General Biology

The aardvark (Orycteropus afer) is nocturnal, fossorial, and myrmecophagous and is the only living representative of the order Tubulidentata, belonging to the superorder Afrotheria.⁵ The aardvark’s tooth is unique in that each molar consists of fused, elongated, hexagonal, perpendicular, dentine columns surrounded by a layer of cementum.¹³ This structure gives rise to the order’s name: the Latin tubuli, tube, and dentis, tooth. The common name, aardvark, is derived from two Afrikaans words, aarde, earth, and vark, pig.³ Fossil records indicate that aardvarks once existed in Europe and Asia; however, their current distribution is restricted to sub-Saharan Africa.⁵ They are found over a wide range of habitats, from semi-arid zones to tropical rainforests, but are totally absent from deserts.^3,12,14

Aardvarks are solitary and almost exclusively nocturnal, but wild individuals may be observed feeding before sunset during winter. They are efficient burrowers, digging in search of either food or shelter. Burrows provide a microhabitat that is thermally buffered from external ambient extremes (heat and cold) and has a higher relative humidity.¹⁶ Vocalization is restricted to a vigorous snuffling and the occasional grunt or a rare bleat.^3,13 Life expectancy is 10 years in the wild and early 20s in captivity; a single individual is reported to have lived to 29 years of age.³

Unique Anatomy

Aardvarks have evolved anatomic adaptations that allow them to feed on ants and termites.^9,12,13 Long, sharp claws combined with an inability to supinate the wrist provides strength for digging. The radius is shorter than the humerus, and webbing between the digits assists in burrowing.¹² The aardvark’s head is elongated and narrow, with a long (25–30 cm), sticky vermiform tongue.^9,12,13 Aardvarks have an excellent sense of smell and hearing. However, their eyesight is poor.^3,12,13

The skin is thick, with a sparse covering of hair and no subcutaneous fat layer, possibly making the aardvark susceptible to temperature fluctuations.^3,9 Adult body mass is 40 to 65 kilograms (kg), with total body length up to 200 centimeters (cm) and shoulder height of 65 cm. Males are heavier and slightly larger than the females.^3,13,15

The adult dental formula is: incisors (I) 0/0, canines (C) 0/0, premolars (P) 2/2, molars (M) 3/3, although variations may occur, as in four to seven teeth in the mandible. Teeth lack enamel and grow continuously.^3,13 The stomach is muscular and gizzard-like for grinding up food ingested with sand and soil, and a large cecum is present, which is unusual for an insectivore.^3,13

Both male and females have a distinct genital eminence that may be confused with a scrotum. Unlike in other Afrotheria, which are testicond, in the aardvark, testes are descended but are ascrotal.² The penis is soft, short, and shaped like a truncated cone, and the vulva is a long cleft with a large heart shaped clitoris behind the center of the genital eminence. The genitalia and a pair of genital scent glands are visualized by opening a sphincter-like fold of integument.^7,13

Physiology

Body temperature in the aardvark varies between 34° C to 37° C and is regulated, in part, through the use of burrows. However, aardvarks appear to be susceptible to hypothermia as they return to their burrows once temperatures fall below 2° C.^12,13 Aardvarks drink infrequently and seem able to obtain all their water requirements from their prey.¹²

Special Housing Requirements

Aardvarks are best displayed in a nocturnal exhibit with reversed day and night periods.^1,3 The enclosure should be concrete or metal lined to prevent the animals from burrowing out; they should be devoid of sharp edges to prevent tongue injuries and have a substrate of soil, woodchips, or shavings.^1,9 Moats are to be avoided as aardvarks are good swimmers.¹ In the wild, aardvarks are solitary animals; however, in zoos, they are frequently exhibited in groups of two to four animals and any combination of sexes. Pregnant females are separated shortly before or after parturition.³

Indoor temperatures are best kept between 20° C to 27° C and the relative humidity above 70%.^1,3,16 Low humidity may lead to drying and cracking of the skin, especially in young animals.⁹ In most zoos, a sleeping box or a den with a sand or straw substrate is provided.¹

As aardvarks are prone to stereotypical behavior, environmental enrichment is essential, and it may include scatter feeding, the use of hole feeders, and substrates for digging.^1,3

Feeding

The natural diet of aardvarks consists almost exclusively of ants and termites; a small proportion may include seeds, fly and scarab beetle pupae, and wild cucumber (Cucumis humifructus).^{6,10,13,14,17} A substitute high-protein, low-carbohydrate diet, with added vitamin and minerals, is fed as a thick soupy gruel to captive animals.⁹ The ingredients may include ground beef, chicken, or horse meat, commercial dog or cat food, mealworms, eggs, oatmeal, corn flakes, milk, low-fat curd cheese, and a variety of fruit and vegetables. Mazuri Insectivore Diet is used at many facilities.³