| Nine-banded armadillo | |
|---|---|
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| Male nine-banded armadillo inFlorida, US | |
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| Female nine-banded armadillo inNuevo León,Mexico | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Cingulata |
| Family: | Dasypodidae |
| Genus: | Dasypus |
| Species: | D. novemcinctus |
| Binomial name | |
| Dasypus novemcinctus | |
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| Nine-banded armadillo range | |
| Synonyms[2] | |
Tatusia novemcincta(Linnaeus, 1758) | |
Thenine-banded armadillo (Dasypus novemcinctus), also called thenine-banded long-nosed armadillo orcommon armadillo, is a species ofarmadillo native toNorth,Central, andSouth America, making it the most widespread of the armadillos.[3]
Its ancestors originated inSouth America, and remained there until the formation of theIsthmus of Panama allowed them to enter North America as part of theGreat American Interchange.The nine-banded armadillo is a solitary, mainlynocturnal[4][5] animal, found in many kinds of habitats, from mature and secondaryrainforests tograssland anddry scrub. It is aninsectivore, feeding chiefly onants,termites, and other smallinvertebrates. The armadillo can jump 91–120 cm (3–4 ft) straight in the air if sufficiently frightened, making it a particular danger on roads.[6] It is the state small mammal ofTexas.
North Americansubspecies exhibit reducedgenetic variability compared with the subspecies of South America, indicating the armadillos of North America are descended from a relatively small number of individuals that migrated from south of the Rio Grande.[7]
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Nine-banded armadillos generally weigh from 2.5–6.5 kg (5.5–14.3 lb), though the largest specimens can scale up to 10 kg (22 lb). They are one of the largest species of armadillos.[8] Head and body length is 38–58 cm (15–23 in), which combines with the 26–53 cm (10–21 in) tail, for a total length of 64–107 cm (25–42 in). They stand 15–25 cm (5.9–9.8 in) tall at the top of the shell.[8][9] The outer shell is composed ofossified dermalscutes covered by nonoverlapping,keratinizedepidermalscales, which are connected by flexible bands of skin. This armor covers the back, sides, head, tail, and outside surfaces of the legs. The underside of the body and the inner surfaces of the legs have no armored protection. Instead, they are covered by tough skin and a layer of coarse hair. The vertebrae attach to thecarapace.[7]The claws on the middle toes of the forefeet are elongated for digging, though not to the same degree as those of the much largergiant armadillo of South America.[10]Their lowmetabolic rate and poorthermoregulation make them best suited for semitropical environments.[7]Unlike the South Americanthree-banded armadillos, the nine-banded armadillo cannot roll itself into a ball. It is, however, capable of traversing rivers by inflating itsintestines and floating, or by sinking and running across the riverbed. The second is possible due to its ability to hold its breath for up to six minutes, an adaptation originally developed for allowing the animal to keep its snout submerged in soil for extended periods while foraging.[7] Although nine is the typical number of bands on the nine-banded armadillo, the actual number varies by geographic range.[7]Armadillos possess theteeth typical of allsloths andanteaters. The teeth are all small, peg-likemolars with open roots and noenamel.Incisors do form in the embryos, but quickly degenerate and are usually absent by birth.[7]
The nine-banded armadillo evolved in a warm, rainy environment, and is still most commonly found in regions resembling its ancestral home. As a very adaptable animal, though, it can also be found inscrublands, openprairies, andtropical rainforests. It cannot thrive in particularly cold or dry environments, as its large surface area, which is not well insulated by fat, makes it especially susceptible to heat and water loss.[10] Recently, nine-banded armadillo have been found as far north as Virginia, with several studies suggesting this could get more common as temperatures rise.[11]
The nine-banded armadillo has been rapidly expanding its range both north and east within theUnited States, where it is the only regularly occurring species of armadillo. The armadillo crossed theRio Grande fromMexico in the late 19th century, and was introduced inFlorida at about the same time by humans. By 1995, the species had become well established inTexas,Oklahoma,Louisiana,Arkansas,Mississippi,Alabama,Georgia and Florida, and had been sighted as far afield asKansas,Missouri,Tennessee,Kentucky, and theCarolinas. A decade later, the armadillo had become established in all of those areas and continued its migration, being sighted as far north as southernNebraska,southern Illinois, andsouthern Indiana.[12]The primary cause of this rapid expansion is explained simply by the species having few naturalpredators within the United States, little desire on the part of Americans to hunt or eat the armadillo, and the animals' high reproductive rate. The northern expansion of the armadillo is expected to continue until the species reaches as far north asOhio,Pennsylvania,New Jersey andConnecticut, and all points southward on theEast Coast of the United States. Further northward and westward expansion will probably be limited by the armadillo's poor tolerance of harsh winters, due to its lack of insulating fat and its inability tohibernate.[12]As of 2009, newspaper reports indicated the nine-banded armadillo seems to have expanded its range northward as far asOmaha, Nebraska, in the west, andKentucky Dam andEvansville, Indiana, in the east.[13][14][15] In 1995, armadillos were only seen in the southern tip of South Carolina, and within two to three years, they had swept across most of the state.[10] In late 2009, North Carolina began considering the establishment of a hunting season for armadillo, following reports that the species has been moving into the southern reaches of the state (roughly between the areas ofCharlotte andWilmington).[16][17]Outside the United States, the nine-banded armadillo ranges southward through Central and South America into northernArgentina andUruguay, where it is still expanding its range.[10]
A 2014 genetic study byShapiroet al. found that a 10,000-12,000 year-old fossil tibia from Medford Cave, central Florida, which was previously thought to belong to the extinctbeautiful armadillo (D. bellus), actually belonged to the nine-banded armadillo. This suggests that the nine-banded armadillo naturally inhabited the southeastern United States, including Florida, during theLate Pleistocene until its extirpation from the region early in theHolocene. It is unknown why the armadillo did not recolonize the United States until European settlement of the region, but it has been suggested that hunting byCoahuiltecan tribes and habitat clearance by intentionally-set brushfires prevented armadillos from previously recolonizing the region. Armadillo movement patterns also often follow corridors such as railroads and roads, which likely helped to facilitate its rapid expansion into and throughout the United States.[18][19]
Nine-banded armadillos are generallyinsectivores. They forage for meals by thrusting their snouts into loose soil andleaf litter and frantically digging in erratic patterns, stopping occasionally to dig upgrubs,beetles (perhaps the main portion of this species' prey selection),ants,termites,grasshoppers, otherinsects,millipedes,centipedes,arachnids,worms, and other terrestrialinvertebrates, which their sensitive noses can detect through 8 in (20 cm) of soil.[20][21] They then lap up the insects with their sticky tongues. Nine-banded armadillos have been observed to roll about on ant hills to dislodge and consume the resident ants. They supplement their diets withamphibians and smallreptiles, especially in more wintery months when such prey tends to be more sluggish, and occasionallybird eggs and babymammals.Carrion is also eaten, although perhaps the species is most attracted to themaggots borne by carcasses rather than the meat itself. Less than 10% of the diet of this species is composed by nonanimal matter, thoughfungi,tubers,fruits, andseeds are occasionally eaten.[22][23]
Nine-banded armadillos are solitary, largely nocturnal animals that come out to forage around dusk. They are extensive burrowers, with a single animal sometimes maintaining up to 12 burrows on its range. These burrows are roughly 20 cm (8 in) wide, 210 cm (7 ft) deep, and 760 cm (25 ft) long. Armadillosmark their territory with urine, feces, and excretions fromscent glands found on the eyelids, nose, and feet. Males hold breeding territories and may become aggressive in order to keep other males out of their home range to increase chances of pairing with a female.[24] Territorial disputes are settled by kicking and chasing. When they are not foraging, armadillos shuffle along fairly slowly, stopping occasionally to sniff the air for signs of danger.
If alarmed, nine-banded armadillos can flee with surprising speed. Occasionally, a large predator may be able to ambush the armadillo before it can clear a distance, and breach the hard carapace with a well-placed bite or swipe. If the fleeing escape fails, the armadillo may quickly dig a shallow trench and lodge itself inside. Predators are rarely able to dislodge the animal once it has burrowed itself, and abandon their prey when they cannot breach the armadillo's armor or grasp its tapered tail.[10] Due to their softer carapaces, juvenile armadillos are more likely to fall victim to natural predation and their cautious behavior generally reflects this. Young nine-banded armadillos tend to forage earlier in the day and are more wary of the approach of an unknown animal (including humans) than are adults. Their known natural predators includecougars (perhaps the leading predator),maned wolves,coyotes,black bears,red wolves,jaguars,alligators,bobcats, andlarge raptors. Many thousands fall victim toroadkill caused by auto accidents every year.[25][26]
Mating takes place during a two-to-three month long mating season, which occurs from July–August in theNorthern Hemisphere and November–January in theSouthern Hemisphere. A single egg is fertilized, but implantation is delayed for three to four months to ensure the young will not be born during an unfavorable time. Once thezygote does implant in the uterus, a gestation period of four months occurs, after which the zygote splits into four identicalembryos via collapse of the common amnion and subsequent division of the embryonic shield.[27] Each of the four embryos has a separate amnion and umbilical cord,[28] but all four are attached to a common placenta.[29] They are born in March and weigh 85 g (3 oz).[30] After birth, thequadruplets remain in the burrow, living off the mother's milk for about three months. They then begin to forage with the mother, eventually leaving after six months to a year.[10][7]
Nine-banded armadillos reach sexual maturity at the age of one year, and reproduce every year for the rest of their 12-to-15-year lifespans. A single female can produce up to 56 young over the course of her life. This high reproductive rate is a major cause of the species' rapid expansion.[10]
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The foraging of nine-banded armadillo can cause mild damage to the root systems of certain plants.Skunks,cotton rats,burrowing owls,pine snakes, andrattlesnakes can be found living in abandoned armadillo burrows.[10] Occasionally, the armadillo may threaten the endangeredgopher tortoise by aggressively displacing them from their burrows and claiming the burrows for themselves.[22] Studies have shown thefan-tailed warbler habitually follows armadillos to feed on insects and other invertebrates displaced by them.[31]
They are typically hunted for their meat, which is said to taste likepork, but are more frequently killed as a result of their tendency to steal the eggs of poultry and game birds. This has caused certain populations of the nine-banded armadillo to become threatened, although the species as a whole is under no immediate threat.[10]They are also valuable for use in medical research, as they are among the few mammals other than humans susceptible toleprosy.[7]In Texas, nine-banded armadillos are raised to participate in armadillo racing, a small-scale, but well-established sport in which the animals scurry down a 12-metre (40 ft) track.[10]
During theGreat Depression, the species was hunted for its meat inEast Texas, where it was known as "poor man's pork",[32] or the "Hoover hog" by those who considered PresidentHerbert Hoover to be responsible for the Depression.[33] Earlier, German settlers inTexas would often refer to the armadillo asPanzerschwein ("armored pig").[34] In 1995, the nine-banded armadillo was, with some resistance, made the state mammal of Texas,[35] where it is considered a pest and is often seendead on the roadside. They first forayed into Texas across theRio Grande from Mexico in the 19th century, eventually spreading across the southeast United States.[33]
