12 



THE MUSKRAT. 



seems to be collected accidentally ^Yith the roots. From the part of 

 the structure above the water an interior chamber is excavated, from 

 which two or three passages lead downward through the mass to the 

 water, reaching it at points well below the frost line. If the water 

 is shallow, the animals excavate deej^er channels leading from the 

 house to various parts of the pond. 



The houses are mostly for winter shelter and food and are seldom 

 used as receptacles for the 3^oung. A single family usually occupies 



a house. Occasionally, however, when driven from other houses or 

 when excluded from underground burrows by barriers of ice or 

 frozen ground, a larger number may temporarily occupy a house. 



When banks of streams or ponds are high enough for the purpose, 

 muskrats burrow^ into them. Entrances to the tunnels are almost 

 always under water, and the approach to them is, if possible, by 

 channels of sufficient depth to prevent ice from closing the passage. 

 The tunnels extend upward into the bank above the level of the 



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