MAMMAL ENEMIES OF MICE. 41 



grass, corn, blueberries, and cultivated grapes show a somewhat mis- 

 cellaneous diet. A writer in Forest and Stream states that in the 

 stomach of a gray fox (Urocyon cinereoargenteus) , taken at Mil ford, 

 Conn., he found rabbit hair, parts of a field mouse, sweet corn, pieces 

 of apple, remains of a woodcock, and some leaves.* 



That shrews destroy many field mice is certain, although the evi- 

 dence is largely circumstantial. It is known that they eat dead mice 

 that have been caught in traps. It is proved that they are able to 

 capture a live field mouse in its burrow by the fact that when both 

 animals are confined in the same cage the shrew kills and partly eats 

 the other animal. Shrews are often trapped in the burrows of field 

 mice, and it is highly probable that they habitually feed upon the 

 rodents. As they eat only the flesh and blood of their victims it is 

 difficult to identify their food by stomach examinations. 



The common brown rat {Mus norvegicus) is an enemy of field mice 

 where both occur in the same locality. On the Potomac flats, south 

 of Washington, D. C, both rats and meadow mice (M. pennsylvani- 

 cus) are abundant. On various occasions, while trapping mice there, 

 specimens in small cage traps were destroyed by rats. Several times 

 I had occasion to uncover burrows and runways of the mice by 

 removing piles of dry weeds. On the following mornings I found 

 that rats had enlarged the burrows in pursuit of mice, and the 

 remains of fur and stains of blood on the ground showed that the 

 pursuit had been successful. It is unfortunate that rats are even 

 worse pests than the field mice they destroy. 



Of the other wild mammals that destroy field mice — wolves, coy- 

 otes, lynxes, raccoons, and opossums — it may be said that the mouse- 

 eating habit is not always prominent and that their economic status 

 can not be determined by it alone. On the whole, however, their 

 general effect in checking the increase of rodents must be regarded 

 as an important item to their credit. 



DOMESTIC MAMMALS. 



Some of the domestic animals assist in the destruction of field mice. 

 Cattle and horses in pastures undoubtedly trample upon and destroy 

 many mice, especially the young. Hogs in fields and Avood lots root 

 them from burrows and nests and eat them. Aristotle mentions the 

 ancient practice of turning swine among mice ; ' to root up their 

 runs." 6 But the more important of their enemies among domestic 

 animals are dogs and cats. 



Dogs follow the farmer to the field and at plowing and harvest are 

 ready to pounce upon and kill every mouse that is uncovered in fur- 



« Forest and Stream, vol. 55, p. 464, Dec. 15, 1900. 



& Aristotle's History of Animals, Book 6, chap. 30, p. 178, Bonn's edition, 

 London, 1862. 



