Aardvark

Name and taxonomy

The name aardvark is Afrikaans and means earth pig, after the animal's digging. It is also called the antbear or the Cape anteater, though it is no relation of the South American anteaters. The genus name Orycteropus means burrowing foot, and afer means African. The order name Tubulidentata refers to the teeth, which are built from tiny tubes. GBIF also lists the English name earth-hog.

Peter Simon Pallas described the southern form in 1766 from the Cape of Good Hope. The aardvark is usually treated as one variable species. Seventeen subspecies have been named, but they are poorly defined and many will probably be merged. Its likeness to the anteaters and the pangolins is the result of convergent evolution toward the same diet.

Evolution and relatives

The aardvark belongs to the Afrotheria, a group of African mammals that also holds elephants, manatees and hyraxes. Within that group its closest kin are the elephant shrews, the tenrecs and the golden moles. It is the largest member of that inner group, the Afroinsectiphilia. Its chromosomes have changed little since the early placental mammals, so geneticists call it a living fossil.

Early relatives appeared in Africa near the end of the Paleocene. The first clear member of the order was probably Myorycteropus africanus, from Miocene deposits in Kenya. The oldest known Orycteropus, O. mauritanicus, comes from the middle Miocene of Algeria. Fossils of the aardvark itself, about 5 million years old, have been found across Europe and the Near East. A Madagascan animal, Plesiorycteropus, was once called an aardvark relative but is now placed nearer the tenrecs.

Appearance

The aardvark has a stout body with a strongly arched back and a thick tail that tapers to the tip. Adults weigh 40 to 82 kilograms, measure 100 to 158 centimetres in head and body, and stand about 60 cm at the shoulder. The tail can add up to 70 cm, which brings some animals to 2.2 metres in all. Males and females look alike and are the same size.

A short, thick neck carries the long head, and a flat disc with the nostrils ends the snout. The ears are 20 to 25 cm long and look like a rabbit's. The eyes are small and hold only rods, so the animal sees in the dark but not in colour. The mouth is small and tubular, and the tongue is thin and can stretch about 30 cm.

The skin is thick and tough, and it is the animal's main protection. Coarse hair grows in sparse clusters of three or four, longer on the legs than on the head and tail. The colour is pale yellowish grey, but most animals are stained red-brown by the soil. The front feet have four toes and the hind feet five, each with a broad flat nail between a claw and a hoof.

The teeth are unlike those of any other mammal. Each one is a bundle of thin upright tubes of dentine, up to about 1,500 in the largest tooth, with no enamel. They wear away and grow all through life. Adults keep only cheek teeth, 14 above and 12 below, because the front teeth of the young fall out and never return.

Habitat and range

The aardvark lives throughout sub-Saharan Africa, from Ethiopia south to the Cape of Good Hope. It is absent from the rainforests of West and Central Africa and from the coasts of Namibia, Ivory Coast and Ghana. It does not occur in Madagascar. GBIF holds records from 37 countries.

It uses savanna, grassland, open woodland, bush and semi-arid country. It has been recorded as high as 3,200 metres in the Ethiopian highlands. Two things matter most: deep soft soil to dig in, and enough ants and termites all year. It avoids rock, hard compact ground, swamp forest and land that floods.

A home range covers about 2 to 5 square kilometres, and densities are always low. In the Nama Karoo of South Africa, where prey is dense, ranges run from 130 to 350 hectares. Elsewhere the ranges are probably larger. The main burrow can have eight or more entrances and reach 6 metres underground, and some run 13 metres long.

Diet and feeding

The aardvark eats almost nothing but ants and termites. Ants make up the larger share. In the Karoo one ant, Anoplolepis custodiens, can supply 70% of the diet, with the termite Trinervitermes trinervoides next. In winter, when ants are scarce, it turns more to termites and feeds at mounds when the winged forms are present. It avoids driver ants and red ants, and it sometimes takes beetle larvae.

When it forages, the aardvark keeps its snout at ground level and points both ears forward. It digs small V-shaped trenches and sniffs them to find a nest. Then it tears into the mound with its front claws, seals its nostrils against the dust, and keeps its ears up for danger. The sticky tongue sweeps up the insects, and their bites and stings fail against the thick skin. As many as 50,000 insects have been counted in one night's meal.

A stomach with a muscular gizzard-like region grinds the food, so the aardvark barely chews. It rarely destroys a colony, and it leaves a nest alone for five to eight days so the insects can recover. Columns of marching termites 10 to 40 metres long give an easy meal. The one fruit it eats is the aardvark cucumber, which grows underground and provides water. The seeds pass through the animal and sprout in the loose soil beside its burrow.

Behaviour and social life

The aardvark is nocturnal and solitary, and it is seldom seen. It leaves its burrow in the late afternoon or soon after sunset. Before it goes, it pauses at the mouth of the burrow for about ten minutes to sniff and listen. Then it bounds out about 10 metres, stops, pricks its ears, and moves off in a zigzag to feed. Most feeding happens in the first four hours of the night.

A night's walk covers 2 to 5 kilometres, and tracked animals in Uganda went as far as 14 km. In subtropical South Africa its nightly activity lasts up to nine hours in summer, but only seven in winter. When food runs short it may shift to daytime activity, which is often a sign that it is in trouble. In bad weather it stays underground.

It digs three kinds of hole: quick foraging pits, short refuge burrows, and a deep permanent home. It can dig a metre of tunnel in about five minutes, and it changes the layout of its home burrow often. Only a mother and her cub share a burrow, though in good country a large burrow may hold two or three animals. It is a strong swimmer and can cross fast water.

Communication and senses

Smell is the aardvark's chief sense. Its nose holds nine to eleven turbinate bones, against four or five in a dog. It also has nine olfactory bulbs, a record among mammals. The smell centre of the brain is so large that it gives the skull a swollen profile. Hearing is very sharp, and each ear can turn on its own or fold back and close while the animal digs. Sight is poor, and the animal is colour-blind.

The aardvark is quiet. It grunts softly while it feeds and loudly as it heads for its burrow. When badly frightened it bleats. Both sexes have scent glands on the elbows and hips and a strong-smelling anal gland, and the male's genitals give off musk. These glands probably help the animals space themselves out, though no one has seen deliberate scent marking.

Reproduction and life cycle

Aardvarks meet only to mate, and the system is thought to be polygynous. The male grips the female's back with his claws, which can leave deep scratches. Births fall between May and July in South Africa and between October and November in the north. Pregnancy lasts about 7 months, and one cub of 1.7 to 1.9 kilograms is born in the burrow.

The newborn is naked and wrinkled, with floppy ears, but its eyes are open. The wrinkles fade after two weeks, the ears stand up at three weeks, and hair grows from five to six weeks. The cub follows its mother out of the burrow at two weeks and tastes termites at nine weeks. Weaning comes between three months and 16 weeks.

At six months the cub can dig its own burrow, but it often stays with its mother until the next mating season. The father takes no part in rearing. Both sexes mature at about two years. A wild aardvark lives about 18 years, and one captive animal reached 29.8.

Predators and threats

Lions, leopards, hyenas and pythons kill aardvarks. People are the main predator, hunting them for meat and hide. The aardvark's first defence is its hearing, which warns it early. It then runs in a zigzag or digs itself out of sight, which takes about 10 minutes.

If it cannot escape, it rears up on its hind legs and tail or rolls onto its back. It then lies still and lashes out with all four feet, its claws, its tail and its shoulders. Those claws can do real damage to an attacker. If attacked inside a tunnel, it digs onward and leaves fresh earth between itself and the enemy.

Farmers kill aardvarks because their holes injure livestock and wreck vehicles. Ploughing and pesticides remove the ants and termites it needs. Drought is a growing danger, because it cuts insect numbers. In one Kalahari study, five of six aardvarks died after a drought.

Population and conservation

The IUCN lists the aardvark as Least Concern because of its wide range. No one has a reliable count, because the animal is nocturnal and secretive. It is not common anywhere, but its range is so large that the total stays adequate. Numbers look stable in southern Africa and may be falling in the east, north and west.

The aardvark is exterminated in many farming districts and is rare or gone where people are dense. CITES lists it in Appendix II, so trade in its parts is controlled. Its future rests on its insect prey, so any collapse in termites would hit the whole species. Rising temperatures and drought are the threat researchers now watch most closely.

Aardvarks adapt well to zoos. London Zoo kept the first, an animal from South Africa, in 1869.

Relationship with humans

Some African communities hunt the aardvark for its meat, which is said to taste like pork. The hide and other parts are also used, and the bushmeat trade takes a share. Trade in aardvark products is restricted by international agreement.

Farmers and ranchers dislike the burrows, which can break a cow's leg or a truck's axle. On the other side, the aardvark eats termites and ants that damage crops and buildings. Its digging loosens and enriches the soil, which helps plants and many small animals. It is otherwise harmless, and it flees from people.

Zoos have kept aardvarks since 1869, and they breed there. Captive records show a gestation of about 243 days and a birth weight of 1.3 to 1.9 kg. Most of what science knows about the species comes from South African studies and from zoo animals.

In culture and myth

In African folklore the aardvark is admired for its tireless search for food and its calm in the face of soldier ants. In Hausa tradition, magicians pound its heart, skin, forehead and nails with a tree root to make a charm. A burglar who wears the charm on his chest is said to walk through a wall or a roof after dark. In Margbetu and Logo tradition, aardvark teeth are made into bracelets for luck. The Dagbon people of Ghana credit the aardvark with supernatural power.

In Dogon tradition in Mali, the aardvark appears in the creation story recorded by Marcel Griaule in 1948. Scholars have noted that the animal head of the Egyptian god Set looks something like an aardvark. The children's character Arthur Read, created by Marc Brown in 1976, is an aardvark, though his nose grew shorter with each book. The cartoon series The Ant and the Aardvark, from 1969 to 1971, paired a blue aardvark with a red ant it could never catch. The Goon Show on BBC radio made a running joke of the animal in the 1950s.