82 DISCOVERY REPORTS 



northern whales remaining in tropical waters later than the majority of their fellows, and 

 may migrate with them to the north. He uses this hypothesis to explain the peculiarities 

 of the species described as M. bellicosa by Cope in 1871, and of an individual caught off 

 Iceland in 1867 and described by Hallas, on the supposition that they are southern 

 Humpbacks which have strayed into the northern hemisphere and are to be dis- 

 tinguished structurally from the northern race. As has been shown above, there is little 

 reason to think that the Humpbacks of the northern and southern hemispheres can be 

 distinguished, and if even occasional migration from one hemisphere to the other be 

 granted, the consequent mixing of blood would appear to decrease the chances of dif- 

 ferentiation. Hinton (1925) states that there is no evidence of migration from the 

 northern to the southern hemisphere : but if migration in the reverse direction is pos- 

 sible, there would appear to be no valid reason why it should not occur, and every 

 probability that occasionally it does. 



The migration of the Humpback whale can, then, be summarized as a southern feeding 

 migration, as far south as there is open water in the southern summer, followed by a 

 migration towards the north which is pursued mainly in the coastal waters of the con- 

 tinents. The northward migration reaches the neighbourhood of the equator in August, 

 when most of the females give birth to their calves, and the return migration begins at 

 once; pairing takes place during its course and is, for the most part, over by the end of 

 the year when the whales are on their southern feeding grounds. Some Humpbacks are 

 present on the South Georgia whaling grounds during the winter and may be non- 

 migrating individuals which have spent the summer farther to the south. The migration 

 is not restricted only to breeding whales, but includes immature as well as mature whales, 

 pregnant as well as non-pregnant females. 



DESTRUCTION OF THE STOCKS OF HUMPBACKS 



Whenever new whaling grounds have been opened up the Humpback whale has 

 always been the predominant species in the catch for the first few years, and has then 

 rapidly declined in numbers. This is partly due to the fact that when whaling was started, 

 in, for instance. South Georgia and South Africa, the plant then available was not 

 suitable for dealing with any numbers of the larger species of whale. After a few years, 

 when better facilities were installed, fewer Humpbacks were taken. Nevertheless the 

 taking of the larger species coincided with a definite decrease in the numbers of Hump- 

 backs available. 



It must be remembered that the Humpback is a slow moving, coast-frequenting 

 species of whale which is comparatively easy to catch. When feeding or pairing they 

 are very easy to approach: as Risting (1912) says, "a Humpback in the midst of krill 

 appears to have no thought for anything but provisions, and an enamoured humpback 

 forgets all regard to caution ". The whalers state that the decrease in its numbers is due 

 to its being frightened away from its former haunts, but there seems to be no valid 

 reason why this species should be more easily frightened than any other, unless it is very 



