Interesting Creatures... The Greater Rhea (Rhea americana)

Interesting Creatures… The Greater Rhea (Rhea americana)

Dec 08, 2019 Interesting Creatures in Guyana, News

The greater rhea (Rhea americana) is a species of flightless bird native to eastern South America. Other names for the greater rhea include the grey, common, or American rhea; ñandú (Guaraní and Spanish) or ema (Portuguese).
One of two species in the genus Rhea, in the family Rheidae, the greater rhea is native to Argentina, Bolivia, Brazil, Paraguay and Uruguay. It inhabits a variety of open areas, such as grasslands, savannah or grassy wetlands. Weighing 20–27 kilograms (44–60 lb), the greater rhea is the largest bird in South America.
In the wild, the greater rhea has a life expectancy of 10.5 years. It is also notable for its reproductive habits, and for the fact that a population has established itself in Northern Germany in recent years.
The adults have an average weight of 20–27 kg (44–60 lb) and often measure 127 to 140 cm (50 to 55 in) long from beak to tail; they usually stand about 1.5 m (4 ft 11 in) tall, with a typical range of 1.4 to 1.7 m (4 ft 7 in to 5 ft 7 in), 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 23 kg (51 lb) 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 16 kg (35 lb).
In some areas, male greater rheas weights of up to 35 kg (77 lb) are not uncommon and even females of up to 30 kg (66 lb) have been weighed, both weights higher than the maximum known mass for the lesser rhea. Large males can weigh up to 40 kg (88 lb), stand nearly 1.83 m (6.0 ft) tall and measure over 150 cm (59 in) long, although this is uncommon.
The head and bill are fairly small, the latter measuring 8–10.4 cm (3.1–4.1 in) in length. The legs are long, with the tarsus measuring between 33.5 and 37 cm (13.2 and 14.6 in), 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 grey 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.
The natural predators of adult greater rheas are limited to the cougar (Puma concolor), which are found in most areas inhabited by greater rheas and are certain to be their leading predator, and the jaguar (Panthera onca), which are found with greater rheas and opportunistically hunt them in the Paraguayan chaco, central Bolivia and the Brazilian cerrado.
Feral dogs are known to kill younger birds, and the southern caracara (Caracara plancus) is suspected to prey on hatchlings. Armadillos sometimes feed on greater rhea eggs; nests have been found which had been undermined by a six-banded armadillo (Euphractus sexcinctus) or a big hairy armadillo (Chaetophractus villosus) and the rhea eggs were broken apart.
Predation on young rheas has also been reportedly committed by greater grisons (Galictis vittata).
Captive-bred greater rheas exhibit significant ecological naïvete. 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.
The greater rhea is considered a Near Threatened species according to the IUCN, and they have a decreasing range of about 6,540,000 square kilometres (2,530,000 sq mi). The species is believed to be declining due to increased hunting and the conversion of central South American grasslands to farmland and ranchland.
The populations of Argentina and Uruguay are most seriously affected by the decline.
Farmers sometimes consider the greater rhea pests, because they will eat broad-leaved crop plants, such as cabbage, chard and bok choy. Where they occur as pests, farmers tend to hunt and kill greater rheas. The burning of crops in South America has also contributed to their decline.
International trade in wild-caught greater rheas is restricted as per CITES Appendix II. The rheas in Germany are legally protected in a similar way to native species. In its new home, the greater rhea is considered generally beneficial as its browsing helps maintain the habitat diversity of the sparsely populated grasslands bordering the Schaalsee biosphere reserve.
[Source: Wikipedia]