The Zoologist/4th series, vol 4 (1900)/Issue 703/Stray Notes on Mimicry, Witchell
STRAY NOTES ON MIMICRY.
Prof. Newton's limitation of mimicry to the status of unconscious resemblance (cf. Zool. 1899, p. 529) is in accord with that prevailing tone of thought which denies to the lower animals the power of abstract reasoning so constantly evident in man. I hope that Mr. Distant will not conclude his highly interesting treatment of the mimetic faculty without some reference to vocal mimicry, for this demonstrates (as it would seem, beyond dispute) the occurrence of a desire on the part of certain animals to do something that another animal is doing or has done, solely for the purpose of mimicking it. The Parrot is a common instance; but the Starling is, I think, a better one, since the studies of the latter bird are purely voluntary, and have no possible reference to the furnishing of a supply of food by a human owner. The Sedge-Warbler, with its construction of novel strains by the repetition of some notes of other birds in a set order, is another instance of a bird exhibiting a voluntarily exercised mimetic faculty. If a bird's mimicry is unconscious, then all its other actions may be unconscious, and the creature an automaton, which is absurd, except on the hypothesis that man also is one. But we must not hastily assume that similarity of action indicates mimicry; it may suggest inheritance as the governing factor. Take the case of the hissing of nesting birds. The hissing of these birds seems generally to be the ultimate expression of hate and rage, and to have no intended reference or similarity to that great enemy of the nest—the snake; for a bird will hiss when on the nest, and at no other time, and which has yet never seen a snake, or, apparently, never heard a hiss: such is a town-bred fowl or duck. The Blue Tit, again, hisses on the nest; but, so far as I can ascertain, this bird has never yet been heard to mimic the note of even another genus, and still less would it be likely to reproduce the note of a reptile, and a note which probably it had never once heard. For Snakes do not hiss, as birds sing, for amusement or occupation. Probably they never hiss at all, except in combat. This is at least true of the Common Snake (natrix), and the Viper (berus), both of which I have had (numbers of them) in captivity. The Common Snake, even when the sexes unite, utters no audible vocal sound, and, when angry with another of its species, it only shakes or rattles its tail a little; and the Viper seems to be equally silent. Both of these animals make much more noise by their rustling through herbage than by their vocal efforts, except on the special occasion of combat. I have seen the Common Snake feed, say, a thousand times, and never heard a hiss from it then, though sometimes there would be a slight expulsion of air, causing a sound like a little coughing, while a Newt or fish was being swallowed. The Blue Tit must therefore be as ignorant as a cockney fowl, so far as the hissing of Snakes is concerned.
The hissing of birds would therefore seem to be an inherited expression of rage, derived from a very remote ancestry.
With regard to butterflies perching in positions where they are inconspicuous (Zool. 1899, p. 230), I have often observed that the Common Blues are fond of sleeping not only on grass-stems (as recorded by Mr. Cornish), but also on the dead and dry seed-heads of plants, on which they are not noticeable. I have a note of once finding quite a number of Blues (eight or nine; the MS. is not with me) sleeping at evening on one small dead flower-head, which they would never have noticed in the sunny hours of day.
A Peacock Butterfly (Vanessa io) that lived one summer in a garden where I was at Stroud, spent the day at one side of the garden amongst the flowers, and at evening, or when the weather darkened, it entered the shelter of an upper branch on the shady side of a cypress tree on the other side of the garden, and amongst the black stems the insect was wholly invisible. At other times it never alighted on a cypress. The Peacock does not always choose such a dormitory. I have generally found it prefer the overhanging ledges of banks. The Red Admiral (V. atalanta) I have seen retire to the branch of a beech tree at evening, and in this case also the colour of the insect in repose was similar to that of its support.
At Ceres, South Africa, I noticed that some of the grass insects, looking like bits of grass (they were seen in March), always alighted on the stems in such a way that they seemed to form part of the plant; they never posed at right angles to the stems, in which case they would have been less obscured by their environment.
I have observed two instances of what seemed to be an accurate idea of the advantage of similarity of colouring in relation to a bird and its environment. On a warm day in winter I noticed a curious Robin-like bird in a hedge, and tried to identify it by means of the telescope; but it kept its back toward me, and this was practically inconspicuous in the hedge. The bird was quite at ease, for it occasionally flew to the ground or elsewhere to catch an insect. Soon it was clear that the bird did not wish me to see its breast. At last, after quite a quarter-hour of following and circling round it (in the most careful manner), I saw the bird's breast, and was able to identify a female Stonechat. I do not suggest that it wished to be mistaken for a Robin, but that it knew that its back, in that situation, was less noticeable than the breast, though this had sober colouring.
The other instance was much more definite and conclusive. In the garden at Stroud, in winter, we fed the birds on a small grass-plot near the house, from which a bank sloped up into the shade of two yew trees. The Thrushes, when disturbed feeding, generally ran up this bank or flew up into the trees, which spread at some six feet above the ground. One day, going out with food, I noticed a wounded Thrush which had been feeding there for some days. It ran a little way up the bank, and I carefully avoided alarming it. It only ran half-way up the bank, and then squatted down in a little hollow; not with its back toward me, but with its breast to me, and with the head raised considerably, so that the beak was almost vertical. The speckled breast and under side of the neck were practically all of it that I could see, and they were of so much the colour of the surrounding rubbly soil that for a moment I could not discover the bird when I looked for it. The tail, I could see, was pressed quite against the steep bank, so that the bird was not in a very comfortable posture. The Thrush does not habitually turn its breast toward an observer, and in this case the reason for the behaviour of the bird hardly needs arguing. I was certainly not more than twelve feet from it.
With regard to physical mimicry generally, I would suggest (at the risk of ridicule) that there may be some occult influence causing animals to resemble things that they like, be those things mates or surrounding substances. I am aware that the sexual passion is not credited with this effect, but we know that breeders of prize poultry are careful to keep their male birds from running with birds not of the same variety, because if they do they will "throw" feathers like those of their companions. I have seen this occur in a well-bred East Indian drake that ran with a white Duck, and in a Black Hamburgh that ran with other fowls.
I have also noticed some curious evidence among people. A man who went to a colony early in life, and had control of many people of colour, and who would not be likely to be particular, afterwards married an exceedingly good-looking and quite strong Englishwoman. The first child, a son, was very like a black in all except colour, and yet he resembled his father. The next child had only a faint trace of the same odd resemblance, and the younger children were distinctly handsome. One has quite a reputation for good looks.
I am aware that this suggestion is not scientific, but if a bird throws unusual feathers after having shown a partiality for a strange bird, why should it not throw an unusual feather when it finds that a certain tree or a stone saves it from a Hawk? The dread of an enemy is a more constant sentiment than the love for a mate.
The so-called feigning of death seems to me to have no relation to mimicry, but to an exaggeration of that stillness which so many animals adopt to avoid observation. This stillness may often be seen to be directly proportionate to the imminence of the danger threatened. I used to witness a very clear demonstration of this in the Stickleback (Gasterosteus leiurus). When suddenly alarmed these fishes held themselves curved, the more readily to dart away; but they seemed unable to remain in this position long, and yet they would then retreat not by a slow movement, but by sudden darts alternated with periods of stillness, as though they well knew that in movement they were the more visible, and that quick movement was the least likely to be detected. The usual mode of escaping notice when approached slowly is to remain still, lying straight. If the danger be not pressing, the fins and tail are still moved a little, in the customary way; but on the threat of greater peril these members are held motionless; and in still greater danger even the movement of the gills in respiration is so restricted as hardly to be visible, even from the distance of a foot. These gradations of stillness are successively adopted even though the aggressor be but another Stickleback; and this especially occurs when a female fish is hoping to escape the notice of an approaching pugnacious male.
The Viviparous Lizard (Lacerta vivipara), wild or tame, has a similar appreciation of stillness, and of the advantage of rapid movement in retreat; and this reptile, like the fish, will refrain from breathing in order to escape detection. I have had perhaps hundreds of these reptiles in captivity, and have often crept up to them while they basked on their native banks, and watched their movements. The movement of the lungs in breathing is very apparent at the shoulders.
I have seen the feigning of death by two Ringed Snakes (Tropidonotus natrix) only out of a hundred or more handled. These were the only two I ever recaptured after liberation—one after a fortnight's liberty in the garden, and the other after nine months' freedom in his native haunt. These, on recapture, behaved in the same manner. The whole reptile became utterly limp; the tongue protruded, and the filaments at the end united (as they never are in life), and there was no hissing or apparent breathing. I never saw a Lizard feign death, nor any Batrachian.
- This has been referred to. Cf. Zool. 1889, p. 476.—Ed.
- I have everywhere noticed that in expressing rage birds tend to revert to generic cries. Young children, in the same mental trouble, perform some Monkey-like actions, and utter cries like those of Monkeys.