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