Occasionally the beavers did daytime work. While on the lookout one afternoon an old beaver waddled up the slope and stopped by a large standing aspen that had been left by the other workers. At the very bottom this tree was heavily swollen. The old beaver took a bite of its bark and ate with an expressionless face. Evidently it was good, for after eating the old fellow scratched a large pile of trash against the base of the tree, and from this platform gnawed the tree off above the swollen base. While he was gnawing a splinter of wood wedged between his upper front teeth. This was picked out by catching it with the double nails of the second toe on the right hind foot. This aspen was ten inches in diameter at the point cut off. The diameter of trees cut is usually from three to six inches. The largest beaver cutting that I have measured was a cottonwood with a diameter of forty-two inches. On large, old trees the rough bark is not eaten, but from the average tree which is felled for food all of the bark and a small per cent of the wood is eaten. Rarely will a beaver cut dead wood, and only in emergencies will he cut a pine or a spruce. Apparently the pitch is distasteful to him.
One day another beaver cut a number of small aspens and dragged these, one or two at a time, to the pond. After a dozen or more were collected, all were pushed off into the water. Against this small raft the beaver placed his forepaws and swimming pushed it to the food-pile near the centre of the old pond.
At the close of harvest the beavers in Broken Tree colony pond covered their houses above waterline with mud, which they dredged from the pond around the foundations of their houses. Sometimes this mud was moved in their forepaws, sometimes by hooking the tail under and dragging it between their hind legs. Then they dug a channel in the bottom of the pond, which extended from the houses to the dam. Parallel with the dam they dug out another channel; the excavated material was placed on the top of the dam. They also made a shallow ditch in the bottom of the pond that extended from the house to the canal that united the two ponds.
The following summer was a rainy one, and the pond filled with sediment to the height of the dam. Most of this sediment came from the landslide débris or its sliding place. The old Broken Tree colony was abandoned.
Different from most animals, the beaver has a permanent home. The beaver has a strong attachment, or love, for his old home, and will go to endless work and repeatedly risk dangers to avoid moving away. He will dig canals, build dams, or even drag supplies long distances by land through difficult and dangerous places that he may live on in the old place. Here his ancestors may have been born and here he may spend his lifetime. In most cases, however, a colony is not continuously occupied this long. A flood, fire, or the complete exhaustion of food may compel him to move and seek a new home.
In abandoning the Broken Tree pond, one set of dwellers simply went up stream and took possession of the pond which the landslide had formed. Here they gathered supplies and dug a hole or den in the bank but they built no house. An underground tube or passageway connected this den with the bottom of the pond.
The remainder of the colonists started anew about three hundred feet to the north of the old pond. Here a dam about sixty feet long was built, mostly of mud and turf excavated from the area to be filled with water for their pond. They commenced their work by digging a trench and piling the material excavated on the lower side—the beginning of the dam. This ditch was then widened and deepened until the pond was completed. All excavated material was placed upon the dam.
Evidently the site for the house, as well as for the pond, was deliberately selected. The house was built in the pond alongside a spring which in part supplied the pond with water. The supply of winter food was stored in the deep hole from which the material for the house was excavated. The water from the spring checked freezing near the house and the food-pile, and prevented the ice from troubling the colonists. Beavers apparently comprehend the advantage of having a house close to a spring. This spring commonly is between the main house entrance and the winter food-pile.
Their pond did not fill with sediment. As the waters came entirely from springs they were almost free of sediment. After eighteen years of use there was but a thin covering of sediment on the bottom of the pond. Neither brook nor stream entered this pond. Was this pond constructed in this place for the purpose of avoiding sediment? As beavers occasionally and with much labour build in a place of this kind, when there are other and easier near-by places in which to build, it may be that this pond was placed here because it would escape sediment. This was the founding of the Spruce Tree colony. It is still inhabited.