DAMAGE TO PROPERTY BY MAMMALS 49 



vegetation cannot again get a foothold. To make matters worse, sand 

 and gravel from the slopes, washed out into the valleys, often bury and 

 ruin fields and meadows in the lowlands and choke the channels of the 

 streams. Then the more rapid run-off from barren hills, where the 

 water is no longer absorbed by soil and vegetation and thus retarded 

 in its movement, fills the choked channels, overflows and causes dis- 

 astrous floods. This is not an imaginary picture, but a description of 

 just what has happened in various parts of the United States and other 

 parts of the world. In the semi-arid West and portions of the South 

 especially have many hills been denuded by erosion and many fields 

 been ruined by deposition of the debris. All this more or less directly 

 affects valuable game and other wild animals. Where slopes are so gen- 

 tle that destruction of vegetation by overgrazing and trampling of 

 domestic stock does not cause extensive erosion, it often results in the 

 substitution of worthless weeds for the original vegetation. 11 



In the preceding chapter we have seen that predatory mammals de- 

 stroy $20,000,000 to $30,000,000 worth of livestock annually in the 

 United States. 12 A considerable part of this loss consists of meat, but 

 in addition it includes the skins, a large amount of wool and many 

 horses. 



11 Ligon, Wild life of New Mexico, New Mexico State Game Commission, pp. 

 35-49, 1927. Reynolds, Grazing and floods: A study of conditions in the Manti Na- 

 tional Forest, U. S. Forest Service Bull. 91, 1911. Colville, Forest growth and sheep- 

 grazing in the Cascade Mountains of Oregon, U. S. Division of Forestry Bull. No. 15, 

 1898. 



12 Bell, Hunting down stock killers, Yearbook U. S. Dept. Agric. for 1920, pp. 289- 

 301. 



