_FRESH-WATER SNAKES._
THE frequent allusion to water snakes in the preceding chapters seems
to render this a suitable place to describe them more in detail; and
among them are of course the sea snakes, and ‘The Great Sea Serpent’
must not be omitted.
In many books on natural history, particularly if herpetology occupy
any space, we find the subject wound up with a chapter on ‘The Sea
Serpent,’ forming a sort of apologetic little addendum, as if the
creature of questionable existence must claim no space in the heart of
the volume, yet is not quite so unimportant as to be omitted altogether.
On the part of some other authors, a total and summary dismissal of the
‘monster’ is apt to exclude with it any reference to the smaller sea
snakes, whose actual existence is therefore a fact less known than it
should be; and many persons, seeing the doubt cast upon the celebrated
individual whose reputed reappearance on the prorogation of Parliament
has become an annual joke, conclude that all sea snakes are similarly
mythical.
Admitting it to be a dubious creature, with neither name nor
ancestry in ophidian annals, I must not give it precedence of the
recognised water snakes; but it shall figure in the heart of my book
notwithstanding.
‘_Fresh-water snakes_’ form the fourth, and ‘_Sea snakes_’ the fifth
of the five groups into which Dr. Günther has separated the ophidian
families; but the gradations between the land and the fresh-water
species, and between the latter and the salt-water snakes or the true
_Hydrophidæ_, are, like all other herpetological features, extremely
close. There are water-loving land snakes and land-frequenting water
snakes, that is, those which are equally at home in both. In the
true water species, however, we find modifications of ordinary rules
which show them to be peculiarly protected and adapted for an aquatic
existence.
One notable characteristic in all, both salt-water and fresh, is the
position of the nostrils on the top of the snout, and in many these are
protected by a valve which closes at will. As air-breathing animals
they must come to the surface, but the timid, stealthy ophidian
instinct which seeks to hide from observation can be indulged even
in the water, with the nostrils so situated that only a very small
surface of the head need be exposed. Could we examine the interior
of the mouth we should doubtless find some slight variation in the
position of the glottis also. In a foregoing chapter we saw that the
trachea opens exactly opposite to and close behind what Dumeril calls
the ‘arrière-narines;’ ‘leur glotte qui est à deux lèvres et qui
represente un larynx très simple, s’ouvre dans la bouche derrière
le fourreau de la langue ... elle s’élève pour se presenter dilatée
sous les arrière-narines.’[71] The glottis of water snakes must have a
still more upward direction to present itself to those air passages.
Perhaps water snakes do not require to yawn so frequently as is the
habit of their terrestrial relatives; and if they do, it must be a rare
privilege to be able to inspect the process, as one can so frequently
do with the pythons and vipers at home. Our authorities do not give us
much information on this point.[72]
Their moderately long tapering tail is used as a propelling power.
Exteriorly, too, water snakes have smooth non-imbricated scales, though
exceptions exist in those species which frequent both land and water,
as the _Tropidonoti_, a large family of which our common English ring
snake is a member, and which, as their name denotes, have all keeled
scales, from τρόπις, τρόπιδος, _a keel_. These, also, can elevate
their ribs, and so flatten the body in the water, another assistant in
swimming.
A marked exception to the smooth-scaled, water-loving snakes is the
African viper, known as the ‘River Jack’ from its partiality to water.
_Vipera rhinosceros_, from the spinous scales which have the appearance
of horns on its nose, is allied to those described in the 18th chapter.
Though not strictly a water snake, it much frequents it, and glides
through it with ease, the more remarkable because, in common with those
other ‘horned vipers’ of Africa, it has a short, insignificant little
tail, which can be of little use as a propelling power. Altogether,
it is one of the ugliest and most ferocious-looking of the whole
serpent tribe, with a thick, heavy body, a dingy, rough exterior, and
strongly-carinated scales. Excepting in colour, and a more horizontal
inclination of its horns, it is not unlike the _V. nasicornis_ of the
coloured illustration, chap. xviii.
While all the _Homalopsidæ_ or true fresh-water snakes are innocent,
there are many other venomous kinds known as ‘water serpents,’ both
in Africa and America. For example, the ‘water viper,’ or ‘water
moccasin,’ _Cenchris piscivorus_, whose aquatic and fish-eating
propensities were described in the chapter on Tails. This ‘thorn-tail’
viper has not, however, the nostrils of the true fresh-water snakes or
_Homalopsidæ_. In Australia also are several poisonous species, known
vernacularly as ‘water snakes;’ but strictly speaking, and on the
authority of Günther, the true _Homalopsidæ_ are all non-venomous.
To describe these more minutely from Günther, Krefft, and Dr. E.
Nicholson, ‘they have a body moderately cylindrical, a tail somewhat
compressed at the root, and more or less prehensile. Many of them have
a distinctly prehensile tail, by which they hold on to projecting
objects;’ and in times of storms and strong currents we can imagine
the importance of this security to them. Their eyes, though prominent,
are small, and thus less exposed to injury; and the nostrils, as
already stated, are on the upper surface of the head, and provided
with a valvule. Another peculiarity is that the last or back tooth of
the maxillary bone is a grooved fang, a transitional tooth between an
ordinary one and a fang; but there is no evidence of any poisonous
saliva connected with it. Indeed, as we may repeat, Dr. Günther
distinctly affirms that all the fresh-water snakes are harmless and
_thoroughly aquatic_, though a few are occasionally found on the
beach. They inhabit rivers and estuaries, feeding on fish, and rarely
coming to land; some of them frequent brackish waters, and even enter
the sea. These latter in their organization approach the true marine
serpents. One Indian example, _Hydrinus_, is semi-pelagic. They are all
viviparous, producing their young in the water; and they belong to the
tropical or semi-tropical regions. In Australia they are found only
in the far north; but in America some so-called ‘water snakes,’ which
spend most of their time in the water, frequent rivers which are frozen
over in winter, during which season they probably undergo hibernation
in holes near the banks.
Several of the older naturalists describe ‘water snakes’ in words which
leave us no doubt as to the _numbers_, though of their name we cannot
be so certain. Carver in 1796 mentioned some small islands near the
western end of Lake Erie, so infested with snakes that it was dangerous
to land upon them. It is impossible that any place can produce a
greater number of all kinds of snakes, particularly the ‘water snake,’
than this. He says: ‘The lake is covered near the banks of the islands
with the large pond lily, the leaves of which lie on the surface of the
water so thick as to cover it entirely for many acres together, and
on each of these lay wreaths of water snakes, amounting to myriads,
basking in the sun.’ A sight of the last century this. I have passed
over that part of Lake Erie and through the Detroit river, and remember
the islands and the water-lilies and other attractive objects, but
‘wreaths of water snakes’ were not of these.
Lawson, too, can assure us of their habitat, but not their name, and
his account is of worth chiefly to verify their swarming numbers. It is
possible that some of those which he describes are now extinct or very
rare. ‘Of water Snakes there are four sorts. The first is of the Horn
Snake’s Colour, though less.’ (This might be the young of the ‘water
moccasin,’ _Cenchris_, or _Trigonoceph. piscivorus_.) ‘The next is a
very long Snake, differing in Colour, and will make nothing to swim
over a River a League wide. They hang upon Birches and other Trees by
the Water Side. I had the Fortune once to have one of them leap into
my Boat as I was going up a narrow River. The Boat was full of Mats,
which I was glad to take out and so get rid of him. They are reckoned
poisonous. A third is much of an English Adder Colour, but always
frequents the Salts, and lies under the drift Seaweed, where they are
in Abundance, and are accounted mischievous when they bite. The last
is of a sooty, black Colour, and frequents Ponds and Ditches. What his
Qualities are, I cannot tell.’
Catesby is responsible for having called _Tropidonotus fasciatus_
‘the brown water viper,’ a stumbling-block to many ever since, much
confusion existing between this and the true ‘water viper,’ the
dangerous moccasin snake. Occasionally they are very dark. They are
rather thick and viperish-looking as well, but are perfectly harmless.
This is the snake to which almost this book owes its origin, the
specimens at the Zoological Gardens called ‘Moccasins’ tripping me up
at the outset, as my preface sets forth. Holbrooke describes it as
spending most of its time in the water, or about pond and river banks.
It swims rapidly, and hundreds may be seen darting in all directions
through the water. They are very common in the United States, and might
have formed the ‘wreathed myriads’ on Lake Erie formerly. In summer
they roost on the lower branches of trees, overhanging the water, like
_Trigonocephalus piscivorus_, the true ‘water moccasin,’ or ‘cotton
mouth.’ At the time of writing there are examples of both these at
the Gardens, the harmless ‘moccasin,’ a rather handsome snake, and
the venomous one (not there recognised as the well-known moccasin of
the United States), so nearly black that we can account for its being
occasionally called the ‘black water viper.’
It is probably _Tropidonotus_ which Parker Gilmore describes as ‘water
vipers.’[73] At Vincennes in Indiana, he says, ‘On the side where some
alder bushes grow in the water, I have seen, on a very warm and bright
day, such numbers of water vipers twined round the limbs and trunks
which margin the pond, that it would be almost impossible to wade a
yard without being within reach of one of them. They certainly have all
the appearance of being venomous; the inhabitants say, however, they
are harmless. They feed principally on fish, frogs, and small birds.’
Of American water snakes, the anaconda deserves special mention. Of
it Seba says, ‘Ce serpent habite plus les eaux que les rochers;’ and
in its having the nostrils situated on the top of the head, and in
possessing some other features in common with the _Homalopsidæ_, we
are justified in calling it a water serpent, notwithstanding it is a
true constrictor. ‘Mother of waters,’ the aborigines of South America
call it. It is the _Boa aquatica_ of Neuwied, and _Eunectes murinus_
of Wagler, the latter name being the one most frequently used by
modern herpetologists. Dumeril adopts it, _l’Eunect murin_, giving the
origin of the generic name, _bon nageur_, from the Greek εὐ, _bien_,
_fort_, and νηϰτής, _nageur_—_qui nage bien_. As to the meaning of the
specific name _murinus_, there can be but little doubt, though some
have attributed it to its mouse-coloured skin or spots. _Le mangeur de
rats_, Bonnat called it; _le rativoro_, Lacepède. Seba, who was one of
the first to describe it, says, ‘Il font guerre aux rats;’ and Bonnat,
on his authority, says, ‘Il se nourrit d’une espèce de rats.’ ‘Serpent
d’Amerique à moucheteur de tortue,’ Seba also describes it, and with
‘jolies écailles magnifiquement madrées de grandes taches, semblable de
celles des tortues; taches semées sans ordres, grands, petits,’ etc.
_Murinus_, therefore, clearly refers to its food, not its colour.
Dumeril’s description is of more scientific exactness: ‘Pas de
fossettes aux lèvres. On peut aisément reconnaitre les Eunectes seul
entre les boa, ils ont les narines percées à la face supérieure du bout
du museau et directement tournées vers le ciel.’ These, being extremely
small, and with a power to close hermetically, declare its aquatic
habits. Its eyes are prominent, and so placed that the reptile can see
before it, and also below—that is, down into the waters.
On first sight it might be a matter of wonder that so large a serpent
should condescend to a meal of rats and mice; but to explain this we
must again go back to the early naturalists, when we discover that what
Seba called _le rat d’Amerique_ was a rodent quite worth constricting
for dinner. Under the order _Muridæ_ were included in those days a
number of the larger rodents, such as the Paca, _Mus Braziliensis_; the
Coypu, _Mus coypus_; _Myopotamus_, the Capybara; the Murine opossum,
and several others, aquatic in their habits, and large enough to
attract the ‘Giant of the Waters.’
From the vernacular _Matatoro_, or ‘Bull killer,’ also a whole century
of misrepresentations have arisen, the said ‘bull’ being really as
small in proportion as the ‘rats’ and ‘mice’ were large. ‘The deer
swallower’ is another of its local titles, showing that it is a serpent
of varying tastes. Stories are told of this ‘monster’ killing itself
in attempting to gorge large animals with enormously extended horns,
animals not to be found among the Brazilian fauna; and familiar to
most persons are the illustrations of anacondas of untraceable length,
the posterior portion coiled round a branch fifty feet high, and the
anterior coiled round a bull as big as a prize ox. These illustrations
are the offspring of ignorance rather than reality, and though
occasionally _Eunectes_ might come to grief by attacking a somewhat
unmanageable meal, yet its recognised specific, _murinus_ or _murina_,
points more clearly the true nature of its food, viz. rodents of at
most some two feet long.
No less exaggerated than its appetite is its length. Possibly anacondas
may have attained greater size formerly when there were fewer enemies
than at present, if it be true, as some have affirmed, that serpents
grow all their lives. Thirty feet is the utmost length on record.
Wallace affirms that he has never seen one exceeding twenty feet. Those
individuals at the Zoological Gardens have rarely exceeded this, and
Günther gives twenty-two feet as their average length in the present
day.
Of those known in South Africa as ‘water snakes,’ one is _Avusamans_
vernacularly, a black one and common, and another, _Iffulu_, of a
beautiful bright green. Mr. Woodward, whose scientific egg-sucker
has been already mentioned in chap. iii., states that both these are
poisonous, that he never saw the green one out of water, and that
it is unsafe to bathe where they are. On referring to Dr. Andrew
Smith’s _Zoology of South Africa_, I am not able to identify these
with certainty, and do not, therefore, give the above as scientific
information.
But before concluding this part of the subject, I would add a word or
two on the importance of an accurate description of the snake, as far
as possible, when one is found in some unusual situation; because a
snake being found in the water is no proof that it is a water snake, or
even that it was there by choice. Livingstone, in his _Expedition to
the Zambesi_, p. 150, describes the number of venomous creatures, such
as scorpions, centipedes, etc., that were found on board, ‘having been
brought into the ship with wood.’ ‘Snakes also came sometimes with the
wood, but oftener floated down the river to us, climbing easily by the
chain cable. Some poisonous ones were caught in the cabin. A green one
was there several weeks, hiding in the daytime.’
Often in newspapers are stories of ‘sea snakes’ as having appeared
quite out of their geographical range. These on investigation may
reasonably be traced to land snakes which have been carried out by the
tidal rivers. In _Land and Water_ of Jan. 5, 1878, was such a story.
Again, March 31, the following year, a correspondent, ‘J. J. A.,’ on
‘Animal Life in New Caledonia,’ stated that the sea inside the reefs
is sometimes covered with both dead and living creatures carried out
by the violence of the currents after heavy rains. ‘The flooded rivers
rush with great force from the mountains,’ and numbers of reptiles were
among the victims of that force. He saw ‘incredible numbers of snakes,’
and described the common sea snakes as ‘stupid, fearless things, that
will not get out of your way.... The small sand-islands are literally
alive with them.’ The writer made no pretensions to be a naturalist, or
to state confidently what the snakes were specifically. New Caledonia
would seem to be rather beyond the range of sea snakes proper, and
those ‘incredible numbers’ may have been only land snakes involuntarily
taking a sea bath, or certain species frequenting brackish waters, like
those in South Carolina described by Lawson.
About the same time an American newspaper contained an account given
by Captain O. A. Pitfield, of the steamship _Mexico_, who stated that
he had ‘passed through a tangled mass of snakes’ off the Tortuga
islands, at the entrance to the Gulf of Mexico. The ship was ‘more
than an hour’ in passing them. ‘They were of all sizes, from the
ordinary green water snake of two feet long, to monsters, genuine “sea
serpents,” of fourteen to fifteen feet in length.’ I replied to both
these communications at the time (_Land and Water_, April 5, 1879),
inviting further information, and describing the features by which
true water and true sea snakes could be easily distinguished. Nothing
further appeared on the subject, and I have little doubt but that, in
both cases, the ‘shoals of sea snakes’ were land species that had been
merely carried out to sea by force of rivers. I have since been more
strongly inclined to this opinion on learning from Dr. Stradling that
similar transportations of snakes occur through the force of some of
the South American rivers. ‘Do you know the snakes which belong to the
River Plate proper?’ he asks me by letter. ‘So many are brought down by
floods from Paraguay—even the big constrictors—that it is difficult
to determine from occasional specimens.’
I could not, unfortunately, refer to any books that afforded much
information on this subject; for amongst the greatest literary needs
experienced by an ophiologist is some complete and special work on
the South American snakes, corresponding with Günther’s _Reptiles of
British India_, and Krefft’s _Snakes of Australia_.
Other writers have mentioned the occurrence of boa constrictors and
anacondas far out at sea occasionally, beguiling the unsophisticated
into reporting a veritable ‘sea serpent’ to the _Times_ by the first
homeward-bound mail.
[Illustration]