Rheas are from South America only and are limited within the continent to Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay.
For the most part, rheas are vegetarian and prefer broad-leafed plants but they also eat fruits, seeds and roots, as well as insects such as grasshoppers and small reptiles and rodents.

The rheas (/ˈriː.əz/REE-əz), also known as nandus /ˈnænduːz/NAN-dooz) or South American ostriches, are large ratites (flightless birds without a keel on their sternum bone) in the order Rheiformes, native to South America, distantly related to the ostrich and emu. Most taxonomic authorities recognize two extant species: the greater or American rhea (Rhea americana), and the lesser or Darwin's rhea (Rhea pennata). The IUCN classifies the puna rhea as a another species instead of a subspecies of the lesser rhea. The IUCN currently rates the greater and puna rheas as near-threatened in their native ranges, while Darwin's rhea is of least concern. In addition, a feral population of the greater rhea in Germany appears to be growing, though control efforts are underway, and seem to be succeeding in controlling the birds' population growth.