Tubulidentata

Aardvarks

(Orycteropodidae)

Class Mammalia

Order Tubulidentata

Family Orycteropodidae

Number of families 1

Thumbnail description
Small- to medium-sized stocky anteater with short, powerful limbs (front shorter than back) with claws used for digging; tapering, muscular tail, pig-like snout, elongated head, and pale, yellowish gray sparsely haired bodies; long, tubular ears are held upright

Size
Length 67–79 in (170–200 cm); tail length 18–25 in (45–63 cm); weight 99–139 lb (45–65 kg)

Number of genera, species
1 genus; 1 species

Habitat
Savanna and woodland

Conservation status
Vulnerable

Distribution
Sub-Saharan Africa

Evolution and systematics

The Tubulidentata are the last living group of primitive ungulates. The only extant species in the order, the aardvark, was once thought to be an edentate. However, it has no phylogenetic ties with this group, and the similarities between the aardvark and the South American anteater result from convergent evolution since both animals feed on termites and ants. The Tubulidentata arose in Africa, and the modern aardvark existed as early as the middle Tertiary (Miocene). In the Pliocene, there were aardvarks in southern Europe and western Asia, and during the Pleistocene they were on Madagascar as well. All modern aardvarks belong to one species, Orycteropus afer. None of the 18 subspecies are considered of taxonomic importance any longer.

The taxonomy for this species is Orycteropus afer (Pallas, 1766), Cape of Good Hope, South Africa.

Physical characteristics

The head is elongated and the snout is long and pig-like. The ears are tubular, and the yellow-gray colored body has little hair. The fore feet have four toes and well-developed claws, while the hind feet have five toes. The tail is well developed and resembles the tail of a kangaroo.

The name aardvark, Afrikaans for earth pig, is derived from the pig-like snout and digging behavior. The aardvark is uniquely shaped: the short neck joins the massive body with an elongated head and a narrow, rounded snout. The nasal openings can be closed. The muscular tail has a circumference of 18 in (40 cm) at its base. The legs are short, with the hind legs longer than the fore legs. The fore feet have toes adapted for digging; the claws of the five toes on the hind feet are somewhat shorter and weaker. Although the hind feet have soles, aardvarks always move on their toes. The soles do rest on the ground when the aardvark assumes its characteristic stooped position as it digs up termite hills.

There are many embryonic teeth, which rest in tooth cavities, but adults have teeth only in the rear of the jaw. They are columnar and rootless, and have hexagonal prisms of den-tine. The tooth formula is 0 0 2 3/0 0 2 3. The teeth are un-usual in that they grow throughout life and are not coated in

enamel. Instead, each tooth has numerous hexagonal prisms of dentine surrounding tubular pulp cavities. The largest tooth, the second molar, is composed of 1,500 such hexagonal prisms. An aardvark typically has five functional molars in each jaw half, though sometimes as few as four or as many as seven. The canines are usually missing.

Distribution

Aardvarks have a wide distribution on the continent of Africa alone, but are not common anywhere and, as a result of their secretive nocturnal habits, are rarely seen. They occur across Africa south of the Sahara, but generally avoid true forests (although they have been recorded in the northeastern parts of the Congo Basin forests) and extremely arid areas.

Habitat

Aardvarks are found in a variety of habitats in their range, although their local occurrence is determined by the availability of food and the distribution of sandy soils. They are also capable of utilizing heavier soils, but will avoid rocky terrain, preferring more open areas.

Behavior

Aardvarks usually live alone and are never found in large numbers. Being nocturnal animals, they are rarely seen in the wild. They normally emerge from their burrows shortly after nightfall, though they may emerge late in the afternoon during winter. They forage on both dark and bright moonlit nights, but may take shelter in one of several burrow systems within their home range during spells of adverse weather or when disturbed. They forage over distances varying 1.2–3 mi (2–5 km) per night at a speed of about 1,640 ft (500 m) per hour. In the arid Karoo (South Africa), home ranges vary from 321–988 ac (130–400 ha). Although the ranges of neighboring aardvark overlap, individuals spend about half their time

in a core area represented by one-quarter to one-third of their home range.

Aardvarks can dig with astonishing speed in suitable soil. The burrow can be 6.5–9.8 ft (2–3 m) long, on a 45° angle, and with a diameter of about 16 in (40 cm). It terminates in a rounded chamber where the aardvark sleeps coiled up and where the female bears her young. There is typically just one entrance, but some aardvark burrows form tunnel systems with numerous entrances; the main burrow may have several side tunnels. Abandoned aardvark burrows are used as dens by creatures such as warthogs, porcupines, wild dogs, viverrids, jackals, hyenas, birds (such as ant thrushes), and the bat Nycteris thebaica.

Enemies of aardvarks, besides man (some do eat aardvark meat), include lions, hyenas, and leopards. Pythons occasionally enter aardvark burrows and may eat the young. An aardvark can defend itself only with the claws on its fore feet. When it is threatened, it lies on its back, raises up all four legs, and threatens with its claws. When it is pursued, it starts running in leaps and bounds to gain speed, then continues at a trot.

Feeding ecology and diet

In the wild, practically the only food for aardvarks is termites and ants. In the savanna, they feed chiefly on the termite genera Trinervitermes, Cubitermes, and Macrotermes. In the semi-arid Karoo (South Africa), the ant Anoplolepis custodiens is the main food item throughout the year, followed by a termite (T. trinervoides). In the Karoo, termites are fed on more often in winter than in summer, coinciding with a decrease in the availability of ants. Aardvarks cannot fully satisfy their hunger by breaking open termite hills. The only way they can get enough termites is to find termite colonies making mass movements on the ground. Swarms of harvester termites (Trinervitermes) contain thousands of individuals marching in armies with columns 33–130 ft (10–40 m) long; Macrotermes and Hodotermes form similar nocturnal marches. Aardvarks usually dig up the termite hills at the base, using the sharp claws of the fore feet. As soon as termites appear at the surface, the aardvark extends its long tongue and licks the termites, which stick to the tongue. Aardvarks even press their disc-shaped snout against termite hills and suck the termites in.

Aardvarks occasionally consume the underground fruits of the cucumber species, Cucumis humifructus, a plant that in South Africa is known as the "aardvark pumpkin" or the "aardvark cucumber." The plant fruits underground and occasionally thrives in the vicinity of abandoned aardvark burrows. The Kung San people know the plant as "aardvark dung." The aardvark buries its feces outside the burrow, and thereby also the seeds of this plant, enabling the plant to reproduce.

Reproductive biology

Little is known about aardvark reproduction or raising of the young. The gestation period is about seven months. Usually one young of less than 4.4 lb (2 kg) is born at a time. In the southern Congo region, aardvarks mate between April and May, and the young are born in October or November. Females in Ethiopia bear their young in May or June. Anecdotal accounts from Africa suggest that aardvarks do not construct a birth nest in the burrow. A newborn aardvark is naked and has tender, flesh-colored skin. After about two weeks the young aardvark begins accompanying its mother on forays. Once the young

aardvark is six months old it digs its own burrow, just a few feet (meters) from the mother's, although it continues hunting with her. During the next breeding season, the young male aardvark leaves its mother, but the young female stays with her until after the next offspring is born. The males roam about, associating with females only during the short mating period. Due to the fact that only the females keep a consistant home range, aardvarks are thought to be polygamous.

Conservation status

In being a specialized feeder, aardvarks are extremely vulnerable to habitat changes. While intensive crop farming over vast areas may reduce their numbers, increased cattle herding, whose trampling creates better conditions for termites, may increase their numbers. However, although they are widely distributed, aardvarks are not common anywhere. Though not listed by the IUCN, the aardvark is considered worthy of protection, according to the South Africa Red Data Book. There are no known conservation efforts directed primarily at aardvarks, but they do occur in most large conservation areas in Africa.

Significance to humans

Apart from aardvark flesh, which is said to taste like pork, various parts of the aardvark's body are prized. Its teeth are worn on necklaces by some tribes of the Democratic Republic of the Congo (Zaire) to prevent illness and as a good-luck charm. Its bristly hair is sometimes reduced to powder and, when added to local beer, regarded as a potent poison. It is also believed that the harvest will be increased when aardvark claws are put into baskets used to collect flying termites for food.

Resources

Books

Lindsey, Andrew P. The Feeding Ecology and Habitat Use of the Aardvark Orycteropus afer. Pretoria: MSc thesis, University of Pretoria, 1999.

Skinner, John D., and Reay H. N. Smithers. The Mammals of the Southern African Sub-region. Pretoria: University of Pretoria, 1990.

Taylor, Andrew. The Ecology of the Aardvark Orycteropus afer (Tubulidentata-Orycteropodidae). Pretoria: MSc thesis, University of Pretoria, 1999.

van Aarde, Rudolph J. "Aardvark." In The Complete Book of Southern African Mammals, edited by Gus Mills and Lex Hes. Cape Town: Struik, 1997.

Periodicals

Melton, D. A. "The Aardvark at Night." Animals' Magazine 16 (1974): 108–110.

——. "The Biology of the Aardvark (Tubulidentata-Orycteropodidae)." Mammal Review 6 (1976): 75–88.

Melton, D. A., and C. Daniels. "A Note on the Ecology of the Aardvark Orycteropus afer." South African Journal of Wildlife Research 16 (1986): 112–114.

Taylor, Andrew, Peter A. Lindsey, and John D. Skinner. "The Feeding Ecology of the Aardvark Orycteropus afer." Journal of Arid Environments 50 (2002): 135–152.

van Aarde, Rudolph J., et al. "Range Utilization by the Aardvark, Orycteropus afer (Pallas, 1766) in the Karoo, South Africa." Journal of Arid Environments 22 (1992): 387–394.

Rudi van Aarde, PhD