FUR-SEAL CENSUS, PRIBILOF ISLANDS, 1917. 101 



Percentage op Increase or Decrease in the Number of Pups in 1917 from 1916. 



Rookery. 



Total pups 

 1916. 



Total pups 

 1917. 



Percentage 

 of increase 

 ( + ) orde- 



ST. PAUL ISLAND. 

 Kitovi , 



Lukanln , 



Gorbatch , 



Ardi^iien , 



Reef. 



Sivutch 



Lagoon 



Tolstoi 



Zapadni , 



Little Zapadni , 



Zapadni Reef , 



Polovina 



Polovina Cliffs 



Little Polovina , 



Morjovi , 



Vostochni 



Total 



ST. GEORGE ISLAND, 



North 



Staraya ArtU 



Zapadni 



South 



East Reef 



EastClifls 



Total 



Total, both islands 



"2,520 



2,235 



a 8, 649 



a 726 



17,442 



a 5, 060 



466 



o 15, 433 



358 

 4,918 

 1,761 

 1,260 

 12,921 

 28,249 



6,246 

 5,545 

 965 

 19 

 1,585 

 3, 762 



a 6, 783 

 o 5, 642 



1,050 

 24 



1,786 

 14,050 



18,122 



116,977 



b+ 1. 94 

 + 4.39 



f>- 2. 49 



b+ 3.71 

 + 6.80 



b+ .79 

 +20. 10 



b +27. 91 

 + LSI 



b+ 9.35 

 +34.58 

 + 3.66 

 + 4.63 

 + 17.31 



b+ 5.79 



6+15.83 



+ 9.94 



+ 8. 50 

 + 1. 74 

 + 8.80 

 +26.31 

 + 12.68 

 + 7. 65 



a Estimated. b Based on estimated number of pups in 1917. 



Percentage of Annual Increase of Pups, 1912-1917. 



It will be noted that the percentage of increase of pups for the herd 

 is 9.44. The difference in the increase on the two islands may appear 

 strange, but is entirely in accord with the facts gathered through 

 six years of counting, and conforms to the general law of fur seals 

 that their instincts cause them to flock to the centers of greater num- 

 bers, and the smallest rookeries grow most slowly. 



This increase of 9.44 per cent is below what is generally believed 

 to be the normal of 11 per cent. We see a reason for this in the lean 

 year of 1914. Female pups born then gave birth to their first pups 

 in 1917. Therefore the small increase in 1914 should be felt in 1917. 

 Another factor which goes to make a small increase may be somewhat 

 noticeable this year. This is the death rate of cows on land. In 

 1913, 1914, and 1915 the number of dead cows noted during the count 

 on the rookeries was considered negligible. But in 1916 there was a 



