FUR SEALS AND OTHER LIFE, PRIBILOF ISLANDS, 1914. 45 



increases took place on rookeries of any particular type more than another nor that 



decreases were due to any general cause unless it were excessive mortality of old cows 



produced by pelagic sealing. A point of possible significance is seen in the fact that the 



increases or decreases in cows on a given rookery have no definite relation to the niunber 



of bulls. In a number of instances a decrease in cows was shown on rookeries which 



had an increased number of bulls. Thus, Tolstoi had 120 harem bulls in 1913 and 161 



in 1914. The 120 bulls of 1913 had the management of 10,026 cows, whereas the 161 



bulls of 1914 had only 9,934 cows, from which it is evident that the number of cows on 



a given rookery is not wholly dependent upon the number of bulls that are there to 



receive them. 



THE CENSUS IN THE FUTURE. 



The great element of uncertainty in all censuses thus far made is our imperfect 

 knowledge of the percentage of young seals that naturally survive to the age of three 

 years. Such information as we now have regarding this important matter is derived 

 from data obtained largely in the days of pelagic sealing when unnatural conditions 

 prevailed, making wholly reliable conclusions impossible. Under proper authority 

 this percentage of survival can be so definitely ascertained in 191 5 that the full strength 

 of the herd may be estimated with a degree of accuracy sufficient for all practical pur- 

 poses. With this knowledge in hand, differences of opinion as to the actual size of 

 the herd should be reduced to a negligible minimum. 



Until every possible influence of past sealing on both land and sea has disappeared 

 and until all uncertainty is relieved regarding rates of increase and numerical propor- 

 tions, it will be advisable to make an annual census. That this time has not yet arrived 

 is evident from the results gained in 1914, particularly the count of pups. The more 

 regularly and carefully censuses are made now while the herd is still relatively small the 

 less necessity there will be for such work in the future when the size of the herd will 

 render the task more difficult and more expensive. Another census, therefore, will be 

 required for 1915 and probably another for 1916. For later years, partial counts may 

 suffice and perhaps the counting of pups may be discontinued. 



As the herd grows counts will be made with increasing labor and expense, but 

 although all future conditions can not be predicted, it is probable that the difficulties 

 of counting harems and pups will never be quite insuperable. To continue the harem 

 counts when the herd has reached large proportions will require improved facilities 

 not now available, and to make pup counts at that time will involve the employment 

 of a corps of capable men, but if necessary the work can be done. 



THE BREEDING OR HAREM BULLS. 



STRENGTH AND VIGOR. 



The 1,559 harem bulls of 1914 showed every indication of full strength and vigor. 

 So far as outward appearance and actions are concerned, they were normal animals in 

 good condition as were all other classes of seals. The strain which they undergo without 

 food during some six weeks of almost constant physical exertion and sustained sexual 

 excitement is scarcely paralleled among animals. It is such that any weakness would 

 be likely to manifest itself at once, and when no such weakness can be detected it must 

 be concluded that none exists. 

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