14 CIRCULAR 925, U. S. DEPARTMENT OF AGRICULTURE 
a small part of the plant cover. Many other plant species in addition 
to those listed furnish some forage, but the contribution of each is 
extremely small except in a few areas. 
Blue grama, a desirable and highly palatable forage species in the 
Southwest and Plains regions, is utilized only very lightly on the Inter- 
mountain winter sheep ranges. Average use of the herbage of this 
species was only 20 percent. 
Bearded bluebunch wheatgrass, considered to be one of the major 
forage species on the spring-tfall ranges of Utah and Idaho, is found on 
only a few of the foothill areas of the winter ranges, and is utilized only 
about 30 percent. 
Bottlebrush squirreltail, a species generally considered to have low 
palatability on spring-fall and summer ranges, is one of the most palat- 
able of all winter forage species. The basal leaves of this plant begin 
to grow in the late fall and they remain green and succulent during 
the winter. Sheep relish this green foliage. Only scattered plants of 
squirreltail occur on the heavily grazed winter ranges. However, under 
moderate grazing or protection, this species increases in abundance on 
the foothill areas. 
More exact information on the relative importance of several plants 
as forage was obtained within the seven moderately grazed range 
pastures during the period 1935-45 (table 2). Of the forage used 
_ during this period, shrubs made up 59 percent, grasses 36 per cent, and 
forbs 5 percent. Seven species contributed almost 95 percent of the 
total forage. Five of these—winterfat, shadscale, Indian ricegrass, 
galleta, and sand dropseed—produced 80 percent of the herbage and 
furnished 88 percent of the forage. 
Differences between the proportion of total herbage produced and 
that utilized as forage are due primarily to differences in palatability, 
although several other factors such as growth habits of plants also 
influence the degree of utilization. As table 2 shows, the more palat- 
able species—winterfat, Indian ricegrass, galleta, bud sagebrush, and 
globemallow—contributed a higher proportion of the forage than of the 
total herbage. The species of lower palatability—shadscale and sand 
dropseed—provided a lower proportion of forage than of herbage. 
PERIODIC TRENDS IN UTILIZATION 
When sheep first begin to graze a winter range they select primarily 
the choicest portions of the more palatable forage species such as the 
seed stalks of black sagebrush and Indian ricegrass. At later intervals 
as the choicer forage is consumed, more of the moderately palatable 
forage is eaten. Toward the end of a winter grazing period, sheep 
subsist mainly on the less palatable species. 
This pattern of utilization is typical of both the early and midwinter 
grazing periods when the vegetation is cured and dry, and little if any 
new erowth is available to the sheep. Table 3 shows the percentage 
utilization of several forage plants during a 40-day midwinter period on 
a typical moderately grazed range allotment. During the first 10 days, 
sheep ate 45 percent of the globemallow, 40 percent of the black sage- 
brush, and 35 percent of the Indian ricegrass herbage, and only small 
amounts of bud sagebrush, winterfat, galleta, and shadscale. During 
the second 10-day interv al, rather heavy use of globemallow, black 
sagebrush, and Indian ricegrass continued, but during the third interval 
