Animal Diversity Web

Geographic Range

Darwin's Rhea only occurs in South America--Patagonia, in the Andes in Argentina, Chile, Bolivia and Peru. ( http://www.scz.org/pampas/drhea1.html)

• Biogeographic Regions
• neotropical
  • native

Habitat

Darwin's Rhea lives exclusively on the open plains of South America, in areas of open scrub, like in the puna of the Andean plateau, and also in the areas of steppe which extend over the eastern slope of the Andes and into the lowlands of Patagonia. Darwin's Rhea prefers to be near a lake, river or swamp for breeding, even though its habitats are quite arid. (del Hoyo, Elliot, and Sargatal, 1992)

• Terrestrial Biomes
• savanna or grassland
• scrub forest

Physical Description

Darwin's Rhea stands at 92.5 to 100 cm. It resembles the ostrich, although it is considerably smaller, and is therefore sometimes called the South American ostrich. Its wings are proportionally larger than those of other ratites, though it is also flightless. It is able to manuver quite well when running because of its wings. It has three toes, and a strong claw on the end of each wing that is often used effectively as a weapon. Its feathers are smooth and soft, and cover its thighs and the top of the tarsi. It has brown plumage with white flecking throughout, though the female is duller and has fewer white spots on the back. The juvenile is browner, without the white spotting. The typical adult plumage is gained gradually in the third or fourth year. ( http://www.scz.org/pampas/drhea1.html; del Hoyo, Elliot, and Sargatal, 1992)

• Other Physical Features
• endothermic
• bilateral symmetry

• Range mass

  15 to 25 kg

  33.04 to 55.07 lb

Reproduction

The breeding season for Darwin's Rhea is fairly variable. At the onset of the season, males compete for territory in short fights. After securing territory, males attempt to attract females into it by running at them quickly with outspread wings. When he has succeeded in gathering 2-12 females, he then begins a courtship display, which involves various calls and running around them, shaking his wings. After copulation, the male leads the females in a group to the nest, where they lay their eggs one after another. Then the females leave, also in a group. In the weeks that follow, they return every 2 or 3 days to deposit more eggs. The eggs are yellowish olive green, but fade to buff, and average 127x87 mm. Once laying is over at a particular nest, the females leave to mate with another male and to lay eggs in the corresponding nest (del Hoyo, Elliot, and Sargatal, 1992). The male is then left on his own for incubation and chick-rearing. Incubation begins 2-8 days after egg laying begins, and may continue for 35-40 days. The male becomes aggressive toward anything that approaches, including females who come to lay more eggs, so often they just lay them nearby. The male rolls the nearest into the nest, but some remain out of his reach and get left behind. Those rotting eggs attract flies, which become food for the male and the newly hatched chicks. The nest usually ends up with 13-30 eggs. When one chick hatches, it begins calling, stimulating the others to hatch. Thus they all hatch synchronously in a period of 24-28 hours. The chicks are grayish brown with blackish stripes, and the tarsi is fully feathered (del Hoyo, Elliot, and Sargatal, 1992).

The chicks are led away from the nest by the male after a few days, and they keep in touch by means of contact whistles. Whenever the chicks are in danger, or too hot, or too cold at night, they either crouch on the ground or hide under the male's wings. The male is very protective. Lost chicks are often adopted by another male with his own chicks, which leads to a wide range of ages within one group. The period of parental care is 6 months, but the juveniles generally remain in their groups until they are sexually mature at 2-3 years old (del Hoyo, Elliot, and Sargatal, 1992)

• Key Reproductive Features
• iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

Behavior

Darwin's Rhea is fairly sociable and lives in mixed groups of all ages and both sexes. They normally travel in groups numbering 5-30 individuals. During the breeding season, females tend to break off into small groups while males become territorial. It has been observed that a small percentage of males go live alone in seclusion at an advanced age (del Hoyo, Elliot, and Sargatal, 1992). Though they are sociable, individuals must keep a certain distance away from each other, or else a "head-forward" threat display may ensue. The head-forward threat display involves the bird throwing its head forward and hissing with its bill open. It occurs most often when the bird is sitting.

Darwin's Rhea can reach speeds of 60 km/h. It is a strong swimmer and has been observed to cross rivers. It has excellent eyesight and good hearing. Though it can easily outrun predators, it has a habit of retracing its steps when being pursued, and then suddenly squatting down in the bushes and flattening its body against the ground. Despite its large size, it goes completely unnoticed. Another tactic it uses to confuse its predators is to run in a zigzaging pattern, or to turn sharply at right angles. Although it is fast, it has low stamina, and it runs with its neck horizontal and its wings folded in order to be able to pass more easily through the bushes. It is diurnal, with some exception during very hot periods (del Hoyo, Elliot, and Sargatal, 1992).

A rhea wanders while it feeds, and sometimes groups with other wild herbivores. This is beneficial for both parties because the combination of the rhea's good eyesight with the latter's good sense of smell helps them to detect predators at a distance more efficiently.

• Key Behaviors
• motile

Communication and Perception

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

The diet of Darwin's Rhea consists of various types of plant matter, including roots, fruits, seeds, and leaves. A small percentage of animal matter is also consumed, including insects and small vertebrates. It drinks little water, because most of the liquid requirements are satisfied by plants. It also ingests pebbles. It does not have to move around a lot for food, because the abundance of vegetation in its habitat means that it generally has sufficient resources all year long (del Hoyo, Elliot, and Sargatal, 1992).

Economic Importance for Humans: Positive

The rhea's habit of wandering around with cattle can be beneficial to farmers because it often eats burr-like seeds that become entangled in sheep's wool. It is sometimes used for food, and some parts are used for medicine. It is also used for commercial ends, especially the feathers. The skin is used for rugs and more commonly for burning--the smoke produced is believed to be beneficial to the coca plants.

Conservation Status

It is hunted for its feathers, meat, eggs and other body parts. Its habitat is being destroyed by agriculture. In some mining areas, they are hunted from jeeps. (del Hoyo, Elliot, and Sargatal, 1992; http://www.scz.org/pampas/drhea1.html)

• IUCN Red List

  Near Threatened
  More information

Other Comments

Darwin's Rhea lives about 20 years in the wild, and 40 in captivity. Its toes are good luck charms in South America.

Contributors

Alicia Ivory (author), University of Michigan-Ann Arbor.

References

del Hoyo, J., Elliot, A., and Sargatal, J. Handbook of the Birds of the World, Vol. 1. Lynx Edicions, Barcelona, 1992.

http://www.scz.org/pampas/drhea1.html