Armadillo

For other uses, see Armadillo (disambiguation).
Armadillo
Temporal range: 58.7–0 Ma

Late Paleocene – Recent

Nine-banded armadillo (Dasypus novemcinctus)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Xenarthra
Order: Cingulata
Families

Chlamyphoridae
Dasypodidae

Nine-banded armadillo skeleton.

Armadillos are New World placental mammals with a leathery armour shell. Chlamyphoridae and Dasypodidae are the only surviving families in the order Cingulata, part of the superorder Xenarthra, along with the anteaters and sloths. The word armadillo means "little armoured one" in Spanish. The Aztecs called them āyōtōchtli [aːjoːˈtoːt͡ʃt͡ɬi], Nahuatl for "turtle-rabbit": āyōtl [ˈaːjoːt͡ɬ] (turtle) and tōchtli [ˈtoːt͡ʃt͡ɬi] (rabbit).[1]

About 9 extant genera and 21 extant species of armadillo have been described, some of which are distinguished by the number of bands on their armour. 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 54 kg (119 lb), while the pink fairy armadillo is a diminutive species, with an overall length of 13–15 cm (5–6 in). All species are native to the Americas, where they inhabit a variety of different environments.

Recent genetic research suggests that an extinct group of giant armoured mammals, the glyptodonts, should be included within the lineage of armadillos, having diverged some 35 million years ago, much more recently than previously assumed.[2]

History and Distribution

Like all of the Xenarthra 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.[3] (Some of their much larger cingulate relatives, the pampatheres and chlamyphorid glyptodonts, made the same journey.)[3]

Today, all extant armadillo 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 central Indiana.[4] Their range has consistently expanded in North America over the last century due to a lack of natural predators.

Habitat and anatomy

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 13–15 cm (5.1–5.9 in) in total length. The largest species, the giant armadillo, can be the size of a small pig, weigh up to 54 kg (119 lb) and can be 150 cm (59 in) long.[5] 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.

Paws of a hairy and a giant armadillo

In common with other xenarthrans, armadillos, in general, have low body temperatures of 33–36 °C (91–97 °F) and basal metabolic rates (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).[6]

The armour 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 armour covers the top of the head, the upper parts of the limbs, and the tail. The underside of the animal is never armoured, and is simply covered with soft skin and fur.[7]

This armour-like skin appears to be the main defense of many armadillos, although most escape predators by fleeing (often into thorny patches, from which their armour protects them) or digging to safety. Only the South American three-banded armadillos (Tolypeutes) rely heavily on their armour 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.[8]

Armadillos have short legs, but can move quite quickly. The ninebanded armadillo is noted for its movement through water[9] which is accomplished via two different methods: it can walk underwater for short distances, holding its breath for as long as six minutes; also, to cross larger bodies of water, it is capable of increasing its buoyancy by swallowing air, inflating its stomach and intestines.[10]

Armadillos have very poor eyesight, and use their keen sense of smell to hunt for food.[5] They use their claws for digging and finding food, as well as for making their homes in burrows. They dig their burrows with their claws, making only a single corridor the width of the animal's body. They have five clawed toes on their hindfeet, and three to five toes with heavy digging claws on their forefeet. Armadillos have a large number of cheek teeth, which are not divided into premolars and molars, but usually have incisors or canines. The dentition of the nine-banded armadillo is P 7/7, M 1/1 = 32.[11]

Gestation lasts from 60 to 120 days, depending on species, although the nine-banded armadillo also exhibits delayed implantation, so the young are not typically born for eight months after mating. Most members of the genus Dasypus give birth to four monozygotic young (that is, identical quadruplets),[12] but other species may have typical litter sizes that range from one to eight. The young are born with soft, leathery skin, which hardens within a few weeks. They reach sexual maturity in three to 12 months, depending on the species. Armadillos are solitary animals that do not share their burrows with other adults.[7]

Classification

Pink fairy armadillo

Family Dasypodidae

Family Chlamyphoridae

† indicates extinct taxon

Armadillos and humans

In science

Armadillos are often used in the study of leprosy, since they, along with mangabey monkeys, rabbits and mice (on their footpads), are among the few known species that can contract the disease systemically. They are particularly susceptible due to their unusually low body temperature, which is hospitable to the leprosy bacterium, Mycobacterium leprae. (The leprosy bacterium is difficult to culture and armadillos have a body temperature of 34 °C (93 °F), similar to human skin.) Humans can acquire a leprosy infection from armadillos by handling them or consuming armadillo meat.[14] Armadillos are a presumed vector and natural reservoir for the disease in Texas and Louisiana.[15] Prior to the arrival of Europeans in the late 15th century, leprosy was unknown in the New World. Given that armadillos are native to the New World, at some point they must have acquired the disease from humans.[14][15]

The armadillo is also a natural reservoir for Chagas disease.[16]

The nine-banded armadillo also serves science through its unusual reproductive system, in which four genetically identical offspring are born, the result of one original egg.[17][18][19] Because they are always genetically identical, the group of four young provides a good subject for scientific, behavioral or medical tests that need consistent biological and genetic makeup in the test subjects. This is the only reliable manifestation of polyembryony in the class Mammalia, and exists only within the genus Dasypus and not in all armadillos, as is commonly believed. Other species that display this trait include parasitoid wasps, certain flatworms and various aquatic invertebrates.[18]

Armadillos (mainly Dasypus) are common roadkill due to their habit of jumping three to four feet vertically when startled, which puts them into collision with the underside of vehicles. Wildlife enthusiasts are using the northward march of the armadillo as an opportunity to educate others about the animals, which can be a burrowing nuisance to property owners and managers.[17]

As musical instruments

Main article: Charango

Armadillo shells have traditionally been used to make the back of the charango, an Andean lute instrument.

In the news

Armadillo shells are so strong that two people have been reported as being injured by bullets ricocheting off armadillos' shells.[20]

References

  1. ↑ Karttunen, Frances E. (1983). An Analytical Dictionary of Nahuatl. University of Oklahoma Press. p. 17. ISBN 978-0-8061-2421-6. View entry at "ayotoch" in Nahuatl Dictionary, by the Wired Humanities Projects, Stephanie Wood (ed.) Retrieved 2015-07-22.
  2. ↑ "Study finds relationship between glyptodonts, armadillos". AMNH. Retrieved 2016-02-22.
  3. 1 2 Woodburne, M. O. (14 July 2010). "The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens". Journal of Mammalian Evolution 17 (4): 245–264 (see p. 249). doi:10.1007/s10914-010-9144-8. PMC 2987556. PMID 21125025.
  4. ↑ "Armadillos slinking their way into Indiana". TheIndyChannel. The Associated Press. 7 June 2014. Retrieved 2014-06-16.
  5. 1 2 "Armadillos, Armadillo Pictures, Armadillo Facts". National Geographic. Retrieved 2015-07-22.
  6. ↑ McNab, Brian K. (November 1980). "Energetics and the limits to the temperate distribution in armadillos". Journal of Mammalogy (American Society of Mammalogists) 61 (4): 606–627. doi:10.2307/1380307. JSTOR 1380307.
  7. 1 2 Dickman, Christopher R. (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 781–783. ISBN 0-87196-871-1.
  8. ↑ "How high can a nine-banded armadillo jump?". Everyday Mysteries: Fun Science Facts from the Library of Congress. Library of Congress. 12 February 2009. Archived from the original on 2009-12-06. Retrieved 2009-12-17.
  9. ↑ McDonough, Colleen M.; Loughry, W. J. (2013). The Nine-Banded Armadillo: A Natural History. University of Oklahoma Press. pp. 181–182. ISBN 978-0-8061-8921-5.
  10. ↑ Vijayaraghavan, R. (2009). "Nine-banded Armadillo Dasypus novemcinctus Animal Model for Leprosy (Hansen's Disease)". Scandinavian Journal of Laboratory Animal Sciences 36 (2): 167–176. Retrieved 2015-07-22.
  11. ↑ Freeman, Patricia W.; Genoways, Hugh H. (December 1998). "Recent Northern Records of the Nine-banded Armadillo (Dasypodidae) in Nebraska". The Southwestern Naturalist 43 (4): 491–504. Retrieved 2010-06-07.
  12. ↑ Bagatto, B.; Crossley, D. A.; Burggren, W. W. (1 June 2000). "Physiological variability in neonatal armadillo quadruplets: within- and between-litter differences". Journal of Experimental Biology. 159 203 (11): 267–277. PMID 10804163.
  13. ↑ Billet, Guillaume; Hautier, Lionel; de Muizon, Christian; Valentin, Xavier (2011). "Oldest cingulate skulls provide congruence between morphological and molecular scenarios of armadillo evolution". Proceedings of the Royal Society 278 (1719): 2791. doi:10.1098/rspb.2010.2443.
  14. 1 2 Harris, Gardiner (27 April 2011). "Armadillos Can Transmit Leprosy to Humans, Federal Studies Confirm". The New York Times. Archived from the original on 2011-05-06. Retrieved 2011-05-03.
  15. 1 2 Truman, Richard W.; Singh, Pushpendra; Sharma, Rahul; Busso, Philippe; Rougemont, Jacques; Paniz-Mondolfi, Alberto; Kapopoulou, Adamandia; Brisse, Sylvain; Scollard, David M.; Gillis, Thomas P.; Cole, Stewart T. (April 28, 2011). "Probable Zoonotic Leprosy in the Southern United States". The New England Journal of Medicine (Waltham, MA: Massachusetts Medical Society) 364 (17): 1626–1633. doi:10.1056/NEJMoa1010536. PMC 3138484. PMID 21524213. Retrieved 2011-05-03.
  16. ↑ Yaeger, R. G. (March 1988). "The prevalence of Trypanosoma cruzi infection in armadillos collected at a site near New Orleans, Louisiana". The American Journal of Tropical Medicine and Hygiene 38 (2): 323–326. PMID 3128127.
  17. 1 2 Schaefer, Joseph M.; Hostetler, Mark E. (January 1998). "The Nine-banded Armadillo (Dasypus novemcinctus)". University of Florida, IFAS Extension. Archived from the original on 2010-01-02. Retrieved 2009-12-17.
  18. 1 2 Loughry, W.J; Prodohl, Paulo A; McDonough, Colleen M; Avise, John C. (May–June 1998). "Polyembryony in Armadillos" (PDF). American Scientist 86 (3): 274–279. Bibcode:1998AmSci..86..274L. doi:10.1511/1998.3.274.
  19. ↑ Hamlett, G. W. D. (September 1933). "Polyembryony in the Armadillo: Genetic or Physiological?". The Quarterly Review of Biology 8 (3): 348–358. doi:10.1086/394444. JSTOR 2808431.
  20. ↑ Holpuch, Amanda (1 August 2015). "Texas man hospitalized after bullet bounces off armadillo". The Guardian. Retrieved 2015-09-04.

Further reading

External links

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