THE SPERM WHALE 159 



with the men grouped round it also shows that it is not a female. In the statistics for 

 seasons 1923/4-1925/6 from the South Shetlands, eight female Sperm whales appear. 

 These are all incorrectly recorded, because their lengths are given as between 50 and 

 60 ft., a length which no female Sperm whale reaches. They are all males. As mentioned 

 above, whalers are sometimes surprisingly incorrect in identifying the sex of whales. 

 There appears to be some reason for believing that competition for the possession of the 

 females is considerable between the males, for, in addition to the well-known belief of 

 the whalers that each school of cows is accompanied by from one to three proprietor 

 bulls, Lillie (1915) gives the record, and a figure, of thirty-six bulls and one cow stranded 

 on Perkin Island, Tasmania, in February 191 1, when, it is alleged, the bulls pursued the 

 cow into shallow water so that the entire school was stranded. 



Townsend (1935) gives interesting charts plotting the position and time of capture of 

 36,908 Sperm whales taken by American whalers between 1761 and 1920, and the general 

 conclusion to be drawn from a study of these charts is that Sperm whales are present 

 at all times in tropical and equatorial waters, but that in the months of April to 

 September inclusive the vast majority were taken from the equator northwards to 

 temperate regions, and from October to March inclusive, from the equator southwards 

 to temperate regions. Smaller numbers were taken in north temperate latitudes in the 

 months April to September and vice versa. A general movement towards the equator 

 from temperate regions in the winter season of each hemisphere is thus indicated. 



An examination of the length frequencies of Sperm whales in Fig. 67 shows that 

 though the catches of males at South Georgia are entirely composed of sexually mature 

 and large bulls of one age class, the catches of males off Natal are quite different. There 

 are two well-marked age classes, with indications of a third. The largest number of 

 males belongs to the same age class as those taken at South Georgia, but nearly as many 

 of a smaller class are taken as well. This class consists of sexually mature whales which 

 are, however, on the average, 2 m. shorter than those of the older class. If the males 

 which migrate alone into high latitudes are in fact, as has been alleged, driven out of the 

 schools by younger males, this second age class of males, from 13-14 m. long, would 

 appear to be the one which drives the older ones away on their solitary journey. There 

 is also some indication of a third age class at lo-ii m. of length: this class consists of 

 males that are sexually immature. Lesser numbers of still younger ones are taken. The 

 second age class is the one forming the bulk of the catch at Cape Province. The females 

 all fall into one class, as shown by their length, from which it is concluded that after 

 reaching sexual maturity female Sperm whales grow very slowly, though, as has been 

 shown above, growth does not entirely cease until long after sexual maturity is attained. 



The general outline of the movements of the Sperm whale to be gleaned from the in- 

 formation available, meagre as it is, is that the headquarters of the species is the tropics, 

 that in summer in the northern and southern hemispheres there is movement towards 

 the north or south respectively, that pairing takes place during this migration and the 

 females give birth to their young in subtropical and temperate waters. Further, a small 

 proportion of the males, though fully active sexually, leave the females at the height of 



9-2 



