“Nine-banded armadillos always give birth to four genetically identical quadruplets, all developed from a single fertilized egg.”
The nine-banded armadillo is the only mammal encased in a true bony shell. It always gives birth to four genetically identical quadruplets from a single fertilized egg — a trait unique among mammals.
By An Nguyen · Published · Updated
Dasypus novemcinctusCingulataDasypodidae
Browse armadillo photographs—from bony armor and digging behavior to quadruplet pups.
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Core article
A closer look at habitat, diet, behavior, reproduction, and conservation.
The nine-banded armadillo (Dasypus novemcinctus) is the most widespread armadillo and the only one found in the United States. It is the only mammal wrapped in a true bony shell — a mosaic of interlocking plates called osteoderms — and it has a reproductive quirk found nowhere else in mammals: every litter is four genetically identical quadruplets, all cloned from a single fertilised egg. A stocky, nocturnal omnivore with a powerful nose for buried grubs, it is also one of the few mammals actively expanding its range.
The armadillo's carapace is genuine bone: plates of osteoderm grown in the skin and covered by a layer of keratin. It is arranged as a solid shield over the shoulders, another over the hips, and a set of movable bands across the middle — usually nine, sometimes eight or ten — that give the animal some flex. Despite the popular image, the nine-banded armadillo cannot roll into a ball; only the South American three-banded armadillo can fully seal itself inside its shell. This armour evolved in the armadillo line around 58 million years ago as a defence against predators, and it arose entirely independently of the superficially similar scales of pangolins — a case of convergent evolution. Armadillos belong to the ancient superorder Xenarthra alongside sloths and anteaters.
The nine-banded armadillo ranges from the southern United States down through Mexico and Central America across most of South America to Uruguay and northern Argentina, using grassland, scrub, forest edges, and riverbanks with loose, diggable soil. Remarkably, it has been pushing north through the U.S. since it first crossed the Rio Grande in the mid-1800s, now reaching as far as Nebraska and Illinois. What limits the spread is cold, not competition: with little body fat, no insulating underfur, and a low metabolism, armadillos cannot survive prolonged freezes. Each digs burrow systems 5 to 25 feet long with a main entrance and satellite exits.
Armadillos are omnivores with a heavy insect bias — ants, termites, beetles, and grubs make up over 90% of the diet, rounded out with small vertebrates, eggs, fruit, seeds, and fungi. Foraging is almost entirely nocturnal: the armadillo shuffles nose-down, probes the soil by smell, then digs fast with its heavy foreclaws and laps up insects with a long, sticky tongue, taking tens of thousands of ants at a sitting. Its unusually low body temperature — about 89°F, among the lowest of any placental mammal — reflects a slow metabolism matched to that low-calorie, insect-based diet.
Armadillos are largely solitary, with overlapping home ranges but separate burrows and little interaction outside breeding. A cornered or startled armadillo makes a distinctive vertical leap, three to four feet straight up — a reflex that may startle a predator but is disastrous around cars, driving heavy road mortality in the U.S. If chased it bolts for a burrow and wedges itself in with its shell. It is also a capable swimmer: in shallow water it can walk along the bottom holding its breath for up to six minutes, and for deeper crossings it gulps air to inflate its intestines for buoyancy and paddles across.
Armadillos mate in summer but delay implantation for three to four months; once the embryo implants, active gestation runs about 120 days, with births in spring. The signature trait is obligate polyembryony: a single fertilised egg splits into four, so every pregnancy yields four identical, same-sex young. The pups are born fully formed with soft, leathery skin that hardens into armour within weeks, nurse for two to three months, and reach adult size and maturity by about a year. Wild armadillos live 12 to 15 years, up to 20 in captivity.
The nine-banded armadillo is Least Concern with an increasing population — one of the few New World mammals whose range is actively growing. The main hazard to individuals in the U.S. is vehicle strikes, worsened by that startle-jump into a car's undercarriage. Habitat loss affects local populations, but the species' high reproductive rate and flexibility offset it. Armadillos are also a natural reservoir of the bacterium that causes leprosy (Hansen's disease), which draws public-health interest, though human infection is rare and generally needs direct, prolonged contact.
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Cingulata
Family
Dasypodidae
Genus
Dasypus
Species
D. novemcinctus
Nine-banded armadillos always give birth to four genetically identical quadruplets, all developed from a single fertilized egg.
Despite popular belief, nine-banded armadillos cannot roll into a ball — only the three-banded armadillo can do that.
Armadillos can hold their breath for up to six minutes while walking along the bottom of streams and ponds.
To cross deeper water, armadillos swallow air to inflate their intestines, using them as flotation devices.
Armadillos have a body temperature of only 89°F (32°C), one of the lowest among placental mammals.
The name 'armadillo' means 'little armored one' in Spanish, referring to their bony shell of dermal plates.
Select a question to reveal the answer.
An armadillo is a small omnivore mammal covered in a shell of bony plates called osteoderms. The nine-banded armadillo is the most widespread species, found across the Americas from the southern United States to Argentina.
Armadillos inhabit grassland, scrubland, and forest-edge habitats from the southern United States through Central and South America. They prefer warm climates with loose soil suitable for burrowing.
Armadillos are omnivores that feed mainly on insects — ants, termites, beetles, and grubs — which they locate by smell and dig up with powerful claws. They also eat small vertebrates, fruits, and seeds.
The nine-banded armadillo cannot roll into a ball. Only the South American three-banded armadillo can fully enclose itself in its shell. This is one of the most common misconceptions about armadillos.
Nine-banded armadillos produce four identical offspring because a single fertilized egg splits into four embryos — a process called obligate polyembryony. All four pups are genetic clones of each other.
Armadillos can walk along the bottom of shallow streams while holding their breath for up to six minutes. In deeper water, they swallow air to inflate their intestines and float across the surface.
Armadillos can reach speeds of up to 30 mph in short bursts when fleeing predators. They also jump straight up when startled — a reflex that unfortunately makes them vulnerable to vehicle strikes.
Armadillos are not aggressive and generally flee when approached. However, they are one of the few animals that can carry the bacterium that causes leprosy (Hansen's disease), though transmission to humans is rare.
Nine-banded armadillos measure 15 to 23 inches (38–58 cm) in body length with a 9 to 15-inch tail, and weigh 8 to 17 pounds (3.5–7.7 kg). The giant armadillo, a separate species, can reach over 100 pounds.
The nine-banded armadillo is listed as Least Concern with an increasing population trend. It is one of the few mammal species actively expanding its range northward in the United States.
Armadillos rely on their bony shell, speed, and burrowing ability for defense. When threatened, they dash for their burrows or press flat against the ground, using their armor as a shield against bites.
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