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 number 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 maximum 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 
