FUR-SEAL CENSUS, PRIBILOF ISLANDS, 1917. 



By G. Dallas Hanna. 

 SCOPE OF 1917 CENSUS. 



In each of the five summers preceding that of 1917 a complete census 

 was taken of the fur seals resorting to the Pribilof Islands in so far 

 as this was possible, that is, all the adult males and all the young 

 of the season were actually counted. On account of the large influx 

 of male seals resulting from the cessation of commercial killing each 

 succeeding census was marked by increased difficulties. 



In 1916 it was barely possible to count all the pups with the force 

 available. While a complete pup count could not be made in 1917, 

 a sufficient proportion of the pups was enumerated to establish good 

 averages which were applicable to the remainder. The 1917 census 

 is therefore entirely comparable with the five preceding ones, and 

 owing to its greater detail probably second to none in accuracy taken 

 previous to 1912. 



The rookery rocks which were numbered and marked with white 

 paint by the Coast and Geodetic Survey in 1897 were repainted and 

 relocated where necessary. This work was carried as nearly to com- 

 pletion as possible. The photographic stations occupied by the 1895 

 investigation were relocated and marked with paint. All these data 

 were plotted on Coast Survey charts. 



At the height of the breeding season harem bulls and idle bulls 

 were counted on all the rookeries on St. George and St. Paul Islands. 

 Hauling-ground seals were estimated at the same time. The breeding 

 areas were carefully plotted on Coast Survey charts at this time. A 

 complete series of photographs was taken from the historical stations 

 of 1895. 



After the height of the breeding season was over and the bulls had 

 lost much of their viciousness, but before the pups had learned to 

 swim, the latter were counted on eight rookeries on St. Paul Island 

 and on three rookeries on St. George Island. 



From these data obtained in the above-described field work a com- 

 putation of the entire number of seals was made. The computation 

 was intended to be complete to August 10, 1917. 



HABITS OF FUR SEALS. 



To begin an account of the fur-seal herd as it now exists it is neces- 

 sary to outline briefly the important facts in its life history which have 

 a direct bearing upon the methods of study pursued. Complete 

 accounts have been published many times in the past and are readily 

 accessible. 



The mature females or cows arrive at the islands mostly between 

 June 15 and July 15 and give birth to one young from a few hours 

 to a few days after coming ashore. Cows have been seen as early as 

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