REPORT OF BRITISH COMMISSIONERS. . 105 



1891, made in the liglit of evidence previously published, and with the 

 aid of formal and informal questioning- and conversation with all those 

 actnally engaged in the Avork on the islands, as well ks with many who 

 had previously w^orked on the islands, but were at the time in other 

 independent employments. 



370. The differiug ages at which the males and females respectively 

 reach maturity and enter into the breeding class, together with the 

 varying times at which the sexes are supposed to continue in this class, 

 witli other circumstances already detailed as to the habits of the fur- 

 seals, together afford the data for very elaborate calculations as to the 

 rate of increase or decrease of numbers of seals under various condi- 

 tions, and subject to the killing of certain numbers of seals of specified 

 sexes and ages. Such calculations, from a practical ])oint of view, are, 

 however, more curious than useful: lirst, because of the uncertainty of 

 many of the data, due to a want of necessarily precise information; 

 and second, from the imi)ossibility of including the consideration of the 

 varying natural causes of loss, which in some years may be so serious 

 as to entirely vitiate any arithmetical result which may be arrived at 

 by such a calculation. An attempt of a very general character has, 

 nevertheless, been made to illustrate the normal increase and possible 

 killing of seals, which maybe presented for the purpose of putting the 

 matter in point. In this calculation roughly approximate data only are 

 employed, because it is believed that such data are, under the circum- 

 stances, likely to yield results as trustworthy as any assumptions of a 

 refined and definite character. 



371. The state of the breeding rookeries of the fur-seal, under normal 

 circumstances, and while the surplus of males is being annually killed 

 off, may, it is believed, be fairly represented by a unit value consisting 

 of — breeding males 10,000, breeding females 100,000. Bryant's esti- 

 mate (which appears to be the best) of young surviving to reach matu- 

 rity, under normal circumstances, is 30 per cent, of the entire number 

 born; or with an annual birth-rate corresponding to the above "unit" 

 of 100,000, 30,000 would reach "maturity" each year.* 



It may further be assumed that the average age of "maturity" in the 

 two sexes is 4 years, and that the whole number of seals upon the rook- 

 eries during four x)receding years has remained constant. 



372. Under these assumptions, 30,000 4-year-old seals w^ould be added 

 each year; and it may be postulated, though it has not been actually 

 ascertained, that of these 15,000 are males and 15,000 females. Of 

 these it may be sui^posed that 10 per cent, is required in each case to 

 re])lace natural losses by death annually of the breeding classes, or, say, 

 10,000 females and 1,000 males. 



373. Under these assumi)tions, it is evident that a surplus of the 

 yearly increment, consisting of 14,000 males and 5,000 females, may be 



killed each year without damage to the existing state of the rook- 

 67 eries, which should thus remain at a fixed number. The death- 

 rate allowed is probably sufficient to cover all but very excep- 

 tional natural causes of loss. 



If, however, uuder-these circumstances, no females be killed, an addi- 

 tion of 5,000, or 5 per cent., on the whole number of females, will accrue 

 to the rookeries yearly; and such increase, to maintain the requisite 

 proportion of the sexes, will call for a similar increase of 5 per cent, in 

 males, or 500 males; thus reducing the number of males which may be 

 killed, if killing is restricted to this sex, to 13,500 annually. 



* Bryant estimates that during? the first year 60 per cent, of the young are lost, 

 during- the second year 15 j'cr cent., but before tliey arrive at maturity at least 10 

 per cent, more are destroyed. "Monograph of North American Pinnipeds," p. 407. 



