272 DISCOVERY REPORTS 



island at the beginning of the season, and this would be reflected in the catches. To 

 explain the later Blue-whale maximum Harmer postulates a northward movement of 

 some of the Blue whales. He also says : ' The immature individuals, probably arriving 

 from the north, which make their appearance at about the New Year, are probably also 

 important in this connexion.' 



At all events it is clear that on the Antarctic whaling grounds as a whole the major 

 part of the Fin-whale stock makes its appearance later than the Blue whales. South 

 Georgia occupies a peculiar position where Antarctic conditions extend into a com- 

 paratively low latitude, and Fin whales may be plentiful there before they have reached 

 the higher latitudes elsewhere. It is not until about the New Year that the big herds of 

 Fin whales make their appearance on the pelagic grounds. 



The largest numbers of Humpbacks are taken in mid-season, December and January, 

 both on the pelagic grounds and at South Georgia. 



THE MONTHLY SEX RATIO 



It has been shown above that a large body of data indicates a slight excess of males over 

 females. If the sex ratio is compared month by month there is a certain amount of 

 irregular variation, but a very large number of records would be needed to demonstrate 

 with certainty any definite differences in the movements and distribution of the 

 sexes. 



The numbers of each sex caught month by month are not given in the International 

 Statistics. I have particulars, however, of the catches of four factory ships, one in which 

 Mr A. H. Laurie worked in the season 1932-3, and three in which Commander 

 H. Buckle sailed as Whaling Inspector in 1934-5, I 935 _D an d 1936—7. Dr F. D. 

 Ommanney in 1939-40 and Mr P. R. Crimp in 1939-40 and 1940-1 examined a con- 

 siderable number of whales in factory ships, and these were a random sample of the 

 total catches. For South Georgia there are the Discovery Committee's data. With this 

 material the monthly sex ratios are shown, again as percentages of males, in Table 25. 

 Humpbacks examined at South Georgia and by Laurie, Ommanney and Crimp in factory 

 ships were too few for the monthly figures to be of any value here, and are therefore 

 omitted. A few whales examined at South Georgia in September and May are also 

 omitted. 



The ' Southern Princess ' data show a reduction in the percentage of male Blue whales 

 in February and March. As explained on p. 223 this probably results from the late 

 arrival in high latitudes of females which were lactating (or which had recently weaned 

 their calves), the catching of which had not yet been prohibited in 1932-3. The figures 

 for Fin whales are inconclusive. 



The sex ratio of Blue whales taken by the ' Southern Empress ' fluctuates a little, but 

 shows no definite trend. In 1934, however, the catching of females with their calves was 

 no longer allowed. Male Fin whales seem to increase a little in the later months, and 

 there is a distinct increase in the ratio of male Humpbacks, but it is difficult to know 

 whether any significance should be attached to it. 



