386 WHALES 



milk is not at present fit for human consumption, despite the enormous 

 yield, and despite the milk's high fat content. 



Analyses of the milk of Blue, Fin, Humpback, Grey and Sperm Whales 

 and of porpoises. Belugas and Pilot Whales show that the composition of 

 Cetacean milk is: water, 40-50 per cent; fat, 40-50 per cent; protein, 

 1 1-12 per cent; lactose, 1-2 per cent; salts and vitamins, i per cent. The 

 Beluga's milk was shown to have an exceptionally large proportion of 

 water (66 per cent) and small proportion of fat (22 per cent), possibly 

 owing to experimental errors, and the Sperm Whale's milk fat, just as the 

 oil from its liver, was found to be a real fat and not a wax-like product 

 like sperm oil and spermaceti. 



If we compare these figures with those for other mammals, it becomes 

 clear \vhy whale milk has the thick appearance of condensed milk. For, 

 while whale milk has a water content of only 40-50 per cent, the milk of 

 most domestic animals has a water content of 80-go per cent. Whale milk 

 is therefore three to four times as concentrated as the milk of cows, goats 

 and also of human beings. For this reason, young whales can be suckled 

 for shorter periods, and the mother loses less water, with which, as we saw 

 in Chapter 10, she has to be most economical. The fat content of the milk 

 of terrestrial mammals which varies from 2 per cent (human being) to 

 I 7 per cent (reindeer), is about 4 per cent in cattle and about 9 per cent in 

 bitches, while the milk of seals has much the same fat content as that of 

 Cetaceans, which is not surprising when we consider that the combustion 

 of fat releases not only a maximum of energy but also a maximum of water, 

 both of which are required to an exceptional degree by marine mammals. 

 In Chapter 10 we saw that the blubber of newly-born Cetaceans contains 

 relatively little fat, and thus offers relatively poor protection against the 

 cold, while their relatively large body surface exposes them to far greater 

 heat losses than mature animals. Thus a high metabolic rate together with 

 the ingestion of concentrated foodstuffs is a sine qua non of their survival. 



On the other hand, the sugar content of milk which varies in most 

 mammals from 3 to 5 per cent, and which in man and elephants may be 

 as high as 6 to 8 per cent, is very low in Cetaceans and also in seals, whose 

 milk is often practically devoid of sugar. We have seen why aquatic 

 mammals must oxidize fats rather than sugar, but whether this is the only 

 reason for the small percentage of sugar in their milk requires further 

 investigation. Cetacean milk contains roughly twice as much protein as 

 that of the average terrestrial mammal. In Rorquals, the need for extra 

 proteins may well be due to the quick rate of growth of their calves (see 

 below), but the same explanation can certainly not be offered in the case 

 of dolphins, which grow no more quickly than other mammals. Moreover 

 the milk of rabbits and rats also has a protein percentage of about 13. 



