120 THE FUR SEALS OF THE PRIBILOF ISLANDS. 



REMOVAL OF SUPERFLUOUS MALE LIFE BENEFICIAL. 



Moreover, the removal of this superfluous male life is not only possible, but is 

 really beneficial to the herd. As already indicated, the only deaths among adult 

 bulls and cows discovered upon the rookeries of the islands resulted from the strug- 

 gles of the bulls among themselves or to obtain possession of the cows. In the death 

 of young pups also this lighting and struggling of the bulls is a small but by no means 

 insignificant cause of loss. In 18!>G the great early mortality among nursing pups was 

 wrongly ascribed to the trampling of the fighting bulls. But while the more complete 

 and satisfactory investigation of 1897 shows another and more important cause, then- 

 still remains a considerable loss from this- source. This loss is now insignificant. 

 compared with what it was in the wild state of the herd. When the number of adult 

 males and females was practically equal, the destruction both among the cows and 

 among the pups must have been enormous. It undoubtedly rivaled the ravages of 

 the worm Uncinaria in its destructive work and combined with it to offset the natural 

 increase of the herd. 



POSSIBILITY OF OVERKILLING. 



While as a general principle the removal of these superfluous males is beneficial 

 to the herd, excessive removal would undoubtedly lead to disastrous results. The 

 percentage of males required for the needs of propagation is small, but it is essential, 

 and if reduced too low or cut off entirely the effect must be injurious. Such excessive 

 killing would be felt in the scarcity of bulls, from which cause, through inadequate 

 service, the usual increase of pups would not be born and the herd must ultimately 

 begin to fail. It is on this ground that land killing becomes a possible source of 

 danger to the herd. 



A HYPOTHETICAL CASE. 



To understand how such killing would act, let us take a hypothetical case. If in 

 any given year absolutely every 3-year-old male was killed to fill the quota, this 

 would involve the absence of representatives of this class of seals from the reserve of 

 bulls for the replenishment of the rookeries in subsequent years. It would not affect 

 the breeding bulls, nor the reserves of four, five, and six years. These latter would 

 supply the deficiency in the breeding stock caused by old age for at least ten years, and 

 it would take that period at least to show the effect of the close killing. If it was 

 not repeated, no influence would be felt. The 7-year-old bull of the following year 

 would simply enter the rookeries as a 6-year-old. 



But suppose the killing was continued through a series of years, every 3-year- 

 old being killed, the reserve would in time be cut off and the stock of breeding bulls 

 would die out. It is impossible to say how long it would take to produce this effect, 

 because we do not know the length of the life of the bull. We may infer, however, 

 that it is not less than fifteen years, and therefore the injurious effects of this exces- 

 sive killing begun in any given year and continued indefinitely would not be seen 

 within ten years at least. 



This is only a hypothetical case, but it shows what is meant by too close killing 

 of males in filling the quota. The killing of males, which would produce immediate 

 and disastrous results, must strike at the adult males. To destroy this class or any 

 considerable number of them would at once weaken the herd. But there would be 

 no object in such killing, and it has never been thought of. 



