222 WHALES 



a number of American biologists began to investigate the sounds made by 

 Pilot Whales, Spotted Dolphins and Bottlenose Dolphins in the Marine- 

 land Aquarium and in the Lerner Marine Laboratory, by means of a 

 hydrophone (Fig. 115), \\hile other investigators managed to make a 

 recording of the voice of a Beluga in the Saguenay River near Quebec. 



The most frequent noise made by all the species investigated so far is 

 a peculiar shrill whistle (which can be heard without an amplifier) of 

 7,000-15,000 cycles per second in the Bottlenose Dolphin and of 500- 

 10,000 cycles per second in the Beluga, which have a deeper voice. The 

 sounds are always accompanied by an escape of air bubbles from the 

 blowhole, and undoubtedly serve the animals as a means of communica- 

 tion. It has been observed that young Bottlenose Dolphins keep in constant 

 contact with their mothers by 'whistling', and that contact between 

 individual members of a school is maintained in the same way. Tomilin 

 confirmed these observations in the case of Black Sea Dolphins. Thus 

 dolphins are not only herd animals, but herd animals which communicate 

 with one another. Similarly, large groups of monkeys keep up an incessant 

 chatter, unlike solitary apes (orang-utan, gorilla), which are usually silent. 



In Chapter 6 we saw that social distinctions are very important 

 in all herd animals, and in Bottlenose Dolphins, just as in dogs, social 

 superiority is frequently asserted by making threatening noises. Dolphins 

 produce these noises by shutting their jaws vigorously. 



During feeding, the Bottlenose often makes a barking noise accompanied 

 by a release of air bubbles. However, such air bubbles are never emitted 

 when the animal occasionally makes a noise which sounds like a miaow. 

 In the mating season, Bottlenoses also produce a weird whine, and, when 

 they investigate some unfamiliar phenomenon, they sound like a rusty 

 creaking hinge. These creaking sounds, which have a frequency of 20-170 

 kilocycles, appear to be completely supersonic, and we shall return to them 

 later. Meanwhile, it must be noted that it is not only the Bottlenose but 

 other dolphins as well which produce such sounds. The Beluga, in addition, 

 can chirp and make chiming sounds, and the Pilot Whale has been heard 

 whining, belching, and smacking its lips. Its belch was known to Bartho- 

 linus who noted as early as 1654 that the Pilot Whale 'horrendum emittit 

 ructum\ 



Mysticetes, on the other hand, appear to be much more silent, and it is 

 questionable whether they can emit any underwater sounds at all, though 

 McCarthy, during a trip to the Antarctic in 1946, thought that his asdic 

 picked up definite sounds made by Rorquals. Each sound, he states, 

 resembles a high-pitched whistle whose frequency increases rapidly during 

 the second it persists. The whistling was kept up intermittently for a whole 

 minute. A few sofar stations and also some American patrol boats have. 



