THE BALANCE OF NATURE 19 



upon mice. Therefore the clover crop may depend upon the number 

 of enemies of the mice in the neighborhood, which in turn would de- 

 pend upon the number of cats. Cabot has furnished an illustration 

 that deserves to rank with Darwin's. In Labrador, mice had been 

 abundant and bears, wolves, wolverenes and other carnivorous mam- 

 mals, birds of prey and even trout were feeding largely upon the ro- 

 dents. 



In the spring of 1906 the mice disappeared with the snow. . . . With the vanishing 

 of the mice the change in the visible life of the country was remarkable. The 

 falcon cliffs were deserted. ... In the trout reaches of the Assiwaban fish were 

 numerous, but they were living on flies now, with what minnows they could get, 

 and were no longer mousey, but good and sweet. Our bear of the year were living 

 on berries. Ptarmigan were all but wanting, old birds and young. It is fair to 

 suppose that in previous years they were let alone by their natural enemies in 

 the presence of the superabundant mouse supply. . . . Once the wolves found 

 themselves upon the hard times of early 1906 they may have sought the caribou 

 and started them to move. They certainly did move, as the twelve or fifteen 

 hundred carcasses [killed by the Indians] at Mistinipi that year went to show. 

 The bearing of the mouse situation on the human interests of the region is 

 easy to see. It affected all the game, food game and fur. The abundance of mice 

 tended to build up the ptarmigan, which are of vital importance in the winter 

 living of the Indians through the whole forested area to the Gulf. Likewise it 

 built up the caribou herd by providing easier game than they for the wolves. The 

 departure of the mice did the reverse, reducing the deer and ptarmigan. . . . 

 Nor were the shore people by any means untouched. All their land game came and 

 went, was plenty or wanting, shy or easily taken, according to the supply of mice. 

 London and St. Petersburg, easily, were affected through their great fur trade. 9 



Innis also discusses the fact that the abundance of mice upon which 

 certain fur-bearing mammals feed affects the fur supply of the world. 10 



9 Cabot, Labrador, Boston, 1921 ; quoted in Allen, Journ. Mammalogy, in, 56-57, 

 1922. Hewitt. The conservation of the wild life of Canada, pp. 214-215, 219, 1921. 



10 Innis, The Canada fur trade, pp. 90-91, 1927. 



