It is nothing surprising that the different species of walrus,
inhabitants of the ocean, should feed partly on shell-fish, but perhaps
you would not expect to find among their enemies animals strictly
terrestrial. Yet the oran otang and the preacher monkey often descend to
the sea to devour what shell-fish they may find strewed upon the shores.
The former, according to Carreri Gemelli, feed in particular upon a
large species of oyster, and fearful of inserting their paws between the
open valves, lest the oyster should close and crush them, they first
place a tolerably large stone within the shell, and then drag out their
victim with safety. The latter are no less ingenious. Dampier saw
several of them take up oysters from the beach, lay them on a stone, and
beat them with another till they demolished the shells. Wafer observed
the monkeys in the island of Gorgonia to proceed in a similar manner;
and those of the Cape of Good Hope, if we are to credit La Loubere,
perpetually amuse themselves by transporting shells from the shore to
the tops of mountains, with the intention undoubtedly of devouring them
at leisure. Even the fox, when pressed by hunger, will deign to eat
muscles and other bivalves; and the racoon, whose fur is esteemed by
hatters next in value to that of the beaver, when near the shore lives
much on them, more particularly on oysters. We are told that it will
watch the opening of the shells, dexterously put in its paw, and tear
out the contents. Not, however, without danger, for sometimes, we are
assured, by a sudden closure, the oyster will catch the thief, and
detain him until he is drowned by the return of the tide. The story,
I regret to say, appears somewhat apocryphal.
These are amusing facts; the following, to the epicure at least, may
be equally interesting. In some parts of England it is a prevalent and
probably a correct opinion, that the shelled-snails contribute much
to the fattening of their sheep. On the hill above Whitsand Bay in
Cornwall, and in the south of Devonshire, the _Bùlimus acùtus_ and
the _Hèlix virgàta_, which are found there in vast profusion, are
considered to have this good effect; and it is indeed impossible that
the sheep can browse on the short grass of the places just mentioned,
without devouring a prodigious quantity of them, especially in the
night, or after rain, when the Bùlimi and Hèlices ascend the stunted
blades. "The sweetest mutton," says Borlase, "is reckoned to be that
of the smallest sheep, which feed on the commons where the sands are
scarce covered with the green sod, and the grass exceedingly short; such
are the towens or sand hillocks in Piran Sand, Gwythien, Philac, and
Senangreen, near the Land's End, and elsewhere in like situations. From
these sands come forth snails of the turbinated kind, but of different
species, and all sizes from the adult to the smallest just from the egg;
these spread themselves over the plains early in the morning, and,
whilst they are in quest of their own food among the dews, yield a most
fattening nourishment to the sheep." (_Hist. of Cornwall_.)
Among birds the shell-fish have many enemies. Several of the duck and
gull tribes, as you might anticipate, derive at least a portion of their
subsistence from them. The pied oyster-catcher receives its name from
the circumstance of feeding on oysters and limpets, and its bill is so
well adapted to the purpose of forcing asunder the valves of the one,
and of raising the other from the rock, that "the Author of Nature,"
as Derham says, "seems to have framed it purely for that use." Several
kinds of crows likewise prey upon shell-fish, and the manner in which
they force the strong hold of their victims is very remarkable. A friend
of Dr. Darwin's saw above a hundred crows on the northern coast of
Ireland, at once, preying upon muscles. Each crow took a muscle up in
the air twenty or forty yards high, and let it fall on the stones, and
thus broke the shell. Many authorities might be adduced in corroboration
of this statement. In Southern Africa so many of the Testàcea are
consumed by these and other birds, as to have given rise to an opinion
that the marine shells found buried in the distant plains, or in the
sides of the mountains, have been carried there by their agency, and
not, as generally supposed, by eruptions of the sea. Mr. Barrow, who
is of this opinion, tells us, in confirmation of it, that "there is
scarcely a sheltered cavern in the sides of the mountains that arise
immediately from the sea, where living shell-fish may not be found any
day of the year. Crows even, and vultures, as well as aquatic birds,
detach the shell-fish from the rocks, and mount with them into the air:
shells thus carried are said to be frequently found on the very summit
even of the Table Mountain. In one cavern at the point of Mussel Bay,"
he adds, "I disturbed some thousands of birds, and found as many
thousands of living shell-fish scattered on the surface of a heap of
shells, that for aught I know, would have filled as many thousand
wagons." The story, therefore, of the ancient philosopher whose bald
pate one of these unlucky birds mistook for a stone, and dropped a
shell upon it, thereby killing at once both, is not so tramontane as
to stumble all belief.
Land shells furnish a few birds with part of their sustenance, and the
principal of these are two well known songsters, the blackbird and the
thrush. They,
----"whose notes
Nice finger'd Art must emulate in vain."
depend in great measure, when winter has destroyed their summer food,
on the more common species of Hèlices (snails.) These they break very
dexterously by reiterated strokes against some stone; and it is not
uncommon to find a great quantity of fragments of shells together, as
if brought to one particulur stone for this very purpose.--_Loudon's
Magazine_.