352 EEPOETS OF BERING SEA COMMISSION. 



On what birth- of the liei'd, requires the i^resevvatiou of the ivliole 



rate depends. 



of the class of breeding females, while only a 

 small number of virile males are necessary or at 

 all concerned in the matter. 



This is the great essential difference between 

 the importance of the life of the female and that 

 of the male to the conservation of the herd, and 

 it is the fundamental proposition on which hangs 

 the solution of the whole problem. 

 Explanation of We liave ventured to illustrate this by means 



diagrams. 



of a graphic exhibition of a hypothetical herd of 

 eighty thousand seals, in tiie accompanying dia- 

 grams, in which the effect of killing males is 

 shown to be harmless, if kept within certain 

 limits. In these diagrams the age of the seals is 

 shown on the horizontal line at the base of the 

 figure and the number of seals at any given age 

 is proportional to the length of the vertical line 

 on the diagram at the point representing the age. 

 Unfortunately we have no 'tables of mortality' 

 for seals; we know only approximately their 

 maximum age and we have little knowledge as 

 to the distribution of their deathrate. Based on 

 the best iaiformation available, we have assumed 

 the normal age lo be twenty years, and, to be on 

 the safe side, have further assumed that one-half 

 of the seals born die during the first year after 

 birth. The outer curve of the diagram, showing 



