Armadillo

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Armadillo
Temporal range: Paleocene-Recent, 58.7–0Ma
Nine-banded armadillo, Dasypus novemcinctus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Xenarthra
Order: Cingulata
Family: Dasypodidae
Gray, 1821
Genera

See text

Nine-banded armadillo skeleton

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. The Aztecs called them āyōtōchtli [aːjoːˈtoːt͡ʃt͡ɬi], Nahuatl for “turtle-rabbit”:[1] āyōtl [ˈaːjoːt͡ɬ] (turtle) and tōchtli [ˈtoːt͡ʃt͡ɬi] (rabbit).[1]

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.[2] (Some of their much larger cingulate relatives, the pampatheres and glyptodonts, made the same journey.[2])

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.[3]

Habitat and anatomy[edit]

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 150 cm (59 in) long.[4][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 (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).[6]

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.[7]

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.[8]

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.[9]

Armadillos have very poor eyesight, and use their keen sense of smell to hunt for food.[10] 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[edit]

Family Dasypodidae

† indicates extinct taxon

Armadillos and humans[edit]

In science[edit]

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. Armadillos are a presumed vector and natural reservoir for the disease in Texas and Louisiana.[14] 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 only exists 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[edit]

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

References[edit]

  1. ^ a b Nahuatl dictionary. (1997). Wired humanities project. Retrieved 10 September 2012, from link
  2. ^ a b 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. 
  3. ^ Armadillo Expansion. Msu.edu. Retrieved on 2012-08-23.
  4. ^ San Diego Zoo's Animal Bytes: Armadillo. Sandiegozoo.org. Retrieved on 2012-08-23.
  5. ^ Genus Chlamyphorus. Msu.edu. Retrieved on 2012-08-23.
  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. ^ a b 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)". Loc.gov. 12 February 2009. Archived from the original on 6 December 2009. Retrieved 17 December 2009. 
  9. ^ Armadillos – Nine-Banded Armadillo – Texas Wildlife. flex.net.
  10. ^ Armadillo. animals.nationalgeographic.com
  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 7 June 2010. 
  12. ^ Bagatto, B; D.A. Crossley and W.W. Burggren (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. ^ Guillaume Billet, Lionel Hautier, Christian de Muizon and Xavier Valentin (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. ^ a b Truman, Richard W. (April 2011). "Probable Zoonotic Leprosy in the Southern United States". The New England Journal of Medicine (Massachusetts Medical Society) 364 (17): 1626–1633. doi:10.1056/NEJMoa1010536. PMC 3138484. PMID 21524213. Retrieved 3 May 2011. 
  15. ^ Gardiner Harris (27 April 2011). "Armadillos Can Transmit Leprosy to Humans, Federal Studies Confirm". The New York Times. Archived from the original on 6 May 2011. Retrieved 3 May 2011. 
  16. ^ Yaeger RG. 1988. The prevalence of Trypanosoma cruzi infection in armadillos collected at a site near New Orleans, Louisiana" Am J Trop Med Hyg 38(2) 323-6.
  17. ^ a b "The Nine-banded Armadillo (Dasypus novemcinctus)". Edis.ifas.ufl.edu. Archived from the original on 2 January 2010. Retrieved 17 December 2009. 
  18. ^ a b Loughry, W.J; Prodohl, Paulo A; McDonough, Colleen M; & Avise, John C (May–June 1998). "Polyembryony in Armadillos". 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. 

Further reading[edit]

  • Gardner, A. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 94–99. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  • Superina, Mariella; Pagnutti, Noralí; Abba, Agustín M. (2014). "What do we know about armadillos? An analysis of four centuries of knowledge about a group of South American mammals, with emphasis on their conservation". Mammal Review 44 (1): 69–80. doi:10.1111/mam.12010. 

External links[edit]