Discover Reading Level 3 Nonfiction Reader Learn all about alligators and crocodiles in this nonfiction reader. Students will develop vocabulary and understanding of the species and their characteristics. Sample Text: Alligators and crocodiles look very similar and are sometimes difficult to tell apart. Alligators have shorter heads, more "U-shaped" snouts and only their top teeth are visible when their mouths are closed. Crocodiles have longer heads and more "V-shaped" snouts. If you look at them from the side, when their mouths are shut most of their teeth are visible. Crocodiles are also much more aggressive than alligators.