SCHOOLING 277 



growth rings in teeth for age determination of elephant seals, and it appears that this method has 

 been successfully applied in studies on the pilot whale in Newfoundland (Rep. Fish. Res. Bd. Can. 

 1954, p. 54; 1955, p. 58). In cross-section the teeth of sperm whales also show concentric rings which 

 may be associated with age: sperm teeth from female whales have been collected at Horta since 1953, 

 but these teeth have not yet been sectioned and examined. 



Regarding growth to sexual maturity it can only be noted that male and female sperm whales of the 

 North Atlantic are estimated (pp. 264-5) to mature at similar means lengths: these are 9-6 m. (31 ft.) 

 or less, and 8-8 m. (29 ft.) respectively. Should it be found that they mature at similar ages, then the 

 great difference in size between the sexes must develop after sexual maturity, when the physiological 

 demands of the female's protracted breeding cycle are likely to slow down her growth relative to that 

 of the male. 



At Horta observations have been made on the progressive ankylosis of epiphyses to centra in the 

 vertebral column, but these are not yet sufficient to yield any reliable conclusions about physical 

 maturity. 



Table 26. Sperm whales fastened, then lost in the Azores but subsequently captured, 

 being identified after a lapse of years by marked harpoons 



Fastened then lost Captured 

 a . , • , Interval 



Sex Date Locality Date Locality in years 



— 1918 North of San Jorge 1920 Caxorro Bay, Pico 2 



<J 191 1 Prainha do Sul, Pico 1943 Prainha do Sul, Pico 32 



Probably? 1929 San Jorge Channel 1951 Capelo, Fayal 22 



Some information on the longevity of sperm whales is provided by three instances of lost harpoons 

 recovered from whales in the Azores. Senhor Jacinto Silviera de Medeiros, of Horta, has kindly 

 provided me with the details which are recorded in Table 26. The island whalemen preserve the 

 ancient custom of 'marking craft' (Clarke 19540, p. 318), and so it happens that in a captured whale 

 there is occasionally found and identified a hand harpoon surviving after the lapse of years from some 

 previous encounter when the whale was fastened but subsequently lost. In the present instances the 

 sex of the three captures was not noted, but the second is recorded in Table 26 as a male since it 

 boiled out fifty barrels, a yield of oil which only a male can be expected to give; and the third after 

 twenty-two years at large only boiled out twenty barrels, and so was almost certainly a female. 

 Table 26 is therefore evidence that male and female sperm whales may live for at least thirty-two and 

 twenty-two years respectively. 



SCHOOLING 



The sperm whale is a typically gregarious species. The schooling habit, besides its intrinsic interest, 

 deserves attention because it appears to affect discussion of breeding and the sex ratio. 



The supposed polygamous habit of sperm whales, briefly discussed by Matthews (1938, p. 159), is 

 accepted here. Polygamy must greatly influence the pattern and stability of the various kinds of 

 schools. 



In certain whaling returns examined at Horta, there were entries which stated whether each capture 

 had been solitary or in a school when sighted. The returns available were confined to the catches of 

 three islands or districts in 1948. From the data Table 27 has been constructed. It illustrates at once 

 a characteristic of the species, namely, that females are invariably in schools, whereas males may be 

 in schools or they may be solitary. 



