Diet of greater rheas in an agroecosystem of central Argentina

Using microhistological analysis of feces, we studied the diet of wild greater Rheas (Rhea americana) by comparing plant species frequency in feces with availability. Green material composed 90% of the diet of rheas, followed by seeds (9%), fruits, and fragments of invertebrates and vertebrates. Wild and cultivated gramineous plants were eaten in low quantity throughout the year (11% of the green material), and were not preferred by rheas. Alfalfa and wild dicots were frequent in the diet (89%) and preferred in some seasons. Rheas consume alfalfa in higher proportions during the winter when this plant is not available to large domestic livestock. Therefore, greater rheas would probably compete more with sheep and goats than with horses and cattle. So the conservation and management of rheas for sustainable use could be compatible with traditional cattle ranching.