The skin is remarkably modified to provide a double-layered covering of horn and bone over most of the upper surface and sides of the animals, and some protection to the underparts and limbs. Young look like miniature adults when they're born, and within a few days their leathery skin hardens into armor. Underparts are covered with soft-haired skin.
Hair sometimes projects from under the side plates.
The three-banded armadillo's name refers to the hinged bands on the back that enable armadillos to curl up and protect their soft underparts from predators. The three-banded armadillo has the system perfected so that it can make a perfect ball with the armored head and tail exactly filling the chinks left when the body is curled. When threatened, it leaves a small opening between the edges of the shell and, when touched on the chest or abdomen, snaps the edges together like a steel trap. Our native nine-banded armadillo cannot roll that tightly into a ball. The armor on the three-banded armadillo is also considerably thicker which reflects its dry forest and savanna habitat in central South America.