The supply of roots ran out and the bark of the green aspens was eaten off, and still this mountain region was white with winter and the pond locked and sealed with ice. Beavers are strict vegetarians. There were trout in the pond, but these were not caught; nor were the bodies of the starved ones eaten, as sometimes occurs among other animals. The beavers must escape from their now foodless prison or perish. Spring examinations which I made indicated that they had tried to escape through the long tunnel which had been made to obtain the aspens, but this had nearly filled with ice. They had then driven several feet of a new tunnel, but evidently found they could not accomplish it through the frozen, gravelly earth. Beavers are engineers--the handling of earth in building dams or in the making of canals is as much in their line as tree felling--but cutting and tunnelling 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 powerful 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. Tracks of six muddy-footed fellows on the snow at the outer end of the successful tunnel told the number who survived the winter’s food-shortage. Spring came, and warmth and flood water broke up the ice on the pond about a month after they escaped. No young beavers were seen. These surviving beavers lived in bank holes along the stream until summer. Then they wandered away. Late that August they, or six other beavers, came to the place. They completed the dam and repaired the house, and by mid-October had a huge pile of food stored in the pond for the winter. CHAPTER XVI DOG-TOWN DIGGINGS