Armadillos

views updated May 21 2018

Armadillos

Distribution and habitat

Physical appearance

Feeding and defense

Reproduction

Resources

Armadillos are bony-skinned mammals native to Central and South America. Armadillos (family Dasypodidae) number 20 species in eight genera. The species include the long-nosed armadillo (six species), the naked-tailed armadillo (four species), the hairy armadillo (three species), the three-banded armadillo (two species), the fairy armadillo (two species), the six-banded or yellow armadillo (one species), the pichi (one species), and the giant armadillo (one species).

Distribution and habitat

Armadillos are found throughout the whole of South and Central America, from the Strait of Magellan northward to eastern Mexico.

The common long-nosed (or nine-banded) armadillo is the most widespread and is the only species found in the United States. In the 1850s, several armadillos were recorded in Texas, and their descendants spread rapidly through the Gulf States toward the Atlantic in what has become the swiftest mammalian distribution ever witnessed. In 1922 a captive pair of common long-nosed armadillos escaped in Florida, and in a few decades their descendants numbered in the tens of thousands. Moving westward, the eastern population met and merged with the Texas group.

Rivers and streams present no barrier to the spread of armadillos. Gulping air into their stomachs and intestines to buoy themselves, armadillos float leisurely across the water. Others have been observed walking into streams on one side and strolling out on the other side a few minutes later.

While water presents no barrier to armadillos, cold does, and winter temperatures have slowed their

northern advance in the United States. Armadillos are poorly insulated and cannot withstand chilling. Cold also reduces the abundance of insects that armadillos depend on for food. Because of this, armadillos have moved northward only as far as Oklahoma and southern Kansas.

Armadillos are found in habitats ranging from pampas (grasslands) to arid deserts and from coastal prairies to rainforests and deciduous forests.

Physical appearance

Armadillos appear to be a conglomeration of other animal parts: the shell of a turtle, the ears of an aardvark, the feet of a lizard, the face of a pig, and the tail of a dinosaur. However, the patches and bands of coarse bristles and hairs on their bodies reveal them to be true mammals.

Extinct species of armadillo grew to enormous sizes, and their bony shells were used as roofs and tombs by early South American Indians. Surviving species are nowhere near that large, ranging in size from the 99132 lb (4560 kg) giant armadillo to the 2.83.5 oz (80100 g) lesser fairy armadillo. The familiar common long-nosed armadillo weighs in at 610 lb (2.74.5 kg).

The most obvious and unusual feature of armadillos is their bony skin armor, found in no other living mammal. Bands of a double-layered covering of horn and bone develop from the skin and cover most of the upper surfaces and sides of the body. These bony bands or plates are connected by flexible skin. The top of the head is capped with a bony shield and the tail is usually encased with bony rings or plates. Their underside is covered only with soft, hairy skin. Armadillos have a flattened and elongated head with a long, extendable tongue. Numerous small, peg-like teeth are set in their jaws. The teeth are not covered by enamel and grow continuously. Their hind limbs have five clawed toes, while the powerful forelimbs end in three, four, or five curved digging claws.

Feeding and defense

Armadillos are predominantly nocturnal in their foraging habits, and their teeth dictate their diet. Those with sturdy teeth eat insects, snails, worms, small lizards, carrion, tubers, and fruits. Those with soft teeth eat primarily insects such as ants and termites. Using their long, sticky tongues to remove insects from their nests, they have been observed to eat as many as 40,000 ants at one feeding. It is estimated that a single armadillo can eat 200 lb (90 kg) of insects in a year.

A keen sense of smell helps the armadillo locate prey as much as 6 in (10 cm) underground. Pressing its nose to the ground to keep the scent, and holding its breath to avoid inhaling dust, the armadillo digs into the soil and litter with astonishing speed.

Armadillos also defend themselves by burrowing into the earth, disappearing completely in a few minutes. Once dug in, they expand their bony shell and wedge themselves into the burrow. They can also run surprisingly fast and, if cornered, will use their claws to fight. Once a predator catches an armadillo it must deal with its bony armor. The three-banded armadillo can roll up into a tight ball, presenting nothing but armor to its enemies. Their armor also protects them from cactus spines and dense, thorny undergrowth.

While some species of armadillo are hunted by humans in Central and South America for their meat, the greatest danger to armadillos in the United States is the automobile. Dozens of armadillos are run down as they wander onto highways at dusk. Their habit of leaping several feet into the air when startled contributes to many of the automobile-related deaths. In addition to being a food source, armadillos have a further, unusual significance for humans. Since armadillos are the only animals that can transmit leprosy, they are used as research models in the study of this disease and the development of a vaccine.

Reproduction

Armadillos are solitary creatures that seek companions only during the mating season. After mating, female armadillos can suspend their pregnancy for up to two years. Another reproductive peculiarity of armadillos that has caught the attention of geneticists

KEY TERMS

Distribution The natural range or area inhabited by a species or group of organisms.

Litter A layer of decaying matter on the floor of a forest.

Pampas Treeless plains of South America, especially those of Argentina.

is the ability to produce multiple births from a single fertilized egg: depending on the species, 4, 8, or 12 genetically identical offspring may be produced.

Young armadillos are born in nest chambers within a burrow. At birth, the young are pink and have soft, leathery skin. This soft skin hardens within a few weeks. Young armadillos stay close to their mother for about two weeks before striking out on their own.

Resources

BOOKS

Gould, Edwin, and Gregory McKay, editors. The Encyclopedia of Mammals. 2nd ed. New York: Academic Press, 1998.

Nowak, Ronald M. Walkers Mammals of the World. 6th ed. Baltimore: Johns Hopkins University Press, 1999.

PERIODICALS

Gilbert, Bil. That Little Armored Thing Doesnt Get By on Looks Alone. Smithsonian 26 (October 1995): 142.

Loughry, W. J., et al. Polyembryony in Armadillos: An Unusual Feature of the Female Nine-banded Armadillos Reproductive Tract May Explain Why Her Litters Consist of Four Genetically Identical Offspring. American Scientist 86 (May-June 1998): 274.

Smith, Dwight G. The Armored Pig. The World and I 14 (August 1999): 174.

Watson, Jim. Rising Star. National Wildlife (October/November 1989): 47.

Dennis Holley

Armadillos

views updated May 11 2018

Armadillos

Armadillos are bony-skinned mammals native to Central and South America . Armadillos (family Dasypodidae) number 20 species in eight genera. The species include the long-nosed armadillo (six species), the naked-tailed armadillo (four species), the hairy armadillo (three species), the three-banded armadillo (two species), the fairy armadillo (two species), the six-banded or yellow armadillo (one species), the pichi (one species), and the giant armadillo (one species).


Distribution and habitat

Armadillos are found through the whole of South and Central America, from the Strait of Magellan northward to eastern Mexico.

The common long-nosed (or nine-banded) armadillo is the most widespread and is the only species found in the United States. In the 1850s several armadillos were recorded in Texas, and their descendants spread rapidly through the Gulf States toward the Atlantic in what has become the swiftest mammalian distribution ever witnessed. In 1922 a captive pair of common long-nosed armadillos escaped in Florida, and in a few decades their descendants numbered in the tens of thousands. Moving westward, the eastern population met with the Texas group only within the last decade.

Rivers and streams present no barrier to the spread of armadillos. Gulping air into their stomachs and intestines to buoy themselves, armadillos float leisurely across the water . Others have been observed walking into streams on one side and strolling out on the other side a few minutes later.

While water presents no barrier to armadillos, cold does, and winter temperatures have slowed their northern advance in the United States. Armadillos are poorly insulated and cannot withstand chilling. Cold also reduces the abundance of insects that armadillos depend on for food. Because of this, armadillos have moved northward only as far as Oklahoma and southern Kansas.

Armadillos are found in habitats ranging from pampas (grasslands ) to arid deserts and from coastal prairies to rainforests and deciduous forests .


Physical appearance

Armadillos appear to be a conglomeration of other animal parts—the shell of a turtle, the ears of an aardvark , the feet of a lizard, the face of a pig, and the tail of a dinosaur . However, the patches and bands of coarse bristles and hairs on their bodies reveal them to be true mammals.

Extinct species of armadillo grew to enormous sizes and their bony shells were used as roofs and tombs by early South American Indians. Surviving species are nowhere near that large, ranging in size from the 99–132 lb (45–60 kg) giant armadillo to the 2.8–3.5 oz (80–100 g) lesser fairy armadillo. The familiar common long-nosed armadillo weighs in at 6–10 lb (2.7–4.5 kg).

The most obvious and unusual feature of armadillos is their bony skin armor, found in no other living mammal. Bands of a double-layered covering of horn and bone develop from the skin and cover most of the upper surfaces and sides of the body. These bony bands or plates are connected by flexible skin. The top of the head is capped with a bony shield and the tail is usually encased with bony rings or plates. Their underside is covered only with soft, hairy skin. Armadillos have a flattened and elongated head with a long, extendable tongue. Set in their jaws are numerous small, peglike teeth. The teeth are not covered by enamel and grow continuously. Their hind limbs have five clawed toes while the powerful forelimbs end in three, four, or five curved digging claws.


Feeding and defense

Armadillos are predominantly nocturnal in their foraging habits and their teeth dictate their diet. Those with sturdy teeth eat insects, snails , worms, small lizards, carrion, tubers, and fruits . Those with soft teeth eat primarily insects such as ants and termites . Using their long, sticky tongue to remove insects from their nests, they have been observed to eat as many as 40,000 ants at one feeding. It is estimated that a single armadillo can eat 200 lb (90 kg) of insects in a year.

A keen sense of smell helps the armadillo locate prey as much as 6 in (10 cm) underground. Pressing its nose to the ground to keep the scent and holding its breath to avoid inhaling dust, the armadillo digs into the soil and litter with astonishing speed.

Armadillos also defend themselves by burrowing into the earth, disappearing completely in a few minutes. Once dug in, they expand their bony shell and wedge themselves into the burrow. They can also run surprisingly fast and, if cornered, will use their claws to fight. Once a predator catches an armadillo it must deal with its bony armor. The three-banded armadillo can roll up into a tight ball presenting nothing but armor to its enemies. Their armor also protects them from cactus spines and dense, thorny undergrowth.

While some species of armadillo are hunted by humans in Central and South America for their meat, the greatest danger to armadillos in the United States is the automobile . Dozens of armadillos are run down as they wander onto highways at dusk. Their habit of leaping several feet into the air when startled contributes to many of the automobile-related deaths.

Reproduction

Armadillos are solitary creatures that seek companions only during the mating season. After mating, female armadillos can suspend their pregnancy for up to two years. Another reproductive peculiarity of armadillos that has caught the attention of geneticists is the ability to produce multiple births from a single fertilized egg: depending on the species, 4, 8, or 12 genetically identical offspring may be produced.

Young armadillos are born in nest chambers within a burrow. At birth , the young are pink and have a soft, leathery skin. This soft skin hardens within a few weeks. Young armadillos stay close to their mother for about two weeks before striking out on their own.


Resources

books

Gould, Edwin, and Gregory McKay, eds. The Encyclopedia of Mammals. 2nd ed. New York: Academic Press, 1998.

Nowak, Ronald M. Walker's Mammals of the World. Baltimore: Johns Hopkins University Press, 1999.

periodicals

Schueler, Donald G. "Armadillos Make Me Smile a Lot." Audubon (July 1988): 73.

Storrs, Elanor. "I'll Think about That Tomorrow." Discover (16 February 1990): 16.

Watson, Jim. "Rising Star." National Wildlife (October/November 1989): 47.

Dennis Holley

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Distribution

—The natural range or area inhabited by a species or group of organisms.

Litter

—A layer of decaying matter on the floor of a forest.

Pampas

—Treeless plains of South America, especially those of Argentina.

Dasypodidae

views updated May 14 2018

Dasypodidae See DASYPODOIDEA.

armadillos

views updated May 18 2018

armadillos See DASYPODOIDEA.