52 



BULLETIN OF THE BUREAU OF FISHERIES. 

 IRf^GULAR DISTRIBUTION. 



As in the case of other classes of seals, the presence of a larger or a smaller number 

 of idle bulls on a given rookery is doubtless governed by a variety of circumstances, only 

 a few of which can be recognized. At least it is obvious that the distribution of idle 

 bulls is very irregular, and a considerable number may be present about one rookery 

 while scarcely any are found on another. It may be possible also, as observed in 191 4, 

 for idle bulls to be present at one end of a rookery while harems are held by half-bulls at 

 the other end. The fact that the herd as a whole includes a number of idle bulls, there- 

 fore, is not inconsistent with their complete absence and an actual shortage of harem 

 bulls on certain rookeries. This being the case, it can not be safely assumed that no 

 shortage of harem bulls exists unless there be idle bulls on every rookery. To this extent 

 at least it is apparent that a certain number of idle bulls are desirable and necessary. 



In 1 91 4 there were several rookeries ha\ang no idle bulls whatever and the range of 

 variation from rookery to rookery was very great, as shown by the subjoined table: 



Percentage of idle bulls on different rookeries, IQI4. 



IDLE BULLS AS A DESIRABLE BREEDING ELEMENT. 



The idea that the idle bull is literally a surplus or superfluous bull, only valuable as 

 a reserve or as an indication of a sufficiency of harem bulls, seems open to serious doubt. 

 It is quite conceivable that a moderate number of idle bulls may be an actual necessity 

 for normal breeding. When a sufficient number of idle bulls are present, it is apparent 

 that they are the principal, if not practically the only, agents for the sersace of the virgin 



