San Francisco State University

Department of Geography

Geography 316:  Biogeography In progress 12/7/99

The Biogeography of  the Nine-Banded Armadillo (Dasypus novemcinctus)

by Raquel Avila, Geography 316 Fall 1999

Kingdom: Animalia
   Phylum: Chordata
      Class: Mammalia
         Family: Dasypodidae
            SubFamily: Dasypodinae
               Genus: Dasypus
                  Species: Dasypus novemcinctus
 

Introduction
    There is a Mayan legend that describes an event where two rebellious gods were taught a lesson. The legend says that the Mayan Sun God sat the two unruly gods down on a bench before all the other gods. The bench was suddenly altered into a pair of armadillos, which immediately jumped up in the air--tumbling the two disobedient gods onto their backsides in disgrace (Gilbert, 1995). I'm not familiar with Mayan legends, but I do know that armadillos are known for jumping vertically into the air. Armadillos are also known to be unique mammals because they have managed to migrate within a remarkable range.
    The nine-banded armadillo (Dasypus novemcinctus) is an unevenly distributed mammal ranging from northern Argentina to the southern United States. The nine-banded armadillo is the only species out of 20, today, that inhabits the southern portion of the United States. The armadillo, which is considered to be an ancient and primitive species, is one of the only living remnants of the order Xenarthra.

This paper will discuss the natural history, distribution, and evolution of the nine-banded armadillo (Dasypus novemcinctus), as well as other interesting facts. This paper will also discuss, briefly, the ancient disease of leprosy and its affiliation with the nine-banded armadillo

Description of Species:
        The physical characteristics of the nine-banded armadillo (Dasypus novemcinctus) are pretty unique and primitive looking. The name Dasypus is derived from the Greek word for “rabbit” (Smith, 1984). Combining novem, “nine” with cinctus, “band” you have a “nine-banded rabbit” (Smith, 1984). Literature has stated that the nine-banded armadillo without its shell or carapace resembles a rabbit.
        The nine-banded armadillo is a medium sized animal, with a length of about 2.5 feet and weighing around 14 pounds – the male being slightly larger. (Smith, 11). It is covered with an armor like shell from head to toe, except for underneath the belly, which is basically a thick skin covered with coarse hair. (Storrs, 1982). The carapace is divided into three sections – a scapular shield, a pelvic shield, and a series of bands around the mid-section. (Fox, 1996). Even though it is called a nine-banded armadillo, some tend to have between 7 and 11 bands, depending on the range of their location.  Most nine-banded armadillos are brown and gray in color (Myers, 1999) and have hairs that are yellowish white (Texas Parks & Wildlife, 1997).
    The postcranial skeleton of the nine-banded armadillo is made for digging and to accommodate the shell (Myers, 1999). Also the skull of these creatures are flattened with a long lower jaw (Myers, 1999). The nine-banded armadillo has around 30 peg-like teeth (Texas Parks & Wildlife, 1997), even though they belong to an ancient order of animals, the Edentata, which means “toothless”.
 

Natural History:
armadillo3.jpg (43972 bytes)
Photo by Jeff Foott

    The first nine-banded armadillo (Dasypus novemcinctus) to be seen in the United States was in 1849 (Taulman, 1996). Prior to that, the nine-banded armadillo had been recorded to be seen as far back as the 4th and 14th centuries by native hunters in Mexico (Taulman, 1996). The Spanish name armadillo, which means “little armored one”, originated from the Spanish conquistadores (Nixon, 1995), who encountered these beasts in the New World. The nine banded armadillo resides in the areas of northern Argentina through the South American continent east of the Andes, northward into Central America, and is widely spread throughout southern and central Mexico (Smith, 1984).
    It is thought by scientists and researchers that the nine-banded armadillo could have evolved or replaced the extinct species Dasypus bellus, which resembles the Dasypus novemcinctus, but bigger in size. After the Panamanian strip of land submerged from the sea, two and a half million years ago, it is thought to have been the corridor for these prehistoric armadillos to migrate as far north as Florida (Storrs, 1982). Unfortunately these ancient armadillos (Dasypus novemcinctus) became extinct for reasons, to this day, are unknown. The nine- banded armadillos that remain today are thought to be descendents of a pair that escaped from a small zoo about fifty years ago in Cocoa, Florida (Storrs, 1982 & Watson, 1989). But there is an event recorded of a nine-banded armadillo being introduced to Florida prior to the two that had escaped.
 

Evolution:
    There isn't much information on the evolution of the nine-banded armadillo. It's known that the closest relatives of the armadillo are sloths and anteaters, who also belong to the order Xenarthra. The order first evolved around fifty million years ago, in what we now know as South America (Nixon, 1995). The armadillos that once roamed in South America, more than 10,000 years ago, were much bigger in size.
    It is said by researchers that once the corridor between North and South America emerged, large canine and feline predators migrated south and began to prey upon these giant armadillos (Stuart, 1986). This in turn contributed to the extinction and the migration of the giant armadillo (Dasypus bellus) out of South America towards North America. Migrating northward as far as the Ohio river valley, the armadillo survived for up to 10,000 years (Nixon, 1995). Sooner or later, for unknown reasons, the armadillo became extinct in North America. Remarkably, a smaller version of the armadillo re-established themselves north of the Rio Grande.

Distribution
    The nine-banded armadillo (Dasypus novemcinctus) has become an unevenly distributed creature along the southeastern portion of the U.S. This uneven distribution of the nine-banded armadillo is thought to be due to the lack or abundance of vegetation, climatic factors, as well as human intervention. Climatic factors, such as precipitation levels and weather, tend to be the main cause of where the nine-banded armadillo resides. It is thought that the armadillos westward migration will come to a stop where precipitation levels drop below 38 cm (15 inches) due to the need of moisture in the soil, where the armadillos main food source (invertebrates) thrive in (Wilson, 1997). Freezing winters could be a problem for the nine-banded armadillo as well. The maximum amount of “freeze days” that the nine-banded armadillo is limited to is fewer than 9, which need to be spread out over several winter months (Taulman, 1996). The nine-banded armadillo does not hibernate and needs to eat on a daily basis (Wilson, 1997). It has been recorded that armadillos cannot survive in areas where it snows due to their feeding habits (Wilson, 1997). Their type of habitat tends to be temperate forests as well as a wide variety of tropical and subtropical habitats (Taulman, 1996), which means if the nine-banded armadillo is introduced to California it will be able to survive.
    The nine banded armadillo at this moment inhabits eight states in the U.S. – Texas, Louisiana, Arkansas, Oklahoma, Alabama, Mississippi, Florida, and Georgia (Smith, 1984). Under good conditions, the nine-banded armadillo may increase its range by a few hundred square miles in one year (Smith, 1984). It is known that the colonization of the nine-banded armadillo was a slow and natural process in Louisiana, Southern Arkansas, and eastern Oklahoma as opposed to a human dispersal and/or escaping from captivity in Florida, Georgia, and Alabama (Smith, 1984).
    The first recorded nine-banded armadillo seen in the U.S was in Texas by two men, Audubon & Bachman, in 1849. However, there is the possibility that these armadillos were introduced prior to that due to reports in the 1830’s and 1840’s sighting nine-banded armadillos east of the Rio Grande (Smith, 1984). The entry zone of the nine-banded armadillo into Texas is considered to be between Brownsville and Rio Grande City (Smith, 1984), which led the armadillo to move northward and extend southeast into favorable conditions. By the 1880’s, nine-banded armadillos were extending their habitats into the western portion of Texas and by the mid-1900’s these creatures had occupied two-thirds of Texas (Smith, 1984)
    By the 1930’s, the nine-banded armadillo had spread to Mississippi, Louisiana (1916/1917), Arkansas (1921), and in Oklahoma (1936), which have similar climatic and topographic features and helped the nine-banded armadillo to thrive (Smith, 1984). By  1970, the population of nine-banded armadillos had increased dramatically, occupying most of southern Arkansas and two-thirds of Oklahoma, except for in the arid portions of these states (Smith, 1984).
    As mentioned before, the introduction of the nine-banded armadillo east of the Mississippi River, was contributed through human intervention. In most of the literature I obtained it was mentioned that the introduction of these armadillos was due to a pair that had escaped a zoo in Florida. But it has been recorded that in 1922, a boy caught a nine-banded armadillo near Miami (Smith, 1984). An investigation led to a Marine in Texas who was stationed in Hialeah during World War I, where he admitted to bringing a pair of armadillos and releasing them after the war was over (Smith, 1984). Today, it is estimated that the current population of Dasypus novemcinctus is between 30-50 million (Gilbert, 1995), and found as far north as Nebraska (Myers, 1999).
 

Map of Distribution:
armadillo2.jpg (73143 bytes)
 
 

Other interesting issues:

Food Habits
 

armadillo4.jpg (39663 bytes)
Photo by Jeff Foott

     The nine-banded armadillo (Dasypus novemcinctus), is generally considered an insectivore, in most cases about 75% of their total diet consists of insects (Redford, 1985), like ants, beetles, wasps, caterpillars, roaches, termites, and larvae. Even though the nine-banded armadillo is considered to be an insectivore, it will eat other organisms out of that category, like small reptiles, amphibians, and even dead birds (when held in captivity) (Smith, 1984). There was a study done in 1954, where the stomach contents of 232 Dasypus novemcinctus were looked at. Researchers were able to identify 488 different food items in these nine-banded armadillos from Texas. By volume, 93% of food was of animal origin—78% was insect material, 7% was plant matter, 6% were other anthropods, and 2% were other vertebrates (Redford, 1985).
    The nine-banded armadillo has been accused for many years on damaging crops by damaging the roots of plants, which has its benefits and disadvantages. The damages are weighed against the benefits of soil aeration and pest control (Storrs, 1982). Another accusation, which has little evidence, is that the nine-banded armadillo feeds on the eggs of ground-nesting birds. A study was done in 1943, where 400 “dummy” quail nests containing half of quail eggs and the other half containing hen eggs were planted and observed by researchers, (Talmage, 1954) as well as a few natural nests. It was found that only a little more than 5% of all nests were evidently destroyed by the nine-banded armadillo (Talmage, 1954). An examination, after this study, was done in 281 stomachs of these nine-banded armadillos. It was found that out of these 281 nine-banded armadillos, only 5 contained bird eggs (Talmage, 1954). It has been noted in most of my research that the possibility of an armadillo to break an egg is slight since this is a learned trait rather than instinctive.
    Reproduction
    Reproduction has only been studied closely in the Dasypus novemcinctus. The nine-banded armadillo is a successful reproducer. The nine-banded armadillo mates missionary style (Schueler, 1988) as early as July and as late as December and gives birth during the months oMarch and April (Smith, 1984), when not stressed or when climate conditions are at there best. The nine-banded armadillo with a few close cousins are the only known creatures to give birth to same gender quadruplets (never more or less) from the same embryo. Even though the nine-banded armadillo produces one ovum per year, the development of polyembryony contributes to their massive reproduction rate (Watson, 1989). Implantation of the fertilized egg may be delayed for up to fourteen weeks after conception (Smith, 1984) and the gestation period is known to be 150 days or longer (Smith, 1984). The delay of the of the implantation of the embryo in the uterine wall is thought to be caused by stress (Watson, 1989).
    Armadillos are born with their eyes open and begin to move around within a few hours (Smith, 1984). The young armadillos tend to stay with their mother during the spring and summer months, and then move on their own by the following year (Smith, 1984). The armadillo’s life span can range from four to seven years, but it has been known to survive up to ten in captivity.
 

Behavior
    Nine-banded armadillos (Dasypus novemcinctus) are nocturnal creatures. Temperature is definitely a critical factor when it comes to being active in the wild, since armadillos tend to be sensitive to cold environments and are not able to adjust well to
desert conditions (Smith, 1984). The nine-banded armadillos have poor eyesight but have a keen sense of smell. Its sense of smell helps it find food underneath the forest litter as well as in the soil, since it finds food with its snout close to the ground.
    The nine-banded armadillo is also known for digging sizable burrows close to the trunks of trees (Storrs, 1982), as well as in the banks of streams or in limestone cliffs near surface water supplies. (Smith, 1984). These burrows are anywhere from four to twelve feet long and tend to join (if there’s more than one) at a central den. Armadillos tend to have more than one burrow, some being active and others are forgotten.
    Another behavior that has been a fatal one for the nine-banded armadillo is the ability to jump 3-4 feet vertically into the air when it is startled (Wilson, 1997). In the southeastern portion of the U.S., automobiles are constantly killing nine-banded armadillos. At first it was thought that the tires or the front of the car was impacting these armadillos, which do not look both ways before they cross a road. Later it was observed that when an automobile drove over an armadillo, it would be startled and would end up jumping vertically against the car (Storrs, 1982).
One behavior that is thought to have helped the armadillo to reach the southern part of the United States is the ability to cross bodies of water. It is thought that the nine-banded armadillo arrived in Texas by crossing the Rio Grande in the mid-19th century (Schueler, 1988). The nine-banded armadillo has been observed to get across a body of water by two methods. The first method is the ability to float across by gulping air into their stomachs and intestines (Watson, 1989), and secondly if the body of water is shallow enough, the nine-banded armadillo is able to walk across the bottom by holding its breath for up to five minutes (Watson, 1989).
 

Leprosy and the Nine-Banded Armadillo
armadillo6.jpg (15666 bytes)
photo by Larry Aiuppy

   The nine-banded armadillo has become an important animal in the research of Hansen’s disease, also known as leprosy, which effects 4,000 individuals in the United States (15 million worldwide). Armadillos do not develop human type leprosy; the disease among the nine-banded armadillo is usually severe and fatal (Storrs, 1982). The time between infection and development of symptoms in nine-banded armadillos is between six months to four years, as opposed to three to six years in humans (Storrs, 1982). For reasons unknown, the nine-banded armadillo is known to carry the disease. It is thought that leprosy attacks the armadillo because of its low body temperature of 92-95 degrees Fahrenheit (28-33 degrees Celsius), which in turn affects the brain, spinal cord and lungs – which is not affected in humans (Storrs, 1982).
     The concern of being infected from armadillos to humans did not arise until the mid-1980’s (Wilson, 1997). At first it was thought that nine-banded armadillos weren’t able to procure leprosy due to their location. Eventually, people in Texas and in Louisiana were infected with the disease, which was later discovered that it was due to the extensive handling of nine-banded armadillos – racing armadillos, extracting meat, and making souvenirs from their shells (Wilson, 1997). Today, the nine-banded armadillo has become an important animal in the study of Hansen’s disease.
 

Conclusion
    The nine-banded armadillo has become an important animal in the research of Hansen’s disease, also known as leprosy, which effects 4,000 individuals in the United States (15 million worldwide). Armadillos do not develop human type leprosy; the disease among the nine-banded armadillo is usually severe and fatal (Storrs, 1982). The time between infection and development of symptoms in nine-banded armadillos is between six months to four years, as opposed to three to six years in humans (Storrs, 1982). For reasons unknown, the nine-banded armadillo is known to carry the disease. It is thought that leprosy attacks the armadillo because of its low body temperature of 92-95 degrees Fahrenheit (28-33 degrees Celsius), which in turn affects the brain, spinal cord and lungs – which is not affected in humans (Storrs, 1982).
     The concern of being infected from armadillos to humans did not arise until the mid-1980’s (Wilson, 1997). At first it was thought that nine-banded armadillos weren’t able to procure leprosy due to their location. Eventually, people in Texas and in Louisiana were infected with the disease, which was later discovered that it was due to the extensive handling of nine-banded armadillos – racing armadillos, extracting meat, and making souvenirs from their shells (Wilson, 1997). Today, the nine-banded armadillo has become an important animal in the study of Hansen’s disease.
 
 

Bibliography

Fitch, Henry S., Phil Goodrum, and Coleman Newman.  1952. “The Armadillo in the
 Southeastern United States." Journal of Mammalogy. Vol. 58, No. 3: 411-413

Fox, David L.  1996 January 18. "Dasypus novemcinctus: Nine-Banded Armadillo."
 [Yahoo].  http://animaldiversity.ummz.umich.edu/acounts/dasypus/d._novemcinctus.html
 [November 3, 1999].

Gilbert, Bill. 1995. "The 'little armored thing' doesn't get by on looks alone."
 Smithsonian. 142-151.

Humphrey, Stephen R.  1974. “Zoogeography of the Nine-Banded Armadillo (Dasypus
 novemcinctus) in the United States.” Bioscience. Vol. 24, No. 8: 457-462.

Layne, James N. and Debbie Glover.  1977.  “Home Range of the Armadillo in Florida.”
 Journal of Mammalogy. 58: 411-413.

Myers, Philip. 1999 June 12. "Dasypus: armadillo." [Yahoo].
  http://animaldiversity.ummz.umich.edu/chordata/mammalia/xenarthra/dasypodidae.html
 [November 18, 1999].

Newman, H.H.  1913. "The Natural History of the Nine-Banded Armadillo."
 The American Naturalist. Vol. 47, No. 561: 513-539.

Nixon, Joshua P.  1995 October. "The History of the Armadillo: where did armadillos
 come from?" [Yahoo]. http://www.stonedoctor.com/fun/armfact.htm  [November 18,
 1999].

Redford, Kent H.  1985. "Food Habits of Armadillos (Xenarthra Dasypodidae)." The
 Evolution and Ecology of Armadillos, Sloths, & Vermilinguas. (ed). G.G. Montgomery. Washington & London: Smithsonian Institute Press.
 429-434.

Schueler, Donald G.  1988. "Armadillos Make Me Smile." Audobon. Vol. 90, No. 6:
 46-49.

Smith, Larry L. and Robin W. Doughty. 1984. The Amazing Armadillo: Geography of a
 Folk Critter. University of Texas Press, Austin Texas.

Storrs, Eleanor E.  1982. “The Astonishing Armadillo." National Geographic.
 Vol. 161 No. 6: 820-830.

Stuart, Anthony. 1986. "Who (or what) killed the giant armadillo?" New Scientist. 17: 29-31.

Talmage, R.V. and G.D. Buchanan. 1954. "The armadillo (Dasypus novemcinctus): A
 Review of it's natural history, ecology, anatomy, and reproductive physiology."
The Rice Institute Pamphlet. Vol. 41, No. 2: 2-37.

Taulman, James F. and Lynn W. Robbins. 1996. “Recent range and expansion and
 distributional limits of the nine-banded armadillo (Dasypus novemcinctus) in the
 United States.” Journal of Biogeography. Vol. 23, No. 5: 635-648.

Texas Parks & Wildlife. 1995 September. "Nine-Banded Armadillo: Dasypus
 novemcinctus." [Yahoo].  http://www.tpwd.state.tx.us/nature/wild/mammals/dillo.htm  [November 3, 1999].

Texas Parks & Wildlife. 1997 December 24. "Nine-Banded Armadillo." [Yahoo].
 http://www.nsrl.ttu.edu/tmot/dasynove.htm     [November 3, 1999].

Watson, Jim. 1989. "Rising Star." Natural Wildlife. Vol. 27, No. 6: 46-49.

Wilson, Suzanne J.  1997 March 3. "Armadillos." [Yahoo].
http://www.conservation.state.mo.us/conmag/1997/03/3.html    [November 18, 1999].
 

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