Decembeb 26, 1913] 



SCIENCE 



919 



should be about 25 per cent. The breeding life 

 of the female is about 10 years. Approxi- 

 mately 10 per cent, of the adult stock of 

 females disappear in each winter migration 

 through natural termination of life, and the 

 net gain of the herd should be about 15 per 

 cent. That the gain of 1912 is 12* per cent, 

 instead of 15 is explained by the fact that the 

 increment of three-year-old females for the 

 past season was derived from the birthrate of 

 1910, when pelagic sealing was still in opera- 

 tion and pups in considerable numbers died 

 unborn with their mothers or starved to death 

 on the rookeries later because of the death of 

 their mothers. In short the season of 1913 

 has not been quite normal. The season of 1914 

 should show normal conditions because its 

 increment of gain will come from the birth- 

 rate of 1911, the first season under exemption 

 from pelagic sealing. If the count of pups is 

 repeated for that season, the normal rate of 

 gain will be established. 



All elements in the fur-seal census can 

 not be measured by counts. The bachelor 

 seals of four years and under, and the 

 young females of two years and under, 

 come and go from the sea in an irregular 

 fashion which makes counting impossible. A 

 basis of reasonably accurate estimate for these 

 classes of animals, however, rests in the data 

 arising from the quota of killable seals, and 

 counts of animals rejected at the killings as 

 too small or too large. Utilizing this form of 

 estimate to supplement the counts of bulls, 

 cows and pups, the appended completed census 

 of the fur-seal herd is obtained, the figures for 

 both 1912 and 1913 being given for purposes 

 of comparison. 



The stock of breeding and reserve bulls in 

 1913 shows an increase adequate to meet the 

 needs of the expanding herd. The relation of 

 the two sexes on the breeding grounds has in 

 this season been more nearly ideal than at any 

 time in the past 17 years. Could present con- 

 ditions remain undisturbed, accurate informa- 

 tion regarding the herd's future condition 

 would be certain. Unfortunately this is not 

 to be. The suspension of land killing, incor- 

 porated in the law of August 24, 1912, will 



break the present equilibrium and throw all 

 factors of the problem into new confusion, by 

 swamping the breeding grounds with an over- 

 stock of idle bulls. The real effect of the sus- 

 pension is not at present visible, except in that 

 the hauling grounds were in 1913 filled with 

 superfluous young males, the killing of which 

 was prevented by law. Ten thousand of these 



njR SEAL CENSUS 



animals (with skins worth $350,000 to $400,- 

 000), were left to grow up as useless fighting 

 bulls, and this condition is to be multiplied 

 through four more seasons. Its consequences 

 ten years hence will prove a veritable calamity 

 to the herd. 



Leaving aside this discouraging feature of 

 the situation, however, it is a source of genuine 

 gratification that the suspension of pelagic 

 sealing, accomplished by the treaty of 1911, 

 has been so immediate and salutary in its 

 effect. Not merely has the decline on the 

 Pribilof Island rookeries — persistent through 

 30 years — ^been stayed, but the breeding herd 

 has taken on a rapid growth. Its initial stock of 

 92,000 breeding females makeg a splendid 

 nucleus and will compound at an annual rate 

 of 15 per cent. 



George Archibald Clark 



Stanford University, Cal., 

 November 29, 1913 



