COMMON MAMMALS OF WESTERN MONTANA. 



31 



mended for chipmunks. (Formula III or IV.) Owing to the fact 

 that house mice are sometimes able to eat out the centers of poison- 

 coated kernels of wheat or groats, the tallowed grain described in 

 Formula IV is best suited for poisoning them. 



WOOD RATS. 



Wood rats (fig. 22), called also pack rats and mountain rats, occur 

 in the mountains and along the edges of valleys throughout western 

 Montana. They are active only at night and do not hibernate. They 

 are especially fond of tender green vegetation and berries, but readily 

 eat seeds, grain, and table scraps. 



AS TICK HOSTS. 



Wood rats living in " tick country " are usually infested with 

 young wood ticks; and this fact is especially important because 



Fig. 22. — Young wood rat. 



infested animals often live in temporarily unoccupied dwellings. 

 Two shot in one of the buildings of an abandoned railroad construc- 

 tion camp were fairly covered with seed and nymphal fever ticks, 

 there being at least 100 on them. Many of these young ticks would 

 have developed into adults in the buildings where the rats were 

 killed; and, if one or both of the rats had had the spotted fever, 

 it is quite possible that any person moving into the house might have 

 contracted the disease. 



DESTROYING WOOD RATS. 



Wood rats do not readily eat loose poisoned grain but can prob- 

 ably be effectively poisoned with " biscuits " made as described in 

 Formula II, though only about half as much strychnine (1 ounce to 

 16 quarts of grain) is required for these animals. 



A number of wood rats had been living for several years in the 

 house mentioned in the woodchuck poisoning experiment described 



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