I91S.] PARKER— THE PROBLEM OF ADAPTATION. 3 



ling males on arrival associate with the pups and cows rather than 

 with the other bachelors. The bachelors may begin breeding at 

 five years of age or even four, but they do not normally undertake 

 this function until they are six or seven years old, when they desert 

 the bachelors' hauling grounds for the breeding rookeries. The 

 period of their normal breeding life covers, therefore, a term of 

 perhaps some seven years or more. 



It is not impossible that the yearling females do not return to 

 the islands or, if they do, it is probable that they do so only in small 

 numbers and late in the season. The two-year-old females return 

 to the islands in July and August as virgin females, pair with the 

 younger bulls, and reappear a year later, the end of their third year, 

 with tEeir first pup. From that time on they enter into the regular 

 breeding of the herd and continue in all probability to produce one 

 pup annually. Their breeding life, therefore, extends over some 

 ten or more years. 



These in brief are the main facts concerning the breeding habits 

 of the Alaskan fur seal, an animal that exhibits one of the most re- 

 markable examples of concentrated and localized breeding known. 

 When it is recalled that these seals range over thousands of miles 

 in the northern Pacific and that all sexually active members of the 

 species without exception congregate in the appropriate season on 

 the two small islands of St. George and St. Paul for breeding, the 

 very exceptional nature of their reproductive activities must be 

 evident. 



The proportion of the two sexes at birth is very nearly equal, 

 yet when the breeding age has been reached, the natural relations 

 are not far from one male to thirty or forty females. As there is 

 no reason to suppose that the death rate is higher in males than in 

 females and as the length of the breeding life of the two sexes is 

 not very different, about seven years for the bulls and about ten for 

 the cows, it follows from the sexual proportions already mentioned, 

 that we should expect an excess of bulls to be present. As a matter 

 of fact, such is the case, for even in 1914, after the excessive com- 

 mercial killing of males in the past, the so-called idle bulls were 

 much in evidence. It thus appears that the Alaskan fur seal pro- 

 duces at birth approximately equal numbers of males and females 



