Bison

• Bison eat 93 percent grass, 5 percent forbs and 2 percent browse.Jupiterimages/Photos.com/Getty Images
  
  Bison are grazing animals that can be found across the United States. The United States Department of Agriculture estimates that around 220,000 Bison live in the United States as of 2011. Bison live on blue stem, gamma grass and buffalo grass. Bison eat around 24 lbs. or 1.6 percent of their body mass in grass per day.
  
  

Elk

• Elk are larger than deer and feed on many types of grasses.Jupiterimages/Photos.com/Getty Images
  
  Elk feed on the Buffalo grass that can be found in the natural habitats of elk herds such as the Western United States, Wisconsin, Michigan, Minnesota and Pennsylvania. There are about 1 million elk in the United States; they are are often hunted for food and their antlers. An elk's stomach has four chambers; one chamber stores the food and the other three digest it.
  
  

Buffalo

• The buffalo consumes more during the dry season as the grass has a higher fibre content at this time.Jupiterimages/liquidlibrary/Getty Images
  
  The name buffalo grass is derived from the fact that buffalo graze upon this type of grass. Buffalo have the most efficient digestive systems of all the ruminating animals. They are able to digest fresh grass as easily as old or burnt grasses. When food is easy to come by, buffalo will become more selective eaters, preferring red grass, buffalo grass, small buffalo grass and finger grasses. Buffalo are sensitive to heat and so tend to feed at night and spend their days in the shade as much as possible.
  
  

Prairie Dogs

• Prairie dogs are part of the squirrel family and live on the grasslands.Jupiterimages/Photos.com/Getty Images
  
  Prairie dogs are part of the squirrel family and are found on the prairies or open grasslands of the western United States. The prairie dog's diet consists of the grasses that are found in the prairies, including western bluegrass, blue gamma, buffalo grass, six-weeks fescue and tumblegrass. Prairie dogs also consume roots, seeds, fruit, buds and flowers that can be found in their natural habitat. Prairie dogs live in burrows and tend to eat more grass during the fall.