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Potentially Misidentified Species:
Dasypus novencinctus is unmistakable in Florida.
II. HABITAT AND DISTRIBUTION
Regional Occurrence:
Dasypus novencinctus is originally from South America and has historically
occurred from Puru and northern Argentina north into the southern part of Texas.
Range expansion within the United States has been occurring since the 1850s and
the animal now occurs throughout most of Texas and is typically also found east
into Louisiana, Alabama and Florida and as far north as Oklahoma and Kansas
(Wolfe 1968, Fox1999). The animal is occasionally encountered in Missouri and
South Carolina (Schaefer and Hostetler 2003). Van Deelen et al. (2002)
reported a single dead specimen from central Illinois and indicated this was
the northernmost record of the species east of the Mississippi River.
IRL Distribution:
Schaefer and Hostetler (2003) report that Dasypus novencinctus now occurs in
upland habitats throughout Florida including the entire IRL watershed. Only
the Keys and parts of the Everglades and Big Cypress swamp remain free from
established armadillo populations.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Individuals range in size from 60-80 cm total length and 3.6-7.7 kg with males
tending to be larger than females. They are long-lived animals , surviving for
as much as 20 years (Fox 1999, Schaefer and Hostetler 2003).
Abundance:
Sizable nine-banded armadillo populations are established in 67 Florida counties.
Reproduction:
Dasypus novencinctus become reproductive shortly into their second year of
life. Young born in the spring are capable of breeding n the early summer of
the following year. The breeding season begins in July, and by the end of the
month, approximately half of the reproductive females have become pregnant
(Davis and Schmidly 1997). Actual gestation lasts for five months, but
delayed implantation (see below) results in a pregnancy that persists for
approximately three additional months (Schaefer and Hostetler 2003).
Embryology:
The embryology of Dasypus novencinctus is notable in several ways. Within a
week of mating, the fertilized ovum forms a blastocyst and is passed to the
uterus. There, development ceases and the blastocyst remains unattached in the
uterus but nevertheless receives oxygen and nutrition from uterine secretions.
Implantation is delayed until November, more than three months after
fertilization. At the time of implantation, the blastocyst divides to form
four distinct embryonic growth centers which attach to the uterus via a shared
placenta. This phenomenon, termed specific polyembryony, results in litters
typically consisting of identical quadruplets. After implantation, embryonic
development then proceeds normally. A litter is born fully formed
and with eyes open in approximately 4 months, usually in March. The young are highly
precocial, walking within hours of birth and foraging with their mother within
a few weeks. They likely wean within two months but may remain with their
mother for a few months more (Davis and Schmidly 1997).
Delayed implantation may facilitate the success of pioneering armadillos in
temperate climates. Rather than being born around the start of winter, delayed
implantation allows young to be born in spring when survival odds are greatest
(Davis and Schmidly 1997).
IV. PHYSICAL TOLERANCES
Temperature:
The lack of a dense coat of hair and insulating body fat leaves armadillos, particularly
younger animals, susceptible to the effects of climate (Nixon
1995). Seasonal behavioral thermoregulation is utilized to mediate body
temperature. Individuals are most active in the cool evening hours during the
summer months, but in the winter they shift their diel patterns such that they
are most active in the heat of mid-afternoon. Nine-banded armadillos do not
hibernate and they are not physiologically capable of surviving prolonged
winters. (Davis and Schmidly 1997).
Along with rainfall (see below), temperature is the likely determinant of the
northern limits of persistent, reproductive Dasypus novencinctus populations
in North America. Nixon (1995) suggests that stable colonies fail to become
established if the average January temperature is below -2°C.
Water:
Nine-banded armadillos require a dependable constant source of water. Stable
colonies typically occur in areas receiving 38 cm/year or more of rainfall
(Nixon 1995).
V. COMMUNITY ECOLOGY
Trophic Mode:
Dasypus novencinctus is a rooting generalist forager that consumes primarily
animal matter such as insects and other arthropods, earthworms, other
inverebrates, small reptiles and amphibians. Plant matter and carrion are
also eaten and on occassion birds and small mammals may be eaten as well. The diet
is broad and opportunistic; analysis of the stomach contents of more than 800
individuals revealed nearly 500 different dieary items, with animal matter
comprising more than 90% of the diet by volume (Davis and Schmidly 1997).
Carrion is readily eaten when available, and dead carcasses of animals
frequently are visited not only for the carrion present but also for the
maggots and pupae of flies found on or near them.
Associated Species:
Nine banded armadillos are solitary foragers with overlapping home ranges
(McDonough, 1994). They are natural carriers of the prokaryote Mycobacterium
leprae, the pathogen causing lepromatid leprosy. D.
novemcinctus and humans are the only mammals known to naturally contract
the disease Fox 1999). M. leprae is cultured in the foot pads of
captive armadillos in leprosy research laboratories.
VI. INVASION INFORMATION
Invasion History:
Dasypus novencinctus is a highly successful pioneering species. Generalist habitat and
dietary requirements, long lifespans, and various reprodctive specializations
(i.e., delayed implantation, see above) allow small founder populations to
successfully colonize and establish themselves in new areas (Nixon 1995).
Historic natural range expansion of D. novemcinctus into the U.S. was
first documented in 1854 with an occurrence in extreme southern Texas along the
Rio Grande (Fox 1999). Natural range expansion in the subsequent 150 years is
impressive, and has likely been facilitated by anthropogenic habitat
alteration, including predator removal and livestock grazing activity. Average
rates of range expansion vary from 4-10 km/year in the absence of physical or
climatic barriers. Invasion is most rapid in riparian habitats parallel to
water courses where armadillos are capable of traversing rivers both through breath-holding
and walking across and by ingesting air to impart buoyancy. River and stream banks are
probably important avenues for dispersal (Davis and Schmidly 1997).
Armadillos were first introduced to Florida in 1924 and the present-day Florida
population of D. novemcinctus is derivd from several sources of
introduction. The western population resulted from westward range expansion of
the Texas population nto the Florida panhandle, and the Atlantic coast
population resulted from several human-facilitated introductions (including escape from
zoos and from the pet trade) from the 1920s to the 1970s. The panhandle and
peninsular populations expanded and eventually merged so D. novemcinctus
can now be found in upland habitats nearly statewide (Greenbaum 2002, Schaefer
and Hostetler 2003).
Potential to Compete With Natives:
The rooting activities of to Dasypus novencinctus can damage below-ground
portions of native vegetation through exposure to air, sunlight, and
desiccation (Greenbaum 2002).
D. novemcinctus occasionally prey on the young of ground-nesting birds.
Armadillos may also occasionally eat the eggs of quail, turkey, and
other ground nesters, although gut analyses have demosntrated minimal
importance of eggs in the diet (Davis and Schmidly 1997, Fox 1999). On the
other hand, armadillos in Florida have been implicated in the destruction of
sea turtle nests and the impacts may be significant. In some areas (e.g., Hobe Sound) where
studies have been conducted, D. novemcinctus has raided as many as 14% of
all sea turtle nests, accounting for as much as 95% of all nest raiding. As
this behavior had not been documented until 1988, it may represent a
newly-learned behavior of this highly adaptable invader (Engeman et al. 2002, Greenbaum 2002).
Possible Economic Consequences of Invasion:
Some commercial crop damage is attributable to Dasypus novencinctus, although
it is moderate compared to the damage caused by feral pigs. Armadillo
burrowing activity can exacerbate erosion and has on occasion undermined
structural foundations (Greenbaum 2002).
Although D. novemcinctus has been implicated as a vector for leprosy in
humans, the species is probably of overall positive benefit with regard to the
disease because it serves as an important leprosy research model. Armadillos
are also used as medical research models in the fields of multiple births,
organ transplants, birth defects, as well as typhus and trichinosis pathology (Fox
1999, Greenbaum 2002).
Armadillos may be of positive economic effect with regard to their imact on
populations of insect pests (Davis and Schmidly, 1997). In Latin Amrica and in
small pockets within the southern U.S., armadillos are also utilized by humans
as food (Fox 1999).
VII.
REFERENCES
Davis W.B. and D.J. Schmidly. 1997. The Mammals of Texas - Online Edition.
Texas Tech University. Available online.
Engeman R.M., Shwiff S.A., Constantin B., Stahl M., and H.T. Smith. 2002. An economic analysis of predator removal
approaches for protecting marine turtle nests at Hobe Sound National Wildlife Refuge. Ecological Economics 42:469-478.
Fox D. 1999. Dasypus novemcinctus Animal Diversity Web species profile.
Available online.
Greenbaum M. 2002. Nine-banded armadillo species profile. Columbia University
Introduced Species Summary Project. Available online.
McDonough C.M. 1994. Determinants of aggression in nine banded armadillos. Journal of Mammalogy 75:189-198.
Nixon J. 1995. Armadillo Online! Available online.
Schaefer J.M and M.E. Hostetler. 2003. The nine-banded armadillo (Dasypus
novemcinctus). UF/IFAS document WEC 76. Available online.
Van Deelen T.R., Parrish J.D., and E.J. Heske.2002. A nine-banded armadillo (Dasypus novemcinctus) from central Illinois. Southwestern Naturalist
47:489-491.
Wolfe J.L. 1968. Armadillo distribution in Alabama and northwest Florida. Quarterly Journal of the Florida Academy of Sciences 31:209-212.
Report by:
J. Masterson, Smithsonian Marine Station
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