Author: Matthew Greenbaum
Common Name: Nine-banded armadillo (9BA); common long-nosed armadillo; cachicamo; tatu-hu; tatu verdadeiro.
Scientific Name: Dasypus novemcinctus (L.)
Classification:Phylum or Division: Chordata
Identification: Immediately recognizable. Most of the body is covered with an armored carapace: a double layer of horn and bone, segmented into bands. The top of the head and the sides of the limbs are shielded with polygonal bony scutes, and the tail is encased in a succession of bony rings. Typical coloration is a mottled mixture of brown and yellowish-white. The snout is long and pointed, the ears cylindrical. Head and body length typically 40 cm, with the tail an additional 30 cm. Weight is usually 3-4 kg. Despite its common name, the number of armor bands on this species varies by location: in North America it has eight.
Original Distribution: South America, west of the Andes to northwestern Peru, Colombia, and Venezuela; east of the Andes throughout the continent to Argentina and the islands of Grenada, Margarita, Trinidad, and Tobago; all throughout Central America, as far north as the lower Rio Grande valley between Mexico and Texas.
Current Distribution: Now additionally found throughout the southern and southeastern United States: Texas, Oklahoma, Kansas, Nebraska, Colorado, Missouri, Arkansas, Mississippi, Louisiana, Alabama, South Carolina, Georgia, and Florida.
Site and Date of Introduction: First seen in Texas above the Rio Grande in 1849; in New Mexico, 1905. First introduced to Florida in 1924.
Mode(s) of Introduction: Armadillos migrated from Mexico into the southern U.S. under their own power. The Florida population was established by escapees from private zoos and traveling circuses. The expanding fronts of both populations subsequently met and merged. 9BAs regularly stow away aboard trains, and the species supported a thriving pet trade for many years due to its novelty and docility.
Reason(s) Why it has Become Established: As European settlers, ranchers, and farmers spread southwest through the United States, they facilitated the invasion of D. novemcinctus by transforming the landscape into one that it would find both more accessible and more hospitable. The rise of farming and ranching in the southern U.S. demanded that regional rivers--including the Rio Grande, formerly impervious to armadillos--be diverted or lowered for irrigation. Fire suppression programs converted grasslands into densely-littered underbrush, the species' preferred habitat. Settlers also displaced Native American hunter-gatherer cultures and pursued extensive hunting and predator-control campaigns against black bear (Ursus americanus), red wolf (Canis rufus), and coyote (C. latrans). Together these factors allowed 9BAs to migrate into the United States and presented them with large stretches of favorable habitat in which they faced a lessened threat of predation. Range expansion was then accelerated greatly by repeated anthropogenic dispersals, significantly the pet trade. The overall expansion rate of the 9BA has been calculated at 4-10 km per year, which is higher than would be expected from a mammal; this is likely the result of the concurrent action of multiple dispersal mechanisms.
The species also boasts innate features that mark it as a likely invader. It appears naturally resistant to parasites. It has generalized dentition and a broad omnivorous diet, apparently eating nearly any organic matter it can locate in the leaf litter. Reproductive potential is quite high: females annually bear a litter of four offspring, each of which are genetically identical haploid clones of one another (monozygotic polyembryony). Coupled with females' ability to delay implantation of fertilized eggs for up to 14 months after mating, and their rather long lifespan (~20 years), the 9BA's reproductive strategy makes it easy for small independent propagules to persist. Long-term viable populations can be established by a single female pregnant with male young.
Ecological Role: The 9BA is most at home in forests and brushland. In its original range it is a nocturnal burrower with a preference for consuming ants and termites. In the United States its diet has become broader, its behavior more diurnal, and its burrows larger, all of which suggest a degree of ecological release from competitors and predators. Where still extant, large predators such as alligators (Alligator mississippiensis) and pumas (Felis concolor) include 9BAs in their diet.
Benefit(s): Critically important for biomedical research. North American armadillos provided the first and, to date, only animal model useful for the study of leprosy (Mycobacterium leprae). The disease cannot be grown in laboratory cultures and nearly all test bacilli must be acquired from armadillos. Researchers use armadillos to trace the disease's progression and pathology, and to develop vaccines. Rural homeowners may appreciate them for eating spiders, scorpions, and insect larvae. They also serve as an important prey item for the highly endangered Florida panther (F. concolor coryi).
Threat(s): The species functions as a leprosy model because it is a natural carrier of the disease, and it has been implicated in the spread of leprosy to humans. Its pervasive burrow systems have been known to accelerate and worsen erosion and undermine the foundations of buildings. Its continual rooting about in the leaf litter is thought to damage the underlying layers by exposing them to greater sunlight penetration and dehydration.
The introduced populations of armadillos in Florida have been known to prey upon and destroy the nests of endangered sea turtles, including the leatherback (Dermochelys coriacea), loggerhead (Caretta caretta), and green (Chelonia mydas). 9BAs have been known to raid as many as 14% of nests within observed areas, and are thought to be responsible for up to 95% of total nest raiding. First reported in 1988, this is not considered part of the species' natural suite of behavior: it seems to be a newly-learned behavior resulting from its continuing adaptation to large-scale range and niche expansion.
Control Level Diagnosis: Highest Priority where sympatric with sea turtle nesting sites and to prevent further spread into such areas; no more than Medium Priority elsewhere. The 9BA's greatest potential for ecological harm lies in the raiding of sea turtle nests. The southeastern U.S. is home to the world's second largest nesting concentration of loggerhead turtles, and the largest such population to be found in a geopolitically stable region with the resources and will to enforce conservation action. The survival of that species, then, may depend on its persistence in the U.S. Green and leatherback turtles nest less frequently in the U.S. than the loggerhead, but are considerably more endangered: thus the protection of their every nest is of global concern. Where the 9BA's range includes sea turtle beaches, it should be monitored especially closely and controlled or extirpated when feasible. Potential routes of transportation into these areas (such as boxcars and the pet trade) should be monitored and / or curtailed.
In areas where 9BAs have already become established and no such harm is visible, monitoring and control efforts should not be a priority. The species is already well integrated throughout a very broad swath of the U.S., and removal is probably impossible. However, the further expansion of 9BAs presents some cause for concern, in light of the unpredictable behavioral plasticity that they displayed after spreading through new areas and undergoing further ecological release. It is quite likely that the species could abruptly manifest new harmful behaviors in much the same way as it learned to exploit sea turtle nests. As it stands, further range expansion is all but assured, with the maximum boundaries likely to be determined by climatic factors: 9BAs seem unable to tolerate regions that experience more than 24 total frigid days and / or more than nine consecutive frigid days per year. Within habitable climate boundaries, rail travel and commerce should be monitored to prevent the spread of 9BAs into areas with novel ecosystem types, especially those hosting rare animals that lay eggs on or beneath the ground.
Control Method: Live capture with cage traps has proven effective. Staff at Florida's Hobe Sound National Wildlife Refuge include in their daily routine the removal of armadillos and other turtle-nest predators whenever encountered in the reserve; this accounts for an estimated 10% of the annual work time of a typical ranger. By 2000, nest raiding in the reserve was at 50%. That year rangers enlisted the aid of USDA Wildlife Services predator control specialists, and began to optimize their armadillo management program using a system of "passive tracking." This coordinated the removal of nest predators both spatially and temporally, and emphasized the identification of predator movements and predator-friendly habitat patches in order to predict their behavior in the subsequent nesting season. In its first year of use, passive tracking techniques reduced nest raiding to 28%. 2002's nest raiding, as of August, was less than 1%.
Armadillo Expansion. 2002 (November 18, 2002)
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Top left: http://www.pirweb.org/armadillo.htm
Top right: Rodney Sullivan, http://www.msu.edu/~nixonjos/armadillo/dasypus.html
Map: Adapted from Taulman and Robbins (1996), http://www.msu.edu/~nixonjos/armadillo/expansion.html