Beaver Dam, Lodge, and Pond, near Ishpeming, Michigan.
The entire construction was evidently made with a correct knowledge of the strength that was necessary to resist the outward pushing force that was exerted against it. When an engineering work of this nature, so great in proportion to the power and intelligence of its constructors, is examined, and its fitness for the object for which it has been made and for the duty it has to perform, has been ascertained, it occurs to the mind to consider whether such operations are the results of instinct or of some exceptional degree of reasoning faculties.
Within the pond was the lodge. It was placed near to the bank which by its curve gave the most shelter. It was shaped like a rounded beehive and measured nearly eight feet in diameter, and twenty-two feet over the outer circumference. The exterior was composed of small sticks cut in nearly equal lengths, and so intertwined, crossed and plastered with mud as to give great cohesion.
There were three entrances, two of them leading in the direction of the bank, and one towards the middle of the pond. The former are said to be used as the approaches to the inner room, and the latter for escape. All these entrances were below the surface of the water, and ran upwards into the dwelling room which was a dry comfortable apartment, the floor being well above the highest water level.
The beavers, when cutting the branches of the trees into the requisite lengths, seem to have an accurate perception of what is necessary for the special works that are then in progress. Thus in their lodges, which are chiefly made for shelter and warmth, the sticks composing them are small, and when well plastered together with mud make a good compact residence. The dams which have a different purpose are differently built, and in these the sticks are often of considerable size, being sometimes fully six feet long. Some of the cuttings, however, are small and many of them are like short poles, having a diameter about the size of a man’s arm.
The methods of forming the foundations of their dams are most practical, and the manner in which earth, stones, mud, twigs, fibres and brushwood are combined, not only show marvellous ingenuity, but prove that beavers work perseveringly together with incessant labour for long periods of time.
The superstructures are differently made. They are composed of a framework of sticks placed at various angles inclined upwards. This open form of disposition appears to be intended to allow the surface waters to escape to the extent that is necessary to keep the level of the pond at the uniform height that is desirable.
Although it is usually considered that the intelligence of the beaver communities is chiefly shown by their ability in raising works of construction, I was informed by men who were intimately acquainted with the habits of these animals, that a greater sagacity was displayed in the methods adopted by them, under especial circumstances, for maintaining communications between their dwelling places and the woods from which they obtained their food and building materials.
These rare and singular works of excavation are called beaver canals. One of these, which was the largest that was known to occur in this part of Michigan, I examined with the utmost attention. It was an open trench or channel, about half a mile long, two to three feet wide, and from one to two feet deep. The bottom was of the same width as the surface, the sides being perpendicular. It connected a large pond with the adjacent forest. The canal was sufficiently large to give room for a beaver to swim in it and push in front of him the cutting of birchwood that was to be conveyed to the lodge and there stored for the winter supply of food. The depth was enough for the purpose of concealment.