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8 Facts You May Not Know About The Armadillo Shell

There is only one species of armadillo in North America, the nine-banded armadillo.  This armadillo, also known as the long-nosed armadillo, has a hard outer shell, and I wanted to find out how it used it to its advantage.

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 that it lives in.

The shell of an armadillo is made up of bony, external plates that are overlaid with scales.  The shell is flexible, with softer skin underneath that helps to expand and contract between the bands.  The shell helps protect the armadillo from some predators, although they can still be prey for other animals such as coyotes and bears. 

I find armadillos very interesting and wanted to find out more about the shell and its use.

What Is The Shell Made From?

The shell of an armadillo is a material made from a composite of hard mineral tiles.  These are connected by soft non-mineralized collagen fibrils (Sharpey’s fibers).  The bony armor called the osteoderm is made up of a top-level of keratin.  Beneath this top layer, there are hexagonal or triangular tiles that are made from bone.   

The Sharpey’s fibers connect the different tiles making up the shell.  This gives the shells properties of hard and soft tissue.  The shell does not cover the face or ears.  The shell is made of three sections, the pectoral shield, banded shield, and pelvic shield. 

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How Doe The Shell Help Against Predators?

The shell does make the armadillo look tough, and this alone can put some smaller predators off.  The armadillo will stand motionless to see if the predator will ignore them.  The nine-banded armadillo, if startled, can jump three to four feet in the air.  If this does not scare off the predator, then the armadillo can also use its shell as protection.

Armadillos can defend themselves by quickly digging themselves a burrow large enough to fit their soft underside.  Their long legs and long claws make them ideal for this purpose.  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 it isn’t easy.  Subsequently, once the armadillo knows that the predator has given up and moved away, they will then move out from their protection. 

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. 

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Photo of armadillo with shell

The bony shell can also protect the armadillo from stinging or biting insects and prey.  Parasites also have fewer spots to attach themselves, with most being found on the armadillo’s unprotected underside.

Are Armadillos Born With Their Shells?

A baby armadillo is called a pup.  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 as live young.  The armadillos are born with their shells intact.  The pup is born with the shell, called a carapace, already developed.  The shell is softer and not yet fully hardened at birth.  The shell feels like leather with a greyish color. 

The shell hardens as the animal grows, with bone being deposited under the skin to make a solid shell.  This process is called ossification.

How Thick Is An Armadillo Shell?

Armadillos are unlike some other animals with protective shells such as tortoises.  Armadillos can be very fast, and their shell helps them achieve speeds of up to 48 km/h.

Although the shell could slow them down, the animal has evolved strong plates that are also quite thin.

In the skin are plates called Osteoderms, which are bony deposits that form the shell.  The thickness on the nine-banded armadillo shells is approximately one-tenth of an inch thick. 

Although quite thin, the shell can weigh up to 15% of the total armadillo’s weight.

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Does The Shell Overheat?

The armadillo is likely to overheat in the afternoon’s heat, which is due in part to the shell.  As the shell can weigh up to 15% of their total weight, the armadillo needs to cool down.  In the afternoon, the armadillo will burrow down into the ground to get away from the heat.

Armadillos will sometimes burrow into the base of termite mounds.  The termite mounds are made up of many chambers that act as ventilation to the mound.  The armadillo uses these ventilation chambers to cool down.  This also allows the armadillo an almost unlimited number of ants to eat while there.

The shell is also thought to help when burrowing.  The carapace protects the armadillo against abrasions in the ground.  As the armadillo likes to be subterranean, the shell protects its body when tunneling.

Does The Shell Affect Breathing?

Armadillos are burrowing animals who live on insects.  As they have low metabolic rates, they keep their snouts in the soil much of the time.  This can impair the rate that they can take oxygen into their bodies.

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. 

Armadillo with shell

The shell makes the thorax of the animals 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.


With a hard shell, the issue of mating could be quite complicated, but armadillos have this covered.  The nine-banded armadillo reaches sexual maturity at approximately a year old.  They reproduce almost every year. 

The male armadillo has a penis that can reach 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 can give birth to as many as 56 offspring in their life. 

The female armadillo gives birth after a gestation period of 5 months.  The armadillo can delay the gestation period after conceiving, with it being noted that this can happen up to 18 months before giving birth.

The mothers allow the pups to come out of the burrow once ready to start foraging for food.  Nine-banded armadillos start to venture outside after two to three weeks, their shells already hardening.

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Armadillos of North America

There are only two armadillo species found outside South America and only one, the nine-banded armadillo found in North America.  The other, Northern Naked-tailed armadillo, is found 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 a mammal. 

Sightings further North in the United States are more common.  Before 1850, the nine-banded armadillo had not crossed the Rio Grande.  Unsuitable habitat, hunting, and other factors are thought to contribute to the armadillo moving 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 estimates indicating that precipitation of 15 inches annually would be needed for good conditions.

The armadillo can be found all over Texas but has been spotted in California, Washington, Oregon, Nebraska, and over most southern states east of Texas.


The armadillo is a fantastic creature with a shell used for protection against predators and its environment.  Made out of  The armadillo is the only mammal with this shell making it unique in the animal kingdom.

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