90 U. S. BUREAU OF FISHERIES 



July it did not appear that the number to be killed would be greater 

 than in the previous season. At that time, however, all classes of 

 seals arrived in large numbers, immediately changing the outlook. 

 The final results exceeded all expectations. 



BULLS 



In order to determine whether suflScient males were on hand for 

 breeding requirements, a census of harem and idle bulls was again 

 taken. Reef and Gorbatch rookeries, on St. Paul Island, were counted 

 by Robert B. Payne and the writer. All other rookeries on St. Paul 

 Island were counted by Mr. Payne and A. Chris toff ersen. The count 

 on St. George Island was made by Lee C. McMillin and the writer. 

 All rookery counts are made by two persons, thus affording a means 

 of verifying the results. When necessary to estimate small uncount- 

 able areas a conservative figure is arrived at by close comparison 

 with surrounding areas. 



Sivutch rookery on Sea Lion Rock was visited on July 30. At 

 that time harems were broken up, but a careful observation of the 

 number of bulls remaining indicated that the estimated number of 

 bulls on this rookery is very conservative. Harem areas were still 

 so congested that it was not possible to make an accurate count, even 

 at that late date. A very small portion of the rock was occupied by 

 bachelors, but it is not known whether the bulls permit them to occupy 

 this area during the more active portion of the season. 



South rookery, St. George Island, maintained the abnormal increase 

 of last season, with a resulting inaccurate figure for the average harem. 

 As stated in previous reports, however, this will not affect the average 

 harem for the island as a whole. 



Probably due to some unusual condition, there was a wider diver- 

 gence than usual in rates of growth of rookeries, as shown by the count 

 of harem bulls and the abnormal increase in killings on some rook- 

 eries. This may be due to the early filling up of the more advanta- 

 geous areas, thus requiring bulls to move to other rookeries to secure 

 suitable harem space. 



The surplus bull plays an extremely important part in increasing the 

 rate of growth of the herd. The idle bull is a potential harem bull. 

 He occupies a space in the rear or side of the rookery, and as the rook- 

 ery fills up with cows he is likely to become a harem bull. Then 

 additional surplus bulls appear and become idle bulls and finally 

 harem bulls. The surplus bulls that do not become idle or harem 

 bulls continually roam around on the outskirts of the breeding areas 

 and hauling grounds. After the active breeding season is over, they 

 take care of the thousands of virgin cows that arrive — this year's 

 estimate places the number of virgin cows at 78,410. Without these 

 surplus bulls a large proportion of the virgin females would remain 

 unimpregnated. At that late date the harem bulls have either re- 

 tired or are too exhausted to constantly move around in search of 

 virgin cows. They prefer to find a quiet resting place away from the 

 continual uproar of the rookeries. It is essential, therefore, to have 

 a large number of surplus bulls, even though they interfere with 

 driving throughout a great part of the season. 



