of this black-and-white oryx head that Roosevelt writes: "A curious instance of the lengths to which some protective-coloration theorists go is afforded by the fact that they actually treat these bold markings as obliterative or protective." Colonel Roosevelt, like the rest of the world, seems never to have thought to find out how these patterns look from a lower level, such as lions and leopards necessarily see from, they being under three feet tall, while the oryx and zebra are nearer five. This great oversight invalidates almost all that has ever been written on this subject.
- ↑ "African Game Trails," Appendix E.
- ↑ Erasmus Darwin perceived this principle, but got confused in carrying it out—trying to make it explain the juxtaposition of brown backs and white bellies; the white of the bellies being, he thought, nature's attempt to match the white of the sky, for eyes beneath. Of course this under white can not do that, being always in shadow, and therefore practically dark brown—utterly too dark to match the over-head sky. On the other hand, white patterns on animals' upper slopes obey in every respect the law he foresaw, and operate upon the sight of such beholders as look from a lower level, except, of course, when the wearer is directly over them.
- ↑ "The Mountains," Chapter X., On Seeing Deer.
- ↑ One of the many surprises in store for Roosevelt is the potently obliterative character of the summer dress of the male bobolink, when seen from the hawk's viewpoint.
- ↑ "Concealing Coloration in the Animal Kingdom."
- ↑ Moonlight, of course, or the uneven illumination from a cloudy sky, can make white show momentarily brighter than the sky; but nature has to deal in averages, and these very irregularities of illumination cause the prongbuck's white just as often to look too dark as too light. Contradicting what he says of the skunk's white, Colonel Roosevelt says: "After nightfall the zebra's stripes would be entirely invisible." Here again he is completely wrong, as if he had never hunted by night. These stripes are invisible at night until the enemy is near enough to endanger the zebra. Looked at as near as this, all colors except white, show strongly against a starlit sky.