August 8, 1902.] 



SCIENCE. 



217 



table reveals the curious fact that the pro- 

 portionate number of females has not in- 

 creased. 



The present system of trapping on St. 

 George, vinder which all females were 

 spared, was commenced by Agent Judge 

 during the season of 1897-8. In that 

 season 324 females and 102 males were 

 branded and released. Undoubtedly there 

 were more foxes on the island during that 

 time than those which had been through 

 the trap, but taking the foregoing figures 

 as a basis, giving an increase of only two 

 pups each year for every female, to allow 

 for females which did not bear young, and 

 releasing one male for every four trapped, 

 we should have for the succeeding years 

 the following results, presuming that the 

 sexes are born in equal proportions, viz.. 



Year. Males. Females. 



1897-8, 102 324 



1898-9, 106 648 



1899-00, 188 1,296 



1900-01, 371 2,.592 



thus showing that in four years the pro- 

 portion of the sexes, in theory at least, 

 ought to bear the relation to each other of 

 one to seven, which it is believed is not 

 sufficient to serve the purposes of breeding. 



The rate of increase estimated for each 

 breeding female in the above table is ab- 

 surdly small. Litters of foxes have been 

 stated by the natives to have been found 

 having as many as twelve or thirteen young 

 ones. But even at this small rate, it will 

 be seen that there should be over 2,000 

 breeding females on the island at the close 

 of the trapping season of 1900-01. The 

 trapping last season, however, has shown 

 that but 690 females were found on the is- 

 land after months of trapping, and that the 

 number of females was but little in excess 

 of that of the males. 



The experiment of the Semidi Propagat- 

 ing Company has been similar to that ob- 

 tained on St. George. This company. 



about fifteen years ago leased the Semidi 

 Islands and, obtaining several pairs of blue- 

 foxes from the Pribilof Islands, begam 

 operations. The foxes have been fed and 

 cared for, all the females released, and a 

 certain proportion of males, at first one 

 male to seven females, and, later on, a 

 larger proportion. But in spite of this the 

 foxes on the Semidi Islands have not in- 

 creased as was anticipated, their numbers 

 being far below what they theoretically 

 should be. 



What becomes of the females released, 

 each year, and their natural increase, is 

 a question. Some, of course, die of old 

 age and disease. There is a possibility, 

 too, that some few are carried away on the 

 ice when the latter siirrounds the island,! 

 but as natural infirmity and ice are agents; 

 which may be supposed to operate on botk 

 sexes alike, it will be hard to believe that 

 proportionately they cause the loss of more 

 females than males. It is more probable 

 that the increase even at the rate mentioned 

 did not occur. If not, the only explana- 

 tion is that all females on the island did 

 not bear young and that a considerable 

 percentage of the young that were born 

 did not reach maturity. 



The reason why all the young do not 

 reach maturity is probably that in some 

 instances the extreme young are eaten by 

 the adults. There also may be present 

 on the islands the same cause which re- 

 sulted in . the death, in the National 

 Zoological Park, where several pairs were 

 deposited by the Semidi Company for ex- 

 perimental purposes, of the only litter of 

 blue foxes born there that attained any: 

 growth whatever, namely, Uncinaria. It 

 would seem that the provision, as far as 

 possible, of a male consort for every breed- 

 female, would in large measure provide 

 against the eating of the young, if we are 

 to believe that the male is instrumental iit 



