The Armadillo-Neither Native Nor Harmless

The Nine-banded Armadillo shows little fear of humans. Photo from Wiki[pedia

The Nine-banded Armadillo shows little fear of humans. Photo from Wikipedia

If you live in the  southern or south-central U. S.  (or further north, lately), you may have  encountered the plodding  Nine-banded Armadillo  in your yard, along roadsides or in almost any kind of dry, open habitat. This species, along with  close relatives like  the the Six-banded Armadillo of  South America, are members of a small group of mammals (the Edentata) that lack teeth and retain epidermal scales in addition to hair.   Armadillos  are   remarkable in how close they allow humans to approach them. In fact, simply grabbing one is often possible (but hardly recommended).  They leave an impression of  being  from an ancient, almost dinosaurian line of  mammals  adapted to survive  by being inconspicuous,  omnivorous and of course, armored.  In the U. S., they are  rather recent visitors from Mexico. In the mid-19th century they were seen only in far southern Texas.  Although appearing sluggish, the armadillo is regarded as a pioneer species which probes the edges of its range, seeking to expand into new habitat.  Such wandering  animals  are at high risk of mortality and of not finding mates, yet represent the chief natural means of  range expansion.  In the U.S., however, because of their apparent docility and small size, armadillos also are sometimes relocated intentionally by humans.

By the early 20th century, the critters had expanded their range across much of southern and central Texas, including a westward extension along the Pecos River nearly to the border with New Mexico. Eastward extension into Louisiana and into southern

Map of Nine-banded Armadillo distribution from

Map of Nine-banded Armadillo distribution from

 and western  Mississippi and parts of Alabama came later.  Meanwhile, 3 purposeful introductions  of  armadillos were made in Florida in the 1920s and 1930s, facilitating their rather rapid colonization by 1972 of  all of the state except the Everglades and the Panhandle Region.  Southern Arkansas, Oklahoma and Georgia soon followed.  The current range extends to Kansas, Missouri and most of  South Carolina. Outliers beyond that range may or may not represent real range extension.  Global  warming   would favor range expansion in response to decreasing number of  freeze-days even though it seems unlikely to explain the initial expansion out of Mexico.  See S. R. Humphrey (BioScience vol. 24, pages 457-462, 1974) for further discussion of range extension and climatic effects.

Undoubtedly  the armadillo’s least attractive feature  is its vulnerability to leprosy or Hansen’s Disease. In fact, this dreaded  bacterial disease which destroys the liver and kidney if not treated  early, infects only armadillos and humans, no other species!  Perhaps thought of as a problem restricted to the tropical regions, 150 to 250 human cases occur annually in the U.S.  About a third of these are traceable to contact with infected armadillos.   Many cases are found in Louisiana and Texas where armadillos are hunted, skinned and eaten!  Leprosy thus has  joined  the growing list of diseases like West Nile Virus that have spread from animals to humans.  In armadillos, leprosy is apparently much more recent than in humans.  The disease is believed to have been unknown in the New World prior to the trans-Atlantic voyages of Columbus and other explorers, but has a long history in the Old World in humans, but, of course, not in armadillos, which are found only in the Americas. Thus we have a seldom discussed aspect of the Columbian Exchange!

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