Deer mouse populations apparently responded to the size of the previous year's 

 pine and fir seed crop. Mice reproduce frequently and their population can respond 

 rapidly to increased food supplies. Figure 6 supports this hypothesis when the average 

 catch of these mice per 100 trap nights at Bluesky is compared with the pounds of coni- 

 fer seed dispersed per acre the previous year. For example, from 1949 to 1950, the 

 mouse population declined from nearly seven animals per 100 trap nights to less than 

 three--similar in magnitude to the drop in seed crop from 1948 to 1949, In 1951, the 

 mouse population reached its lowest point, probably because of the extremely small seed 

 crops (both pine and fir) in 1950. A fair seed crop of pine in 1951 was followed by a 

 recovery in the numbers of mice caught in 1952. The 1952 conifer seed crop was poor; 

 however, the mouse population did increase in 1953. Heavy crops of other desirable foods 

 might have been available that year. 



- 6 



'E 

 a 



TO 



o 

 o 



lOr 



8 - 



«- 6 



IV 

 Q. 

 w 



a> 

 .o 



E 



3 



UJ 



O 



2- 



PONDEROSA PINE 



DOUGLAS-FIR 

 MICE 



SEPT. 



1948 



i 



;3 O- 



-a. 



■a. 



MAY SEPT. 



1949 



_L 



M2. 



MAY SEPT. 



1950 



L 



MAY SEPT. I MAY SEPT. | MAY SEPT. 



1951 I 1952 I 1953 



SEPT. MAY SEPT. 



53 1954 



- 4 



Figure 6. — Comparison of the number of mice trapped per 100 trap nights and the amount 

 of seed dispersed per acre, Kootenai National Forest, 1948-1954. 



10 



