Four new species of Ctenomys, a genus of gopher-like mammals found throughout much of South America, have been identified by researchers. The burrowing rodents are commonly called tuco-tucos. The burrowing rodents range from 7 to 12 inches long and weigh less than a pound. They demonstrate the broad range of biological diversity in the lowlands and central valleys of Bolivia, where all four new species were found, a researcher notes.