The nine-banded armadillo is the only armadillo species in North America. Also known as the long-nosed armadillo, it has a hard outer shell, which gives it many advantages.
The armadillo is the only mammal to have a shell. The shell helps protect the armadillo from predators and to protect it from the spiky undergrowth and plants in its environment.
The shell of an armadillo is made up of bony external plates overlaid with scales. The body is flexible, with softer skin underneath that helps to expand and contract between the bands. The shell helps protect the armadillo from predators.
What Is The Shell Made From?
An armadillo’s shell is made from a composite of hard mineral tiles. These are connected by soft non-mineralized collagen fibrils known as Sharpey’s fibers. The bony armor called the osteoderm comprises a top-level of keratin. Beneath this top layer, hexagonal or triangular tiles are made from bone.
The Sharpey’s fibers connect the different tiles making up the shell. This gives hard and soft tissue shell properties, but these do not cover the face or ears. The body comprises three sections, the pectoral shield, the banded shield, and the pelvic shield.
How Does The Shell Help Against Predators?
The shell makes the armadillo look tough, which can put some smaller predators off from attacking. The armadillo will stand motionless to see if the predator will ignore them. The nine-banded armadillo, if startled, can also jump three to four feet in the air and is often its first means of defense. If this does not scare off the predator, the armadillo will also use its shell to protect itself.
Armadillos can defend themselves by digging into a burrow large enough to fit their soft underside. Their long legs and long claws allow them to bury themselves quickly. The armadillo will only be left with the shell protruding, wedged into the burrow to protect its soft underbelly.
The predator may claw at them to get them out of the hole but isn’t often successful. Once the predator has given up and moved away, the armadillo will move out of its hole.
Armadillos can run very fast for their size and, if threatened, will use their claws to fight. However, the nine-tailed armadillo is also known for playing dead (like opossums) when caught.
The bony shell can protect the armadillo from stinging or biting insects and prey. Parasites also have fewer spots to attach themselves, with most found on the armadillo’s unprotected underside.
Are Armadillos Born With Their Shells?
A baby armadillo is called a pup, and the mother has four identical pups who develop from the same egg and share the same placenta.
As the armadillo is a mammal, the pups are born alive. Armadillos are born with their shells intact. The pup is born with the shell, called a carapace, already developed. However, the body is soft and not yet fully hardened at birth, feeling like leather with a greyish color.
The shell hardens as the animal ages, with bone being deposited under the skin to make a solid shell. This process is called ossification.
How Thick Is An Armadillo Shell?
In the skin are plates called Osteoderms, bony deposits forming the shell. The thickness of the nine-banded armadillo shells is approximately one-tenth of an inch thick. Although relatively thin, the shell can weigh up to 15% of the total armadillo’s weight.
Armadillos are unlike some other animals with protective shells, such as tortoises. Armadillos are quick runners, and their bodies help them achieve speeds of up to 48 km/h.
Although the shell of animals such as tortoises slow them down, the strong, thin plates the armadillo has, allow them to run quickly.
Does The Shell Overheat?
The armadillo is likely to overheat in the heat due partly to the shell. The armadillo needs to cool down as the shell can weigh up to 15% of its total weight. In the afternoon, the armadillo will burrow down into the ground to escape the heat.
Armadillos will sometimes burrow into the base of termite mounds. The termite mounds have many chambers that act as ventilation. The armadillo uses these ventilation chambers to cool down and gives them an almost unlimited number of ants to eat.
The shell also helps the armadillo when burrowing. The carapace protects the armadillo against abrasions in the ground. As the armadillo likes to be subterranean, the cover protects its body when tunneling.
Does The Shell Affect Breathing?
Armadillos are burrowing animals that live on insects. They often keep their snouts in the soil because they have low metabolic rates.
The shell of an armadillo affects how the armadillo copes with low oxygen levels. Whereas other animals can breathe more deeply when faced with these conditions, the armadillo cannot do this.
The shell makes the thorax of the armadillo rigid, so they cannot take deep breaths. They instead take more shallow, rapid breaths to take in enough oxygen. The shell keeps the armadillo cool in hot temperatures by maximizing heat loss.
The nine-banded armadillo reaches sexual maturity at approximately a year old. They reproduce almost every year.
The male armadillo has a penis reaching up to 60% of its body length. The male mounts the female from behind after a courtship period, which includes touching, sniffing, and making noises. A female armadillo always gives birth to four offspring and can give birth to 56 in their lifetime.
The female armadillo gives birth after a gestation period of 5 months. The armadillo can delay the gestation period up to 18 months after conceiving.
The mothers allow the pups to come out of the burrow once ready to start foraging for food. Nine-banded armadillos venture outside after two to three weeks, and their shells are already beginning to harden.
Armadillos of North America
Only two armadillo species are found outside South America, and only one, the nine-banded armadillo found in North America. The other, the Northern Naked-tailed armadillo, is located in Central America.
The nine-banded armadillo has shown sudden and rapid colonization of the Southern United States. The range expansion per year is approximately ten times faster than the expansion rate expected for most mammals.
Sightings further North in the United States are more common. Before 1850, the nine-banded armadillo had not crossed the Rio Grande. Unsuitable habitats, hunting, and other factors contributed to the armadillo’s move north.
Armadillos are not good at conserving body heat and have very little body fat. Their habitats reflect this, and they cannot breed in temperatures below -2 degrees. Armadillos need a constant water source, with at least 15 inches of rain annually for good conditions.
The armadillo can be found all over Texas but has been spotted in California, Washington, Oregon, Nebraska, and most southern states east of Texas.
References and Further Reading
“Armadillos” by J. David Henry
“The Biology of the Xenarthra” edited by Scott L. Gardner and Gordon K. Bell
“The Evolution and Biology of Armadillos, Sloths, and Vermilinguas” edited by Gordon K. Bell and Richard A. Martin
“The Armadillo: A Study in Animal and Thermodynamic Adaptations” by J. David Henry
“Armadillos and Other Xenarthrans” by Richard A. Martin
“Armadillos, Anteaters, and Sloths: Xenarthrans of the Americas” by Richard D. Estes
“The Evolution of the Xenarthra” by Richard A. Fariña and Richard D. Fernicola
“The Natural History of the Armadillo” by J. David Henry
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.