A CURIOUS EXPERIENCE 331 



tree of average size yields food only to beasts 

 of exceptional type, of which the most con- 

 spicuous in North America are the tree-porcu- 

 pine and the beaver. Even these eat only the 

 bark; no vertebrate, so far as I know, eats the 

 actual wood of the trunk. 



These bark-eaters, therefore, have almost no 

 food rivals, and the forest furnishes them food 

 in limitless quantities. The beaver has de- 

 veloped habits more interesting and extraor- 

 dinary than those of any other rodent — in- 

 deed as interesting as those of any other beast 

 — and its ways of life are such as to enable it 

 to protect itself from its enemies, and to insure 

 itself against failure of food, to a degree very 

 unusual among animals. It is no wonder that, 

 when protected against man, it literally swarms 

 in its native forests. Its dams, houses, and 

 canals are all wonderful, and on the Tourilli 

 they were easily studied. The height at which 

 many of the tree trunks had been severed showed 

 that the cutting must have been done in winter 

 when the snow was deep and crusted. One 

 tree which had not fallen showed a deep spiral 

 groove going twice round the trunk. Evi- 

 dently the snow had melted faster than the 

 beavers worked; they were never able to make 

 a complete ring, although they had gnawed 



