lo DISCOVERY REPORTS 



SEX RATIO 



The records of the numbers of the sexes occurring at South Georgia and off South 

 Africa are of interest. The figures available are those collected by the expedition, those 

 in the British Museum, and those recorded by Hinton (1925), all of which are used here. 

 Of 1057 whales from South Georgia 45-4 per cent were males and 54-6 per cent were 

 females, whereas of 623 from Natal 55-4 per cent were males and 44-6 per cent were 

 females; and of the total of 1680 whales from both places 49-1 per cent were males and 

 5 1 -9 per cent were females. The figures from which these totals are derived are shown in 

 Table II. 



The sex ratio could therefore be taken to be equal between the sexes for the species 

 as a whole, though it varies in different places. The reason for the preponderance of 

 females in the south and of males in the north, if indeed it is of real significance, is 

 probably to be sought in the whales' habits of breeding and migration. An alternative 

 reason may be that the whales taken were not a representative sample of the population. 



It is suggested that the females go north for parturition and pairing, and immediately 

 proceed south again towards the feeding grounds when these are accomplished. The 

 males, on the other hand, probably linger on the breeding grounds off the African coast 

 where they are easily captured, as is mentioned in a later section of this report. Very few 

 sex records of foetuses are available, only twenty-three in all, which are shown in Table 

 III. The numbers are unfortunately too few to give any definite conclusion. 



Hinton (1925) concluded that in the southern Humpback the females outnumbered 

 the males by about two to one, and his evidence, the catch of 191 3-14 given in Table II, 

 and his foetal records, included in Table III, show this ratio very distinctly. But in 

 view of the additional facts here presented, it can be taken that his results were due 

 merely to insufficient data, and that the sex ratios, though having a preponderance of 

 females in the south, are not nearly so uneven as would appear from the figures available 

 to him. Morch (191 1) states that in the South Shetlands in 1910 bulls were in the 

 majority, but unfortunately his statement is not supported by figures, and for this reason 

 cannot be compared with the detailed records discussed here. Hinton (1925), basing his 

 conclusion on the sex records of foetuses, thought that this preponderance of bulls re- 

 ported by Morch was a purely local phenomenon, but, as shown above, the figures 

 available relating to foetuses were insufficient to give a valid conclusion. 



EXTERNAL CHARACTERS 

 BODY PROPORTIONS 

 The Discovery staff measured sixty-two whales, but the complete series of measure- 

 ments, as laid down for Fin and Blue whales, was not always taken. A few of the stan- 

 dard measurements were not taken at all, but for the sake of uniformity the standard 

 numbering has been retained, although some gaps are thereby introduced. The data 

 obtained are set out below and may be taken as a fairly good representation of the ex- 

 ternal proportions of the Humpback whales of South Georgia, and an indication of those 

 of South Africa. There is no indication of any racial difference between the whales from 



