Habitat and anatomy
Armadillos are small to medium-sized mammals. The smallest species, the pink fairy armadillo, is roughly chipmunk-sized at 85 g (3.0 oz) and 11 cm (4.3 in) in total length. The largest species, the giant armadillo, can be the size of a small pig, weigh up to 60 kg (150 lb) and be over 150 cm (39 in) long. They are prolific diggers. Many species use their sharp claws to dig for food, such as grubs, and to dig dens. The nine-banded armadillo prefers to build burrows in moist soil near the creeks, streams, and arroyos around which it lives and feeds. The diets of different armadillo species vary, but consist mainly of insects, grubs, and other invertebrates. Some species, however, feed almost entirely on ants and termites.
Paws of a hairy and a giant armadillo
In common with other xenarthrans, armadillos in general, have low body temperatures (33–36°C) and basal metabolic rates (from 40–60% of that expected in placental mammals of their mass). This is particularly true of types that specialize in using termites as their primary food source.
The armor is formed by plates of dermal bone covered in relatively small, overlapping epidermal scales called "scutes", composed of bone with a covering of horn. Most species have rigid shields over the shoulders and hips, with a number of bands separated by flexible skin covering the back and flanks. Additional armor covers the top of the head, the upper parts of the limbs, and the tail. The underside of the animal is never armored, and is simply covered with soft skin and fur.
This armor-like skin appears to be the main defense of many armadillos, although most escape predators by fleeing (often into thorny patches, from which their armor protects them) or digging to safety. Only the South American three-banded armadillos (Tolypeutes) rely heavily on their armor for protection. When threatened by a predator, Tolypeutes species frequently roll up into a ball. Other armadillo species cannot roll up because they have too many plates. The North American nine-banded armadillo tends to jump straight in the air when surprised, and consequently often collides with the undercarriage or fenders of passing vehicles.
Armadillos have short legs, but can move quite quickly, and have the ability to remain under water for as long as six minutes. Because of the density of its armor, an armadillo will sink in water unless it swallows air, inflating its stomach to twice normal size and raising its buoyancy above that of water, allowing it to swim across narrow streams and ditches.
Armadillos have very poor eyesight, and use their keen sense of smell to hunt. They use their claws for digging and finding food, as well as for making their homes in burrows. They dig their burrows with their claws, making only a single corridor the width of the animal's body. They have five clawed toes on their hindfeet, and three to five toes with heavy digging claws on their forefeet. Armadillos have a large number of cheek teeth, which are not divided into premolars and molars, but usually have incisors or canines.