124 WHALES 



which occur at certain fixed depths. From undigested parts of such 

 cuttlefish in the stomachs of dead Sperm and Bottlenose Whales, we can 

 state with certainty that these animals regularly dive down to 250 fathoms, 

 and probably much deeper also. Thus, in 1932, the crew of the cable-ship 

 All America, which was plying between Balboa and Esmeralda (Ecuador) 

 discovered that almost 200 feet of submarine telephone cable was twisted 

 round the skeleton of a Sperm Whale, which had probably been trapped. 

 The first mate stated that part of the cable had caught in the jaw, and 

 the rest had twisted round the tail. Now, since the cable was 500 fathoms 

 below the surface, it seems clear that the whale must have dived to that 

 depth. Altogether, thirteen similar cases have been reported - eight off 

 the American Pacific coast between I3°N and I3^S; one off Nova Scotia; 

 one in the Persian Gulf; one off Cape Frio (Brazil) ; and two elsewhere 

 off the coasts of South America. In six of these cases, the cable was 450 

 fathoms deep, and in the rest 50-175 fathoms. Some of the cables had 

 snapped and, during repairs, recently killed Sperm Whales had to be 

 disentangled. A similar fate also befell a Humpback Whale off Alaska, but 

 at a depth of only 60 fathoms. 



Little is known about the depths to which other Odontocetes can 

 descend, though it is thought that they do not make very deep dives. 

 Scholander measured the dive of a porpoise by attaching a harness to it, 

 and found that the animal did not go lower than 10 fathoms, slightly less 

 than pearl and sponge divers who usually keep to within 15 fathoms. 

 Otoliths of fishes found in the stomachs of Bottlenose Dolphins off the 

 West African coast (Dakar) show that these animals dive to depths of at 

 least 1 1 fathoms (Cadenat, 1959). Sea otters usually stay within 10 fathoms 

 of the surface, while different species of seal are said to descend to 40, 50, 

 and 140 fathoms and thus to rival the performance of some of the big 

 whales. 



What is involved in deep diving, you might wonder? First of all, of 

 course, the ability to hold the breath while submerged, and secondly 

 immunity to great pressures. With every 5 fathoms from the surface, the 

 pressure of the water increases by about one atmosphere, and a descent 

 to 250 fathoms therefore means that the body has to withstand a pressure 

 of 50 atmospheres. Our Sperm Whale at 500 fathoms must therefore 

 have wrestled for its life under a pressure of 100 atmospheres. 



But this is by no means as astonishing a feat as we might be inclined to 

 think, since living matter is largely made up of water, and water is prac- 

 tically incompressible in our bodies. The only thing that is easily com- 

 pressed is, in fact, the air in the lungs, whose pressure consequently 

 increases until it equals that of the water outside. Now if the external 

 pressure becomes too great and exceeds the contractibility of the thorax, 



