SURFACE-SWIMMING FAUNA (VERTEBRATES).
In the preceding chapter we have considered only those animals of
the surface of the sea, which, owing either to their small size or
the transparency of their bodies, are not as a rule conspicuous to a
passenger on board a mail-steamer. Such a passenger might cross the
ocean many times without realising in the least the wealth of animal
life that there is in every wave that breaks upon the ship, and yet
be impressed with what he has seen of the Whales and Porpoises, the
Sharks, Bonitos and Flying-fish.
It is to these groups of animals that a few lines must be devoted
before closing our story of the surface-swimming Fauna. If the young
and immature stages be for the moment left out of consideration, it may
be said that nearly all the Fish and all the Whales and Porpoises are
large, opaque in appearance, and perfectly conspicuous. Moreover, they
are all strong and rapid swimmers, capable of roaming over wide areas
of the sea in search of prey, and independent of, except in so far
as their prey are influenced by, the currents and winds. It is clear
that they cannot be said to ‘float’ and ‘drift’ about in the ocean,
and consequently they do not strictly belong to the Plankton. The term
used in speaking of them collectively is the Nekton, which means the
swimming population.
The greatest number of the Fish of the sea are shore Fish; that is to
say, they habitually feed at, or close to, the bottom of the shallow
waters near the coasts or sunken banks.
But there is a very considerable number that are strictly pelagic,
living and feeding far away from the shores, bringing forth their young
alive, or shedding floating eggs, and in every way independent of the
shore and of the bottom.
It is difficult to give any general features by which they are
characterised, as so much variety may be observed among them; but as
a general rule they are elongated in form, round or oval in section,
in colour green or gray above, with silvery white bellies. Some of
these, such as the Flying-fish and the Flying-gurnard, are capable of
making very considerable flights in the air, their pectoral fins being
enormously elongated, and when fully expanded somewhat similar to the
wing of an Insect.
The Flying-fish occur in shoals in nearly all tropical and subtropical
seas. When disturbed by a ship on a calm day it is said that they
spring out of the sea, expand their fins, describe a regular parabolic
curve in the air, and then fall with a splash into the water. There is
a considerable controversy raging on the question of the use of their
fins in this flight through the air, some observers believing that
the fins are used only as a kind of parachute, and others that they
are used like wings for raising the body above the water. It is very
difficult to decide which view is correct.
In the Indian Ocean I watched the Flying-fish for several days during
rather rough weather, and my impression was most distinctly that in
the middle of the flight the fins are vigorously flapped four or five
times, the flapping being followed by a decided rise in the air. On the
other hand, it may be that this flapping appearance is caused by the
wind catching the wings in a certain position, and not by the muscles
of the fish. Whether the flying is actually assisted by the flapping
of the wings or not, it is certain that the Fish do rise in gusty
weather to a very considerable height, frequently falling on to the
decks of steamers twenty feet above the water line.
At night, these Fish fly at the ships and not away from them, as
they do in the day-time, and the natives in some parts of the Malay
Archipelago catch them in large numbers by holding up a torch by the
side of a large sheet, when the Fish flying at the bright light and
striking against it, fall into the bottom of the canoe. Flying-fish are
excellent to eat, their flesh being similar in taste to that of the
Herring, but an epicure would probably say that it is not quite so good.
The Bonito is a fish occurring over a wide area of the tropical and
temperate seas, which sometimes makes tremendous jumps out of the
water. I have seen it frequently on the coast of Celebes jump to a
height which I roughly estimated as at least fifteen feet. It is said
to feed upon the Flying-fish, and it is probable that it has acquired
the power of springing out of the water in the pursuit of its prey.
The pelagic Fish, which has acquired the widest reputation, and that
an evil one, is the “blue-Shark.” This occurs in the tropical and
occasionally in temperate seas. Its usual size is from twelve to
fifteen feet, but, according to Dr Günther, individuals of twenty-five
and more feet are occasionally captured. It is extremely voracious,
attacking anything of a fleshy nature that it observes in the water.
One of the most remarkable animals of the open ocean is the Sun-fish.
It has a very wide distribution in the tropical and temperate
regions. In the adult condition it is almost circular in outline and
considerably flattened from side to side like a John Dory. It sometimes
reaches a size of eight feet in diameter and a very great weight. From
the little that is known of its development it apparently undergoes
some extraordinary changes in shape before it reaches the adult form.
[Illustration: +Fig. 34.+
The Sun-fish.]
In addition to these and several other Fish of a large size which may
be found at the surface of the open ocean, there are several species
known to science which never grow to a length of more than a few
inches. Many of these are characterised by remarkably long fin rays,
by their large eyes, or by other features which may be regarded as
special modifications for their peculiar habits.
A very interesting genus is _Scopelus_, which is found very widely
distributed in tropical and other seas. Some of the species live in
very deep water, and are purely abysmal in habit, but most of them rise
to the surface at night, when they may be caught in immense numbers.
In form they are not unlike a small Sprat, but they exhibit on each
side of the body a series of minute eye-like organs, which emit a
phosphorescent light.
In addition to these Fish which are found far out in the open ocean,
there are several genera, which form an important feature of the
surface waters in the neighbourhood of the coasts. Among them we
find such valuable food-fish as the Herrings, Sprats, Mackerels, and
Pilchards.
The complete history of the Herring has yet to be written, for,
notwithstanding the laborious investigations of several naturalists,
working independently, or as officers of the Marine Biological
Association and similar Institutions, there are some facts and stages
which have, up to the present time, escaped observation.
The Herring species is divided into a number of races, which, differing
from one another only slightly in anatomical characters, have different
seasons for depositing their eggs. This fact has only recently been
thoroughly established; and while it assists us greatly in the task
of completing the history of the Fish, it definitely destroys the
validity of many theories which were prevalent among fishermen and
others before the days of the more exact scientific treatment of
fishery questions.
It is well-known that from the end of the month of June to December
immense shoals of Herrings are found in the North Sea. It is quite
impossible to estimate the numbers of Fish in these shoals, but they
are so great that if they could be counted it would probably be found
that the Fish that are annually caught by all the fishing boats, form
but an insignificant fraction of the whole. All of these Fish are in
such a condition that it is evident their spawning time is close at
hand. When they are ready they approach the coasts, the exact time
varying according to the race of Herrings, and the spawn is deposited
on or close to the ground, the eggs becoming attached to stones and
other objects on the bottom. After the Herrings have spawned, they seem
to disperse, or, at any rate, to disappear from the surface waters of
the North Sea. What actually becomes of these shoals of spent Herrings
is not known, but it is a fact that in the spring there are so few
Herrings to be found in the narrower part of the North Sea that it does
not pay the fishing boats to go after them. It is possible, however,
that, after the spawning process, the Herrings migrate to the deeper
water of the Norwegian coasts, in order to feed on the Crustaceans and
other forms of life that are to be found there in abundance.
The Mackerel do not apparently make such extensive migrations as the
Herrings. They spawn in the open sea, five or ten miles from the
coast, during the spring time. The egg of the Mackerel, unlike that of
the Herring, does not sink to the bottom when it is spawned, but, being
provided with a large oil globule, it is light enough to remain on the
surface until the young larva is hatched. After the spawning has taken
place the Mackerel approach the coast, and will even enter bays and
narrow inlets on the shores in pursuit of the young Sprats and other
small Fish upon which they prey.
A great deal could be written on the history of the Pilchards, the
Anchovies, the Sprats, and other Fish which frequent the surface waters
of the sea in the neighbourhood of the European coasts. No two species
seem to have precisely the same habits, and what is known about them
presents us with many curious and remarkably interesting facts. For
further details, however, I must refer the reader to the larger and
more comprehensive books dealing specially with the subject, for space
must still be found for a few words on another group of animals which
play a conspicuous part in the story of life in the seas.
The animals composing the class of Mammals are distinguished from other
Vertebrates by the fact that the females are capable of providing milk
for their young ones after birth. Most of the Mammals are strictly
terrestrial, but three orders, namely, the _Cetacea_, the _Sirenia_,
and the _Carnivora_ contribute to the surface-swimming population of
the sea.
The _Cetacea_ are all aquatic. The order includes the many genera
of Whales, Porpoises and Dolphins.
The Right-whales are distinguished by the enormous size of the mouth
and the absence of the little triangular fin in the middle of the back
which is found in the other Whales.
These animals have no teeth in the adult condition, but are provided
with a series of plates situated at the sides of the mouth which are
used as strainers to catch the small Pteropods and other animals
living in the water which pass through the great gape. The plates are
composed of a substance called “Baleen,”--the well-known whale-bone
of commerce,--they are triangular in shape, and frayed out into a
brush-like edge on the side that faces the cavity of the mouth. The
Greenland Right-whale attains to a size of fifty feet in length when
fully grown, and it is usually found in shoals among the ice floes of
the far north.
In former times many Right-whales belonging to species allied to
the Arctic form occurred in the temperate regions of the Atlantic
and Pacific Oceans, but in consequence of the valuable fishery they
afforded they are now becoming very scarce.
The largest of all the Whales--in fact, the largest existing animal--is
the Blue-whale, which attains to the enormous length of 86 feet. It
spends the winter in the open seas, and approaches the coast of Norway
in the spring.
The Whales, like all the animals of the Class to which they belong,
are air-breathers. They are able, however, to hold their breath for a
considerable time under water. When they come to the surface to renew
the air-supply in their lungs, they first make a violent expiratory
effort from the nostril, and drive a column of spray many feet into
the air above them. This phenomenon is called by the whale fishers
“spouting,” and it was erroneously supposed by them to be a column of
water forced from the mouth into the nostril, and then expelled at the
surface.
The Dolphins and the Porpoises are distinguished from the true Whales
by the fact that they are provided with teeth, on one or both of their
jaws, and there is no “whale-bone.”
The Sperm-whale has probably been called a “Whale” from its enormous
size, but it is anatomically very widely separated from the true whales
and more closely allied to the Dolphins. It has no “whale-bone,” and
the lower jaw is provided with a row of sharp-pointed teeth set in a
groove in the bone. Its great value is due to the fact that there is
a large cavity situated above the skull, containing an oily substance
from which “Spermaceti” is made.
The principal food of these large “Toothed-whales” seems to be
Cuttlefishes, and the examination of the contents of their stomachs,
which has been carried out on board the Prince of Monaco’s private
steam-ship when engaged on a scientific cruise, has yielded some new
forms of these giant Molluscs. The Sperm-whales, however, do not
disdain a Fish diet as well.
The Porpoises are found on our own coasts. They may often be seen
following the “schools” of Whales as they approach the coast in the
summer months, and they occasionally chase their prey some distance up
the estuaries of the English rivers. The habit that Porpoises have of
accompanying ships for long distances affords us many opportunities
of watching their graceful movements, and of estimating the very
great speed with which they can swim through the water for hours at a
stretch. It is difficult to understand the meaning of this habit of
following ships. It has been suggested that the Porpoises mistake the
ship for a huge Sperm-whale, and hope to benefit by stray morsels of
large fish that fall from its jaws. But this theory does not account
for the fact that the Porpoises so often go in front of the ship. The
following extract from Darwin’s “Voyage of the Beagle” gives, in a few
words, a vivid picture of Porpoise life:--
“In our passage to the Plata, we saw nothing in particular, excepting
on one day a great shoal of Porpoises, many hundreds in number. The
whole sea was in places furrowed by them; and a most extraordinary
spectacle was presented, as hundreds, proceeding together by jumps,
in which their whole bodies were exposed, thus cut the water. When
the ship was running nine knots an hour, these animals could cross
and recross the bows with the greatest ease, and then dash away right
ahead.” This description reminds me very forcibly of a sight I once saw
in the Talaut Islands, south of the Philippines. In passing between two
of the islands the strait seemed to be alive with Porpoises tearing
through the water at a terrific pace. They accompanied the steamer for
about six hours and then suddenly disappeared. My impression was that
they were attracted to the ship not from a desire for more food, for
there was an abundance of Herrings in the straits at the time, but from
sheer curiosity. I think the feeling of curiosity, that is to say, the
desire to go and look at something strange or unusual, is much more
prevalent among animals than we generally suspect.
[Illustration: +Fig. 35.+
The common Porpoise.]
It is an interesting fact about the Porpoise that, although it is so
fish-like in shape, it should present some features which remind us of
the Pig. The English word is probably derived from the two French words
_porc_ and _poisson_, and therefore means “Pig-fish.” The
Germans call it Meeresschwein, meaning “Sea-pig,” and the Malay word
for it is “Babi-laut,” which also means “Sea-pig.” But if we make some
allowance for those who call these Cetaceans “Pigs,” we must make none
for those who call them “Fish.”
Like all the other members of their order the Porpoises have a
fish-like tail, but the flaps are placed horizontally and not
vertically as they are in Fish. The skin is quite naked, having no
scales of any kind, and there are no gills or gill-openings. Like
all other Mammals the Cetaceans bring forth their young alive, suckle
them, and breathe air by means of lungs. But there can be no doubt that
they are extremely modified for their aquatic life. The characteristic
covering of Mammals--the hairs--is, in the adult condition of the
Whales, entirely wanting, and is represented in other members of
the Class by only a few bristles on the snout. The heat of the body
is maintained by a thick coat of fat, called the blubber, lying
immediately beneath the skin, and this yields, on boiling, a valuable
oil, which helps to support the whale-fishermen. One of the most
striking modifications, however, is the loss of the hind limbs. It is
only in some species that even rudiments of these have been found. All
of these facts indicate that the Cetaceans must have taken to a mode
of life in the water a very long time ago, and the study of the rocks
proves the existence of Whales as far back as Eocene times, but it is
of interest to note that, in some respects, the oldest fossil Cetaceans
are less specialised than those that are now living.
The class of Mammals called the _Carnivora_ includes the Cats,
Dogs, Ferrets and many other animals which are purely terrestrial,
but one of its divisions is entirely composed of those well-known
aquatic animals the Seals and the Walrus. If we take the common Seal
as an example of this group, and compare it with the Porpoise, as a
representative of the Cetaceans, we find that in habits as well as in
anatomy the former is less completely changed than the latter. The Seal
frequently comes to land to bask in the sun, or to produce and care
for its young, and it is capable of making some progress over the rocks
by the help of its flipper-like fore-limbs; the Porpoise, on the other
hand, never leaves the water of its own free will. Unlike the Porpoise
the body of the Seal is covered with a thick coat of hairs, and the
hind limbs are retained. Although there is a general resemblance in
the form of the body between these two animals--this form being, in
all probability, mechanically the best for rapid progress through
the water--a glance at their skeletons shows great and important
differences, which the merest tyro in anatomy could point out. In
expression, too, there is a marked difference, for while the Porpoise
has a certain cast of countenance which, when seen at a distance,
deserves the epithet “pig-faced,” the face of the Seal, with its large
round eyes, its small nose and high intelligent brow, is almost human
in expression.
The Seal has a habit of raising its head above the water and staring
at an approaching boat, and when doing this it may readily be mistaken
at first sight for a man overboard, but no one could ever mistake a
Porpoise for a human being.
The common Seal has a very wide range occurring near the coast of
both the Atlantic and Pacific Oceans. It is found on some of the more
sequestered parts of the British shores, but not in large numbers,
for the common Seal, unlike many of its allies, does not appear to
congregate in large shoals at any time of the year. They are described
as being timid, inoffensive creatures, easily tamed, passionately fond
of their children and taking an intelligent interest in music.
There are several animals closely related to the Seal, occurring
in different parts of the world; and a few words may be said about
the remarkable animal called the “Sea-elephant,” which is found on
Kerguelen island in the Antarctic Ocean. The popular name was given
to the animal in consequence of the fleshy protuberant nose which has
been compared with the trunk of an Elephant and is possessed only by
the male. The late Professor Moseley, who came across a small herd of
them when the _Challenger_ was at Kerguelen, says: “The trunk is
produced by an inflation of a loose tubular sac of skin placed above
the nostrils, just as is the ‘Cap’ in the northern Bladder-nose Seal.
The trunk is evidently, as appears from both the drawings, sacculated,
and hence irregular in form when inflated.”
The Sea-lions and Sea-bears or the Eared Seals, as they are sometimes
called, form a very distinct family. The one that is best known to
the general public is the Californian Sea-lion, as it often lives in
captivity in the European menageries for many years and attracts the
attention of the visitors by the tricks which it is taught to perform.
In the spring months of the year these creatures may be seen in great
numbers on the rocky islands off the coast of California, where they
come to breed.
The most important of them all, from a commercial point of view, is
the Fur-seal from the Northern Pacific. In the month of May these
animals approach the Prybilov islands in the East, or the Commander
islands in the West of the Behring Sea. The first to arrive on the land
are the old males. These choose for themselves certain areas or ‘homes’
on the shore and fight desperately for their possession with all who
dare to come within their reach. When matters are at length somewhat
settled the time arrives for the females to approach the shore.
The fighting then begins again with renewed vigour, and desperate
encounters take place for the possession of a goodly stock of wives for
the season.
There seems to be little in the way of courtship in the domestic
economy of the Fur-seals, the wives being simply “captured” by the
scruff of their necks when they come within reach of a would be
husband, and retained in his harem just so long as he can prevent
any one of his neighbours from stealing her. The Fur-seal, like all
his relations, is polygamous, but the number of wives that each male
appropriates to himself seems to vary very considerably. Mr Elliott
mentions a case in which there were as many as forty-five females in
one home, but, as a general rule, the number is much less. As there is
only one male to every twelve or thirteen females, there are numerous
males over, which cannot found a home for themselves. These bachelors,
together with a number of the young females, resort to a separate
piece of ground, where they spend their time in playing games. The
play-grounds are however the scene of the tragedies of Seal life, for
they are resorted to by the hunters, who slaughter immense numbers of
the larger males for the sake of their valuable skins. As the skins of
the old male Seals are not of very much value and as it is important,
for the perpetuation of the race, to preserve the females from injury,
the breeding grounds are usually not molested. It is therefore the
bachelor seal of from two to five or six years of age that has to
supply the market. Those naturalists who have visited the Seal
rookeries on these islands say that the numbers of these animals that
can be seen at one time is almost incredible. We can form some estimate
of them when we learn that over a hundred thousand skins are exported
from the Prybilov islands alone every year.
The Seals leave the rookeries in the month of August, and after
swimming about for some time in the neighbourhood of the islands,
eventually depart into the open ocean in search of the food their
famished bodies need so much after the fasting and fighting of the
breeding months.
The largest of all these aquatic Carnivores is the Walrus, which lives
within a short distance of the shores of the lands in the Arctic
regions. It is easily distinguished from the Seals by its great size,
the males reaching a length of 10 or 12 feet, and by the enormous
canine teeth in the upper jaws, which project downwards from the cover
of the lips in the form of two large pointed tusks. These tusks are
used for hoisting the bodies of the animals on to the ice, for digging
in the sand in search of the Mussels upon which they feed, and for
general fighting purposes.
It is said that in former times the Walruses lived in immense herds
in regions much further south than they do now; but the ravages of
the hunter, who chased them for their ivory tusks and their oil, have
driven them into regions where they are rarely visited by anyone but
the Arctic explorer; and to those of my readers who wish to learn more
of their habits, I can but say that in the pages of Dr Nansen’s book,
“Farthest North,” he will find the story of the Walrus written in a
manner which no man living could have done more vividly and brilliantly
than the great Norwegian zoologist and explorer.