The rheas are large flightless birds known as ratites in the order Rheiformes, native to South America, related to the ostrich and emu. There are two extant species: the greater or American rhea (Rhea americana) and the lesser or Darwin’s rhea (Rhea pennata). Both of these rheas are currently rated as near-threatened in their native ranges; a feral population of the greater rhea in Germany appears to be growing.
Rheas are natives of the grasslands and brushy regions of South America. They are found in eastern and central Brazil, Paraguay, Uruguay, Bolivia, and Central Argentina.
Rheas are members of the zoological super order that also includes the ostrich, emu, cassowary, and kiwi, which are collectively known as ratites. All of these birds share in common small or rudimentary wings and a breastbone with no keel. The adult birds are a slate gray color with black on the head, neck, and between the shoulders. The male has more black coloration between the shoulders at the base of the neck. Rheas can also be white in color and sometimes even pure white. This color mutation has been propagated in captivity and is now quite common. Adult rheas stand about 5 feet tall and weigh between 60 and 70 pounds. The male is the larger of the two sexes.
Rheas are polygamous-polyandrous, which means that the roles of the males and females are reversed. The male builds the nest, incubates the eggs, and rears the chicks once they are hatched. The female’s only role is to lay the eggs. When spring arrives, the males become aggressive towards one another and strut around with the feathers on their heads, necks, and chests raised so that they appear larger than they really are. During this time, some males will become aggressive towards humans. The male can be handled by grabbing him by the neck, just below the head, and wrestling him around until he tries to flee.
Once a male has obtained dominance, he will establish a territory and begin to collect a harem of females. He will court the females by spreading his wings, bobbing his head, herding the females around, and by making a booming sound, which sounds like “uh hum”. The male will mate with several females. It is usually best not to exceed 5 or 6 females per male. The females will lay their eggs near the male’s nest and the male will roll the egg into his nest. The nest is a depression in the ground that the male has scraped out and lined with grass. If the male is allowed to sit on the nest, the male will stop mating with the females once he has a clutch of eggs. The females will then join another male and start laying eggs for him.
Female rheas begin laying eggs near the end of April and will lay every other day throughout the summer months. If the eggs are collected from the nest for artificial incubation, a female may lay as many as 50 to 70 eggs. If all the eggs are collected from the nest, the male may abandon the nest and make a new nest in another location. This can make collecting the eggs difficult if the birds are kept in a large enclosure that has many places for the male to hide a nest. A male will usually stay with the same nest if at least one egg is left in the nest. This egg is collected when another egg is laid in the nest. It is a good idea to line the nest with additional hay or straw to keep the eggs clean and dry.
The eggs are butter yellow when they are laid, but they will soon fade to a cream color once incubation has begun. If it is done carefully, artificial incubation is much more efficient than letting the male set on his nest. We incubate the eggs at 98.5oF and a wet bulb temperature of 83oF. The eggs will hatch after 34 to 40 days of incubation. The eggs should be candled after 14 days of incubation to check for fertility. If an egg is not fertile, it should be removed from the incubator so that it doesn’t spoil and possibly contaminate other eggs in the incubator. Eggs should be placed in the incubator as soon as possible after they are laid and no eggs should be held more than 7 days before incubation. Eggs that are placed in the incubator up to a week apart will often hatch at the same time if the eggs are in shell-to-shell contact for at least the last two weeks of incubation.
Hatching and Brooding
Many chicks can be saved by candling the eggs twice a day starting on the thirty-third day and watching for signs that the chick has broken the inner membrane. Once the chick has penetrated the inner membrane, a hole is chipped in the shell where the air sack is and the chick is allowed to continue the hatching process when it is ready. Once the chick is completely hatched from the shell, we leave the chick in the incubator until he is strong enough to stand on his own. This usually takes about 24 hours. The chicks are then placed in a brooder that has artificial turf on the bottom and red infrared heat lamps handing above for heat. The red bulbs help prevent the chicks from picking at one another’s eyes while they are in the brooder. When the weather is warm, we like to get the chicks outside on a mowed lawn as soon as possible. This allows the chicks to exercise, to eat fresh grass, and catch insects. A shelter and a heat lamp should be provided for bad weather and at night.
Rheas are mainly grazers and consume large quantities of grass, clover, dandelions, and other broad-leaf weeds. They will also eat small eggs, insects, earthworms, and small snakes. For adult birds, we feed chunk dog food, a ratite pellet, and green leaf lettuce. During the breeding season, a laying mash is mixed with these other feeds. The chicks are fed a ratite starter pellet, turkey starter, or a gamebird starter. The chicks are also given leaf lettuce and they are put in grass lots as soon as possible.