Why do armadillos have hard armor plates?

Armadillo armor is one of the most distinctive defenses among mammals. The plates are made of dermal bone covered by keratin, the same protein found in hair and nails. This armor helps protect them from bites and scratches while they forage on the ground for insects and small invertebrates. Different species have different numbers of bands, which affect how flexible they are. In some species, the armor is so effective that the animal can roll partly or fully into a ball, though not all armadillos do this.