COMMON MAMMALS OF WESTERN MONTANA. 



33 



novance when the hay is being cut, for they frequently clog the sickle 

 bar. In cases where the mice suddenly increase enormously in num- 



Fig. 24. — Diagram of meadow mouse runway. 



bers they may constitute a serious plague, as happened in Nevada in 

 1907, when they destroyed the alfalfa fields in whole valleys and 

 caused a loss of sev- 

 eral hundred thou- 

 sand dollars. (Fig. 

 26.) To avoid the 

 possible occurrence 

 of such a plague, 

 careful watch of 

 these mice should be 

 kept and any great 

 increase in their 

 numbers reported at 

 once, so that repres- 

 sive measures may 

 be promptly taken. 



Probably the most 

 serious damage 

 caused by meadow 

 mice is in neglected 

 orchards, in which 

 rank vegetation af- 

 fords ample shelter. 

 (Fig. 27.) In one 

 such orchard, con- 

 taining 10 acres of 

 10-year-old trees, an 

 examination of 243 

 trees showed that 32 per cent had been wholly girdled and killed, 

 that 45. S per cent had been partially girdled but not killed, and that 



484 



shelter for meadow mice. 



