Once it was believed that the woodwork was first finished, and that then it was plastered, the tail being used as a trowel for this purpose. But this was a popular error. The tail is used as a rudder, and like that of a dog, is a vehicle for emotion. It is flapped even when a beaver has been tamed and domesticated, especially when the creature is startled. They have a very pretty way of carrying mud and stones in their little fore-paws, holding them close up under the throat. The wood naturally is dragged along, held in the teeth. All their work is done in the night-time, a charming sight for a lover of animals, if he can quietly remain concealed near enough for observation on a clear calm night.
A wonderful instinct, so-called, again prompts the beavers to cover their houses each autumn with fresh mud--as late in the season as they can manage it--so that it may freeze hard and keep them secure against their foe, the wolverine, a creature about the size of our common badger, which is much about during the winter. Wolverines are said to do more damage to the fur trade in smaller animals than all the other creatures of prey put together.
Their lodges are kept clean, their inhabitants always plunging into the water instead of polluting their sleeping quarters.
Sir John Richardson states that their main food consists of a large root, something like a cabbage stalk, which grows at the bottom of lakes and rivers, a yellow water-lily in fact--_Nuphar luteum_. But they eat also the bark of trees--that of the poplar, birch and willow. The latter, however, they cannot procure in winter, when the ice prevents their getting to land, so that roots are then their staple food. In summer the diet is varied by the different kinds of herbage and the berries growing near their haunts. In the part of Colorado I have already referred to, above what is called Hardscrabble Creek, in Fremont County, wild fruits, gooseberries, currants, raspberries, and other berries are in profusion. When the ice breaks up in the spring, the beavers always leave their homes to roam about until the approaching fall of the leaf makes them return; and after laying in their winter stock of wood, they then set to work to repair their homes.