The Narwhal, an arctic type, may be distinguished from all other cetaceans by the single spiral tusk in the left side of the head of the male. Sometimes the right tusk grows as well, and either may attain a length of as much as 8 feet; but in the female both teeth remain undeveloped.
The Common Porpoise of our own seas, distinguished by its rounded head from the equally common beaked dolphin, is too familiar to need much description. It grows to a length of 5 or 6 feet, and is dark in colour on the back and white beneath. Its conspicuous back-fin is always recognisable when it gambols with a herd of its fellows; and a line of these sea-pigs, a mile or so in length, is no uncommon sight, their presence inshore being indicative on some parts of the coast of the coming of east wind. The porpoise, which has, like many of its group, teeth in either jaw, is a voracious feeder, preying in estuaries on salmon and flounders, and on more open parts of the coast on pilchards and mackerel. It is occasionally a serious nuisance in the Mediterranean sardine-fisheries, and I have known of the fishermen of Collioure, in the Gulf of Lyons, appealing to the French Government to send a gunboat from Toulon that might steam after the marauders and frighten them away. One of the most remarkable cases of a feeding porpoise that I can recall was that of one which played with a conger-eel in a Cornish harbour as a cat might play with a mouse, blowing the fish 20 or 30 feet through the air, and swimming after it so rapidly as to catch it again almost as it touched the water.
Photo by A. S. Rudland & Sons.
BOTTLE-NOSED DOLPHIN.
From 8 to 9 feet long, found from the Mediterranean to the North Sea.
The Dolphin, which is in some seasons as common in the British Channel as the more familiar porpoise, is distinguished by its small head and long beak, the lower jaw always carrying more teeth than the upper. It feeds on pilchards and mackerel, and, like the porpoises, gambols, particularly after an east wind, with its fellows close inshore. There are many other marine mammals somewhat loosely bracketed as dolphins. Risso's Dolphin, for instance, a rare visitor to our coasts, has a striped skin, and its jaws are without teeth, which distinguish it from the common dolphin and most of the others. It cannot therefore feed on fishes, and most probably eats squid and cuttle-fish. The Bottle-nosed Dolphin, a species occurring in the greatest numbers on the Atlantic coast of North America, is regularly hunted for its oil. Heavyside's Dolphin, which hails from South African waters, is a smaller kind, chiefly remarkable for the curious distribution of black and white on its back and sides.
Photo by A. S. Rudland & Sons.
HEAVYSIDE'S DOLPHIN.