Similarly to ostriches and emus, rheas are fairly popular livestock and pets, regularly kept and bred on farms, ranches, private parks, and by aviculturists, mainly in North and South America and Europe.

Depending on the South American region, the rhea is known locally as ñandú guazu (Guaraní –or related Tupi nhandú-gûasú– meaning "big spider"[5] most probably concerning their habit of opening and lowering alternate wings when they run),[citation needed] ema (Portuguese), suri (Aymara and Quechua),[6][7] or choique (Mapudungun).

[13] Their wings are large for a flightless bird (250 cm (8.2 ft))[13] and are spread while running, to act like sails.

[13]Rheas are from South America only and are limited within the continent to Argentina, Bolivia, Brazil, Chile, Paraguay, Peru and Uruguay.

On the other hand, the lesser rhea will inhabit most shrubland, grassland, even desert salt puna up to 4,500 metres (14,800 ft).

[13][16][17] A small population of rheas has emerged in Mecklenburg-Western Pomerania, northeastern Germany, after several couples escaped from an exotic meat farm near Lübeck in the late 1990s.

[19] By 2014, there was already a population of well over 100 birds in an area of 150 square kilometres (58 sq mi) between the river Wakenitz and the A20 motorway, slowly expanding eastward.

Still protected by German natural conservation law, a local discussion developed regarding how to handle the situation.

Eventually, Mecklenburg-Western Pomerania's government allowed limited hunting of the birds, explicitly to just reduce the population's growth and not to wipe them out.

By spring 2021, just 247 rheas were counted; this development was attributed to both the hunting and the increased caution of the animals.

[23] By early 2023, 91 rheas were counted in Mecklenburg-Western Pomerania; the population decline was attributed to both hunting as well as harsher weather of previous years.

By this point, German authorities believed a stable population of 50 adult birds would be optimal for the local ecosystem and agriculture.

Researchers concluded that the feral population was subject to substantial fluctuations but remained healthy, adaptable, and entrenched in the area.

Once caught, authorities intend to place them in a suitable nature reserve to allow them to develop as a colony.

[13] Mostly, rheas are herbivorous and prefer broad-leafed plants, but they also eat fruits, seeds, roots, and insects such as grasshoppers, small reptiles, and rodents.

While caring for the young, the males will charge at any perceived threat approaching the chicks, including female rheas and humans.