The
rheas are ratites (
flightless birdFlightless birds are birds which lack the ability to fly, relying instead on their ability to run or swim. They are thought to have evolved from flying ancestors. There are about forty species in existence today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin...
s, with unkeeled sterna) in the genus
Rhea, native to
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. There are two existing species: the Greater or American Rhea and the
Lesser or Darwin's RheaDarwin's Rhea, Rhea pennata, also known as the Lesser Rhea, is a large flightless bird, but the smaller of the two extant species of rheas. It is found in the Altiplano and Patagonia in South America.-Description:...
. The genus name was given in 1752 by
Paul MöhringPaul Heinrich Gerhard Möhring , aka Paul Mohr, was a German physician, botanist and zoologist.Möhring was physician to the Prince of Anhalt. In 1752 he published Avium Genera, an early attempt to classify bird species, which divided birds into four classes and shows the beginnings of the modern...
and adopted as the English common name. Möhring's reason for choosing this name, from the
RheaRhea was the Titaness daughter of Uranus, the sky, and Gaia, the earth, in Greek mythology. She was known as "the mother of gods". In earlier traditions, she was strongly associated with Gaia and Cybele, the Great Goddess, and was later seen by the classical Greeks as the mother of the Olympian...
of classical mythology, is not known. Depending on the South American region, the rhea is known locally as
ñandú guazu (
GuaraníGuaraní, specifically the primary variety known as Paraguayan Guaraní , is an indigenous language of South America that belongs to the Tupí–Guaraní subfamily of the Tupian languages. It is one of the official languages of Paraguay , where it is spoken by the majority of the population, and half of...
, meaning big spider, most probably in relation to their habit of opening and lowering alternatively wings when they run),
ema (
PortuguesePortuguese is a Romance language that arose in the medieval Kingdom of Galicia, nowadays Galicia and Northern Portugal. The southern part of the Kingdom of Galicia became independent as the County of Portugal in 1095...
),
suri (
QuechuaSouthern Quechua , or only Quechua, is the most widely spoken of the major regional groupings of mutually intelligible dialects within the Quechua language family, with about 5 million speakers...
), or
choique (Mapudungun).
Description
Rheas are large, flightless birds with gray-brown
plumagePlumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
, long legs and long necks, similar to an
ostrichThe Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
. Males of
R. americana can reach 1.5 metres (4.9 ft), and weigh up to 40 kilograms (88.2 lb). Their wings are large for a flightless bird and are spread while
runningCursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
, to act like
sailA sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in a wind—in essence a propulsion wing. Sails are used in sailing.-History of sails:...
s. Unlike most birds, rheas have only three toes. Their
tarsusIn tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
has horizontal plates on the front of it. They also store
urineUrine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
separately in an expansion of the
cloacaIn zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
.
Taxonomy
The recognized extant species are:
- Greater Rhea Rhea americana
- R. a. americana, found in the cerrado
The Cerrado, is a vast tropical savanna ecoregion of Brazil, particularly in the states of Gioas and Minas Gerais...
s (bushlands) of central and eastern BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
.
- R. a. intermedia, southeastern Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in Rio Grande do SulRio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
and UruguayUruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
.
- R. a. nobilis, eastern Paraguay
Paraguay , officially the Republic of Paraguay , is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, and Bolivia to the northwest. Paraguay lies on both banks of the Paraguay River, which runs through the center of the...
, east of Rio Paraguay.
- R. a. araneipes, chaco of Paraguay to Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
and Mato GrossoMato Grosso is one of the states of Brazil, the third largest in area, located in the western part of the country.Neighboring states are Rondônia, Amazonas, Pará, Tocantins, Goiás and Mato Grosso do Sul. It also borders Bolivia to the southwest...
in Brazil.
- R. a. albescens, plains of Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
south to Rio NegroRío Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
.
- Lesser Rhea Rhea pennata
- R. p. garleppi, puna
The Puna grassland ecoregion, of the montane grasslands and shrublands biome, is found in the central Andes Mountains of South America. It is considered one of the eight Natural Regions in Peru, but extends south as far as northern Argentina and Chile....
of southeastern PeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
, southwestern Bolivia, and northwestern Argentina.
- R. p. tarapacensis, northern Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
from Atacama to TarapacáThe I Tarapacá Region is one of Chile's 15 first order administrative divisions. It borders the Chilean Arica and Parinacota Region to the north, Bolivia's Oruro Department on the east, the Antofagasta Region on the south and the Pacific Ocean on the west. The port city of Iquique The I Tarapacá...
.
- R. p. pennata, Patagonian steppes in southern Argentina and southern Chile.
Rhea pennata was not always in the
Rhea genus. In 2008 the
SACCThe American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
, the last holdout, approved the merging of the genera,
Rhea and
Pterocnemia on August 7, 2008. This merging of genera leaves only the
Rhea genus. A third species of rhea,
Rhea nana, was described by
LydekkerRichard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
in 1894 based on a single
eggAn egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
found in
PatagoniaPatagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
, but today no major authorities consider it valid.
Individual and flocking
Rheas tend to be silent birds with the exception being when they are chicks or when the male is seeking a mate. During the non-breeding season they may form flocks of between 10 and 100 birds, although the lesser rhea forms smaller flocks than this. When in danger they flee in a zig-zag course, utilizing first one wing then the other, similar to a rudder. During breeding season the flocks break up.
Diet
They are
omnivorousOmnivores are species that eat both plants and animals as their primary food source...
and prefer to eat broad-leafed
plantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, but also eat seeds,
rootIn vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s,
fruitIn broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
,
lizardLizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s,
beetleColeoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s,
grasshopperThe grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...
s, and carrion.
Reproduction
Rheas are polygamous, with males courting between two and twelve females. After mating, the male builds a nest, in which each female lays her eggs in turn. The nest consists of a simple scrape in the ground, lined with grass and leaves. The male incubates from ten to sixty eggs. The male will utilize a decoy system and place some eggs outside the nest and sacrifice these to predators, so that they won't attempt to get inside the nest. The male may utilize another subordinate male to incubate his eggs, while he finds another harem to start a second nest. The chicks hatch within 36 hours of each other. The females, meanwhile, may move on and mate with other males. While caring for the young, the males will charge at any perceived threat that approach the chicks including female rheas and humans. The young reach full adult size in about six months but do not breed until they reach two years of age.
Human interaction
Rheas have many uses in South America. Feathers are used for feather dusters, skins are used for cloaks or leather, and their meat is a staple to many people.
The Rhea is pictured on the coinage of Argentina's 1 Centavo coin minted in 1987.
External links