Reproductivity and raising of Greater Rhea (Rhea americana) and Lesser Rhea (Pterocnemia pennata) -: a review

The Greater Rhea (Rhea americana) and the Lesser Rhea (Pterocnemia pennata) are ratites that have conservation and economic relevance. The two most common schemes for rearing adult rheas are the captive or intensive condition in pens (used by most zoos and farms), and the semi captive or semi intensive condition in large breeding paddocks. Understanding demography of rheas is necessary to design management strategies for these species and to help decision-making at farms and captive breeding programs. The median total number of eggs produced per season by Greater Rhea females under captive condition (40 eggs) is higher than that of Lesser Rheas (18 eggs). Greater Rheas also show a higher egg production under captivity than in semi captivity (24 eggs). The hatching success of Greater Rheas is higher in captivity (median = 60%) than in semi captivity (45%), or in the wild (30%), whereas Lesser Rheas show the opposite trend (captivity = 51%, wild = 60%). Finally, the estimated number of surviving chicks in autumn produced per female rheas are lower than that of other ratites: Ostrich = 14 chicks; Emu = 11 chicks; Cassowaries = 9 chicks; Greater Rheas = 8 chicks; and Lesser Rheas = 4 chicks. Reproductive parameters of all ratites reported in most scientific works show to be more moderate than those commonly claimed in general or commercial literature. Although both rhea species show a comparatively low productivity, incorporating specific management practices suggested in this work into the different rhea production schemes can substantially improve egg laying, hatchability, and survival of chicks and adults.