Narrator: A turtle's shell is as much a part of its body as our rib cage is of ours. In fact, it is their rib cage, and their spine, and their vertebrae, and their sternum. Basically, a turtle's ...

In cartoons, when a turtle is spooked, it retreats into and closes up its shell. While used for comic effect, this imagery is based in fact — although not all turtles are capable of this protective ...