Armadillo, Caleta Valdés, Chubut Province, Argentina, South America

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• published: 08 Jan 2014
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Armadillos are New World placental mammals with a leathery armor shell. The Dasypodidae are the only surviving family in the order Cingulata, part of the superorder Xenarthra, along with the anteaters and sloths. The word armadillo means "little armored one" in Spanish. About 10 extant genera and 20 extant species of armadillo have been described, some of which are distinguished by the number of bands on their armor. Their average length is about 75 cm (30 in), including tail. The giant armadillo grows up to 150 cm (59 in) and weighs up to 59 kg (130 lb), while the pink fairy armadillo is a diminutive species, with an overall length of 12 to 15 cm (5 to 6 in). All species are native to the Americas, where they inhabit a variety of environments. Like all other xenarthran lineages, armadillos originated in South America. Due to the continent's former isolation, they were confined there for most of the Cenozoic. The recent formation of the Isthmus of Panama allowed a few members of the family to migrate northward into southern North America by the early Pleistocene, as part of the Great American Interchange. (Some of their much larger cingulate relatives, the pampatheres and glyptodonts, made the same journey). Today, all extant armadillos species are still present in South America. They are particularly diverse in Paraguay (where eleven species exist) and surrounding areas. Many species are endangered. Some, including four species of Dasypus, are widely distributed over the Americas, whereas others, such as Yepes's mulita, are restricted to small ranges. Two species, the northern naked-tailed armadillo and nine-banded armadillo, are found in Central America; the latter has also reached the United States, primarily in the south-central states (notably Texas), but with a range that extends as far east as South Carolina and Florida, and as far north as Nebraska and midwestern Kansas. Their range has consistently expanded in North America over the last century due to a lack of natural predators. They have been found as far north as southern Illinois. Armadillos are small to medium-sized mammals. The smallest species, the pink fairy armadillo, is roughly chipmunk-sized at 85 g (3.0 oz) and 11 cm (4.3 in) in total length. The largest species, the giant armadillo, can be the size of a small pig, weigh up to 60 kg (130 lb) and be over 100 cm (39 in) long. They are prolific diggers. Many species use their sharp claws to dig for food, such as grubs, and to dig dens. The nine-banded armadillo prefers to build burrows in moist soil near the creeks, streams, and arroyos around which it lives and feeds. The diets of different armadillo species vary, but consist mainly of insects, grubs, and other invertebrates. Some species, however, feed almost entirely on ants and termites. In common with other xenarthrans, armadillos in general, have low body temperatures (33--36°C) and basal metabolic rates (from 40--60% of that expected in placental mammals of their mass). This is particularly true of types that specialize in using termites as their primary food source (for example, Priodontes and Tolypeutes). The armor is formed by plates of dermal bone covered in relatively small, overlapping epidermal scales called "scutes", composed of bone with a covering of horn. Most species have rigid shields over the shoulders and hips, with a number of bands separated by flexible skin covering the back and flanks. Additional armor covers the top of the head, the upper parts of the limbs, and the tail. The underside of the animal is never armored, and is simply covered with soft skin and fur. This armor-like skin appears to be the main defense of many armadillos, although most escape predators by fleeing (often into thorny patches, from which their armor protects them) or digging to safety. Only the South American three-banded armadillos (Tolypeutes) rely heavily on their armor for protection. When threatened by a predator, Tolypeutes species frequently roll up into a ball. Other armadillo species cannot roll up because they have too many plates. The North American nine-banded armadillo tends to jump straight in the air when surprised, and consequently often collides with the undercarriage or fenders of passing vehicles. Armadillos have short legs, but can move quite quickly, and have the ability to remain under water for as long as six minutes. Because of the density of its armor, an armadillo will sink in water unless it swallows air, inflating its stomach to twice normal size and raising its buoyancy above that of water, allowing it to swim across narrow streams and ditches.