Part 4/4. Life of Mammals Ep.4. David Attenborough looks at rodents, all of whom possess incisor teeth with chisel-sharp enamel on their front edges. Among the animals observed are the agouti, a terrier-sized rodent that can bite through rock-hard shells, the beaver, which can fell trees with its teeth, and the capybara, a relative of the guinea pig, which is the largest rodent in the world.