472 INVESTIGATION OF THE FUR-SEAL INDUSTRY OF ALASKA. 



an individual bull with only a 15-minute intermission were observed. 

 That is detailed in the field notes of my 1912 report, July 23. Serv- 

 ice of 3 cows in 12 hours by the same bull was observed in 1912. 

 That is found in field notes of July 1. We sat on the rookery and 

 Mr. Marsh and myself held under observation two large harems with 

 a view to trying to determine the capacity of the bulls, and in three 

 periods of 4 hours waiting each this bull served 3 cows. There 

 remained 8 hours of the day when we did not observe him. Many 

 observations of two services within an hour have been made. The 

 breeding season covers the period between June 12 and August 12. 

 There would seem to be nothing inherently difficult in the service of 

 60 to 90 cows by one of these animals. The disparity between the 

 sexes — 400 to 500 pounds for the bull; 75 to 85 pounds for the cow — 

 predicates unusual sexual capacity. It may be said that where a 

 bull has charge of 100 or more cows he is practically always under 

 necessity of snaring his task with the neighboring idle bulls. When 

 the cows come in heat too rapidly for his attention, the idle and young 

 bulls push into his harem, or the cows wander out to other neigh- 

 boring harems. 



Fifth, the increment of breeding males. The male is sexually 

 mature at 3 years and under a minimized stock of breeding males 

 would enter upon the office of reproduction certainly at the age of 

 6 years. A large stock of idle bulls simply shuts these animals out of 

 the breeding grounds until they attain full adult strength at 7 to 9 

 years. There is no advantage in forcing an animal to wait two years 

 after he has attained full breeding capacity. 



The life of the male is about 14 years. His breeding life is from 6 to 

 8 years. The theoretical increment of breeding males should be one- 

 eighth to one-sixth of the active stock, for this proportion of the active 

 stock of males perish each winter at sea through natural termination 

 of life. To leave a margin of safety, and to provide against emer- 

 gency conditions, this theoretical increment should be considerably 

 increased — to, say, one-half of the active stock in any season. Thus, 

 for the present stock of 1,400 bulls, there should bean annual reserva- 

 tion of 700 young males, or to provide for the increase in the herd, 

 say, 1,000. No larger increment can be justified under any condition. 



The law of 1912 has caused an increment of 10,000 to be made in 

 1913, with a slightly increased number for each succeeding season till 

 1917; after that for 9 }~ears there is to be an annual reservation of 

 5,000. Thus the law will create a stock of approximately 95,000 

 breeding bulls for a herd of females which in that period — 1913 to 

 1926 — can not possibly use more than 10,000 bulls. This would pro- 

 vide for a complete replacement within the 13 years of a stock of 5,000 

 bulls. It is doubtful whether the stock of breeding males needed in 

 1926 will exceed 5,000, and the increase from 1,400 to this figure will 

 be slow and gradual. 



The recommendation of the advisory board of the fur-seal service 

 in 1909, and the Dixon law of 1910, sought to fix a proper breeding 

 reserve by providing that no more than 95 per cent of the 3-year-old 

 males should be killed in any given year. At that time the survivals 

 to the age of 3 vears were known from the quota to be approximately 

 15,000. 



But the Dixon law does not provide for a breeding reserve as was 

 intended. There are other defects in the Dixon law which I might 



