l88 THE SENSES OF ANIMALS 



noticed that dolphins and whales are frightened away when 

 this apparatus is in use. It is likely therefore that whales 

 can hear not only ordinary sounds but those of far higher 

 frequency than those audible to human ears. 



In recent years techniques have been developed for keep- 

 ing the smaller whales in captivity in aquaria larger than 

 many swimming baths — "oceanarium" is the name invented 

 for them in America. These fascinating marine zoos provide 

 a splendid chance for zoologists to get at close quarters with 

 animals that have for so long been remote and elusive ; and 

 as might be expected much new knowledge has been gathered 

 as a result. 



In the first place it was soon evident that whales are highly 

 intelligent creatures compared with many other mammals; 

 this is perhaps due to the relatively large size and complex 

 convolutions of the whale's brain. Then they are unex- 

 pectedly gentle and docile, and gain confidence in their 

 keepers within a few days — they are, too, unexpectedly and 

 sometimes embarrassingly philoprogenitive. They are quick 

 learners, and, without any coercion, easily learn circus tricks 

 for the amusement of visitors to the oceanaria; one was even 

 broken to harness and trained to tow a surf-board with a 

 bathing belle riding on it. Moreover they invent games for 

 their own amusement, such as a sort of water polo with 

 objects dropped into the pool— one dolphin took a mis- 

 chievous dislike to women dressed in black, and many a nun 

 visiting his oceanarium left soaked to the skin after he had 

 greeted her with an unexpected splashing. (See Plate 14.) 



Zoological experiment soon followed simple observation, 

 and it was established that whales produce a wide range of 

 noises and can hear ultrasonic vibrations up to 80 kilocycles 

 a second — the upper limit of human hearing is about 20 

 kilocycles a second in adults. Some years ago the late Arthur 

 McBride, when curator of the oceanarium in Florida, noted 

 evidence that sound is used by dolphins in navigation. He 

 found that the animals cannot be caught in a fine-meshed 

 net but jump over the line of corks supporting the headrope. 

 They can, however, easily be caught in a net of ten-inch 

 square mesh, but as soon as one is trapped and drags the 

 headline with the corks under water, the others at once make 



