Snakes: Curiosities and Wonders of Serpent Life

by Catherine Cooper Hopley

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.

Portion of the under side of a sea snake, above and below the anus, with no distinction in tail scales.

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.