2QO ECONOMIC MAMMALOGY 



snails, mussels, crustaceans, insects, fishes and occasionally small 

 birds. 56 The muskrats at one Minnesota locality "had been cutting down 

 some young shoots of poplar, about the size of a lead pencil in thick- 

 ness, from which the leaves had been stripped and eaten, as shown by 

 the stomach contents." 57 Their mussel-eating habit is well known and 

 has been mentioned by many writers. The fishes caught by muskrats 

 are mostly sluggish species of little value, such as carp. On the other 

 hand, it is asserted that in the north they are helpful to fish by keeping 

 airholes open, thus aerating the water. 58 A muskrat was seen catching 

 a salamander, and they are known to eat crippled ducks during the hunt- 

 ing season. 59 



Muskrats sometimes damage river levees, reservoir dams and canal 

 banks by their burrows, thus flooding fields, or injuring rice fields by 

 draining them at the wrong season. Such damage may often be pre- 

 vented by 3-foot woven wire fences, the lower edge set 6 inches be- 

 neath the surface of the soil. 60 In Europe the introduced muskrats are 

 said to have endangered whole systems of waterways by burrowing 

 into the embankments and strict regulations have been issued to curtail 

 their spread. 61 Although muskrats are said to sometimes injure rice 

 fields, it has been said that they are necessary to the existence of wild 

 rice fields. 62 



Since its introduction into Europe the muskrat has spread very 

 rapidly and become locally abundant. Because of its damage to crops 

 of corn, potatoes, kohlrabi, turnips, carrots, frogs, mussels and fish, 

 and the damage done to roads and embankments by its burrows, it is 

 proposed to prohibit its introduction into other localities. In 1921 from 

 60,000, to 80,000 European muskrat skins were sold at prices com- 

 paring favorably with those paid for American skins. 63 



The nutria of South America is "a little rat known as coypu, some- 



56 Bailey, N. Amer. Fauna, No. 49, p. 102, 1926. Lantz, Farmers' Bull, No. 396, 

 pp. 15-21, 1910; No. 869, pp. 8, 10, 1923. Arthur, The fur animals of Louisiana, pp. 

 232-243, 1927. Johnson, Roosevelt Wild Life Bull, in, 247, 1925. The muskrat in 

 Czechoslovakia, The Nautilus, xxxvm, 103, 1925. 



57 Johnson, Notes on the mammals of northern Lake County, Minnesota, Journ. 

 Mammalogy, in, 37, 1922. 



58 American Forests and Forest Life, xxxiv, 120, 1928. 

 50 Warren, Mammals of Colorado, p. 106, 1910. 



60 Bailey, N. Amer. Fauna, No. 49, p. 102, 1926. Burnett, Office Colorado State 

 Entom. Circular No. 25, p. 13, 1918. Lantz, Farmers' Bull., No. 396, 1910; No. 869, 

 1923. 



61 Ahrens, Muskrats in central Europe, Journ. Mammalogy, n, 236-237, 1921. 



62 Lucas, A viewpoint on the disappearance of rice beds, Fins, Feathers and Fur, 

 No. 36, pp. 123-124, 1923; Journ. Mammalogy, v, 140, 1924. 



63 The muskrat in Europe, Nature, cxxni, 775, 1929. The muskrat in Czecho- 

 slovakia, The Nautilus, xxxvm, 103, 1925. 



