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Orycteropus aferaardvark

By Elizabeth Ratzloff

Geographic Range

Aardvarks are found throughout sub-Saharan Africa, except for the West and Central rain forest regions. (Kingdon, 1997; "Oxford Reference Online", 2009)

Habitat

Aardvarks occupy grassland and savanna habitats in sub-Saharan Africa, preferring areas that have a large abundance of ants and termites year round. The location of their burrow may differ from where they forage, in which case they walk between the two sites at night. They are rarely found in areas that have hard, compact soil, rocky areas, or areas that frequently flood. They often live in temporary holes that are a few meters in length, but can also live in complex and intricate burrows, which can have eight or more entrances and extend as much as 6 meters underground. Burrow entrances are often plugged with a vent left at the top. (Kingdon, 1997; Lehmann, 2009; "Oxford Reference Online", 2009)

Physical Description

Aardvarks are the size of small pigs, but have very thick skin and do not possess a fat layer. They are notable for their long nose, which is wider at the distal end, their squared-off head, and a tail that tapers off toward the tip. The body is massive and they have very muscular limbs ending in thick-nailed digits. The hair is short on the head, neck, and tail, but longer and darker on the rest of the body, especially the limbs. Hair is often worn off in adults, but apparent on the young. The sides of the face and tail are pale colored, lighter in females and darker in males. During the wet season, aardvarks have fat deposits that are likely fueled by termite consumption. (Kingdon, 1997; Knöthig, 2005; "Oxford Reference Online", 2009)

Aardvarks have 4 toes on the forefeet and 5 toes on the hind feet, each ending in a spade-like claw that helps them to dig with great speed and force. Digging is used both to acquire food and as a means of escape. The stance is digitigrade. (Kingdon, 1997; Knöthig, 2005; "Oxford Reference Online", 2009)

Aardvarks have peg-like molars and premolars, but no incisors or canines; the dental formula is 0/0 0/0 2/2 3/3. Their teeth lack enamel and are made up of densely packed tubules, composed of a modified form of dentine. The tubules are contained in a sleeve of dental cement. Embryos and infants have a full set of vestigial milk teeth, including canines. (Kingdon, 1997; Knöthig, 2005; "Oxford Reference Online", 2009)

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • Range mass
    40 to 82 kg
    88.11 to 180.62 lb
  • Range length
    100 to 158 cm
    39.37 to 62.20 in
  • Average basal metabolic rate
    34.275 W
    AnAge

Reproduction

Aardvarks are solitary and territorial, coming together only to breed. They are believed to be polygynous. (Kingdon, 1997; Knöthig, 2005)

Male aardvarks have genitals that secrete a powerful musk and both males and females have glands on their elbows and hips. These glands might help with individual spacing and/or be involved in mating, but obvious scent marking has not been reported. Northern African aardvarks give birth between October and November, while aardvarks in South Africa give birth between May and July. (Kingdon, 1997; Knöthig, 2005)

Usually one young is born after a gestation period of about 7 months. Offspring are born naked and with eyes open. The young begin to follow their mother at 2 weeks. They nurse until 3 months, at which time they begin to eat insects. At about 6 months, they become independent of the mother, and at about 2 years, they become sexually active. Aardvarks live to be about 18 years of age. (Kingdon, 1997; Knöthig, 2005)

  • Breeding interval
    Aardvarks breed once yearly
  • Breeding season
    It is believed that aardvarks breed earlier in the year the closer they are to they equator.
  • Range number of offspring
    1 to 2
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Average gestation period
    7 months
  • Average gestation period
    225 days
    AnAge
  • Average weaning age
    3 months
  • Average time to independence
    6 months
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    730 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    2 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    730 days
    AnAge

Female aardvarks give birth in their burrow and the young remain underground for several weeks, while maturing. Offspring are taken care of by the mother until they are independent at about 6 months, after which they dig their own burrows. (Kingdon, 1997; Knöthig, 2005)

  • Parental Investment
  • altricial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

Aardvarks live for up to 18 years in the wild. In captivity, aardvarks are expected to live for about 23 years. (Knöthig, 2005)

Behavior

Aardvarks are solitary, except when accompanied by young, and are very shy. Where aardvarks are most common, large and well-established burrows may be used by two or three animals. Aardvarks are rarely seen, rather their presence is indicated by their tracks, burrows, and scratch marks left by their powerful claws. Aardvarks forage at night, covering distances of 2 to 5 km each night. Before foraging, aardvarks leave their den in a ritualistic way. They first stop at the den opening to look for enemies, then run out, jump repeatedly, look around, and jump around more, before finally trotting off to forage. (Kingdon, 1997; Knöthig, 2005; Mutlow and Mutlow, 2008; Taylor and Skinner, 2003; Taylor, et al., 2002)

  • Range territory size
    1 to 5 km^2
  • Average territory size
    3.5 km^2

Home Range

Aardvarks inhabit large home ranges (2 to 5 square kilometers) and are typically found in very low densities. (Kingdon, 1997)

Communication and Perception

The only known sounds made by aardvarks are grunts and, in cases of extreme fear, bleats. Both sexes have glands on their elbows and hips, which may aid in mating or spacing of individuals. However, scent marking has not been observed. (Kingdon, 1997; Knöthig, 2005)

Aardvarks have poor vision because their retinas contain only rods, which allow them to see at night, but leave them colorblind. They have a very acute sense of hearing and long ears that can be moved independently, as well as folded back and closed while tunneling. Aardvarks have an exceptional sense of smell due to structures in the nose that increase turbinal surface area, improving the detection of olfactory signals. The olfactory region of the brain is highly developed in aardvarks, giving the middle profile of the skull a swollen appearance.

Food Habits

Aardvarks eat at night and are myrmecophagous, i.e. they specialize on ants and termites, with the majority of their diet being ants. They dig rapidly into the sides or center of ant and termite nests or mounds, while feeding at the same time. The ants and termites are swept into their small mouth with their long, sticky tongue. Aardvarks swallow without chewing their food, or after chewing their food very little. The insects are digested in the pyloric region of the muscular, gizzard-like stomach. Some of the predator defenses that ants and termites use against myrmecophagous animals, such as pangolins, anteaters, and echidnas, include biting, stinging, chemical defenses, and building hard mounds. These defenses do not seem to affect aardvarks. Colonies of ants and termites are rarely destroyed after an aardvark feeds and can be built back up and reestablished. (Kingdon, 1997; Knöthig, 2005; Mutlow and Mutlow, 2008; Taylor and Skinner, 2003; Taylor, et al., 2002)

  • Animal Foods
  • insects

Predation

If confronted by a predator, an aardvark will attempt to dig a hole in which to hide, taking about 10 minutes to completely cover itself up. If it cannot dig a hole, it will stand upright on its hind legs and tail, or lay on its back, and defend itself with its large front claws. Humans are the primary predator of aardvarks, but lions, hyenas, and leopards are also known to kill them. (Kingdon, 1997; Knöthig, 2005; "Oxford Reference Online", 2009)

Ecosystem Roles

Aardvarks are important in their ecosystem because the holes they dig are used by a variety of other animals for shelter. These include hyenas, warthogs, squirrels, hedgehogs, mongooses, and bats, as well as birds and reptiles. (Kingdon, 1997; Knöthig, 2005; "Oxford Reference Online", 2009)

Mutualist Species

Economic Importance for Humans: Positive

Sometimes humans hunt aardvarks for their meat and hide, although products made out of aardvarks are subject to trade restrictions. Aardvarks may help control termite and ant populations, which are pests to humans. (Knöthig, 2005)

  • Positive Impacts
  • food
  • body parts are source of valuable material
  • controls pest population

Economic Importance for Humans: Negative

Aardvark burrows can present a hazard for vehicles. (Kingdon, 1997; Knöthig, 2005)

Conservation Status

Aardvarks are widespread, however, they have been exterminated in many agricultural areas. They are vulnerable in all settled areas and endangered or extinct in areas with a high concentration of people. They are often hunted by farmers and ranchers who find their hole digging inconvenient or dangerous. Cultivation and pesticide use has resulted in the elimination of their food source in some areas. (Kingdon, 1997; Knöthig, 2005)

Other Comments

Recent studies based on DNA sequence analysis have placed aardvarks in a taxon referred to as Afrotheria. Other animals in this group include elephants, hyraxes, sirenians, elephant-shrews, golden moles, and tenrecs. Afrotherians are thought to have originated and evolved in Africa. Fossil records and morphology are beginning to support the molecular evidence. The order to which aardvarks belong, Tubulidentata, is unique because it is the only mammalian order that is represented by a single species. (Lehmann, 2009; Tabruce, et al., 2008)

Contributors

Elizabeth Ratzloff (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

nomadic

generally wanders from place to place, usually within a well-defined range.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

soil aeration

digs and breaks up soil so air and water can get in

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Oxford University Press. 2009. "Oxford Reference Online" (On-line). A Dictionary of Zoology. Accessed March 26, 2010 at <http://www.oxfordreference.com.proxy1.cl.msu.edu/views/ENTRY.html?subview=Main&entry=t8.e6175>.

Kingdon, J. 1997. The Kingdon Field Guide to African Mammals. Princeton and Oxford: Princeton University Press.

Knöthig, J. 2005. "Biology of the Aardvark" (On-line). Accessed March 18, 2010 at http://www.tierseiten.com/roehrenzaehner/aardvark.pdf.

Lehmann, T. 2009. Phylogeny and systematics of Orycteropodidae (Mammalia, Tubulidentata). Zoological Journal of the Linnean Society, 155: 649-702.

Mutlow, A., H. Mutlow. 2008. Caesarian section and neonatal care in the aardvark (orycteropus afer). Journal of Zoo and Wildlife Medicine, 39: 260-262.

Tabruce, R., R. Asher, T. Lehmann. 2008. Afrotherian mammals: a review of current data. Mammalia, 72: 2-14.

Taylor, W., P. Lindsey, J. Skinner. 2002. The feeding ecology of the aardvark Orycteropus afer. Journal of Arid Environments, 50: 135-152.

Taylor, W., J. Skinner. 2003. Activity patterns, home ranges and burrow use of aardvarks (orycteropus after) in Karoo. Journal of Zoology, 261: 291-297.

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