Dasypus

Dasypus are xenarthran mammals known for their hard armor like shell, called a carapace. Their ossified dermal plates compose a series of six to eleven movable bands covered by leathery keratinous skin, which surrounds and protects the body. A thin epidermal layer separates each of the armor bands, and joints in the shell allow for flexibility. The face, neck, and underside lack a bony covering and are instead covered with small bunches of hair.[8]

Dasypus species are grey or brown in color and possess long and sharp claws for scavenging and digging burrows. Although they have a very diverse range, armadillos are typically found near bodies of water, and their burrows are often dug into stream banks, tree stumps, or rock or brush piles.[7][9]

When threatened, armadillos run to the nearest burrow or crevice and tightly wedge themselves inside with their back alongside the wall. If no such burrow or shelter is available, armadillos curl up in order to protect their vulnerable underside. Dasypus species are unable to roll into a complete ball like the Brazilian three-banded armadillo due their excessive number of dermal plates.[4]

Because they lack significant hair covering, armadillos are particularly sensitive to climate and are therefore most active during summer nights and winter days. Due to their low fat storage, they spend most of their activity foraging for food, which primarily consists of insects, small reptiles and amphibians, and plants. Armadillos have a small, flattened skull with a long lower jaw and narrow snout. They do have small, rudimentary teeth, but lack incisors, canines, and enamel.[10] Their tongue is particularly long and sticky and is used to forage for ants and termites. They have very poor eyesight and instead rely on their keen sense of smell and enhanced hearing to locate buried insects and detect predators.

Armadillos are fully capable of climbing, swimming, and jumping. Dasypus have a unique ability to build up an oxygen debt and hold their breath for up to six minutes. This allows them to cross streams and ponds underwater by simply walking or running along the bottom. If the water body is too large for this, Dasypus can instead gulp in air, inflating their stomachs and intestines and increasing buoyancy. This allows them to float and more easily swim across the water.[9]

Dasypus are non-territorial, have large progeny, have few predators, and are capable of living in various environments, thus accounting for their large distribution. They are, though, limited by a lack of sufficient insects as a food source and their low metabolic rate, which prevents them from living in cold climates.[9] Dasypus originated from South America but has expanded and diversified across numerous countries.[10] The existence of human developments and construction has generally increased the armadillo's ability to expand by facilitating the crossing of previous obstacles. As of 2011, within the United States, they have not yet migrated south due to the lack of rainfall or water availability.[4]

Cladogram of living Dasypus[11]

There are currently seven recognized extant Dasypus species:

Image	Scientific name	Common name	Description	Distribution
	D. hybridus	Southern long-nosed armadillo or southern lesser long nosed armadillo	Like many Dasypus species, the exact limits of its range are uncertain due to morphological similarities. It weighs about 1–2 kg and is one of the few Dasypus species considered to be near threatened due to significant habitat loss and hunting.[12][13]	Eastern Paraguay, southern Brazil, Argentina, and Uruguay
	D. kappleri	Greater long-nosed armadillo	A larger species at 8–10 kg and distinguished by spurs located on its hind legs. It is one of the few Dasypus species that gives birth to two young instead of four.[12][13] There are two subspecies: D. k. kappleri and D. k. pastasae.[1]	Venezuela, Ecuador, Guyana, Suriname, French Guiana, Peru, Bolivia, and Brazil.
	D. pilosus	Hairy long-nosed armadillo	A small species of about 1.3 kg. It was initially listed as vulnerable, but it has been judged that there is not enough data for evaluation.[12][13]	Peru
	D. sabanicola	Llanos long-nosed armadillo or northern long-nosed armadillo	About 1.5 kg in size. It is considered near threatened due to hunting and extreme habitat loss from biofuel production and other agrochemical productions.[12][13]	Venezuela and Colombia
	D. septemcinctus	Seven-banded armadillo or Brazilian lesser long-nosed armadillo	Very similar in appearance to D. hybridus, D. yepesi, and young D. novemcinctus, making the southern limits uncertain. It is about 1.5–1.8 kg and unlike most Dasypus species that prefer scrub brush areas, it tends to live in grassland areas.[12][13] Gives birth to 8–12 young instead of the typical four.[14]	Brazil, Paraguay, Bolivia, and northern Argentina
	D. novemcinctus	Nine-banded armadillo or long-nosed armadillo	Best known and most widely distributed species. It is the only species that is increasing in range and number.[9][12][13] Average weight is about 2–6 kg. There are six subspecies: D. n. novemcinctus, D. n. aequatorialis, D. n. fenestratus, D. n. hoplites, D. n. mexianae and D. n. mexicanus.[1]	Found throughout the southern United States, Central America, and South America. Within the United States, it currently inhabits Texas, Louisiana, Arkansas, Oklahoma, Alabama, Mississippi, Florida, Tennessee and Georgia. It is found in the Lesser Antilles, Tobago, Grenada and Trinidad. It can also be found in numerous islands of the Caribbean, where it may have arrived on trading ships.
	D. yepesi	Yepes's mulita or Yunga's lesser long nosed armadillo	About 1.5–2 kg in weight[12][13]	Argentina and possibly Bolivia

An additional Dasypus species that is of medium size with noticeably shorter ears and tail is speculated to exist in Paraguay.[8]

Armadillos are most often found in shady forest and brush areas in temperate regions.[7] They thrive in high rainfall habitats most likely due to better soil conditions for burrowing and a higher abundance of food. They are also known to inhabit various other environments ranging from grassland to swamp areas and are able to adapt to numerous regions as long as adequate food and water are available. It has been noted that armadillo species are extremely fond of water and will not only use streams for feeding and drinking but also for mud baths.[17]

Most Dasypus species are sensitive to temperature due to poor insulation. Because of this, they currently are not found in regions with temperatures below -2 degrees Celsius or 24 annual freeze-over days. They are, however, able to withstand short cold periods by remaining in their burrows.

Armadillo's burrow systems may be up to ten meters in length and two meter deep and are complex systems with a conjoined central den. Armadillos are known to have as many as twelve burrow sites and multiple entrances for each. They often have a primary burrow for nesting and additional shallow burrows within their territory as food traps.[7] In certain coastal prairies, armadillos dig additional burrows for flood protection.[17] Armadillos have been documented to occasionally share burrows with other animals such as rabbits or skunks.[9] However, they very rarely share their burrow with another armadillo except during the mating season. One such incidence of adult armadillos sharing burrows is during extreme cold weather, in which sharing may enhance thermoregulation.[4]

Dasypus are typically non-aggressive, solitary animals. They are, however, known to occasionally show slight aggressive behavior during the mating season or while a female is nursing. Such behavior often includes kicking or chasing and does not cause substantial injury. Armadillos are more likely to respond to threats by freezing, jumping into the air, or sprinting away.

Armadillos use olfaction as their main perception for foraging. The nine-banded armadillos are capable of smelling food as much as 20 cm below the ground surface. Once a food item is detected, it digs a small hole using its forefeet. Armadillos are also known to stand on their hind legs using their tail to brace themselves and sniff the air to either locate food or orient themselves.[4][18]

Because of armadillos’ low body temperature, scavenging habits, and damp living environments they are susceptible to certain infections and parasites. Some of these include the bacterium Mycobacterium leprae, which is the causative of leprosy, the organism Trypanosoma cruzi, which is the causative of Chagas’ disease, and the fungus Paracoccidiodies brasiliensis, which is the causative of mycosis in humans. Despite these predispositions, however, armadillos are still considered less prone to get parasites than other common small mammals such as skunks, opossums, and raccoons.[18] No diagnosis of rabies within Dasypus species in Florida has been recorded yet.[7]

In some locations in Florida, Dasypus have more recently been noted to raid and destroy sea turtle nests, specifically those belonging to the endangered leatherback (Dermochelys coriacea), loggerhead (Caretta caretta), and the green (Chelonia mydas). This accounts for 95% of nest raids in the area and may present a large invasive problem. In order to protect the endangered sea turtles, National Wildlife Refuge staff and the USDA Wildlife Services have actively trapped and removed armadillos from nesting locations.[10] However, though the growth of armadillos in Florida may be contributing to sea turtle invasion, they are also serving as an important primary food source to maintain the endangered Florida panther (F. concolor coryi).[19]

Armadillos have a life expectancy of 7 to 20 years. Juveniles lack fully developed and strengthened armor and are much more susceptible to predation, thereby having a much higher mortality rate than adults. Adult armadillos, however, have shown a significant increase in physical damage compared to juveniles. Since juvenile mortality rates are much higher, this most likely indicates an increased ability of adults to escape from predators. Strangely, various physical damages caused to armadillos do not appear to have any significant consequences in breeding or other physical functions.[20] In captivity, armadillos have a much higher life expectancy, with one recorded D. novemcinctus species living 23 years.[4]

One of the largest causes of death of armadillos within North America are highway accidents. This is most likely due to their common response of jumping into the air when startled which causes a direct collision with a passing automobile. Armadillos are also killed by dogs or coyotes as well as hunted by humans as a food source.[7][8][14] Despite hunting, predation, and highway accidents, the IUCN lists the majority of Dasypus species as a least concern endangered animal due to its very large distribution, living tolerance, and large progeny and population. A few species are considered at risk due to habitat loss.[12]

Leprosy is a chronic infectious disease caused by the bacteria Mycobacterium leprae. M. leprae is unculturable on artificial media, and only after years of research was the ability to culture the bacteria on the footpads of mice discovered. However, the development of the bacteria and study was still very limited until the successful infection of lepromatous leprosy in the nine-banded armadillo (Dasypus novemcinctus) by Kirchheimer and Storrs in 1971. Soon after, Convit and Pinardi incurred a second successful inoculation of M. leprae into Dasypus sabanicola. The armadillo became the only known animal other than primates to regularly develop leprosy and has since largely advanced the disease study through use of in vivo propagation of M. leprae. Dasypus was also an ideal model due to the ability to replicate experiments on their genetically identical siblings. Despite the discovery of additional Dasypus species capable of infection (D. septemcinctus and D. pilosus), the nine-banded armadillo remains a favored animal model due to its availability and ideal body temperatures for bacterial hosting. D. sabanicola is also continually used in research due to its adaptability to the lab environment and ease of handling.[23] The nine-banded armadillo's enhanced ability to grow M. leprae has led to suggestions that armadillo species are more susceptible to the disease due to their generally lower body temperatures.

While temperature enhances susceptibility, the actual infection source and mode of transmission are very poorly understood. This is primarily due to the bacteria's slow multiplication rate and long incubation period, making specific infection period identification difficult. The incubation period itself may range from ten months to four years in the nine-banded armadillo, compared to three to six years in humans. The long life of armadillos is particularly useful in the study of chronic effects of leprosy as well as the propagation of M. leprae outside of humans. The armadillo model has been useful for biochemical, immunological, and vaccine research.

Though the majority of nine-banded armadillos contract leprosy, about 15% of the species have been found to be resistant. The resistant specimens are used as a study model in order to develop a possible genetic linkage.[6][9][18]