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Extract from
The Magic of Dolphins
by Horace Dobbs
Published by Lutterworth Press
ISBN 07188 2603-5
In the wild, dolphins sometimes act as a team when feeding. They will form a line and heard a shoal of fish towards a cliff face. When the fish are all bunched together and have no way of escape, the dolphins move in for an easy meal.
The young dolphin learns how to catch fish and to turn them into its mouth so that they can be swallowed head first; for dolphins do not chew their catch. They use their teeth for capture only. The teeth are all roughly the same shape and interlock like a very loose zip fastener.
Dolphins do not feed entirely on fish. The weaned dolphin finds out how to forage on the sea bed, and soon its diet is supplemented with squid, shrimps and even small sharks. The depth to which a dolphin will dive for food depends upon the species. Obviously those who inhabit the open seas will have to go deeper than those in shallow water.
A large brain is the feature which characterises the so-called higher animals. When trying to get an insight into the daily life of a dolphin, a comparison of the size of different parts of the brain which are known to be associated with specific bodily functions can help us to a greater understanding. For instance, smell plays an important part in mating, hunting and survival in some animals. In such species the part of the brain associated with this function is relatively large. In dolphins, though, it is almost non-existent. The conclusion drawn, therefore, is that dolphins have a very poor sense of smell. This is not very surprising when one considers how little time the dolphin actually spends in the air which carries scents and smells.
The region of the brain that involves the decoding and analysis of sound is very large in the dolphin. It has often been stated that dolphins see with sound”. But when we talk about sound vision it becomes difficult to understand just what the dolphin sees”. When dolphins are hunting they emit a range of very high frequency notes and listen for reflected sound. or echo. From this they are able to tell the size of a fish and how far away it is. A major part of the echo will come from the swim bladder - an air filled sack inside the fish which enables it to regulate its buoyancy. Because air has a different density to the rest of the body it gives a different sound signal. The dolphin will therefore “see” inside the fish as well as outside. Thus the information processed in the dolphins brain will be more like an X-ray than a photograph taken with light.
The dolphin’s ability to swim at great speeds give them an obvious advantage when hunting. An accurate speed reading has been obtained for a young female dolphin, just 1 .6m long, who was captured in the Black Sea and then released back into the fast moving school after a line had been attached to her tail. From the speed with which the line ran out, it was calculated that her speed was 44.4 kilometres/hour (27.55 miles/hour). Common dolphins have been clocked doing between 55.2 - 58.8 kilometres/hour (34.5 - 36.8 miles/hour) when riding the bow waves of destroyers. This may not be a true free swimming speed, however, because the dolphins are pushed along by the waves in front of the ships. Nonetheless Common dolphins are amongst the swiftest of all the cetacea
Occasionally a dolphin is born with very little pigment in it’s skin. The young, cream-coloured, albino Common dolphin in the top centre of this photograph was often spotted off Gibraltar.
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the previous books to enjoy Dilo’s continuing adventures with twins Debra and Robin, but having read one, children are sure to want to read the full series.
Instead of swimming to safety he faces fire, oil and choking smoke to go to the rescue.
