(_Phoca vitulina_)
Of all mammals except whales, dolphins, and sea-cows, the true seals,
of which the common British species is the typical representative,
are those which have become most completely adapted to an aquatic
existence. This is shown by the spindle-shaped form of the body, the
total absence of external ears, the conversion of the fore-limbs into
flippers, and the backward direction of the hind pair, which are also
flipper-like, and lie parallel to the short tail to form an efficient
rudder-like organ.
Seals are evidently descended from land Carnivora, and possibly from
that long extinct group the Creodontia. When fully developed, their
cheek-teeth consist of a single middle cusp, flanked by a smaller one
in front and behind; and there are no teeth specially corresponding
with the scissor-like pair characteristic of the modern land Carnivora.
This fact, unless the teeth are degenerate, is all in favour of the
direct descent of seals from creodonts.
From the true seals of the family _Phocidæ_ the eared seals, or
_Otariidæ_, differ by retaining small external ears, as well as by the
fact that the hind-flippers are not permanently turned backwards; this
latter feature being also distinctive of the walrus (_Odobænidæ_). In
addition to being the most specialised of the aquatic Carnivora, the
true seals are also the most widely distributed, inhabiting nearly all
seas, and being likewise found in the Caspian Sea and in Lakes Aral and
Baikal. Although seals go on land nightly to sleep, and likewise spend
a considerable amount of time in the day on the shore or on ice, while
the females give birth to their young on land, none of the _Phocidæ_
regularly leave the water for a period of several weeks during the
breeding-season, after the fashion of their eared cousins. Neither do
any of them yield commercial sealskin, which is a product of certain
members of the eared groups. Commercially, they are therefore valued
only for their hides and oil, for the sake of which vast numbers are
annually slaughtered.
Seals are adepts in swimming and diving, and have the power of closing
their nostrils and the apertures of their ears while under water,
although they are unable to remain beneath the surface for anything
like so long as whales and dolphins. The food of the common seal, as
well as most other kinds, consists chiefly of fishes, for capturing
and holding which their sharply cusped teeth are admirably adapted.
Graceful and active as are their movements in water, on land they are
comparatively awkward and ungainly; progression being effected by means
of the limbs, accompanied by sudden flexures of the body, so that it
in some degree partakes of the nature of hopping. To land, seals shoot
themselves out of the water by a strong and sudden movement of the
hind-limbs. When once on land, they may remain there for days and even
weeks together, till compelled by hunger to return to the sea.
[Illustration]
The senses of the seal are highly developed. The eye, for instance, is
full and globular, and thus specially adapted to catch every ray of
light when the animal is in the water. It is noteworthy that seals can
shed tears under the influence of excitement, and especially when in
pain. And the idea of the ancients that these animals are attracted by
music and singing appears to be founded on fact.
Their usual cry is a sharp bark, but when angered they give vent to
dog-like snarlings. Seals always associate in parties, which may
comprise hundreds of individuals. The young, which are beautiful little
creatures, are tenderly and affectionately nurtured by their parents,
who protect them from danger by every means in their power.
Young seals have a coat quite different from that of the adult; this
baby coat in the case of the second British species, the grey seal
(_Halichærus grypus_), being wholly white. In colour, the common seal
varies greatly, the coat being sometimes yellowish and sometimes light
grey with blackish mottlings and marblings. The so-called grey seal is
generally much darker in colour, but is best distinguished from the
common species by its greatly superior size and its relatively larger
and blunter teeth.
All seals are polygamous, which leads to fights among the males for
the possession of the females; but in other respects they are gentle
and affectionate, easily tamed if taken young, and displaying great
capacity for education. As a rule, only a single cub is produced at a
birth, but there may be twins.