THE PELAGIC OR SEA SNAKES.

THE modifications of ordinary forms which are seen in the fresh-water snakes are still more beautifully developed in the HydrophidÆ, or true marine serpents. The former, being never out of easy reach of shore, could easily find a safe harbour from violent torrents, in holes in the banks or among the strong aquatic weeds along the borders of lakes and rivers; and to be enabled to hold on to these in times of danger or of repose, they possess a prehensile power of tail. In a rough and stormy ocean, a much more powerful propeller and rudder would be necessary for the guidance of the reptile, and to afford resistance against the denser medium of sea water; therefore the tail of sea snakes is not only prehensile but strongly compressed, so as to almost form a vertical fin, answering altogether to that of a fish. This is their most conspicuous and striking feature, and one that would leave no doubt in the mind of the observer between the true marine and those fresh-water species which may by accident drift out to sea by force of current.

Another distinguishing feature is the absence of ventral scales in most of the species. In land snakes we saw how admirably adapted are the broad, ventral plates for assisting those reptiles over rough surfaces, as affording hold; but the HydrophidÆ requiring no such aid in a fluid, those scutÆ would be useless; they are therefore, excepting in one or two species, entirely absent, or but slightly developed, and the belly is ridged instead, like the keel of a boat.

The nostrils are small, placed horizontally on the top of the snout, as in the HomalopsidÆ, and in most of the sea snakes they are contiguous. They are, moreover, furnished with a valve, which is under control of the will, opening to admit air, and closing to exclude water when diving. For, be it remembered, these marine reptiles breathe through their nostrils even more entirely than terrestrial snakes, the latter being better able to indulge their yawning propensities, or to occasionally respire slightly, and through parted lips and the tongue chink as well. Sea snakes, on the contrary, not requiring the continual use of their tongue to feel and explore surroundings, and not using it below water, are not provided with the little centre chink for its exsertion; but the middle plate of the upper lip, i.e. the ‘rostral shield’ (see illus. p. 238), is altogether of a different form. Indeed, the centre plates or shields in both lips are conspicuously modified, the upper one often inclining downwards in a point which fits into the lower one shaped to receive it, so that the mouth is firmly closed to keep out the water. Less required, the tongue is shorter and less developed, the tips are less hair-like, as only these, if at all, are exposed to the sea water, and a very small notch on each side of the pointed rostral shield of some permits the slight egress of these tips. When out of their natural element, the tongue is brought into more active service, for then the bewildered reptiles require its assistance, and it is then seen to be exserted as in land snakes. Their lungs extend the whole length of the body to the anus, and by retaining a large supply of air, these animals are enabled to float easily, as they do for a long while on the surface of the calm tropical seas, not only while sleeping, as mentioned in the chapter on hibernation, but in pure enjoyment, and probably in the lazy postprandial condition.

As has been already stated, the eyes of sea snakes are adapted to see better through the medium of water than through the brilliant atmosphere of their native latitudes. They are very small, and soon blinded by light; consequently, though among the swiftest and most gracile of serpents in their native element, the movements of the HydrophidÆ on land are uncertain and ‘maladroit.’

Some forty years ago, Dr. Theodore Cantor, F.Z.S., devoted a good deal of time to the study of the pelagic serpents, and wrote a somewhat detailed account of them to the Zoological Society. His paper, published in the Zoological Society Transactions, 1842, vol. ii., was considered the most important that had as yet appeared. He, therefore, has been one of our first authorities. Subsequently we are indebted to GÜnther, Dr. E. Nicholson, Gerard Krefft, and Sir Joseph Fayrer for the results of their individual observations. In my foregoing descriptions I have culled from each of these, and as most modern writers on this subject merely reproduce from the works of GÜnther, Cantor, and Fayrer, I will keep chiefly to these in what further has to be said of sea snakes.

First, they belong to the tropical seas of the Eastern hemisphere, and are most numerous in the Indian Ocean, where they abound. The geographical range of a few is, however, somewhat extensive, viz. from Madagascar and that part of the African coast to northern Australia, the Bay of Bengal, and even to the western coasts of Panama; while others are restricted to certain localities. All are highly venomous. They are wild and ferocious as well, and therefore peculiarly dangerous, and are the great dread of fishermen, who carefully avoid them. Accidents, nevertheless, frequently happen through their being caught in the nets, when, from their exceeding activity, it is difficult to disengage them and set them free again. When out of the water they try to bite at the nearest objects, and being dazzled by the light, strike wildly, unable to aim correctly. Cantor informs us that he has known them to turn and strike their own bodies in their rage, and that he has found difficulty in disengaging their fangs and teeth from their own flesh.

Owing to the great danger attending their capture, and also the almost impossibility of keeping them alive when out of the sea, less is accurately known of the pelagic than most other snakes. Even if placed in a large hole in the ground filled with sea water, or a capacious tank similarly supplied, they die very rapidly. Sir Joseph Fayrer in his experiments resorted to every means in order to keep them alive, but informs us that their exceeding delicacy caused their rapid death in spite of the utmost care. Dr. Vincent Richards, however, has succeeded in keeping some alive several weeks.

In length they vary from two to ten feet. Krefft says that the largest he ever saw was nine feet long. GÜnther states that they sometimes attain twelve feet, and sea snakes of even fourteen feet in length have been occasionally reported, though not perhaps from well authenticated sources. It is probable that, like all other reptiles, they attain their greatest proportions in the hottest regions.

Though purely oceanic, and no more found in fresh water than on dry ground, yet they come some distance up the rivers as far as brackish water. When washed on shore by the surf, they are helpless and blind, and at such times ‘peaceable,’ by reason of their helplessness. Occasionally they are seen coiled up asleep on the beach, where they have probably been washed by the tide, and where the next tide will no doubt release them from their uncongenial bed. Those species which have a less keeled body and the partially developed ventral scales might even manage to get back to sea independently of the tide. Even those without ventral scales contrive to wriggle along in their own fashion.

Such an occurrence is related by Mr. E. H. Pringle in the Field newspaper of 3d September 1881. He tracked an Enhydrina fifty feet along the sands, making its way back to the sea from a salt-water pool, where it had probably been left by the tide. This species is the one peculiarly favoured in having tiny orifices for the egress of the tongue tips on each side of its lobulated snout.

Its profile, being somewhat remarkable, is here presented to the reader, who will perhaps detect a certain determination in that very beak-like snout. This species is found along the Burman coast. Another, though keeping to its native element, has explored the Pacific to the very borders of America, and has been seen on the western coast of Panama. This is Pelamis bicolor, of distinct black and yellow, like a striped satin ribbon. The back is black, and the belly brown or yellowish, and its rather short, flat tail is spotted with a bluish colour as well. None of his relatives venture so far from the oriental islands as Pelamis. His presence as far north as New Caledonia has not, that I am aware of, been authoritatively recorded; we cannot suggest, therefore, the probability of ‘J. J. A.’s’ sea snakes, ‘stupid and fearless,’ being ‘incredible numbers’ of the Pelamis family. Dr. Stradling affirms that they are ‘not unfrequently met with along the eastern coast of South America, and that one found its way on board the royal mail steamship Douro, and concealed itself under the covering of the patent lead, having probably climbed up the quarter line as she lay made fast to the wharf at Santos.’[74]

Some slight controversy on the possibility of Pelamis ‘climbing’ followed this statement. But Mr. F. Buckland also recorded one ‘which crawled up the anchor-chain of a man-of-war, when she was moored in the mouth of the Ganges. The midshipman of the watch saw something moving along the chain, and without thinking went to pick it up, when it turned upon him, and bit him. The poor young midshipman did not live many hours after the accident’ (Land and Water, Nov. 15, 1879).

In the same issue the writer described one which was caught in the telegraph wire of the Eastern Extension Telegraph Company. One of the cables was being raised, and when it came to the surface, the snake was found coiled tightly round it. Hydrophis was here exercising his prehensile powers, not understanding the reason of the violent motion. Snakes, as has been already affirmed, are not restricted in their acrobatic achievements; so that even sea snakes, not naturally either climbers or crawlers, can do both on an occasion.

The more interesting question regarding Dr. Stradling’s cable climber is, was it a true Pelamis, or one of the HydrophidÆ at all? If so, it was more likely to be an entirely distinct species from those of the oriental seas. Either Cape Horn or the Cape of Good Hope would be far too southward for their range, they being essentially tropical. When Panama comes to be severed by water communication, some enterprising Pelamis or Enhydrina may find its way through, and get down even to Santos; but at present, as Dr. Stradling did not see the snake, but only heard of it, the evidence of the presence of HydrophidÆ on the eastern coast of South America cannot be fully established.

A further facility to their agile and graceful movements in the water are their smooth, non-imbricated, or only slightly imbricated scales. These, though mostly hexagonal, and laid side by side, different from those of land snakes, yet vary much in size and form; and the head shields particularly are so abnormal, that, as GÜnther affirms, you can tell a sea snake at once by them (see illustrations, chap. xviii.).

To distinguish a pelagic from a fresh-water snake is, however, far easier than to distinguish species among themselves. They present great varieties of form and colour, but the transitions are very gradual, and the female is generally larger than the male, and sometimes of a different colour, which adds to the difficulty.

They are all viviparous, and produce their young in the water, where the little ones are at once able to take care of themselves, and feed on small fish or molluscs. The full-grown HydrophidÆ feed on fish corresponding with their own dimensions, and swallowed head foremost. Even spiny fish are managed by them, notwithstanding that they have a smaller jaw than most land snakes. Being killed by the poison of the bite on being caught, GÜnther explains, the muscles of the fish are relaxed, and the prey being commenced at the head, the armature does not interfere, but folds back flat as the fish is gradually drawn into the jaws.

An interesting study to the lover of nature it is to watch the wonderful movements of these sea reptiles. Swimming and diving with equal facility, flashing into sight and disappearing again in twos or scores, or in large shoals, pursuing fish, many of them of bright colouring, they offer constant amusement to the beholder. Sometimes, when the sailors are throwing their nets, they disappear beneath the waves, and are no longer seen for half an hour or more; when presently, far away from the spot where they vanished so suddenly, up they come to the surface again, to sport once more, or take in a fresh supply of air.

Pity they possess such evil qualities to blind us to their beauties, for they rank among the most venomous of serpents. They belong to the sub-order of venomous colubrine snakes, or Ophidia colubriformes Venenosi, those which outwardly have the aspect of harmless snakes, while yet furnished with poison fangs. In the chapter on Dentition, these distinctions, facilitated by the illustrations, are more fully explained; here it need only be said that though they have smaller jaws and shorter fangs than many other venomous snakes of their size, the virus is plentiful, and so active that the danger from the bite is great. All the pelagic serpents have also a few simple teeth behind the fangs; therefore, as Fayrer warns the natives, it does not do to trust to the appearance of the wound, which, though looking like the bite of a harmless snake, would demand immediate remedies. A certain conviction of danger is that the bite being inflicted in salt water, would leave no doubt as to the nature of the snake. Even a painless wound it is not safe to trust; and Sir Joseph Fayrer gives several such warnings among his cases of bite from sea snakes, two of which I will quote.

Captain S——, while bathing in a tidal river, felt what he thought was the pinch of a crab on his leg, but took no notice of it, and after his bath called on some friends, being to all appearance exceedingly well. He remained about an hour, playing the concertina to amuse the children, and declaring himself never in better health. In about two hours, feeling strange symptoms of suffocation, enlargement of the tongue, and a rigidity of muscles, he sent for a doctor, but still having no suspicion of danger. The next morning a native detected the peculiar symptoms which usually follow the bite of a sea snake; and Captain S——, then examining the foot which the supposed crab had nipped, found marks of fangs no bigger than mosquito bites on the tendon Achilles near the ankle. Immediate steps were taken, and remedies applied which seemed to promise favourable results for a time; but in the evening of the third day the victim was seized with spasms, and died, seventy-one hours after the accident. In this case, owing to the sound health of the captain, and no local pain ensuing to warn him, together with the stimulants and remedies applied, and the bite being where absorption was slow, his death was protracted; otherwise death often occurs within twenty-four hours from that species of snake.[75]

The second case was that of a man who was bitten in the finger by a sea snake, and thinking lightly of it, used no means whatever to arrest the poison, and was dead in four hours.

In some cases the victim becomes quickly insensible, when, if no aid is near, he never wakes to consciousness. Immediate stimulants revive the patient, and if he can be kept awake, these, with local applications, at once applied, may save his life. ‘Hope itself is a powerful stimulant,’ adds the learned experimentalist.

Many other cases are given by Fayrer of bites by sea snakes, some of which yielded to remedies and others were fatal; but for these the reader is referred to the Thanatophidia.

Dr. Cantor had previously made many experiments on various dumb creatures in order to ascertain the virulence of the poison of these hitherto unstudied reptiles. He found that a fowl died in violent spasms eight minutes after a bite; and a second fowl, bitten directly afterwards by the same snake, with its half-exhausted venom, in ten minutes. Fish died in ten minutes; a tortoise in twenty-eight minutes, from the bite of another species; and a harmless snake was paralyzed within half an hour.

Among the fresh-water snakes, Dr. GÜnther tells us of one, Hydrinus, which is semi-pelagic, and which indulges in little excursions down the rivers to exchange greetings with his marine relatives, some of whom, on their part, occasionally go a certain distance up the rivers. Again, among the sea snakes is one who rambles for change of air or diversity of diet over the fields and far away. In him, Dr. GÜnther describes one of those many transitions found in every class and order throughout nature. Platurus is his name; he has the ventral scales of land snakes to enable him to wander over the salt water marshes which he loves. His nostrils are on the side of his head instead of on the top, and his head shields differ from those of all his relatives. His venom fangs are small, and his tail is not prehensile, presenting the united characters of fresh and salt water and land snakes. Thus we have links between sea and land snakes, between fresh water and salt, and between these latter and fishes, for in many instances the affinities are so close that naturalists have doubted in which class to place them. When that remarkable animal, the Lepidosiren, which Darwin calls a living fossil, was first brought from Africa some thirty years ago, it was found to present so many characteristics in common with both reptiles and fishes, that it was for some time a mooted question in which class to place it. In appearance it more resembles the former, with its four curious filamentary limbs, which Owen considers ‘the beginnings of organs which attain full functional development in the higher vertebrates.’ The same high authority has decided that the only character which absolutely distinguishes fishes from reptiles, so closely are some of them allied, is whether or not there is an open passage from the nostrils to the mouth; and the ‘Lepidosiren’ is now known as ‘the mud-fish of the Gambia,’ the ichthyic characters predominating.

Sea snakes were not unknown to the ancients. Aristotle mentions them (Taylor’s Translation, 1812, Book ii. vol. 6), ‘Of sanguineous animals, however, there remains the genus of serpents. But they partake of the nature both of terrestrial and aquatic animals. For most of them are terrestrial, and not a few are aquatic, and which live in potable water. There are also marine serpents similar in form to the terrestrial genus, except that their head more resembles that of a conger. There are, however, many genera of marine serpents, and they are an all-various colour; but they are not generated in very deep places.’

These latter words suggest what has not been mentioned as a positive fact, while yet in part it is corroborated by Cantor, who tells us that the young sea snakes feed on soft-shelled molluscs; we may argue, therefore, that the mother snakes come into shallow water to give birth to their young, where small fish and suitable food may abound. Aristotle was evidently aware of the distinctions between fresh and salt water snakes, and gives us the former as frequenting rivers (‘potable waters’).

The Greek mariners who frequented the tropical seas knew of the poisonous snakes with wholesome dread. Sir Emerson Tennant tells us that the fishermen on the west coast of Ceylon are still in perpetual fear of them. They say there are some with the head hooded like the cobra, that coil themselves up like serpents on land, not only biting with their teeth, but ‘crushing their prey in their coils.’

The ‘hood’ part of the story is not borne out by any scientific writer; and as for the ‘crushing in coils,’ the sailors may possibly mistake the prehensile actions of holding on—even to a large fish—possibly for the action of crushing in the way of constricting. In self-protection, or for safety, venomous serpents do entwine themselves pretty tightly round an object sometimes. An instance of this was just now given. But constricting for the purpose of killing is happily confined to the non-venomous families. It would indeed be terrible if the ‘giants of the waters’ could both constrict and bite with poison fang; and of this a word or two will be said in the following chapter. Admittedly but little has been accurately ascertained about the marine serpents in comparison with the terrestrial ones. And there really may be species hitherto unobserved. The great sea serpent question is not yet satisfactorily settled; and among the lesser kind, the true pelagians, varieties are frequently occurring. Krefft describes one in the Australian Museum which, not being like any other that he had seen, he sets down as a new type. Forty-eight distinct species were described by Cantor. The whole family comprises seven genera, four of which belong to the Indian Ocean.