Aardvark - AccessScience from McGraw-Hill Education http://accessscience.com/content/aardvark/000200

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Article by: Linzey, Donald W. Wytheville Community College, Wytheville, Virginia. Publication year: 2014 DOI: http://dx.doi.org/10.1036/1097-8542.000200 (http://dx.doi.org/10.1036/1097-8542.000200)

Content

Characteristics Threats Additional Readings Breeding and development Bibliography

A large piglike mammal in the order Tubulidentata. The order contains a single family, Orycteropodidae, and a single species, Orycteropus afer. Aardvarks occur throughout Africa south of the Sahara, wherever suitable habitat exists. In the past, tubulidentates were often considered closely related to ungulates. However, recent data from mitochondrial and nuclear genes support a relationship among aardvarks, elephant-shrews, paenungulates (hyraxes, sirenians, and proboscideans), and golden moles (Chrysochloridae). These ecologically divergent adaptive types probably originated in Africa; the molecular evidence implies that they may have arisen there from a common ancestor that existed in the Cretaceous Period, when Africa was isolated from other continents. This order shows the results of an extreme adaptation for burrowing and feeding on small food items (mainly termites). See also: Mammalia (/content/mammalia/402500); Tubulidentata (/content/tubulidentata /713700)

Characteristics

Aardvarks, also known as antbears, resemble a medium-sized to large pig (see illustration). The body is massive with an elongate head and snout. The round, blunt, piglike muzzle ends in circular nostrils that possess fleshy tentacles on the nasal septum and dense tracts of white hairs that can serve as a filter and seal the nostrils to prevent soil from entering the lungs. The tough, thick skin is sparsely covered with bristly hair ranging from dull brownish gray to dull yellowish gray. Numerous vibrissae (hairs with specialized erectile tissues) are present on the face. The waxy, smooth, tubular donkeylike ears are large and can be folded back to exclude dirt when the animal is burrowing, and they can be moved independently of each other. The strong, muscular tail is kangaroolike, tapering to a point. Incisors and canines are lacking in the dentition of adults but are present in the deciduous dentition. Teeth on the sides of the jaw are simple, peglike, open-rooted (not anchored in the jaw), and grow continuously during the animal's lifetime. The teeth are hollow; instead of a pulp cavity, they are transversed by a number of tubules. The dental formula is I 0/0 C 0/0 Pm 2/2 M 3/3 × 2 for a total of 20 teeth. Anal scent glands are present in both sexes. The senses of sight and hearing are acute, but their eyesight appears to be poor. Adult aardvarks have a head and body length of 100–158 cm (39–62 in.), a tail length of 44–71 cm (17–28 in.), and a shoulder height of 60–65 cm (23–25 in.). Most weigh 50–70 kg (110–153 lb), although some individuals may reach 100 kg (219 lb). Aardvarks exhibit a low basal metabolic rate and a low body temperature of about 34.5°C (94.1°F). See also: Dentition (/content/dentition/186400); Scent gland (/content/scent-gland/605300)

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Aardvark, Orycteropus afer. (Photo by Lloyd Glenn Ingles; copyright © 2001 California Academy of Sciences)

The aardvark is one of the world's great diggers. Its short, thick legs (with four toes on the front feet, five on the rear ones) are armed with long, powerful, sharp-edged, spoon-shaped claws that are intermediate between hoof and nail. The aardvark uses its claws to excavate the extensive burrows in which it dwells. Able to dig with amazing speed, it digs shallow holes when searching for food, larger burrows used for temporary shelter, and extensive tunnel systems in which the young are born. Tunnels may be 13 m (43 ft) long with numerous chambers and several entrances. Only mothers and their young share burrows. Burrows dug by aardvarks may be used by a variety of mammals, including warthogs, hyenas, porcupines, jackals, bat-eared foxes, hares, bats, ground squirrels, and civets, as well as monitor lizards and owls. One bird, the ant-eating chat (Myrmecocicla formicivora), nests in occupied burrows. In agricultural areas, burrows may cause damage to farming equipment and earthen dams.

Aardvarks are primarily nocturnal and solitary, and occupy a variety of habitats, including grassy plains, bush country, woodland, and savannah. They appear to prefer sandy soils. The main factor in their distribution is the presence of sufficient quantities of termites and ants. The aardvark is of considerable economic importance in keeping the great hordes of termites in check; if termites are not controlled, they do serious damage. The numbers of termites and ants consumed by the big-bodied aardvark in a single night are staggering. Studies have found that more than 50,000 insects may be consumed by an aardvark in one night. The long, round, thin, sticky, protrusible foot-long tongue is broader than that of the typical anteater or pangolin; together with the well-developed salivary glands, it can retrieve more termites in a shorter period of time than the two others. Since aardvarks do not need to chew their food, they have no need for incisors or canine teeth. Instead, their stomachs have a muscular pyloric area that serves a function similar to a gizzard in grinding up the food. They occasionally eat beetles, grasshoppers, and the fruit of the wild cucumber, known as the aardvark pumpkin, apparently as a source of water. See also: Anteater (/content/anteater/038200); Isoptera (/content/isoptera/356200)

Breeding and development

A single altricial offspring (a young that is born immature and helpless, thus requiring extended parental care) is born after a gestation period of 7–9 months. Births generally occur from July to November. After remaining in the burrow for about 2 weeks, the young aardvark begins accompanying its mother on her nightly foraging excursions. The young can dig for itself when about 6 months old. Sexual maturity is attained at about 2 years of age. Captive aardvarks have lived up to 10 years.

Threats

Large flesheaters such as the lion, leopard, and ratel (a fierce, badgerlike animal) frequently prey on aardvarks. Pythons also take the young. African natives relish the aardvark's meat. They wear its teeth and claws as bracelets or necklaces as good-luck charms and for warding off illnesses. The tough hide may be made into straps and bracelets. Aardvarks have been greatly reduced in numbers and distribution and are now on Appendix 2 of the Convention on International Trade in 2 of 4 3/14/2016 10:34 AM Aardvark - AccessScience from McGraw-Hill Education http://accessscience.com/content/aardvark/000200 Endangered Species (CITES). Termites have caused enormous damage to pasture and cereal crops in areas where aardvarks and other insectivorous animals have been exterminated. See also: Endangered species (/content/endangered- species/757435)

Donald W. Linzey

Bibliography

D. Macdonald (ed.), The Encyclopedia of Mammals, Andromeda Oxford, 2001

R. M. Nowak, Walker's Mammals of the World, 6th ed., Johns Hopkins University Press, 1999

Additional Readings

D. Macdonald (ed.), The Encyclopedia of Mammals, Oxford University Press, Oxford, UK, 2009

H. Marsh, T. J. O'Shea, and J. E. Reynolds, Ecology and Conservation of the Sirenia: Dugongs and Manatees, Cambridge University Press, Cambridge, UK, 2012

T. A. Vaughan, J. M. Ryan, and N. J. Czaplewski, Mammalogy, 5th ed., Jones & Bartlett Learning, Sudbury, MA, 2011

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