SEEING A SNAKE FEED.

IN any person who for the first time witnesses a snake with prey just captured, the predominant feeling must be one of surprise at the seemingly unmanageable size of the animal it has seized; and he probably exclaims to himself, or to his companion, as we did on the occasion described in the introduction, ‘What will he do with it?’ Let us again take our common ring snake, Coluber natrix, that ate a frog for our edification; only, in the present instance, instead of seeing a tame snake in a private residence at Chelsea, we will suppose ourselves to be watching one on the banks of a stream in fine summer weather. A slight movement in the grass causes us to turn our eyes towards the spot, and we are just in time to see the quick dash, and the next instant a recalcitrant frog held aloft in the jaws of a snake that with elevated head glides up the bank. Coluber’s head is no bigger than a filbert, and the frog is nearly full grown, its body inflated to twice its original size, and its legs, of impracticable length and angles, kicking remonstrantly.

‘How in the world is the snake going to manage it?’ again you exclaim, and your amazement is not exceptional. It is what has been witnessed and heard weekly in London when the public were admitted to the Reptilium on feeding days, and it is what the reader will recall in his own case when first informed that a snake was going to swallow that monstrous mouthful undivided.

In the present instance, the injury to froggie’s feelings thus far partakes more of moral than of physical pain, for the grasp of the snake is not violent, and he finds that the more he struggles the more he injures himself. Yet he kicks and struggles on, at thus being forcibly detained against his will. In the mouth of the snake he is as proportionately large as the shoulder of mutton in the jaws of the dog that has just stolen it from the butcher’s shop. How do the canines manage unwieldy food? The dog can tackle the joint of meat, big though it be, because he has limbs to aid him, and he was prepared for emergencies before he stole it. He knew of a certain deserted yard up a passage close by, and of some lumber stacked there; he watched his opportunity, and is off to his hiding-place; and once hidden behind the lumber, he settles down quietly with his ill-gotten dinner firmly held between his fore-paws, while, with eyes and ears on the alert, he gnaws away.

The snake, no doubt, knows of a hole in the bank, or in a hollow tree, in which he can hide if alarmed; but he cannot set his frog down for one instant, nor can he relax his jaws in the slightest degree, or his dinner hops away, and he has to pursue it, or wait for another frog, when the same thing may happen again. He has only his teeth to trust to, and these have all the work of paws and claws, and nails and talons, to accomplish, while yet, not for one instant, must they relinquish their hold.

‘Besides!—how much too big that frog is for Coluber’s small mouth!’ And we continue to gaze in wonderment, filled with amazement that brings us to the bookshelves, to endeavour to comprehend the phenomenon. Not, however, until we have seen the end of that frog on the banks of the stream, where the reader is supposed to be waiting.

First, let me explain that in the manner of feeding, snakes may be divided into three classes, viz. those that kill their prey by constriction or by smothering it in the coils of their body; those that kill by poison; and some smaller kinds, which, like the ring snake, eat it alive—the latter a quick process, which may also be said to be death by suffocation. Our little Coluber is in a spot where we can watch it easily; so we keep rigidly still, and soon perceive that though the snake just now had hold of froggie’s side, he now has the head in his mouth. How can this be? and how has he managed to shift it thus, almost imperceptibly, while seeming to hold it still? Now the head begins to disappear, and the snake’s jaws stretch in a most distorted fashion, as if dislocated; its head expands out of all original shape, while slowly, slowly, the frog is drawn in as if by suction. Now its legs are passive; they no longer kick right and left, but lie parallel, as by degrees they also vanish, and only the four feet remain in sight. These presently have been sucked in, and the skin of the snake is stretched like a knitted stocking over the lump which tells us just how far down Coluber’s neck the frog has reached. Gradually the lump gets farther and farther down, but is less evident as it reaches the larger part of the body. The snake remains still for a few moments till his jaws are comfortably in place again; then he yawns once or twice, and finally retires for his siesta, and we to the bookshelves.

‘Snakes work their prey down through the collapsed pharynx,’ says GÜnther. That is, the muscles of the throat seize upon what is presented to them, and do their part, as in other animals. Only, in most other animals there is the action of swallowing, one mouthful at a time; whereas in serpents the action is continuous, the throat going on with the work begun by the teeth, which in a snake is only grasping and working the food in with a motion so gradual as to simulate suction. The reason why the head and jaws have been so enormously stretched and distorted, is because all the bones are, in common language, loose; that is, they are not consolidated like the head-bones of higher animals, but united by ligaments so elastic as to enable them to separate in the way we have seen. This extends to the jaws, and even to the palate, which is also armed with teeth, two rows extending backwards. The lower jaw or mandible being extremely long, the elastic ligament by which the pair of bones is connected in front, forming the chin, enables them to separate widely and move independently. This is the case in a lesser degree with the palate bones, and the upper jaw-bones, all six being furnished with long, fine, recurved, close-set teeth, adapted for grasping and holding, but not for dividing or for mastication in any way.

For, as we have seen, if a snake were to open its mouth one moment for the purpose of what we call biting, the prey would escape. In addition to a very unusual length, the lower jaw is joined to the skull by an extra bone,—one which is not found in mammals, but only, I think, in birds,—a long ‘tympanic’ bone, which forms an elbow, and permits of that wide expansion of the throat necessary for the passage of such large undivided prey.

The illustration of the skeleton of a cobra, on p. 33, will enable the student to distinguish the principal head-bones. There is so much similarity of construction throughout the whole ophidian families that a cobra is chosen here, because the unusually long anterior ribs which form the hood can be observed, and the expansion of which is described elsewhere. The longer teeth in the upper jaw are here fangs; the inclination of the other rows of teeth and the bones sufficiently illustrate those of the non-venomous kinds generally, such as the little ring snake that has just swallowed his frog. A few of the larger constricting snakes possess an additional bone—an intermaxillary in front between the upper jaws, very small, yet sometimes furnished with two or four teeth, thus facilitating the expansion of the jaws as well as the retention of the food.

It is this adaptive development of head-bones that enabled Coluber natrix to turn his frog round to a more convenient position, and then draw it into his mouth so gradually that we scarcely comprehended how it disappeared. The six rows of small teeth form six jaws so to speak, each one of which advanced a very little, while the other five were engaged in holding firmly. In those largest pythons which have the little bone in front between the two upper jaw-bones (intermaxillary) we may say there are seven jaws. As those gigantic snakes have to deal with proportionately large and strong prey, they are thus enabled to retain and manage it.

In the graphic language of Professor Owen let me recapitulate.

The mouth can be opened laterally or transversely, as in insects, as well as vertically, as in other vertebrates. The six jaws are four above and two below, each of which can be protruded or retracted independently of the others. ‘The prey having been caught and held, one jaw is then unfixed by the teeth of that jaw being withdrawn and pushed forward, when they are again unfixed farther back upon the prey; another jaw is then unfixed, protruded, and re-attached, and so with the rest in succession. This movement of protraction, being almost the only one of which they are susceptible, while stretched apart to the utmost by the bulk of the animal encompassed by them: and thus by their successive movements, the prey is slowly introduced into the gullet.’[3]

This working of the jaws would be almost imperceptible excepting to a very close observer. In the lower jaw-bones the independent action can be more readily perceived and is often very grotesque, one side of the mouth opening while the other is closed, conveying the idea of the reptile making grimaces at you; but the gradual disappearance of the prey so much more bulky than the snake itself is quite incomprehensible until we are acquainted with the remarkable phenomena of the six rows of teeth acting independently. Thus, in turning the frog round to adjust it to a more convenient position, the jaws acted like hands in moving, dragging, or shifting some cumbrous article, say a carpet or a plank, when the left hand follows the movement of the right hand until the plank or carpet is worked round or forward in the required direction.

The form and arrangement of the fine claw-shaped teeth assist the process. They are too close together, and the pressure is too slight to inflict a wound; they merely retain what they hold, and it is in vain for the prey to struggle against them, or it might get some ugly scratches as they all incline backwards. In chapter xix. illustrations of teeth, life-size, show their forms and direction; here it only need be added regarding them, that the above description refers chiefly to the non-venomous snakes.

The palate being covered with that armoury of teeth, the snake must have but a slight sense of taste, which is to its advantage, we should say; for having no assistant in the shape of beak or limbs to divide its prey, hair, fur, feathers, dust—all must be swallowed with the meal, completely disguising whatever flesh they cover, so that we should suppose the process of feeding could be productive of very little enjoyment to the reptile. Perhaps out of this state of things has developed their habit of eating so seldom, but when they do take the trouble of feeding, of doing it thoroughly, so that their meal lasts them a long while.

Deglutition is greatly facilitated by an abundant supply of saliva, which lubricates that uncomfortable coating of feathers or fur; but ‘lubrication’ is understood to refer merely to the natural secretions of the mouth, in which the tongue performs no part at all.

The salivary apparatus of snakes is peculiar to them, and very complicated. Even the nasal and lachrymal glands pour their superfluous secretions through small canals into the mouth.[4] These active and abundant glands are excited by hunger or the sight of food, just as in mammals; and for the more common expression of the mouth ‘watering’ that of ‘lubrication’ is here used, because over the rough-coated prey these salivary secretions act as a great aid in deglutition. The erroneous impressions that have obtained on this subject are touched upon in describing the tongue (chap. vi.).

A circumstance happened at the London Zoological Gardens a few years ago, which, although familiar to many, may be referred to as bearing on two of the above features—namely, the dull sense of taste in a snake, and the abundant supply of mucous secretions. It was in the case of a large boa which swallowed her blanket. She was about to change her skin, and, as usual on such occasions, was partially blind, as also indifferent to food. The rabbits given to her dodged her grasp, and her appreciation of flavours was not sufficient to enable her to discriminate between blanket and rabbit fur; so, seizing a portion of the rug, she with natural instinct constricted this, and proceeded to swallow it. She was, however, made to disgorge it afterwards, when it was scarcely recognisable from the thick and abundant coating of mucous in which it was enveloped. Mr. F. Buckland described its appearance as that of a ‘long flannel sausage.’

These highly-developed salivary glands are beneficent provisions in the economy of the serpent race. The reptile cannot, as we said, tear flesh from bones, and discard the latter; nor separate the food from the enveloping feathers or fur; nor reject whatever unsavoury portions other animals might detach and leave uneaten. All must be swallowed by a snake, and all digested; and its digestion, sufficiently powerful, is aided by the excessive flow of saliva, or the insalivation of such food.

It is not difficult to make snakes disgorge their food. They often do so on their own account, when, after swallowing some bulky meal, they are alarmed or pursued, and escape is less easy with that load to carry. The illustration exhibiting the numerous ribs, which are all loosely articulated with the spinal column, enables us to comprehend the capacity for bulk, and the ease with which these fine ribs would expand to accommodate a body even broader than the snake itself. We comprehend, also, why it is that a creature swallowed alive need not be injured or wounded by the mere fact of being swallowed, but would die of suffocation after all. A frog has been known to turn round and escape from the body of the snake, if the latter indulge in a prolonged yawn; and yawning almost always does follow as soon as the prey is swallowed, because the snake has for the time breathed less regularly, and now requires to take in a fresh supply of air. In this act you see the two jaws extended to an enormous degree, almost, indeed, to form one straight line perpendicularly. In such condition the teeth are well out of the way, and the adjustable ribs, expansile covering, and loose head bones render them not insurmountable obstacles to an escape when the prey is uninjured.

One sometimes hears of the egg-stealing snakes, cobras, etc., when surprised and pursued, first relieving themselves of their plunder before they attempt to escape. Often it may be observed, when two snakes are in a cage together, and both get hold of the same frog or rat, that they each advance upon it till their heads meet, when either the stronger or the larger snake will gain the day, and finish his frog, and then proceed to swallow his friend; or else one will relinquish his hold, when, even in those few minutes, the half-swallowed prey will be completely disguised in the mucous saliva which has already enveloped it.

Some snakes, though not quarrelsome at other times, for some reason inexplicable to the looker-on, persistently set their heart on the same bird or frog, though many are presented for their choice. In a pair of Tropidonoti at the Gardens this occurs almost every week; and in such instances the keeper keeps a sharp watch over them; for as neither snake will relinquish its capture, the one that begins first comes in contact with the head of his comrade, who will assuredly be swallowed too, were not a little moral, or rather physical coercion in the shape of a good shaking administered. Sometimes both get their ears boxed, figuratively; yet the discipline has no more than a passing effect, and next week the same thing happens again.

Not many months ago a very valuable snake was thus rescued literally from the jaws of death. A South American rat snake (Geoptyas collaris) began to eat a rabbit that was put in the cage for a python, which also began to eat it. Collaris would not let it go, and so the python continued to advance upon it until he came to his comrade, and proceeded with this prolonged repast. Collaris is a rather large snake of some eight or ten feet long. When nearly the whole of him had vanished, the keeper—who, of course, had been occupied at each cage in turn—fortunately discovered about a foot of tail fast disappearing in the mouth of the python, the whole of Collaris, excepting this caudal portion, having been swallowed. Just in time to rescue the victim, the keeper, by his experienced manipulation, made the python open his mouth, while the assistant helped to pull at Collaris. At last they pulled back all the seven feet of snake, which sustained no further injury than a slight scratch or two against the python’s teeth; but he seemed none the worse, and was no sooner free than he seized a rat, constricted and ate it with a celerity which seemed to say he would make sure of a meal this time.

On the following Friday the very same thing was about to occur again. Collaris had begun to swallow the python’s rabbit, the latter having prior hold; but the keeper was on the watch, and administered a little practical reproof which made the rat snake loosen his hold. Matters were further complicated on this occasion by the python throwing some coils around his intended feast, so that to get a purchase and manage these two constrictors was less easy than on the previous occasion, though then the snake had been swallowed. In the same cage were also two other pythons, quite strong enough to strangle a person had they taken a fancy to hug him round the neck. Both were aroused and displeased at the commotion, and ready to ‘fly’ at the men, who, on the whole, had an exciting time with the four constrictors, all from eight to twelve feet long.

Cannibalism is very common in snakes, particularly among the ElapidÆ, which have small and narrow heads, and can therefore more conveniently swallow a fellow-creature than a bird or a quadruped. The keeper told me that often a box arrives at the Gardens labelled ‘Ten cobras,’ or ‘twelve,’ as may be; when, on opening the box, the number falls short; suggesting that cannibalism has diminished the company. It is a curious fact, however, that snakes, as a rule, seize prey whose bulk far exceeds their own, even when a more manageable kind could be easily caught. It is as if they were aware of the accommodating nature of their multifold ribs; as a snake longer than themselves must be doubled up in their stomach, and those broader than themselves must, one would imagine, be a most uncomfortable meal to dispose of. Yet this is common. Mr. H. W. Bates found in a jarraraca an amphisboena larger than itself, and in another snake a lizard whose bulk exceeded its own. My Brazilian correspondent, Dr. Arthur Stradling, wrote me of a similar circumstance. He received a little Elaps lemniscatus in Maceio, which presented a singularly bloated appearance. It no doubt felt itself in a condition not favourable to rapid escape; or captivity impaired its digestion, for ‘the next morning it disgorged an amphisboena or small serpent (it was half digested) actually longer than itself, and weighing half as much again.’

Prodigious meals engender drowsiness, and thus the Ophidia habitually repose a long while after taking food.

This habit of gorging enormous prey being one of the most striking of ophidian characteristics, it has been introduced thus early in my work, as affording opportunity for a general glance at the anatomical structure. In the next chapter we will enumerate a few other peculiar features, ere proceeding to examine in detail some of the most important organs.