The Beaver: Builder of an empire
By Robert A. Hedeen, Naturalist
Three centuries ago, the beaver ranged throughout the North American continent, and its importance in the human history of all of this vast land cannot be overemphasized. John Jacob Astor and others became millionaires trading for their pelts, and the quest for their hides lured many mountain men to the frontiers of the early West and led to the exploration and settlement of that area. The Indians of the West considered the beaver to be god-like and were aware of the similarity of his ways to their own.
They were trapped so extensively for their luxurious fur that they were almost extirpated by the mid 19th century. Beaver were fairly common in Illinois until about 1850 and had all but disappeared by 1900. Beaver restocking in Illinois began in 1929 with the introduction of a pair at the Savanna Army Depot by the U. S. Fish and Wildlife Service. Additional re-stockings were made in the following years, and, with the migration of emigrants from neighboring states, today, the beaver is present in considerable numbers in most of our state, including the Rock River Valley.
The beaver holds the honor of being the largest member of the rodent family found in Illinois; 30 pounds being the average weight, but some have been known to weigh up to 60 pounds. It is, therefore, larger than the porcupine that formerly lived here.
In recent decades, it has been commercially trapped in Illinois, mainly in a 31-county area in the central part of the Sangamon Valley. For example, the Illinois Department of Conservation reported 8,918 were legally trapped during the 1979-1980 season. During the past 15 years or so, the market for natural furs has plummeted, and fewer trappers now seek them and other fur-bearers.
In appearance, the beaver reminds one somewhat of an overgrown groundhog (the groundhog or woodchuck is a member of the squirrel family), with a large, black, hairless, paddle-shaped tail. He has small front paws, but his hind feet are large with webbed toes. The ears and eyes are small, and his coat is coarse at the end until treated by the furrier. The most distinctive anatomical feature of the beaver is its four, large, curved front teeth. These incisors are about two and one-half inches long. They grow constantly, and the cutting edge is replaced as wear occurs, an ideal arrangement for an animal that can gnaw through a four-inch tree in 20 minutes!
Beavers live in a home in banks that are reached by a burrow below the waters surface. If the depth of the water is sufficient, they construct aquatic lodges of the trees they have harvested. The entrance to the lodge is always under water, but the resting ledges inside are above the water level and covered with dry wood chips. To make sure the entrance to their abode is always underwater, a dam of cut trees, branches, and clay may be constructed to raise the water level above the entrance.
The trees most easily harvested are willows, birches, cottonwoods, and aspens, but sometimes the rodent will undertake the formidable task of felling hardwoods. Some individuals believe the tree-cutting habit of beavers is destructive to the environment, but others consider him to be a master forester and conservation agent whose actions store water to prevent drought and to alleviate overcrowding of woody vegetation. They are vegetarians that almost exclusively utilize as food the bark of many trees and shrubs, leaves, cornstalks, and aquatic plants, such as the roots of water lilies.
The flattened tail, the emblem of beaverdom, serves to balance them while they are cutting down a tree and as an efficient rudder when swimming. It is also used as a communication device to warn others of a possible enemy. When danger approaches, the tail is slapped sharply against the surface, producing a pistol-like report that can be heard for a considerable distance.
In northern climes, when the beavers home pond or stream freezes over, one wonders how he can move about under the ice without suffocating. To accomplish this, the beaver exhales as powerfully as he can, and a large bubble forms between the ice and the water.
By contact with the ice and water, the carbon dioxide in his breath is quickly removed and replenished with oxygen. The animals nostrils are located at the very tip of his nose, so he simply pokes them into the bubble and inhales a fresh supply of oxygen.
I have seen beavers along the Kishwaukee and Rock rivers in our valley and have heard the slap of their tails against the surface in the Borderline Canoe Area of Minnesota and Canada, as well as a mountain lake in the Adirondack Mountains in New York. That, combined with the eerie voice of the loon, is truly The Call of the Wild.
Dr. Robert Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960-1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.