An armadillo is protected by plates that overlap to make body and head armor. The plates are made of bone, wrapped in a leathery skin and separated by soft skin that allows the armadillo to bend. Despite their resemblance to armored tanks, armadillos are vulnerable to predation. Black bears, alligators, coyotes, and humans prey on adults, while the smaller, softer juveniles are eaten by hawks and eagles. When threatened, some species roll up in a ball to protect their unarmored bellies. The sharp claws of armadillos may also help them repel predators. Their claws are specialized for digging burrows. When cornered, an armadillo will retreat to its burrow and brace itself against the sides. Its tail is long and slippery, making it a challenge for a predator to pull it out. Armadillos also take advantage of their shrubby habitats by dashing into thorny bushes to take cover. They are surprisingly fast runners on their short legs.

Mammals are named for their special milk-producing structures called mammary glands. A female mammal may have two (like humans) or as many as 18 mammary glands. Each gland is full of small spaces lined with milk-secreting cells that all drain into a nipple. Newborn mammals have an innate sucking reflex that stimulates the mother's mammary glands to release milk. Milk is a superfood for young mammals, containing a nourishing mix of fats, proteins, vitamins, minerals, and even immune-system chemicals. The first milk (colostrum) contains antibodies from the mother to protect against disease. As the offspring grows, milk changes to maintain the right balance of nutrients. Production of milk (lactation) makes most female mammals temporarily unable to get pregnant, resulting in natural gaps between offspring. The spacing of births benefits both the offspring and the mother in terms of survival. Mother mammals stop nursing (wean) their babies after several days or years, depending on the species and environmental conditions.