42 BULLETIN OF THE BUREAU OF FISHERIES. 



conditions might be due to one or more of three causes: (i) disease, (2) effects of land 

 killing, and (3) effects of pelagic sealing. If disease is in any way responsible, the 

 nature of it is wholly unknown and no direct evidence of its existence in the past or at 

 present is available. Disease, then, can not be considered. 



Taking up the possible effects of land killing, we find room for considerable argu- 

 ment. That land killing may have reduced male life to numbers insufficient for breed- 

 ing purposes is certainly not impossible, for there must be some stage of depletion of 

 males at which cows will begin to escape service. Whether or not a shortage of males 

 existed, land killing can be blamed only in so far as it supplemented pelagic killing. To 

 the effect of land killing was added that of pelagic killing, and the two combined to 

 reduce the stock of breeding males. That land killing alone was not responsible is 

 shown by the increase of harem bulls in 191 3 and 191 4, which were exposed to the full 

 measure of land killing but had a partial respite from pelagic killing. 



If all the cows were not sers'ed in 191 3, this would be evident in 1914 only by a 

 reduced number of births, or by a small increase, since cows without pups might easily 

 come and go undetected. There was only a very small increase of births in 191 4, so, 

 regardless of land killing, it is necessary to determine so far as possible whether or not 

 the supply of males in 1913 was inadequate from any cause whatever. In 1913 there 

 were 1,403 harem bulls, 105 idle bulls, and 259° )'oung or half bulls, a total of 1,767 

 possible breeders. These bulls had the responsibility of 92,269 adult cows and 15,000 

 virgins or nubiles, a total of 107,269 cows, making an average of 60.6 cows to each bull. 

 If the half bulls are not included, the average is increased to 71. These undoubtedly 

 are high averages, much higher than desirable, but that they are so high as to allow 

 cows to go unserv^ed is difficult to prove. Such conditions may be detrimental in the 

 long run, but that the bulls, at least for a time, are equal to such emergencies can not be 

 questioned. Even when bulls are in superabundance, harems of more than 60 cows are 

 voluntarily cared for with great frequency, and there is unlimited evidence that every 

 healthy bull is capable of ser\dng 60 to 70 cows whenever opportunity permits or neces- 

 sity requires. Granting the capacity of the bulls, it remains to inquire what their oppor- 

 tunities were and whether the average is fairly applied. In 191 3, as in 1914 and other 

 seasons, there were doubtless many harems of small size, some in fact consisting of only 

 one cow. Therefore, if all cows are served, some of the bulls must care for a number 

 considerably above the average, and when the elements of time and varying rookery 

 conditions are considered the possibility that at least a few cows may have gone unser\-ed 

 is greatly increased. This possibility could scarcely be admitted if numerous idle bulls 

 were present. At best, however, it can only be regarded as a bare possibility, for the 

 reduced number of males in 191 3 can not be wholly responsible for the small increase of 

 cows and pups in 1914, because the same relative number of males was present in 1912 

 and a large increase of cows and pups followed in 191 3. The results of insufficient male 

 life should have been as apparent in 1913 as in 1914. This makes it clear that other 

 causes than a shortage of bulls must be sought for the small increment of 191 4. 



This brings us to further consideration of pelagic sealing which affected not only 

 males but females. It was stopped in 191 1, so no direct loss of females since that time 



o As shown on a preceeding page, this number is too small, but since it is not certain that all of this class normally breed, 

 this need not be considered here. 



