Marc
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Registered: 11th Aug 02
Location: York
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Imagine riding through the South-American pampa. Suddenly, you see a cow-pat moving. Or was it a stone? Try to get closer to it, it may be one of the most interesting inhabitants of this area: an armadillo. Never heard of it? So, it's time to get to know it, before it's too late. Some species are almost extinct.
Armadillos are often classified together with the sloths and the anteaters as Edentata (teethless). This classification is quite confusing, as giant armadillos have up to 100 teeth. Actually, it only means that they don't have incisors or canines. It would be better to count them as Xenarthra, since their thoracic and lumbar vertebrae have additional joint processes.
Armadillos are found in South America, except one species, the nine-banded armadillo (Dasypus novemcinctus), that has found its way up to Texas. They live in the open fields and near the forests; the giant and the nine-banded armadillo prefer hiding in the jungle.
The majority of the 30 species are active at night and hide during daylight. Their burrow consists of one or more tunnels of several meters each that end in a wide chamber stuffed with dry grass to make it more comfortable. It's amazing how quickly they can burrow with their sharp claws. The shape of the burrow's entrance is round or oval, depending on the species, and is very narrow. It is almost impossible to pull an armadillo out as they use their bands and claws like barbs in the hard ground of the tunnel. There are two ways to get it out: once you are able to catch its tail, you can grasp its hind legs. Or you insert a finger into its rectum, which makes it relax all its muscles.
Anatomy
The English name "armadillo" is a Spanish word that means "little armoured thing". Armadillos are the last mammals that have a shell, that is an ossification of the corium interrupted by several folds of the skin. Its grey or brown surface is quite soft and feels like leather. Thanks to the skinfolds, the animal is very agile. The new-born are covered by soft pink epidermal scales. In the first phase of growth, ossification begins below the scales. Later on the ossificated platelets join to a big shield over the shoulder and one in the sacral region, several rectangular bands on the back and smaller shields on the head, the legs and the tail (excepted the naked-tailed armadillo).
Armadillos have an excellent sense of smell and a good hearing, but they are almost blind and can't see colours. The size varies from 15 cm (fairy armadillo) to 1.5 m (giant armadillo) and a weight between 90 g and 50 kg. The best-known nine-banded armadillo measures from head to tail 60 to 90 cm and weighs about 2.5 to 6 kg, depending on the publication. This information reflects the main problem an interested person has to deal with: there are just a few publications about this little animal, and in most of them the most frequent words are "not known" or "has not yet been studied".
Physiology and other astonishing facts
Nine-banded armadillos always give birth to 4 identical babies. After fertilisation the germ is split up in 4 (rarely 8 or 12) embryos with identical DNA. Only one corpus luteum and one placenta are developed.
Armadillos have a very low need of oxygen. Even when burrowing they can stop breathing for 6 minutes by storing air in the trachea and wide bronchus.
In order to improve the oxygen supply while burrowing and to conserve their body temperature, they have so-called retia mirabilia, that is a plait of very fine arteries, found mainly in the extremities.
Soft armadillos are excellent swimmers; they lower their specific weight by swallowing air and blowing up their stomach and the intestines.
The regulation of the body temperature of about 32°C is a big problem. Armadillos don't survive long periods of frost, except the fairy armadillo that lives in Patagonia and hibernates.
The three-banded armadillo hardly digs a burrow; it protects itself by rolling up like a hedgehog. The only opening is covered by the shields of the head and the tail, so that even a dog can't open this ball. As the body fat would disturb while rolling up, the fat moved to the dorsal part of the animal during evolution.
Armadillos are the only animals that can transmit leprosy. The temperature of 20°C on the surface of their paws seems to be ideal for the growth of Mycobacterium leprae, which is transmitted when a captured animal defends itself with its sharp claws.
Nutrition
Food is smelt up to 20 cm below the surface and is dug out. The menu varies depending on the species: Some armadillos prefer ants and termites and like to dig their burrows just below their hills. They developed big salivary glands in the mandibula that produce a viscous saliva on which the ants will stick and that can be stored in reservoirs. Other armadillos prefer beetles, larvae, caterpillars, grasshoppers, worms or even snakes or carrion, others seem to be vegetarians.
Reproduction
Unfortunately, there have been only a few investigations on this subject. The nine-banded armadillos mate in July (in the South-American winter). The female can delay implantation up to 3,5 months, and after 140 days of gestation are born 4 monocygote, blind and naked babies with soft armour. They are nursed for 2 to 2,5 months, begin to walk around after a week and open their eyes after 3 or 4 weeks. Artificial breeding is possible by using a mixture of 1/3 evaporated milk, 1/3 slime made out of maizena and 1/3 equine serum.
Domestication
In South America nobody would have the idea of domesticating an armadillo; they prefer to eat it, as the white meat is said to be very tasty, and use many excuses to kill it. They say that it destroys plantations, transmits a lot of diseases and that cattle break their legs when stepping into a tunnel. That's the reason why some species are endangered.
On the other hand, people in North America make use of the armadillo for insect control and also keep it as a pet. Even when captured as an adult this curious animal can become very tame and loves to be scratched softly. There are even armadillo races where the owner crawls behind his little pet...
Husbandry
The main problem in armadillo husbandry is that the visitors hardly get to see this animal because it usually hides during daylight. A simple remedy is to hang up an infrared light; armadillos at the zoo in Zurich love to sleep under the warm lamp. They even build a hill out of the bark compost and lie at the top of it to be closer to it. And don't think armadillos are not intelligent: they are even able to adjust the height of the hill depending on the temperature: if sunlight warms up their pen, they remove some of the material, and when it cools down, they stock it up again!
Armadillos should be held in pens constructed of solid materials. They are excellent climbers of wire netting, and injuries from falling may occur if climbing is not prevented.
Since armadillos are burrowing animals, it is imperative to give them a floor surface in which they can dig. Otherwise there may appear serious injuries on claws and feet due to their constant attempts at digging.
The first armadillos held in captivity often died of dehydration. The reason is that the male marks its territory and needs to be constantly surrounded by its own scent. As some guards had the obsession of cleaning the pen continuously, the males were obliged to mark the whole day long until they died.
As it is impossible to breed the huge amount of ants and termites needed to feed an armadillo, some special mixture had to be found. In several zoos a mixture is used which is composed of minced meat, grated carrots and apples, an egg, evaporated milk and vitamines. Crickets, fish, chicks or fruits can be added once in a while. They have a tendency to become overweight, and there may appear injuries of the jaws and the gums if the food is too soft, because they have to abrade their continuously growing teeth.
The stereotypies so far reported are constant digging and eating the nesting material, both of them resulting in health problems.
Diseases
Only a few diseases have so far been reported:
Parasites like sarcosporidia, tapeworms, strongyloides and enteric amoeba can cause gastrointestinal problems which are quite common in armadillos. Bacterial infections like salmonellosis and leptospirosis may also appear, and they are suspected to transmit Trypanosoma cruzi and Mycobacterium leprae. Some other problems that appeared in animals in captivity are superficial wounds and infections, pneumonia, nephritis, dermatitis, otitis, tumors and intoxications after cannibalism, since they have the habit to licking the wounds of a hurt cage mate.
Treatment
Suggested antihelmintics are fenbendazole for nematodes and praziquantel for cestodes. Levamisole and dichlorvos may cause serious side effects. Wounded animals have to be separated because of the constant licking of their cage mates. The wound has to be cleaned and treated with antibiotics.
It is important to consider that the development of a disease is slowed down and the effect of a medicament is prolonged because of the low body temperature of 30 to 35°C and the low activity of the thyroid gland. It is difficult to use inhalant anesthetics since the armadillos are able to hold their breath for 10 minutes. They can be safely anesthetized with sodium pentobarbital, 25mg/kg i.v. into the superficial femoral vein. An alternative is the combination of ketamine, 25 mg/kg i.m. with diazepam, 0.1mg/kg i.m.or acepromazine, 0.1 mg/kg i.m.
Mariella
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