ALASKA FISHERY AND FUR-SE.\L INDUSTRIES, 1920. 119 



age of females, but there are so many differences between the sexes 

 of this species that the age of the male can no longer be based upon 

 that of the female. 



The conditions outlined above are those which are believed to 

 exist when there is a great excess of males. If they had been re- 

 moved by man so that only approximately enough remained for 

 breeding purposes, the losses during the seventh, eighth, and ninth 

 years would not be so heavy. Also it is probable that the bulls live 

 longer when there is no fighting than when thej^ have to wear them- 

 selves out in maintaining a harem position. 



It, therefore, becomes apparent that conditions which obtained 

 during 1917, 1918, 1919. are not normal and may never occur again. 

 Everything now indicates that the younger animals suifered a 

 practically constant mortality until the seventh year, and then their 

 losses amounted to 50 per cent or more annually. Under normal 

 conditions with the great excess removed by man, the loss after the 

 seventh year would be variable and dependent upon the care given 

 to the reserving of a proper number of bulls. 



It seems unnecessary here to make arbitrary assumptions for the 

 annual losses of the class which was termed in 191T~1919 "surplus 

 bulls." It is definitely known that they were greater than the losses 

 assumed and deducted. Thus in 1919, 50 per cent was estimated to 

 have been the loss from the third 3'ear to and including the surplus 

 bull class; that is, animals 7 years old and over. If the loss had 

 been estimated at 50 per cent from the third year to the seventh 

 and at least that much annually thereafter, it would have come nearer 

 the actual condition. But there was nothing until 1920 which would 

 cause one to suspect that the loss had been so enormous. 



It now remains to determine what the annual loss of males is from 

 the third year on, when average conditions accompanying commercial 

 work exist. A division wliich is more or less arbitrary for all ages is 

 as follows: First year, 35 per cent; second, 15 per cent; third, 10 

 per cent; fourth, 10 per cent; fifth, 10 i)er cent; sixth, 20 per cent; 

 seventh, 20 per cent ; eighth, 25 per cent ; ninth, 30 per cent ; tenth, 

 40 per cent; eleventh, 50 per cent: twelfth, 60 per cent; thirteenth, 

 70 ijer cent; fourteenth, 80 per cent; fifteenth, 100 per cent. 



Considerable of the above is conjecture, but it is believed to rep- 

 resent fairly accurately the conditions existing in 1920. It will be 

 noted that there is a slight revision of the percentages lost from the 

 first to the third year. This does not materially affect the result and 

 gives a working basis for the future. Doubtless additional investi- 

 gation will adjust any irregularities in tlie table. It has been used 

 in the preparation of tiie final census for 1920. 



These new percentages of loss were obtainable in 1920, because 

 early in the season it was seen tliat the surplus believed to be in ex- 

 istence from the accumulation of the closed period did not appear. 

 It was evident that if the bulls were coming at all they would have 

 been at the islands before the middle of July. Since they did not 

 appear at that time it was recommended that no more be removed 

 from the herd. As it turned out tlie counts at the height of the sea- 

 son showed that a few more could have been removed with safety. 



