234 CONSERVATION OF CANADIAN WILD LIFE 
dict to a large extent the years of abundance of many of our 
important fur-bearing animals is sufficient to warrant a 
more careful and intensive study of these phenomena and the 
underlying causes. Is the decrease in abundance due to 
starvation, owing to the disappearance of the main article 
of diet, or does a decrease in the food supply affect the fer- 
tility of the predatory species? According to MacFarlane, 
the females are said to be more prolific when the numbers 
of the animals constituting the main food are on the in- 
crease. Does the overfeeding consequent upon the great 
abundance of food affect, in an adverse manner, the repro- 
ductive powers of the predatory species? All these are 
problems which demand further close study in the field. 
It is hoped that such studies, extending over a number 
of years, may be undertaken by competent investigators 
in the future, as such a knowledge of the causes of these 
fluctuations is essential to an adequate understanding of a 
subject having economic possibilities of a very high order. 
