In Great Basin , big sagebrush is a primary forage species and is used throughout the year ; in southern Idaho it form 16 – 21 % of the black @-@ tailed jackrabbit summer diet . Rabbitbrush ( Chrysothamnus spp . ) , spiny hopsage ( gray spinosa ) , and black greasewood are also browsed . Four @-@ wing saltbush ( Atriplex canescens ) is heavily used in western Nevada . In Butte County , Idaho , winterfat comprise 41 % of black @-@ tailed jackrabbits ' annual diet . Grasses comprise 14 % of the diet , with most grass consumption in March and April . Russian thistle ( Salsoda kali ) is an important forb diet item . Needle @-@ and @-@ thread grass ( Stipa comata ) and Indian ricegrass ( Oryzopsis hymenoides ) are preferred grasses . Other preferred native grasses include Sandberg bluegrass ( Poa secunda ) and bluebunch wheatgrass ( Pseudoroegneria spicata ) . Where available , crested wheatgrass ( Agropyron desertorum and Agropyron cristatum ) and barley ( Hordeum vulgare ) are highly preferred . Cheatgrass ( Bromus tectorum ) use is variable : it comprise 45 % of the April diet on two southern Idaho sites , but black @-@ tailed jackrabbit on an eastern Washington site do not use it .