Armadillos are the only living mammals with armor-like shells. Armadillos are born as identical quadruplets (4 exact copies). Armadillos have poor vision, but they have a strong sense of smell. They can smell up to 7 inches below the ground! Armadillos sleep for 18-19 hours a day and are active at night. Some armadillos can roll into a ball when they sense danger, but not all can.