10 Facts About Armadillos

Among the most distinctive-looking of all mammals—looking a bit like a cross between a polecat and an armored dinosaur—armadillos are a relatively common sight in the New World, and objects of intense curiosity elsewhere.

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There Are 21 Identified Armadillo Species

A pink fairy armadillo. Wikimedia Commons

The nine-banded armadillo, Dasypus novemcinctus, is by far the most familiar, but armadillos come in an impressive range of shapes, sizes, and—especially—amusing names. Among the less-well-known species are the screaming hairy armadillo, the greater long-nosed armadillo, the southern naked-tailed armadillo, the pink fairy armadillo (which is only about the size of a squirrel) and the giant armadillo (at up to 120 pounds, a good match for a welterweight fighter). All of these armadillo species are characterized by the armor plating heads, backs and tails, the distinctive feature that gives this family of mammals its name (Spanish for "little armored ones.")

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Armadillos Live in North, Central, and South America

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Armadillos are exclusively New World mammals, originating in South America millions of years ago during the Cenozoic Era, when the Central American isthmus had yet to form and this continent was cut off from North America. Starting about three million years ago, the appearance of the isthmus facilitated the Great American Interchange, when various armadillo species migrated north (and, in turn, other types of mammals migrated south and replaced the native South American fauna). Today, most armadillos live exclusively in central or South America; the only species that ranges across the expanse of the Americas is the nine-banded armadillo, which can be found as far afield as Texas, Florida and Missouri.

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The Plates of Armadillos Are Made Out of Bone

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Unlike the horns of rhinos, or the fingernails and toenails of humans, the plates of armadillos are made out of solid bone—and grow directly out of these animal's vertebrae, the number and pattern of the bands (anywhere from three to nine) depending on the species. Given this anatomical fact, there is actually only one armadillo species—the three-banded armadillo—that's flexible enough to curl up into an impenetrable ball when threatened; other armadillos are too unwieldy to pull off this trick, and prefer to escape predators by simply running away or (like the nine-banded armadillo) executing a sudden vertical leap three or four feet into the air.

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Armadillos Feed Exclusively on Invertebrates

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The vast majority of armored animals—from the long-extinct Ankylosaurus to the modern pangolin—evolved their plates not to intimidate other creatures, but to avoid being eaten by predators. Such is the case with armadillos, which subsist exclusively on ants, termites, worms, grubs, and pretty much any other invertebrates that can be unearthed by burrowing into the soil. On the other end of the food chain, smaller armadillo species are preyed on by coyotes, cougars and bobcats, and occasionally even hawks and eagles. Part of the reason nine-banded armadillos are so widespread is that they're not especially favored by natural predators; in fact, most nine-banders are killed by humans, either on purpose (for their meat) or accidentally (by speeding cars).

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Armadillos Are Closely Related to Sloths and Anteaters

A long-haired armadillo. Getty Images

Armadillos are classified as xenarthrans, a superorder of placental mammals that also includes sloths and anteaters. Xenarthrans (Greek for "strange joints") exhibit a strange property called, you guessed it, xenarthry, which refers to the extra articulations in these animals' backbones; they are are also characterized by the unique shape of their hips, their low body temperatures, and the internal testicles of males. Recently, in the face of accumulated genetic evidence, the superorder Xenarthra was split into two orders: Cingulata, which includes armadillos, and Pilosa, which comprises sloths and anteaters. (Pangolins and aadvarks, which superficially resemble armadillos and anteaters, respectively, are unrelated mammals the features of which can be chalked up to convergent evolution.)

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Armadillos Hunt With Their Sense of Smell

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Like most small, skittering mammals that live in burrows, armadillos rely on their acute sense of smell to locate prey and avoid predators (a nine-banded armadillo can sniff out grubs buried six inches beneath the soil), and they have relatively weak eyes. Once an armadillo homes in on an insect nest, it quickly digs through the dirt or soil with its large front claws, and the holes it leaves can be a huge nuisance to homeowners, who may have no choice but to call in a professional exterminator. Some armadillos are also good at holding their breath for extended periods of time; for example, the nine-banded armadillo can stay underwater for as long as six minutes!

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Nine-Banded Armadillos Give Birth to Identical Quadruplets

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Among humans, giving birth to identical quadruplets is literally a one-in-a-million event, much rarer than identical twins or triplets. However, nine-banded armadillos accomplish this feat literally every day: after fertilization, the egg of the female splits into four genetically identical cells, which go on to produce four genetically identical offspring. Why this happens is a bit of a mystery; it's possible that having four identical offspring of the same sex reduces the risk of inbreeding when the juveniles mature, or it may just be an evolutionary quirk from millions of years ago that somehow got "locked into" the armadillo genome because it didn't have any long-term disastrous consequences.

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Armadillos Are Often Used to Study Leprosy

The bacteria that cause leprosy. Wikimedia Commons

One odd fact about armadillos is that (along with their xenarthran cousins, sloths and anteaters) they have relatively sluggish metabolisms, and hence low body temperatures. This makes armadillos especially susceptible to the bacterium that causes leprosy (which needs a cool skin surface on which to propagate), and thus makes these mammals ideal test subjects for leprosy research. Usually, animals transmit diseases to humans, but in the case of armadillos the process seems to have worked in reverse: until the arrival of human settlers in South America 500 years ago, leprosy was unknown in the New World, so a series of unfortunate armadillos must have been picked up (or even adopted as pets) by Spanish conquistadors!

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Armadillos Used to Be Much Bigger Than They Are Today

A Glyptodon fossil. Wikimedia Commons

During the Pleistocene epoch, a million years ago, mammals came in much bigger packages than they do today. Along with the three-ton prehistoric sloth Megatherium and the bizarre-looking hoofed mammal Macrauchenia, South America was populated by the likes of Glyptodon, a 10-foot-long, one-ton armadillo that feasted on plants rather than insects. Glyptodon lumbered across the Argentinean pampas right up to the cusp of the last Ice Age; the earliest human settlers of South America occasionally slaughtered these giant armadillos for their meat and used their capacious shells to shelter themselves from the elements.

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"Charangos" Were Once Made From Armadillos

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A variant of the guitar, charangos became popular among the indigenous peoples of north-western South America after the arrival of European settlers. For hundreds of years, the soundbox (resonating chamber) of the typical charango was made from the shell of an armadillo, perhaps because Spanish and Portuguese colonialists prohibited the natives from using wood, or perhaps because the smallish shell of an armadillo could more easily be tucked into native garments. Today, some classic charangos are still made out of armadillos, but wooden instruments are much more common (and presumably less distinctive sounding).