222 CONSERVATION OF CANADIAN WILD LIFE 
Foxes.—The red fox and its colour phases, cross fox, 
black fox, and silver fox, exhibit marked periodic cycles, al- 
though they are not so pronounced as those of the lynx. 
This is probably accounted for by the fact that, while the 
fox feeds upon the rabbit, especially when the latter animal 
is abundant, it also feeds largely on mice or voles, supple- 
menting this diet with game-birds of various kinds. If we 
had records of the years of mouse abundance we should 
probably find, judging from the field observations of Cabot, 
that have already been given, Preble, and others, that there 
was a correlation between the abundant years of mice and 
the abundance of foxes. 
The fluctuations in the numbers of foxes is well known to 
trappers and traders. The period of comparative abundance 
may extend over a greater number of years than is the case 
with the lynx; this is indicated in the diagrams by the fact 
that the difference in numbers between the years of abun- 
dance and the years of scarcity is not so great in the case 
of the fox as in the case of the lynx, and the reason is 
probably to be found in the fact that the fox is not so de- 
pendent upon a rabbit diet. 
As the three varieties of foxes—red, cross, and black— 
have similar feeding-habits and inhabit the same territo- 
ries, so far as the forested regions of Canada are concerned, 
it would be natural to assume that their fluctuations in num- 
bers would closely correspond. The Hudson’s Bay Com- 
pany’s returns show that this is the case, as will be seen 
by the diagram. The years of maximum abundance were 
as follows: 
Red fox: 1859, 1868, 1878, 1888, 1898, 1907. 
Cross fox: 1859-1860, 1868-9, 1878, 1888, 1897, 1907. 
Black fox: 1859-1860, 1869, 1878, 1888, 1897, 1907. 
The cycles, therefore, appeared in the following periods of 
years: 
