FLUCTUATIONS OF FUR-BEARING ANIMALS 229 



The marten not only feeds upon the rabbit but it also 

 feeds extensively on mice, and the fluctuations in the abun- 

 dance of the latter animals would no doubt influence the 

 abundance of the marten. In addition its omnivorous diet 

 includes other small rodents, birds and their eggs, insects, 

 frogs, and such vegetable products as nuts and berries. 

 But its chief diet would appear to consist of rabbits, mice, 

 and birds. 



Fisher. — The largest of our martens, namely, the fisher, 

 is not abundant in any part of its range, which extends 

 throughout our northern forests, and during the last fifty 

 years the nmnber of fisher taken annually is little more 

 than half the number taken in years previous. Like its 

 smaller relative the marten, the fisher shows marked peri- 

 odic fluctuations in numbers, as will be seen from the ac- 

 companying chart of the returns of the Hudson's Bay Com- 

 pany. The absence of a very marked difference in numbers 

 between the years of maximum and minimum abundance is 

 probably due to the fact that fisher is not at any time so 

 abundant as other animals which display such a marked 

 difference between the years of maximum and minimum 

 abundance. 



The records show that the years of maximmn abundance 

 of the fisher were: 



1840, 1850, 1860, 1870, 1879, 1890, 1898, 1908. 



The extraordinary regularity of the periodic fluctuations 

 which occurred in cycles of 10, 10, 10, 9, 11, 8, and 10 

 years is very striking in this animal, which has an average 

 periodic cycle of 9.7 years. The slight deviation from the 

 regular ten-year cycle from 1870 onwards, is probably due 

 to disturbances in the country of its environment. 



It is of interest to note that the periodic cycles of the 

 fisher, while remarkably regular, are apparently indepen- 

 dent of the periodic increases of the rabbit, with the increases 



