230 CONSERVATION OF CANADIAN WILD LIFE 



of which the numbers of the marten are, to a large extent, 

 correlated. This would indicate that a predatory animal 

 such as the fisher, which feeds on all kinds of mammals, 

 including the porcupine, birds and their eggs, fish, frogs, 

 and wild fruits, is subject to periodic fluctuations inde- 

 pendent of the fluctuations of any one kind of diet. 



Mink. — The mink is one of our commonest fur-bearing 

 animals, and a study of the Hudson's Bay Company's fur 

 returns shows that it is not only subject to fairly regular 

 periodic fluctuations, but that there has not been any 

 marked diminution in their numbers. The years of maxi- 

 mum abundance were: 



1846, 1858, 1869, 1878, 1885, 1897, 1903., and probably 

 1914. 



The periodic fluctuations occurred, therefore, in cycles 

 of 12, 11, 9, 7, 12, 6, and 11 years, giving an average periodic 

 cycle of 9.7 years. While the chart shows a fairly regular 

 aggregate increase, the years of maximum abundance lack 

 the precise regularity that we have seen in many of the 

 animals already discussed. 



The food of the mink consists primarily of fish, muskrat, 

 and rabbit. We know very little about the fluctuations of 

 the fish portion of the diet, but a comparison of the periods 

 of greater abundance shows some correlation with the years 

 of abundance of rabbit. 



Skunk. — The periodic fluctuations of the skunk are shown 

 in the accompanying chart, and, while the cycles are not 

 regular throughout, they indicate that this animal is sub- 

 ject to very distinct periodic fluctuations in numbers. 

 Feeding mainly on an insect diet composed chiefly of grass- 

 hoppers during the summer months, supplemented by a 

 diet of mice, snakes, and other small animals during the 

 rest of the year, the diet of the skunk is of too general a 

 character to permit the correlation of its abundance with 

 any particular class of diet. 



