Food Ecology of the Rice Rat, Oryzomys palustris (Harlan), in a Georgia Salt Marsh

Examination of 22 stomachs of rice rats taken in summer and fall indicated a predominance of animal food, chiefly insects and small crabs, although plant remains were present in several stomachs. Prédation on eggs and young of marsh wrens was known to occur. Individuals reared in the laboratory from nestlings taken from a Georgia salt marsh preferred foods of an animal source, and made greater weight gains when animal material constituted all or part of the diet. While captives were able to assimilate both plant and animal food efficiently, they ingested more calories when animal food was offered. A daily intake level of 0.15 Kcal/Kcal body tissue was required to maintain body weight in the laboratory; ingestion rates above this level resulted in weight gains. It is concluded that during the summer months the trophic niche of the rice rat in the salt marsh ecosystem is that of a carnivore.