Rhea

The

   Rhea is the common name for any of the large, flightless, ratite birds comprising the genus *Rhea*, characterized by a body with large legs, a long neck, and three-toed feet. Native to South America, the rheas resemble the ostriches of Africa and the emus of Australia. There are two existing species of rhea: the greater or American rhea (*R. americana*) and the lesser or Darwin's rhea (*R. pennata*).

Wild rheas provide important ecological values as part of food chains. Although the adult rhea can kick with a lot of force and has few predators beyond the jaguar and cougar, the eggs, hatchlings, and young birds fall prey to a number of predators, including the tegu lizard, maned wolf, bush dog and some birds of prey. Omnivores, they largely consume broad-leafed plants and seeds, roots, and fruit, but also will consume lizards, carrion, and small invertebrates such as beetles and grasshoppers.

Rheas also provide important values to humans. They provide meat and eggs for consumption, their feathers are used in feather dusters, their hide is used for leather, and rhea oil is used in cosmetics and soaps. Like the ostrich and emu, they are commercially farmed. Beyond these values, rheas provide a unique beauty when seen grazing in the wild.

Despite these values, both species of rheas are considered to be Near Threatened, largely due to habitat destruction, hunting, and egg destruction as a result of crop burning and agricultural activities.

## Description

Rheas are members of a group of birds known was ratites. Ratites are flightless birdscharacterized by a flat, raft-like sternum (breastbone) lacking the keel for attachment of wing muscles that is typical of most flying birds and some other flightless birds. Other ratites are the similar-looking and fast-running emus of Australiaand ostriches of Africa, as well as the much smaller kiwis of New Zealand. The ostrich is the largest living species of bird (reaching 9 feet) and the emu is the second-largest extant bird in the world (reaching 6.5 feet in height).

Rheas are large birds with gray-brown plumage, long legs, and long necks. These birds can reach 5.6 feet (1.7 meters) in height, and weigh up to 88 pounds (40 kilograms).[2] Their wings are large for a flightless bird and are spread while running, to act like sails. Unlike most birds, rheas have only three toes. The emu also has three toes, but the ostrich has only two toes. A rhea's tarsus has horizontal plates on the front of it. They also store urine separately in an expansion of the cloaca.

## Taxonomy

Although the shared shape of the breastbone of ratites is considered by many authorities to be more a product of adaptation to living on the ground rather than shared ancestry, others assume shared ancestry and place the ratites together. A current approach is to combine them as different families within the order Struthioniformes, with rheas in the family Rheidae, ostriches in the family Struthionidae, and emus in the family Casuariidae. However, an alternative classification places the rheas in the order Rheiformes, the emus in the order Casuariiformes, and the ostriches remaining in Struthioniformes.

The genus name *Rhea* was given in 1752 by Paul Möhring and adopted as the English common name. In classical mythology, Rhea is the daughter of Uranus, the sky, and Gaia, the earth, and was known as "the mother of gods." Möhring's reason for choosing this name is not known.

The two recognized extant species are:

* Greater rhea *Rhea americana* (Argentina, Bolivia, Brazil, Paraguay, Uruguay)
* Lesser rhea *Rhea pennata* (Argentina, Bolivia, Chile, Peru)

The greater rhea, *Rhea americana*, derives its name from the Latin form of America. It was originally described by Carolus Linnaeus in his 18th-century work, Systema Naturae. He identified specimens from Sergipe, and Rio Grande do Norte, Brazil, in 1758.

Darwin's rhea, *Rhea pennata*, gets its scientific name from the Greek goddess and *pennata* means winged. The specific name was bestowed in 1834 by Charles Darwin's contemporary and rival Alcide d'Orbigny, who first described the bird to Europeans, from a specimen from the lower Río Negro south of Buenos Aires, Argentina.

*Rhea pennata* was not always in the *Rhea* genus. As late as 2008 it was classified in the monotypic genus *Pterocnemia*. This word is formed from two Greek words *pteron* meaning feathers, and *knēmē* meaning the leg between the knee and the ankle, hence feather-legged, alluding to their feathers that cover the top part of the leg. In 2008, the American Ornithologists' Union*(SACC) subsumed*Pterocnemia*into the genus*Rhea*. This merging of genera leaves only the*Rhea*genus.*

A third species of rhea, *Rhea nana*, was described by Lydekker in 1894 based on a single egg found in Patagonia,[8] but today no major authorities consider it valid.

## Behavior and Ecology

### **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 omnivorous and prefer to eat broad-leafed plants, but also eat seeds, roots, fruit, lizards, beetles, grasshoppers, and carrion.

The bulk of the food of the greater rhea consists of broad-leaved dicot foliage and other plant stuffs, particularly seed and fruit when in season. Favorite food plants include native and introduced species from all sorts of dicot families, such as Amaranthaceae, Asteraceae, Bignoniaceae, Brassicaceae, Fabaceae, Lamiaceae, Myrtaceae or Solanaceae. Magnoliidae fruit, for example of *Duguetia furfuracea* (Annonaceae) or avocados (*Persea americana*, Lauraceae) can be seasonally important. They do not usually eat cereal grains, or monocots in general. However, the leaves of particular grass species like *Brachiaria brizantha* can be eaten in large quantities, and Liliaceae (e.g. the sarsaparilla *Smilax brasiliensis*) have also been recorded as food plants. Even tough and spiny vegetable matter like tubers or thistles is eaten with relish. Like many birds that feed on tough plant matter, the greater rhea swallows pebbles, which help grind down the food for easy digestion. It is much attracted to sparkling objects and sometimes accidentally swallows metallic or glossy objects.

Feral Greater Rhea in cereal field in Mecklenburg-Vorpommern, Germany. The greater rhea species normally uses such monocultures to hide rather to feed on the plants.

In fields and plantations of plants they do not like to eat—such as cereals or *Eucalyptus*—the greater rhea can be a species quite beneficial to farmers. It will eat any large invertebrate it can catch; its food includes locusts and grasshoppers, true bugs, cockroaches, and other pest insects. Juveniles eat more animal matter than adults. In mixed *cerrado* and agricultural land in Minas Gerais (Brazil), *R. a. americana* was noted to be particularly fond of beetles. It is not clear whether this applies to the species in general, but, for example, in pampas habitat, beetle consumption is probably lower simply due to availability while Orthoptera might be more important. The greater rhea is able to eat Hymenoptera in quantity. These insects contain among them many who can give painful stings, though the birds do not seem to mind. It may be that this species has elevated resistance to poison, as it readily eats scorpions. But even small vertebrates like rodents, snakes, lizards, and small birds are eaten. Sometimes, greater rheas will gather at carrion to feed on flies; they are also known to eat dead or dying fish in the dry season, but as with vertebrate prey in general not in large quantities.

### Reproduction

Rheas are polygamous: Males are simultaneously polygynous, females are serially polyandrous. In practice, this means that the females move around during breeding season, mating with a male and depositing their eggs with the male before leaving him and mating with another male. The polygynous males may court between two and twelve females. After mating, the male builds a nest, in which each female lays her eggs in turn. The nests are thus collectively used by several females. The males, which are sedentary after mating, attend the nests with the eggs of the several females and take care of incubation and the hatchlings all on their own. Recent evidence suggests that dominant males may enlist a subordinate male to roost for him while he starts a second nest with a second harem. Greater rheas breed in the warmer months, between August and January depending on the climate.

The rhea nest consists of a simple and wide scrape in the ground, lined with grass and leaves. The nest is kept in a hidden location; males will drag sticks, grass, and leaves in the area surrounding the nest so it resembles a firebreak as wide as their neck can reach.

The male incubates from ten to eighty eggs. The nests of greater rheas can contain as many as 80 eggs laid by a dozen females; each individual female's clutch numbers some 5-10 eggs. However, the average clutch size of the greater rhea is 26 with 7 different females eggs. Greater rhea eggs measure about 130 millimeters × 90 millimeters (5.1 inches × 3.5 inches) and weigh 600 grams (21 ounces) on average; they are thus less than half the size of an ostrich egg. Their shell is greenish-yellow when fresh but soon fades to dull cream when exposed to light.

Some eggs are left outside the nest. These may serve as decoys, being sacrificed to predators, so that predators do not attempt to get inside the nest. If not taken by predators, they may rot and attract flies, which the adult and young can consume. While caring for the young, the males will charge at any perceived threat that approach the chicks including female rheas and humans.

The incubation period is 29–43 days. All the eggs hatch within 36 hours of each other even though the eggs in one nest were laid perhaps as much as two weeks apart. As it seems, when the first young are ready to hatch they start a call resembling a pop-bottle rocket, even while still inside the egg; thus the hatching time is coordinated. Greater rheas are half-grown about three months after hatching, full adult size in about six months, and sexually mature by their 14th month, but do not breed until they reach two years of age.

### Gallery

Animals-united-disneyscreencaps.com-10261.jpgAnimals United (2010) - Greater Rhea only