 In Great Basin , big sagebrush is a primary forage species and is used throughout the year ; in southern Idaho it forms 16 – 21 % of the black @-@ tailed jackrabbit summer diet . <unk> ( <unk> spp . ) , spiny <unk> ( gray <unk> ) , and black greasewood are also <unk> . Four @-@ wing <unk> ( <unk> <unk> ) is heavily used in western Nevada . In <unk> County , Idaho , <unk> comprises 41 % of black @-@ tailed jackrabbits ' annual diet . Grasses comprise 14 % of the diet , with most grass consumption in March and April . Russian <unk> ( <unk> <unk> ) is an important <unk> diet item . <unk> @-@ and @-@ thread grass ( <unk> <unk> ) and Indian <unk> ( <unk> <unk> ) are preferred grasses . Other preferred native grasses include <unk> <unk> ( <unk> <unk> ) and bluebunch wheatgrass ( <unk> <unk> ) . Where available , crested wheatgrass ( <unk> <unk> and <unk> <unk> ) and barley ( <unk> <unk> ) are highly preferred . <unk> ( <unk> <unk> ) use is variable : it comprises 45 % of the April diet on two southern Idaho sites , but black @-@ tailed jackrabbit on an eastern Washington site do not use it . 
