Despite their heavily armored and lumbering appearance, armadillos can reach a top speed of 30 miles per hour. In fact, most species of the armadillo group, including the common nine-banded armadillo, rely upon running rather than rolling up into a ball to protect themselves from predators.
A frightened armadillo will typically flee into nearby burrow as their primary defense against predators, hence their need for such a high sprinting speed. Their distinct shells are actually a secondary defense for when running away to a hiding spot is not possible. The only armadillo which utilizes its shell as a primary defense is the three-banded armadillo. Rather than fleeing, it will curl up so tightly that its body is entirely enclosed by its shell.