SEX RATIO 281 



catches at Fayal show that, although an excess of males persists in all months, the excess is greatest in 

 winter and is progressively reduced in summer, until in August the numbers of each sex approach 

 equality (Table 29); in the months following August the proportion of males steadily increases again. 

 These changes, which will be discussed later (p. 282), must reflect changes in the natural sex ratio of 

 the stock of whales round the island. 



Table 28. Annual catches and sex ratios at Horta between 1939 and 1954, 

 and in the Azores between 1948 and 1954 



Horta, Fayal Azores 



Three likely factors may help to account for the characteristic excess of males in the Azores catches. 

 When opportunity for selection affords, the Azores islanders, like whalemen elsewhere, take the larger 

 whales ; and this means a relatively greater catch of males. This factor should not, however, be over- 

 emphasized, because my impression is that there are frequently sufficient whaleboats at sea to deal 

 with all the whales which are of a size worth catching in a school. A second factor is that some propor- 

 tion of the female stock may be beyond the range over which the whaleboats normally operate from 

 the island coasts: it is likely that (p. 280) the schools of pregnant and of lactating whales tend to segre- 

 gate further from the coast than other classes of females and most of the males. The third factor 

 arises from the seasonal movements of the stock : it appears that the main stock of whales moves 

 away from the Azores before the onset of winter, leaving behind a proportion of the males; and the 

 presence of these winter ' residents ' helps to produce in the catches an excess of males throughout the 

 early and late summer months when the main stock is both reaching and leaving the islands, except 

 in July when the catches are at their peak and the stock may be considered at full strength round the 

 Azores (p. 284). 



