60£ 



SCIENCE 



[N. S. Vol. XLIV. No. 1139 



DISCUSSION AND CORRESPONDENCE 



THE CENSUS OF FUR SEALS, 1914 AND 1915 



Interest in the fur seals of the Pribilof 

 Islands at the present time centers largely in 

 the annual enumeration of the animals. 

 Since 1912 a complete count of the pups born 

 has been made each season, which constitutes 

 an exact enumeration of the breeding females. 

 In 1911 pelagic sealing, which had occasioned 

 the herd's decline, was suspended by inter- 

 national treaty. The count of pups was insti- 

 tuted to secure an exact figure for the breed- 

 ing stock at its lowest point and was con- 

 tinued to secure a measure of its annual in- 

 crease. 



Comparison of the figures for 1912 and 1913 

 showed a gain of 12J per cent. This was ap- 

 proximately what was expected from the ex- 

 perience of many years in taking the annual 

 quota of young male seals. Unfortunately the 

 count of 1914 was made by men not previously 

 experienced in the work and a new set of per- 

 sonal equations was introduced. The result 

 gave a gain of only one per cent., without any 

 adequate explanation for the irregularity. The 

 results of the count for 1915, made by the 

 resident agents on the islands, are now avail- 

 able, and, while they are affected by another 

 new set of personal equations, this time an 

 experienced one, a practically normal condition 

 is found to exist; a gain of 11 per cent, in 

 pups is shown over the count of 1914. 



In the December issues of Science for 1912 

 and 1913 the censuses for these seasons were 

 published. The census for 1914 appears at 

 page 39 of Senate Document No. 980, the re- 

 port of the investigating committee of 1914. 

 The census of 1915 has not as yet been pub- 

 lished. The figures of these two seasons may 

 be contrasted with those for 1913 as follows: 



No particular importance attaches to the 

 final totals or to the estimated groups in this 

 table. The non-breeding animals can not all 

 be seen together at any one time nor counted 

 in any way. The estimates are based on as- 

 sumptions regarding the mortality suffered by 

 the different classes of animals on the winter 

 migrations, and these assumptions are slightly 

 different for each census. The important ele- 



ments are the counted items, giving the three 

 essential factors in the herd — the breeding 

 females, the breeding males, and the reserve of 

 male life — the idle and young bulls growing up. 



Two facts of great importance are estab- 

 lished by these counts. The first is that the 

 herd has made a substantial growth in the 

 years since pelagic sealing was abolished. The 

 stock of breeding females which in 1912 num- 

 bered 82,000 now numbers 103,000. The sus- 

 pension of pelagic sealing, accomplished by the 

 treaty of 1911, has, therefore been effective in 

 staying the decline and in restoring the herd 

 to a condition of normal growth. 



The second fact is that there has been an 

 abnormal increase in the stock of reserve 

 males. In 1913 this reserve was represented by 

 364 animals for an active stock of 1,403 — an 

 adequate reserve, since the breeding life of 

 the male is six to eight years. In 1914, how- 

 ever, this reserve had advanced to 1,830 ani- 

 mals, more than equaling the active stock of 

 1,559. In 1915 it had advanced to 11,944 for 

 an active stock of 2,151, giving a reserve of 

 five times the active stock. The season of 1916 

 having now passed, the 15,848 four-year-old 

 bachelors of 1915 have taken their places in 

 this reserve, bringing it up to a total of about 

 27,000 animals, approximately ten times what 

 the active stock should be. To this again will 

 be added the 18,282 three-year-old bachelors of 

 1915, as reserve bulls of five years and over, 

 in 1917. In that season the law which is occa- 

 sioning this abnormal condition will have 



1 Actual counts. 



2 Estimates. 



