_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.
[Illustration: 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.
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.
[Illustration: _Enhydrina._ From Fayrer’s _Thanatophidia_.]
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.
[Illustration: Natural size.
Same magnified.
Sea snakes’ scales. From the _Thanatophidia_.]
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.
[Illustration]
[Illustration]