46 BULLETIN OF THE BUREAU OF FISHERIES. 



The increased number of bulls, while having some effect on the average size of the 

 harems, did not preclude the formation and successful management of some excep- 

 tionally large harems, and it is evident that an unlimited increment of bulls would not 

 do so. Harems of large size were noted under various conditions, on large rookeries 

 as well as smaller ones, and where idle bulls were present as well as where there were 

 none. The bulls holding such harems, while magnificent animals, possibly superior 

 to the average, were in no respect superior to inany others in nearby positions having 

 harems of moderate size. Harems of at least 80 cows were observed in numbers, in 

 fact on practically every rookery. The largest single harem was noted on Zapadni 

 rookery on St. George Island. This harem on July 13 contained 106 cows, and there 

 was no doubt this was not the full total. At the close of the season the bull in charge 

 of it was much reduced in weight, but still jealously guarded a few cows not yet served 

 and proved so vigorous and belligerent that he could not be dislodged from his posi- 

 tion during the counting of pups. That this bull served more than 100 cows and fin- 

 ished the season in relatively good condition is scarcely open to question. A similar 

 case was noted on Gorbatch. The first harem formed here contained 6 cows on June 

 22 and 22 on June 26, and rapidly increased to not less than 80 on June 30. A few 

 cows had already gone out to feed, so the total number of cows belonging to this harem 

 was doubtless nearly 100 even at this early date. Later in the season it grew still 

 larger, but became so merged with surrounding harems that an exact count of cows 

 was not possible. That it was successfully conducted is evident from the fact that the 

 bull in charge of it was observed covering one of the few remaining cows on July 23. At 

 this date a few bulls from other localities had concliided their labors and were sleeping in 

 the grass behind the rookeries. These instances are sufficient evidence of the sexual 

 capacity of the bulls. In addition, and corroborative of observations of former inves- 

 tigators, a single bull was noted to copulate twice within an hour and three times within 

 24 hours. 



Further and even more conclusive evidence of the sexual capacity of the bulls is 

 found in the average size of the harems. The 93,250 pups of 1914 were sired by the 

 1,403 harem bulls, the 105 idle bulls, and perhaps to a Hmited extent by the half bulls 

 of 1913. Assuming that the number sired by half bulls is at least offset by the cows 

 which died during the winter, it may be concluded that 1,508 harem bulls and idle bulls 

 in 1913 sired the 93,250 pups born in 1914, or an average of 61.8 for each bull. The 

 question of average harems is discussed more fully elsewhere (p. 56), but when it is 

 considered that numerous single-cow harems are always present it is plain that many 

 bulls must have impregnated more cows than the average. It is safe to say, therefore, 

 that a normal bull is capable of serving 75 to 100 cows in a single season. 



SENILE BULLS. 



Only two cases of undoubted seniUty were observed. One of these bulls, when first 

 noted on North Rookery, St. George Island, was in possession of two cows near the 

 edge of the water and some distance from the main part of the rookery. He was relatively 

 thin, lacking in vigor, and plainly very advanced in years. He retreated on our approach 

 like an inexperienced "quitter,'' and his general cowed demeanor, as well as his poor 

 physical condition, indicated that he would not be able to maintain his position. A few 

 hours later he was found dispossessed and dejectedly eyeing a small 5-year-old half bull 



