i64 Field Museum of Natural History — Zoology, Vol. XL 



Lewis H. Morgan secured a large amount of information upon which 

 his valuable work on the Beaver* was based. A few years ago they 

 were nearly exterminated in that locality, but owing to wise protection 

 their numbers are again increasing. At the present time there are a 

 considerable number of beaver inhabiting the rivers and lakes near 

 Champion, Michigan. Several of their dams and houses may be seen 

 near White Deer Lake, and the presence of the animals is shown by 

 the numerous fresh "cuttings" along the banks. 



An adult male Beaver of average size will weigh from 30 to 45 

 pounds, but it is claimed they often grow considerably larger. Audubon 

 and Bachman mention one weighing 61 pounds, and an animal weigh- 

 ing 68 pounds is recorded by Mr. Ernest Thompson Seton.f 



Quiet streams and ponds bordered by poplars or quaking aspens 

 and willows are the favorite haunts of these animals; often a shallow 

 brook with sufficiently high banks is chosen for the site of their home. 

 The locality being selected, a pair of Beaver at once begin work to build 

 a dam and thereby make a pond of sufficient depth and suitable for the 

 use of themselves and their family; meadows are often flooded in this 

 manner until a pond is made having a depth of at least 3 or 4 feet. The 

 dam is built of branches laid one on top of the other, the several ends 

 pointing up stream and fastened down with mud and rocks ; occasionally 

 a fallen tree or drifting log is made use of, but large logs are the ex- 

 ception. The height of the dam varies, commonly ranging from 4 to 

 6 feet, but Morgan describes one ''about 35 feet long, 12 feet in vertical 

 height, and with a slope of interlaced poles on its lower face upwards 

 of 20 feet in length" (/. t., p. 119). The length of the dam depends, of 

 course, on the location and the size of the stream, or pond; there ai'e 

 numerous records of dams 500 feet or more in length and there is one 

 in Beaver Lake, Yellowstone Park, which is estimated by General S. B. 

 Young to be about 700 feet.t 



In building the dams and houses the Beaver uses his forepaws, like 

 hands, to carry the mud and stones used in their construction. The 

 branches are dragged to where they are needed, one end being held in 

 the teeth. Occasionally several dams are made one below the other, 

 thus reducing the pressure on the one highest up stream. When the 

 dam is finished to their satisfaction, they decide on a location for their 

 home. In some instances, where the banks are suitable, they dig 

 burrows, but in others they construct dome-shaped houses in the 

 ponds. In all cases the entrance to their houses is under water with 



* The American Beaver and his Works, Philadelphia, 1868. 



t Life Histories of Northern Animals, 1909, p. 448. 



X Seton, E. T. Life Histories of Northern Animals, I, 1909, p. 457. 



