302 WHALES 



Cetacean skin surface, due largely to streamlining, has, as we have seen, 

 a considerable effect in minimizing heat losses. 



The heat conducting properties of the blubber of a porpoise and a Fin 

 Whale were determined experimentally by Parry (1949). From the result 

 (0-0005 §• c^l- P^^ ^^- c"^' P^'^' second per centimetre thickness, at tempera- 

 ture difference 1° C), together with the known area of the skin and the 

 temperature difference between it and the sea. Parry calculated how much 

 heat the animals would have to produce in order to maintain their 

 temperature. Mammals are believed to be capable of producing forty-five 

 (great) calories per square metre (4-2 calories per square foot) of skin 

 surface per hour. While some biologists think that these figures do not 

 apply to mammals in general, we shall use them here, in the absence of 

 more accurate data. If we do so, we shall find that the amount of heat a 

 porpoise or a Fin Whale at rest loses through its skin considerably exceeds 

 the amount their body is capable of producing in the same time. Hence, 

 the animals cannot possibly stay at rest and must move about rapidly 

 during most of the day if they are not to lose too much heat. As we know 

 from personal experience, the faster we move about, the warmer we get - 

 a fact we use to advantage on a cold winter's day. 



Conversely, we get cold when we are scantily dressed, and Cetaceans 

 cool off so much because their blubber coat is not really thick enough to 

 lag them completely under all conditions. Parry has calculated that the 

 Fin Whale would have to have a 5|-inch thick blubber covering if it were 

 to maintain its temperature at rest. Now, that thickness is only found in 

 particularly fat specimens at the end of the Antarctic season. 



Why then is the blubber so thin, you may ask, particularly if you 

 remember that these animals store a great deal of fat in other parts of the 

 body, i.e. in the skeleton, between the internal organs, and even in the 

 muscles. We may gain a clearer understanding of this question if we 

 investigate how fat is stored by big Rorquals in the course of the Antarctic 

 season. In the beginning of the season, most fat is stored as blubber, so 

 that the thickness of this layer increases rapidly and thermal insulation is 

 consequently increased. After the middle of January, however, the thick- 

 ness of the blubber over most parts of the body increases only very slightly. 

 The exception is the back and especially the region immediately in front 

 of the dorsal fin, where the thickness of the blubber still increases sig- 

 nificantly. Most of the fat, however, is now laid down elsewhere - at first 

 in the skeleton, then chiefly in the muscles and finally between the organs. 

 This strange way of laying down fat is obviously necessary since if, at the 

 end of the season, the blubber grew any thicker than it does, the animals 

 would become too hot when swimming about ; so much so that they might 

 die of heat-stroke in the midst of the ice-cold polar sea. 



