b 



100 

 90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 

 



Shrubs 



Forbs 



Grass 



Aug Sep 



Nov Dec 



Month 



r 

 Feb 



Apr May 



Figure 9 . 1 



Autumn 



Yearlong trend in mule deer use of browse, 

 forbs, and grasses in the Missouri River 

 Breaks, Montana, 1960-1964. 



General comments about forage use during autumn from 

 Mackie (1970) and Knowles (1975) were supplemented by data 

 from late autumn for 1976-1986 (Table 9.1). The species of 

 forage used was highly variable during autumn, but use of 

 shrubs generally exceeded use of forbs. Exceptions occurred 

 when first-year growth of yellow sweetclover was available and 

 remained succulent into autumn (1978, Table 9.1). Sweetclover 

 was important as long as it remained green, even into winter. 

 Use of grasses during autumn was also variable among years and 

 considerable use of Sandberg bluegrass was recorded during 

 autumn 1977, 1985, and 1986 (30-48% of diet). This increased 

 use of grasses resulted from autumn "green-ups" that occurred 

 after substantial late summer-early autumn rains . Autumn use 

 of green grasses also occurred during 1961 and 1962 (Mackie 

 1970). Relatively heavy use of grasses (14%) also occurred 

 during very dry autumns (1980 and 1984). The majority of that 

 use was of dry grass, apparently eaten incidentally in 

 attempts to eat the few remaining green leaves . 



The major forage species used during autumn of most years 

 was rabbitbrush, primarily rubber rabbitbrush, but also green 

 rabbitbrush. Use of rabbitbrush was seldom great prior to 

 about the first part of October, when flowering was finished 

 (Knowles 1975). Rabbitbrush not the most important forage 

 species only during autumns when sweetclover remained green 



240 



