Greater rhea

The greater rhea was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae. He placed it with the ostriches in the genus Struthio and coined the binomial name Struthio americanus. Linnaeus based his account on the "Nhanduguaçú" that had been described in 1648 by the German naturalist Georg Marcgrave in his book Historia Naturalis Brasiliae. Linnaeus designated the type locality as South America but this has been restricted to the states of Sergipe and Rio Grande do Norte in eastern Brazil based on Marcgrave. The greater rhea is now placed in the genus Rhea that was introduced in 1760 by the French zoologist Mathurin Jacques Brisson. The common name and genus name is from Rhea, a Greek goddess. This species is placed in the family Rheidae, and the order Rheiformes. It closely related to other ratites such as emus, ostriches, cassowaries, and kiwi, along with the extinct forms: moa and elephant birds. Subspecies There are five subspecies of the greater rhea; their ranges meet around the Tropic of Capricorn: Main subspecific differences are the extent of the black coloring of the throat and the height. However, subspecies of the greater rhea differ so little across their range that, without knowledge of the place of origin, it is essentially impossible to identify captive birds by subspecies. ==Description==

Wildlife Park (Somerset, England) , Brazil The adults have an average weight of and often measure long from beak to tail; they usually stand about tall, with a typical range of , to the top of the head. The males are generally bigger than the females. Despite the delineation of this species as the "greater rhea" versus the lesser rhea, some data on body masses indicates that both species average about in weight, but even at mass parity that greater species appears larger and is taller due to its longer legs and neck, whereas the lesser rhea is more compact and more so resembles an outsized, long-necked turkey in build. Elsewhere, the lesser rhea has been cited with a lower average weight of . In some areas, male greater rheas weights of up to are not uncommon and even females of up to have been weighed, both weights higher than the maximum known mass for the lesser rhea. Large males can weigh up to , stand nearly tall and measure over long, although this is uncommon. The head and bill are fairly small, the latter measuring in length. The legs are long, with the tarsus measuring between , and strong and have 22 horizontal plates on the front of the tarsus. They have three toes, and the hind toe is absent. The wings of the American rhea are rather long; the birds use them during running to maintain balance during tight turns, and also during courtship displays. Greater rheas have a fluffy, tattered-looking plumage, that is gray or brown, with high individual variation, The head, neck, rump, and thighs are feathered. In general, males are darker than females. Even in the wild—particularly in Argentina—leucistic individuals (with white body plumage and blue eyes) as well as albinos occur. Hatchling greater rheas are grey with dark lengthwise stripes. ==Distribution and habitat==

The greater rhea is native to Argentina, Bolivia, Brazil, Paraguay, and Uruguay. There are also feral populations of the greater rhea in Germany. In the autumn of 2018, the German population grew to 566 individuals, and hunting of the birds was allowed; additionally, the population was reduced by destroying eggs during breeding season. ==Behavior and ecology==

Individual and flock behavior The greater rhea is a silent bird except during mating season, when they make low booming noises, and as chicks, when they give a mournful whistle. small rodents, reptiles, and small birds. Favorite food plants include native and introduced species from all sorts of dicot families, such as Amaranthaceae, Asteraceae, Bignoniaceae, Captive-bred greater rheas exhibit significant ecological naïveté. This fearlessness renders them highly vulnerable to predators if the birds are released into the wild in reintroduction projects. Classical conditioning of greater rhea juveniles against predator models can prevent this to some degree, but the personality type of the birds – whether they are bold or shy – influences the success of such training. In 2006, a protocol was established for training greater rheas to avoid would-be predators, and for identifying the most cautious animals for release. ==Status and conservation==

The greater rhea is considered a Near Threatened species according to the IUCN, and they have a decreasing range of about . German authorities have issued 'alternatives' to culling the birds which still sparks controversy. ==Relationship with humans==

Ancient humans in the Patagonia region used to hunt greater rhea, and stencils of greater rhea feet dating back to the early Holocene can be found at rock art sites such as Cueva de las Manos. The species is farmed in North America and Europe in a similar fashion to other ratites, such as the emu and ostrich. The main products are meat and eggs, but rhea oil is used for cosmetics and soaps, and rhea leather is also traded in quantity. Male greater rheas are very territorial during the breeding season. The infant chicks have high mortality in typical confinement farming situations, but under optimum free-range conditions chicks will reach adult size by their fifth month. ==References==