DISTRIBUTION AND MIGRATION 



317 



Figure iy6. The 

 main ocean currents 

 between 40° S and 

 the Antarctic Con- 

 tinent. (From John 

 after Schubert, ig55) 



conditions, but then human beings are buik quite differently. Whales are 

 not only the gieatest known gluttons; they are also the greatest known 

 fasters. For while such cold-blooded animals as lizards and snakes, and 

 hibernating animals in general, can laze about without food for even 

 longer periods, whales, with their high metabolic rate, have to travel 

 more than 4,000 miles on an empty stomach, some of them pregnant or 

 suckling. 



The reader may wonder why whales which can withstand cold so well 

 have to travel for such long distances, when they could simply withdraw 

 to the nearest ice-free sea. The answer is probably that, in order to 

 maintain their temperature, they simply have to move about, and that 

 the heat loss is less in the tropics than in the polar seas. Moreover, newly- 

 born whales have a very thin blubber coat and a relatively large skin 

 surface with a consequently much larger loss of heat, and it is desirable 

 that they should be born in warmer waters. Admittedly, some animals 

 stay in the Arctic or Antarctic thioughout the year but it is believed that 

 all of them are either bulls or non-pregnant cows. 



Now, since the distribution and migiation of animals is largely governed 

 by their food supply, we might look more closely at the distribution of 



