STAMP ANIMALS—VI The bottle-nosed dolphin

Press, Volume CXIV, Issue 33514, 20 April 1974, Page 11

STAMP ANIMALS—VI The bottle-nosed dolphin

(By

ARTHUR W. PARROTT)

' At 15ft, the bottlenosed dolphin is one of the larger members of the dolphin family. Its beak is three to four inches long and distinctly marked off from the head. There are 20 to 22 rather large teeth in each jaw, and the very high forehead, rising abruptly from behind the beak, resembles a bottle. The dorsal fin of the bottle-nosed dolphin is relatively large in proportion to the size of its body, and the flippers are rather slender. The upper side of the body is grey or greenish grey, and the ventral surface and lower jaw are white. There is some confusion regarding the identity of the several closely-related" species of the genus Tursiops. Some authorities recognise five species, but whether some of these are merely geographical races,,

or sub-species, is not clear. However, the bottle-nosed dolphin, also known as the cowfish, should not be confused with the bottle-nosed whale of the North Atlantic, which is an entirely different animal. Gregarious in habit, the species is often found in large schools. Although it has been studied extensively in captivity, little is known about its natural breeding habits. Apparently bottle-nosed dolphins mate

during the summer and their gestation period is recorded to vary from 160 to £9O days. One calf, 3ft lOin. long, is born at a time.

Bott! e-nosed dolphins have been bred in captivity and observations show that adult females co-operate during the birth of a calf. Pairs of adult females, for example, support the newborn infant at the surface until it is able to breathe by itself. One method is for two females tow swim close together lodging the calf between their dorsal fins. The mother keeps her calf close to her for its first few weeks; it is not weaned until it is 18 months old. In captivity there appears to be a social order among bottle-nosed dolphins in which an adult male dominates all others. Adult females in turn dominate juveniles, and' juveniles dominate infants. The juvenile males appear to stay together in a sub-school and often attempt to mate with adult females. The older infants also tend to form subschools, returning to their mothers at intervals. There have been several instances reported of members of a school coming to the aid of injured individuals. They are a popular dolphin for keeping in captivity. They adjust themselves well to marinelands around the world and are quick to learn tricks. The common dolphin, too, is often seen in marinelands and is one of the jpecies seen performing at the Napier Marineland.

The famous “Opo”, of Opononi, was a bottlenosed dolphin and Pelorus Jack, of French Pass, is also thought to have been one. Pelorus Jack was for many years considered a Risso’s dolphin, but his habit of following ships close inshore was more in keeping with the behaviour of a bottle-nosed dolphin. Also, Risso’s dolphins have been positively recorded only three or four times in New Zealand waters, and appear to be a very rare visitor to our shores.

The bottle-nosed variety is widely distributed in both the northern and southern hemispheres and in New Zealand waters it is often found off the North Island and the northern coast of the South Island. It is frequently referred to here as a porpoise, but there are no true porpoises in the southern hemisphere. Most dolphins are excellent jumpers and the bottle-nosed variety is one of the best. In 1962 a 5001 b individual named “Pedro” reached a pole 20ft above the water at Marineland, Florida.

It is one of the few whales whose heartbeats we have a definite record of: 110 when breathing and 50 in a dive. White-sided dolphin The white-sided dolphin belongs to a group which virtually lacks the visible beak so typical of the com-

mon dolphin and related species. They are all bluish black above and have varying amounts of white on the underside and flanks of the body. A well-known North Atlantic species, the whitesided dolphin is closely related to the dusky dolphin and the southern whitesided dolphin, both of which are found in New Zealand waters.

The white-sided dolphin is black above, with a white under-surface which shades off into grey at the front under the lower jaw.

One of the most distinctive features of the pattern is a large splash or streak of light colour on each side of the back area, extending from below the dorsal fin nearly as far as the tail flukes.

Large schools of whitesided dolphins are found in the northern parts of the North Sea and around the Orkney and Shetland Islands. These sometimes contain thousands of individuals. The related southern white-sided dolphin is restricted to the southern oceans. It may be recognised by the black mark around its eye; the jaws and top of the head are black: and a dark stripe runs from the angle of the jaw to the eye. There is a broad angular white area extending from the side ot the head above the eye tc just above the base of the tail flukes. This white band is interrupted by a large black area just before th« dorsal fin.

The dusky dolphin maj be distinguished from th* white-sided species by th* absence of a dark zone be hind the flippers along the sides of the body. School: numbering hundreds of in dividuals have been re corded east of Cook Strai during summer.