ALASKA FISHERY AND FUR-SEAL INDUSTRIES, 1921. 



81 



same rookeries the proportion of dead is 0.000673. Applied to the 

 whole herd the number of dead cows would be 119. 



No branded cows were seen on the St. Paul rookeries. During the 

 limited time for observations there branded cows may have been over- 

 looked. On St. George Island one cow bearing the 1902 brand (bar 

 across the back) was seen on East Cliffs rookery, one on North rook- 

 ery, and one on Staraya Artil rookery. Each of these three had 

 large, healthy pups and showed no signs of senility. It is evident that 

 cows may bear pups for 16 years at least. 



BULLS. 



HAREM AND IDLE BULLS. 



The count of harem and idle bulls was made at the height of the 

 season. The accuracy of the count of harem bulls is of the greatest 

 importance, as it is from figures thus obtained that the average harem 

 is determined for the rookeries where the pups are not counted. The 

 error in this count increases in further computations and materially 

 affects the total figures. 



Two tripods were erected on Reef rookery this season as an experi- 

 ment and proved to be invaluable in increasing the accuracy oi the 

 count. The erection of other tripods and the placing of markers has 

 been taken up in another paragraph (p. 78). To secure an accurate 

 count, it is absolutely necessary to reach an elevation from which all 

 seals in a certain area can be seen. Counting from a boat is of some 

 advantage, but many times the condition of the sea prevents the use 

 of such a method. Also, just as the beach line can not always be seen 

 from the rear of the rookery, the rear of the rookery can not always 

 be seen from a boat. 



Two bulls bearing the 1912 brand (T on top of head) were killed on 

 St. George Island. At least three other branded bulls were seen on 

 the rookeries. One badly crippled and wounded was seen among the 

 harems on Staraya Artil rookery. 



Harem and idle bulls and percentage of idle to harem bulls compared to average harem, 



Pribilof Islands, 1921. 



Count of 1920. 



