The tawny-bellied cotton rat is the largest of the Sigmodon species, and dominates other cotton rats where more than one species occurs. Its back fur has a speckled, "salt and pepper" look, and its underparts are buff-colored, giving it two common names: tawny-bellied and yellow-bellied. Learn more about the Sigmodon fulviventer, more commonly known as a Tawny-bellied Cotton Rat, in this easy-to-read species overview by the Smithsonian's National Museum of Natural History.