Wild lesser rheas were studied during two reproductive seasons (2004–2005 and 2005–2006) in three adjacent ranches in Argentine Patagonia. These ranches differed in hunting pressure and egg harvest (protected, moderate and intensive use of the species), and livestock grazing conditions (with and without overgrazing). Density of individuals and nests, clutch size, brood size, hatching success, chick survival and recruitment rate were estimated in each area. At the ranch with intense hunting pressure, egg harvesting and livestock grazing, density of lesser rheas was the lowest and reproductive events were not recorded. None of the recorded demographic parameters differed significantly between the ranch where the species is protected and there is low livestock grazing intensity and the ranch where there is moderate use of the species and intensive grazing. Our work suggests that intense hunting and egg harvesting would have stronger effects than overgrazing on the density and reproductive success of wild lesser rhea populations in Patagonia.
