They have been often seen in the act of constructing their houses in the moonlight nights, and the observers agree that the stones, wood, or other materials are carried in their teeth and generally leaning against the shoulder.

When they have placed it to their mind they turn round and give it a smart blow with their flat tail.

In the act of diving they give a similar stroke to the surface of the water.

They keep their provision of wood under water in front of the house.

Their favourite food is the bark of the aspen, birch and willow; they also eat the alder, but seldom touch any of the pine tribe unless from necessity; they are fond of the large roots of the Nuphar lutea, and grow fat upon it but it gives their flesh a strong rancid taste.