A ratite is any of a diverse group of large, flightless bird
Flightless bird
Flightless 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 of Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

n origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel
Keel (bird)
A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight...

 on their sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...

—hence the name from the Latin ratis (for raft
A raft is any flat structure for support or transportation over water. It is the most basic of boat design, characterized by the absence of a hull...

). Without this to anchor their wing muscles, they could not fly even if they were to develop suitable wings.

Most parts of the former Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...

 have ratites, or did have until the fairly recent past. Their closest living relatives are the tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....

s of South America.

Some taxonomical systems consider the various families of ratites to be orders, but the system used here uses the order "Struthioniformes" to refer to all ratites.

Living forms

The Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

n Ostrich
The 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...

 is the largest living ratite. A large member of this species can be nearly 3 metres (9.8 ft) tall, weigh as much as 159 kilograms (350.5 lb), and can outrun a horse.

Of the living species, the Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n emu
The Emu Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of Emus in Australia...

 is next in height, reaching up to 2 metres (6.6 ft) tall and about 60 kilograms (132.3 lb). Like the ostrich, it is a fast-running, powerful bird of the open plains and woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...


Also native to Australia and the islands to the north are the three species of cassowary
The cassowaries are ratites, very large flightless birds in the genus Casuarius native to the tropical forests of New Guinea, nearby islands and northeastern Australia. There are three extant species recognized today...

. Shorter than an emu, but heavier and solidly built, cassowaries prefer thickly vegetated tropical forest. They can be very dangerous when surprised or cornered because of their razor sharp talon
A talon is a sharp claw of an animal, especially a bird of prey, such as the eagle, hawk, falcon, owl, or buzzard. It may also refer to:Places:* Talon, Nièvre, a commune in the Nièvre département in France...

s. In New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

, cassowary eggs are brought back to villages and the chicks raised for eating as a much-prized delicacy, despite (or perhaps because of) the risk they pose to life and limb.

South America
South America
South 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...

 has two species of rhea
Rhea (bird)
The rheas are ratites in the genus Rhea, native to South America. There are two existing species: the Greater or American Rhea and the Lesser or Darwin's Rhea. The genus name was given in 1752 by Paul Möhring and adopted as the English common name. Möhring's reason for choosing this name, from the...

, mid-sized, fast-running birds of the Pampas. The larger American rhea
American Rhea
The Greater Rhea, Rhea americana, is a flightless bird found in eastern South America. Other names for the Greater Rhea include the Grey, Common, American Rhea, ñandú or ema . One of two species in the genus Rhea, in the family Rheidae, the Greater Rhea is endemic to Argentina, Bolivia, Brazil,...

 grows to about 1.5 metres (4.9 ft) tall and usually weighs 20 to 25 kg (44.1 to 55.1 lb). (South America also has 47 species of the small and ground-dwelling but not flightless tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....

 family, which is closely related to the ratite group.)

The smallest ratites are the five species of kiwi
Kiwi are flightless birds endemic to New Zealand, in the genus Apteryx and family Apterygidae.At around the size of a domestic chicken, kiwi are by far the smallest living ratites and lay the largest egg in relation to their body size of any species of bird in the world...

 from New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

. Kiwi are chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...

-sized, shy, and nocturnal. They nest in deep burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...

s and use a highly developed sense of smell to find small insects and grubs in the soil. Kiwi are notable for laying eggs that are very large in relation to their body size. A kiwi egg may equal 15 to 20 percent of the body mass of a female kiwi. The smallest species of kiwi is the Little Spotted Kiwi
Little Spotted Kiwi
The Little Spotted Kiwi or Little Gray Kiwi, Apteryx owenii, is a small species of kiwi originally from New Zealand's South Island that, around 1890 and 1910 was captured and later released on Kapiti Island...

, at 1.2 kilograms (2.6 lb) and 40 centimetres (15.7 in).

Extinct forms

At least 11 species of moa
The moa were eleven species of flightless birds endemic to New Zealand. The two largest species, Dinornis robustus and Dinornis novaezelandiae, reached about in height with neck outstretched, and weighed about ....

 lived in New Zealand before the arrival of humans, ranging from turkey-sized to the Giant Moa Dinornis giganteus with a height of 3.3 metres (10.8 ft) and weighing about 250 kilograms (551.2 lb). They went extinct by A.D. 1500 due to hunting by Māori settlers, who arrived by A.D. 1300.

Aepyornis is a genus of aepyornithid, one of two genera of ratite birds endemic to Madagascar known as elephant birds. This animal was the world's largest bird until its extinction, about 1000 years ago.-Description:...

, the "elephant bird" of Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

, was the heaviest bird ever known. Although shorter than the tallest moa, a large Aepyornis could weigh over 450 kilograms (992.1 lb) and stand up to 3 metres (9.8 ft) tall.

Eggshell fragments similar to those of Aepyornis were found on the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...

. The fragments date to the middle or late Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

, and no satisfying theory has been proposed as to how they got there due to uncertainties about whether these islands were ever connected to the mainland.

Evolution and systematics

There are two taxonomic
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 approaches to ratite classification: the one applied here combines the groups as families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Struthioniformes, while the other supposes that the lineages evolved mostly independently and thus elevates the families to order rank (e.g. Rheiformes, Casuariformes etc.).

Some studies based on morphology, immunology and DNA sequencing had indicated that ratites are monophyletic. The traditional account of ratite evolution has the group emerging in flightless form in Gondwana in the Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

, then evolving in their separate directions as the continents drifted apart.

However, recent analysis of genetic variation between the ratites conflicts with this. DNA analysis appears to show that the ratites diverged from one another too recently to share a common Gondwanian ancestor. Also, the Middle Eocene fossil "proto-ostrich" Palaeotis
Palaeotis is a genus of paleognath bird from the middle Eocene epoch of central Europe. One species is known, Paleotis weigelti. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect described it as an extinct bustard , and gave it its consequent name . After a suggestion by...

from Central Europe may imply that the "out-of-Gondwana" hypothesis is wrong. Furthermore, recent analysis of twenty nuclear genes has drawn into question the monophyly of the group, suggesting that the flighted tinamou
The tinamous are a family comprising 47 species of birds found in Central and South America. One of the most ancient living groups of bird, they are related to the ratites. Generally ground dwelling, they are found in a range of habitats....

s cluster within the ratite lineage. The authors say the data "unequivocally places tinamous within ratites".

A comparative study of the full mitochondrial DNA sequences of living ratites plus two moas places moas in the basal position, followed by rheas, followed by ostriches, followed by kiwis, with emus and cassowaries being closest relatives. Another study has reversed the relative positions of moas and rheas, and indicated that elephant birds are not close relatives of ostriches or other ratites, while a study of nuclear genes shows ostriches branching first, followed by rheas and tinamous, then kiwis splitting from emus and cassowaries. These studies share branching dates which suggest that, while ancestral moas may have been present in New Zealand since it split off from Gondwana, the ancestors of kiwis appear to have arrived there from Australia more recently, perhaps via a land bridge or by island-hopping. A recent extensive morphological comparison makes South American and Australian ratites a clade, with three successively more distant sister groups consisting of ostriches, elephant birds, and a clade of New Zealand ratites.

All analyses but the most recent morphological study show that rheas and extant Australo-Pacific ratites are monophyletic. The DNA data showing the ostriches branching first would match the sequence of Gondwana's plate tectonic
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

 breakup. Other, but not all, aspects of ratite paleobiogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...

 were found to be consistent with the vicariance
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...

 (plate tectonic
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

 split-up of Gondwana) hypothesis. The sister-group relationship of New Zealand ratities to other ratites proposed on morphological grounds would not be consistent with vicariance, while the proposed South American-Australian clade would be.

Recent phylogenomic studies suggest that tinamous may in fact belong to this group. If so, this would make 'ratites' paraphyletic rather than monophyletic. Since tinamous are weak fliers, this raises interesting questions about the evolution of flightlessness in this group. While the ratites were traditionally thought of as an ancestrally flightless, monophyletic group, the branching of the tinamous within the ratite lineage suggests that ratites evolved flightlessness at least three times. Re-evolution of flight in the tinamous would be an alternative explanation, but such a development is without precedent in avian history, while loss of flight is commonplace.

Physical characteristics

Ratites in general have many physical characteristics in common, which are often not shared by the family Tinamidae, or tinamous. First, the breast
Pectoralis major muscle
The pectoralis major is a thick, fan-shaped muscle, situated at the chest of the body. It makes up the bulk of the chest muscles in the male and lies under the breast in the female...

 muscles are underdeveloped. They do not have keeled sterna
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...

. Their wishbones (furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....

e) are almost absent. They have a simplified wing skeletons and musculature. Their legs are stronger and do not have air chambers, except the femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

s. Their tail and flight feathers have retrogressed or have become decorative plumes. They have no feather vanes, which means they do not need to oil their feathers, hence they have no preen glands. They have no separation of pterylae and apteria, and finally, they have palaeognathous palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...


Ostriches have the greatest dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

, rheas show some dichromatism
Dichromatism is a phenomenon where the hue of the colour in materials or solutions are dependent on both the concentration of the absorbing substance and the depth or thickness of the medium traversed...

 during the breeding season. Emus, cassowaries, and kiwis show some dimorphism, predominately in size.

While the ratites share a lot of similarities, they also have major differences. Ostriches have only two toes, with one being much larger than the other. Cassowaries have developed long inner toenails, used defensively. Ostriches and rheas have prominent wings; although they don't use them to fly, they do use them in courtship and predator distraction.

Feeding and diet

Ratite chicks tend to be more omnivorous or insectivorous; similarities in adults end with feeding, as they all vary in diet and length of digestive tract, which is indicative of diet. Ostriches, with the longest tracts at 14 metres (45.9 ft), are primarily vegetarian. Rheas' tracts are next longest at between 8–9 m (26.2–29.5 ft), and they also have caeca. They are also mainly herbivores, concentrating on broad-leafed plants. However, they will eat insects if the opportunity arises. Emus have tracts of 7 metres (23 ft) length, and have a more omnivorous diet, including insects and other small animals. Cassowaries have nearly the shortest tracts at 4 metres (13.1 ft). Finally, kiwis have the shortest tracts and eat earthworms, insects, and other similar creatures.


Ratites are different from the flying birds in that they needed to adapt or evolve certain features to protect their young. First and foremost is the thickness of the shells of their eggs. Their young are hatched more developed than most and they can run or walk soon thereafter. Also, most ratites have communal nests, where they share the incubating duties with others. Ostriches are the only ratites where the female incubates; they share the duties, with the males incubating at night. Kiwis stand out as the exception with a monogamous relationship.

Ratites and humans

Ratites and humans have had a long relationship starting with the use of the egg for water containers, jewelry, or other art medium. Male ostrich feathers were popular for hats during the 18th century, which led to hunting and sharp declines in populations. Ostrich farming grew out of this need, and humans harvested feathers, hides, eggs, and meat from the ostrich. Emu farming also became popular for similar reasons and for their emu oil
Emu oil
Emu oil is an oil made from the fat of the emu, Dromaius novaehollandiae, a bird native to Australia.Emu oil and eucalyptus oil have been used historically by the Australian aborigines for the treatment of fevers, coughs, arthritic joints, bruises, cuts and sores.Pure emu oil can vary widely in...

. Rhea feathers are popular for dusters, and eggs and meat are used for chicken and pet feed in South America. Ratite hides are popular for leather products like shoes.

United States regulation

The USDA’s Food Safety and Inspection Service
Food Safety and Inspection Service
The Food Safety and Inspection Service , an agency of the United States Department of Agriculture , is the public health agency responsible for ensuring that the nation's commercial supply of meat, poultry, and egg products is safe, wholesome, and correctly labeled and packaged...

 (FSIS) began a voluntary, fee-for-service ratite inspection program in 1995 to help the fledgling industry improve the marketability of the meat. A provision in the FY2001 USDA appropriations act (P.L. 106-387) amended the Poultry Products Inspection Act to make federal inspection of ratite meat mandatory as of April 2001 (21 U.S.C. 451 et seq.).

External links

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