FAMINE IN BEAVER-LAND 213 
nelling through gravelly, frozen earth is near 
impossible for them. 
They then attempted to cut a hole upward 
through the two feet of ice, as I found out later 
when the ice was breaking up. And they had 
almost succeeded. On the edge of their house 
they had raised a working foundation of mud and 
sticks and gnawed upward to within three or 
four inches of the surface. Beavers are expert 
gnawers and have been known with their power- 
ful teeth and strong jaws to gnaw off and fell 
trees more than two feet in diameter. Perhaps 
they might have succeeded eventually, but they 
apparently found another and better way out 
of the pond. 
What they finally did was to tunnel out 
through the unfrozen earth beneath the bottom 
of the dam. They had commenced on the 
bottom of the pond and driven a fifteen-inch 
tunnel nearly level through the base of the dam, 
and a foot or two beneath the water and below 
frostline. This came out in the ice-covered 
stream channel, beneath the frozen earth. As 
this tunnel had to be dug under water, it must 
have been slow work and to have constantly 
called for relay efforts. When a working beaver 
had to breathe it was necessary for him to swim 
to the house and climb up to the floor, above 
water level, in order to obtain air. 
