2 6 2 DISCOVERY REPORTS 



gives them unequal advantages in feeding; that, for instance, the nursing cows might feed less heavily 

 because they are hampered by calves which cannot dive deep. To test this possibility more data are 

 required than those in Table 17, where the figures, although suggestive, are not sufficient to conclude 

 that lactating whales get less food than other classes. There remains the possibility that females, 

 being invariably in schools and feeding socially, have not the freedom in food gathering enjoyed 

 by that proportion of males which are solitary upon the grounds. However, Mizue (1951, p. 85), 

 reporting on a large sample of sperm whale stomachs examined in the North Pacific, concludes 

 that the sexes do not differ in the quantity of food they take. 



Table 15. Males. Monthly abundance of food in stomachs examined 

 at Horta betzveen 1949 and 1954 



No. of stomachs examined 



Amount of food 



Much 

 Little 

 Nil 



Totals 



June 



19 

 19 



o 



38 



July 



13 



23 



4 



40 



Aug. 

 12 



13 



o 



25 



Sept. 



8 

 6 

 o 



Oct. 



5 

 4 

 o 



Nov. 



3 

 1 



o 



Dec. 



o 



2 

 o 



Totals 



60 



68 



4 



132 



(%) 

 45S 

 5*'5 



3-o 



100 



Table 16. Females. Monthly abundance of food in stomachs examined 

 at Horta between 1949 and 1954 



No. of stomachs examined 



Amount of food 



Much 

 Little 

 Nil 



Totals 



June 



July 



16 



32 



5 



53 



Aug. 



13 



27 

 8 



48 



Sept. 



'3 



21 



1 



35 



Oct. 



5 

 11 



o 



16 



Nov. 



Totals 



5° 

 98 



14 



162 



(%) 



30-9 



60-5 



8-6 



100 



Table 17. Females. Abundance of food in the stomachs of the classes 

 of zvhales examined at Horta from 1949 to 1954 



No. of stomachs examined 



Reviewed month by month the data in Tables 15 and 16 are too few to say much about the seasonal 

 abundance of food, except that there is sufficient food in any month between June and November for 

 some whales to fill their bellies. Indeed, the main facts which emerge from these tables are that 

 sperm whales are feeding around the Azores, and that their food supply is a substantial one. 



BREEDING AND LIFE CYCLE 



Sexual maturity 

 Any study of the life cycle of whales needs to discriminate between immature and mature individuals ; 

 and an estimate of the mean length at sexual maturity also permits the proportion of sexually immature 

 whales to be calculated from catch figures which give only the sex and length of captures (see p. 285, 

 Table 31, second footnote). 



