they cutting this dead wood, and why a dam across 

 a rocky flat, a place across which water never 

 flowed? A dam of dead timber across a dry flat 

 appeared to be a marked combination of animal 

 stupidity, but the beavers knew what they were 

 doing. After watching their activities and the 

 progress of the dam daily for a month, I realized 

 that they were doing development work, with the 

 intention of procuring a food-supply. They com- 

 pleted a dam of dead timber. 



At least two accidents happened to the build- 

 ers of this dead-wood dam. One of these occurred 

 when a tree which the beavers had gnawed off 

 pinned the beaver that had cut it between its end 

 and another tree immediately behind the animal. 

 The other accident was caused by a tree falling 

 in an unexpected direction. This tree was lean- 

 ing against a fallen one that was held several feet 

 above the earth by a boulder. When cut off, in- 

 stead of falling directly to the earth it slid along- 

 side the log against which it had been leaning 

 and was shunted off to one side, falling upon and 

 instantly killing two of the logging beavers. 



The dam, when completed, was eighty-five feet 

 144 



