JUN 28 1915 



PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. LIV January-April, 1915 No. 216 



THE PROBLEM OF ADAPTATION AS ILLUSTRATED BY 

 THE FUR SEALS OF THE PRIBILOF ISLANDS. 



By GEORGE H. PARKER. 



{Read April 23, 191 5.) 



The breeding habits of the Alaskan fur seals are so unusual as 

 to make these animals unique among mammals. During much of 

 the year, these seals are strictly pelagic roaming over the eastern 

 expanse of the northern Pacific as far southward as the latitude of 

 southern California. As summer approaches, practically the whole 

 herd consisting of several hundreds of thousands of individuals re- 

 pairs to the two small islands of St. George and St. Paul in Bering 

 'Sea for the breeding season. It is the relative proportions of the 

 various constituents of the herd during this breeding period that 

 affords material for interesting speculation. 



The movements of the fur seals in their arrival and departure 

 from the Pribilof Islands take place with much regularity. Early 

 in May and June the mature males or bulls, having made their way 

 through the passes of the Aleutians, reach the breeding beaches or 

 rookeries on the islands of St. George and St. Paul. Here they 

 take their positions, fighting all intruders while they await the com- 

 ing of the females or cows. The cows arrive on the islands chiefly 

 during June and July. They associate themselves with particular 

 bulls and the bull with his group of cows constitutes the family unit 

 or harem. In 1914 the average harem was not far from one bull 



PROG. AMER. PHIL. SOC. , LIV. 2X6 A, PRINTED JUNE I9, 1915. 



1 



