Armadillo

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For other uses, see Armadillo (disambiguation).
Armadillos
Fossil range: Late Paleocene to Recent
Nine-banded Armadillo
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Xenarthra
Order: Cingulata
Illiger, 1811
Families

Armadillos are small placental mammals, known for having a bony 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 is Spanish for "little armored one".

There are approximately 10 extant genera and around 20 extant species of armadillo, some of which are distinguished by the number of bands on their armor. Their average length is about 75 centimeters (30 in), including tail; the Giant Armadillo grows up to 100 cm (39 in) and weigh 30 kg (66lbs), while the Pink Fairy Armadillos are diminutive species with an overall length of 12–15 cm (4–5 in). All species are native to the Americas, where they inhabit a variety of environments.

In the United States, the sole resident armadillo is the Nine-banded Armadillo (Dasypus novemcinctus), which is most common in the central southernmost states, particularly Texas. Their range is as far east as Florida and as far north as Kansas, and while cold winters have slowed the expansion of their range (due to a lack of sufficient body fat), they have been consistently expanding their range over the last century due to a lack of natural predators and have been found as far as western Kentucky, and are expected to eventually reach Ohio before the cold winters inhibit their expansion.

Contents

[edit] Habitat and Anatomy

Armadillos 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 near which it lives and feeds. The diet of different armadillo species varies, but consists mainly of insects, grubs, and other invertebrates. Some species, however, are almost entirely formicivorous (feeding mainly on ants).

Armadillos have poor vision but are not blind.

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. In most species, there are 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.[1]

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.[2]

Armadillos have short legs but can move quite quickly, and have the ability to remain underwater for as long as six minutes. Because of the density of its armor, an armadillo will sink in water unless it inflates its stomach with air (an ability unique among mammals which allows it to swim across narrow bodies of water), which often doubles its size.[3]

Armadillos use their claws for digging and finding food, as well as for making their homes in burrows. They dig their burrows with their claws, only making a single corridor where they fit themselves. They have five clawed toes on the hindfeet, and three to five toes with heavy digging claws on the forefeet. Armadillos have a large number of cheek teeth, which are not divided into premolars and molars, but usually have incisors or canines.

Gestation lasts anything from 60 to 120 days, depending on species, although the nine-banded armadillo also exhibits delayed implantation, so that the young are not typically born for eight months after mating. Most members of the genus Dasypus give birth to four homozygous young (that is, identical quadruplets), 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, and reach sexual maturity in 3-12 months, depending on the species. Armadillos are solitary animals, that do not share their burrows with other adults.[1]

[edit] Classification

Order CINGULATA

Pink Fairy Armadillo, Chlamyphorus truncatus
Pink Fairy Armadillo, Chlamyphorus truncatus

† indicates extinct taxon

[edit] Armadillos and humans

[edit] 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 non-human animal 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.

The Nine-banded Armadillo also serves science through its unusual reproductive system, in which four genetically identical quadruplets are born in each litter.[4] [5] [6] 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 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 which display this trait include parasitoid wasps, certain flatworms and various aquatic invertebrates. [5]

Armadillos (mainly Dasypus) make common roadkill due to their habit of jumping to about fender height when startled (such as by an oncoming car). 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.[4]

[edit] In American culture

During the Great Depression, this species was known as "Hoover Hog" by down-on-their luck Americans who had to eat them instead of the "chicken in every pot" Herbert Hoover had promised as President.[7] Earlier, German settlers in Texas would often refer to the armadillo as Panzerschwein ("armored pig").[citation needed] In 1995, The Nine-banded Armadillo was, with some resistance, made the state small mammal of Texas,[8] where it is considered a pest and is often seen dead on the roadside. They first forayed into Texas across the Rio Grande from Mexico in the 1800s, eventually spreading across the southeast United States.[7]

[edit] Notes

  1. ^ a b Dickman, Christopher R. (1984). in Macdonald, D.: The Encyclopedia of Mammals. New York: Facts on File, 781-783. ISBN 0-87196-871-1. 
  2. ^ How high can a nine-banded armadillo jump? (Everyday Mysteries: Fun Science Facts from the Library of Congress)
  3. ^ Armadillos - Nine-Banded Armadillo - Texas Wildlife
  4. ^ a b The Nine-banded Armadillo (Dasypus novemcinctus)
  5. ^ a b http://www.valdosta.edu/~jloughry/Reprints/AmSci.pdf
  6. ^ http://links.jstor.org/sici?sici=0033-5770(193309)8%3A3%3C348%3APITAGO%3E2.0.CO%3B2-Q
  7. ^ a b Armadillo from the Handbook of Texas Online
  8. ^ Texas Symbols, Small Mammal: Armadillo - SHG Resources. Accessed March 2, 2008.

[edit] References

[edit] External links

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Extant mammal orders by infraclass
Kingdom: Animalia · Phylum: Chordata · Subphylum: Vertebrata · (unranked): Amniota
Australosphenida
Metatheria
Eutheria