BREEDING AND LIFE CYCLE 271 



The present conclusions on the breeding of whales round the Azores are supported by the experience 

 of Fayal whalemen. They tell me that schools of nursing females appear between July and September 

 and are most numerous in August. Further, they have not seen whales copulating and can volunteer 

 no theories on how copulation takes place. This is to be expected if the majority of pairings take place 

 between March and May when there are very few females on the Azores ground. 



An independent observation of nursing schools tends to generalize for the archipelago the local 

 evidence from Fayal. Collett (1912, p. 636) records that in the summer of 1904 Captain Otto Sverdrup 

 saw round the Azores large schools of sperm whales, including many females with new-born young. 

 One cannot say how important the Azores may be as a calving ground for sperm whales of the North 

 Atlantic, but it seems clear that around the islands in the latter half of summer whales of the local stock 

 drop calves which have been conceived away from the Azores in the spring of the previous year and 

 probably well to the southward where the main part of the stock is believed to spend the winter 

 (p. 285). 



Turning now to the sexual cycle, one needs to ascertain whether males have a sexual season, and 

 if so, when it starts and how long it lasts ; and in females what are the normal periods of oestrus, 

 gestation, lactation and anoestrum. 



Male sexual cycle 



Unfortunately, all months of the year are not represented among the eighty testis samples collected 

 from mature whales at Horta. The collection refers to the period May to November, although only one 

 whale was sampled in May and one in November (Table 23). 



Table 23. Males. Mean diameters of testis tubules of immature and mature whales 

 examined betzveen May and November at Horta in 1949, 1953 and 1954 



Mean diameter of tubules in microns 



* Anomalous tubule diameter of whale F246. See Fig. 9 and p. 273. 



In all mature testis sections it was possible to find some tubules with a more or less abundant prolifera- 

 tion of the germinal epithelium. In some sections there were tubules packed with cells, an appearance 

 in the whale testis which has been described by other writers and taken as a sign of spermatogenic 

 activity. But no tubules in the present material clearly exhibited active spermatogenesis of the normal 

 mammalian pattern, and it may be that since the samples were not fixed until some 18 to 19 hr. after 

 death, the packed appearance in tubules is an artefact caused by desquamation of cells into the tubule 

 lumina. The particular characteristics of these sections were what appeared to be various stages in the 

 degeneration of spermatids, or less commonly and in quite small numbers, of spermatozoa. These 

 appearances, combined with the absence of any clear indications of spermatogenesis, suggest that the 



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