WOODLAND  ENGINEERS

Originally published in our SPRING 2000 edition

Beavers are usually about 30 inches long, and weigh 30-40 pounds. They stand less than 12 inches high, and the broad, flat, scaly tail is about 10 inches long. The body is plump, the back arched, the neck thick, the hind feet webbed, and all toes are clawed. The fur is usually reddish-brown above and lighter or grayish below. The skull is massive, with marked ridges for fixing the muscles that work the jaws.

The two front teeth on either jaw are like those of other rodents, wearing away more rapidly behind so as to leave a sharp, enameled chisel edge. With these the beaver can cut down large trees. It usually selects trees 2 to 8 inches in diameter, but it can fell trees with diameters as large as 30 inches.

Beavers have a pair of anal scent glands, called castors, that secrete a musklike substance called castoreum, probably for marking territories. The animals tend to be monogamous and have a life span of 20 years or more. The female has one litter a year, usually of two to four young.

Beavers are social animals. In areas where food is abundant and the locality secluded, the number of families in a beaver community is rather large. The so-called beaver lodge is a unique structure. Three distinct kinds exist, their differences depending on whether they are built on islands, on the banks of ponds, or on the shores of lakes.

THE  LODGE
The island lodge consists of a central chamber, with its floor a little above the level of the water, and with two entrances. One of these, the "wood entrance," is a straight incline rising from the water, opening into the floor of the hut. The other approach, the
"beaver entrance," is more abrupt in its descent to the water. The lodge itself is an oven-shaped house of sticks, grass, and moss, woven together and plastered with mud, increasing gradually in size with year after year of repair and elaboration. The room inside may measure 8 feet wide and up to 3 feet high. The floor is carpeted with bark, grass, and wood chips, sometimes with special storerooms adjoining.

The pond lodge is built either a short way back from the edge of the bank, or partly hanging over it, with the front wall built up from the bottom of the pond. The lake lodge is built on the shelving shores of lakes.

THE  DAMS
The dams used by beavers to widen the area and increase the depth of water around their homes are constructed either of sticks and poles or more firmly and solidly of mud, brushwood, and stones. As time goes by the beaver repairs and adds to the dam. Floating material lodges there, and vegetation growing on the top adds its roots to the strength of the dam.

Frequently the beaver builds a smaller dam downstream in order to back up some water against the original dam and thus decrease the pressure of water on it from the other side. The dams are about 5 feet high, usually more than 10 feet wide at the base, and narrow at the top. Beaver ponds eventually fill with sediment, and the animals move to a new location. The abandoned area becomes good meadowland.

Although the beaver is a powerful swimmer, it has difficulty dragging over the ground the logs and branches it needs for building and for food. Colonies of beavers therefore often dig canals from the pond to a grove of trees. Such canals are up to 3 feet wide and deep and often a few hundred yards long. The timber is then readily floated down the canal toward the pond.

THE KAWISHIWI RIVER   "ca - WISH - e - we"

Ojibwa (Chippewa) "place of many beaver houses"

Many of you probably remember paddling part of your canoe trip on the Kawishiwi River. Whether it was leaving from our docks, or returning to our base from an outlying landing, you had the chance to see some of the beaver lodges that still punctuate the shoreline.