Rheas are similar in general appearance to the ostrich, except for the fact that they are smaller and do not have the large tail feather plumes of ostriches. Rheas are 4.5 to 5.6 feet (1.3 to 1.7 meters) tall from their feet to the top of their back and weigh 55 to 88 pounds (24.75 to 40 kilograms). Their head, neck, and bodies are covered with soft, loose feathers that are gray or spotted brown and white.
They have long legs with three toes and wings with a claw on the end, an effective weapon against predators. Males are larger than females and the lesser rhea is smaller than the greater rhea.
Rheas are distributed in Argentina, Bolivia, Brazil, Chile, Paraguay, and Uruguay.
Rheas live almost exclusively on grassland although two subspecies of the lesser rhea also inhabit desert areas.
Rheas are omnivores, meaning that they eat both plants and meat. Their diet consists mainly of grass, leaves, herbs, fruit, and seeds, as well as lizards, insects, and small animals.
BEHAVIOR AND REPRODUCTION
Rheas are the largest birds in South America. They are extremely friendly and sociable. In the non-breeding season, the lesser rhea usually live in flocks of five to thirty birds, while the greater rhea live in flocks of ten to one hundred individuals. They are often found grazing alongside herbivorous (plant eating) mammals, such as deer and alpacas. They are fast runners and can reach speeds of up to 37 miles (60 kilometers) per hour, usually running in a zigzag pattern.
Rheas belong to a group of birds called ratites, which are flightless birds that have a flat breastbone rather than a keeled, or curved breastbone like birds of flight. They have a simplified wing bone structure, strong legs, and no feather vanes, making it unnecessary to oil the feathers.
They are polygamous (puh-LIH-guh-mus), meaning they have more than one mate during the breeding season. During breeding season, the male rhea builds a nest in which between two and fifteen females lay their eggs. Nests contain ten to sixty eggs. The male cares for the chicks for about thirty-six hours after they hatch.
During the winter, the flocks split into three groups: single adult males, flocks of two to fifteen females, and yearlings twoyears-old and younger. Males challenge each other and try to attract females. This behavior intensifies as the spring and summer breeding season approaches.
RHEAS AND PEOPLE
Rheas are hunted in the wild by humans for their meat, skin, and feathers. They are raised commercially on farms in the United States and Canada for their meat. They are considered agricultural pests by farmers because they will eat almost any crop.
The greater rhea and lesser rhea are listed by the IUCN as Near Threatened, meaning they are in danger of becoming threatened. Their populations are declining throughout their range, because much of their habitat is shrinking due to conversion to farmland. The Puna rhea, a subspecies of the lesser rhea, has a total population in the wild of only several hundred.