pronghorns prefer open, expansive terrain at elevations varying between , with the densest populations in areas receiving around of rainfall per year. they eat a wide variety of plant foods, often including plants unpalatable or toxic to domestic livestock (sheep and cattle), though they also compete with them for food. in one study, forbs comprised 62% of their diet, shrubs 23%, and grasses 15%, while in another, cacti comprised 40%, grass 22%, forbs 20%, and shrubs 18%. pronghorns also chew and eat (ruminate) cud, which is their own partially digested food. healthy pronghorn populations tend to stay within of water. an ongoing study by the lava lake institute for science and conservation and the wildlife conservation society shows an overland migration route that covers more than . the migrating pronghorn start travel from the foothills of the pioneer mountains through craters of the moon national monument to the continental divide. dr. scott bergen of wildlife conservation society says, "this study shows that pronghorn are the true marathoners of the american west. with these new findings, we can confirm that idaho supports a major overland mammal migration - an increasingly rare phenomenon in the u.s. and worldwide."