LOCOMOTION AND LOCOMOTORY ORGANS 



95 



Figure 51. Rorquals surfacing slowly. [From Discovery Committee Report, igsy. 



Before the Second World War, catcher boats rarely made more than 

 14-15 knots, and therefore had to 'stalk' the much faster whales. The 

 Norwegians called this method of whaling Luse-jag, hut since 1945 Luse-jag 

 has generally given way to another method called Preyser-jag, in which 

 fast vessels not only force the whale to swim faster and thus to surface at 

 an angle and to present a larger target area (see Fig. 55), but also to come 

 up for air at more frequent intervals. For the faster a whale swims, the 

 more, of course, it 'pants'. The spot where a whale sounds is usually 

 betrayed by a smooth and 'oily' patch, called the blow-wake and this was 

 once believed to be the result of a special secretion. It would, however, 

 appear that the blow-wake is, in fact, caused by a current churned up by 

 the diving flukes. Some whales stay submerged for large distances, but the 

 Sperm Whale, for instance, usually sounds vertically, to reappear some 

 thirty minutes later at almost the same spot. 



Fig. 54 shows clearly that when Fin Whales surface, their flukes normally 

 remain submerged. The same is true also of Blue, Sei, and Little Piked 

 Whales, but Right Whales, Humpbacks, and Sperm Whales generally 

 display their flukes, particularly before deep dives (Figs. 56 and 70) . The 

 Greenland Right Whale is even known to shake its flukes to and fro in the 

 air, and it is generally believed that the animal does so because its thick 



