Aardvark

• 1. Introduction

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  The aardvark, known to science as Orycteropus afer, can lick up as many as 50,000 insects in a single night. That count was actually recorded, and it hints at how unusual this animal is. It is a medium-sized mammal of Africa that digs for a living and works after dark. Its name and its snout both point toward other animals, and both clues mislead. So who are its real relatives, and how far back does its family go? Why do so many other creatures depend on the holes it leaves behind? And what happens to a species that eats almost exclusively ants and termites when the rains fail?

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• 2. Kin and Ancestors

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  The word aardvark comes from Afrikaans, where it grew out of the earlier form erdvark and means earth pig or ground pig. It joins aarde, meaning earth, to vark, meaning pig, a nod to the animal's burrowing habits. The pig comparison is misleading, because the aardvark is not closely related to pigs. Its scientific name is more honest. Orycteropus means burrowing foot, and afer simply points to Africa. Colloquial names include African ant bear, Cape anteater, and plain anteater, though it should not be confused with the anteaters of South America.

  South American anteaters share a long snout and a diet of insects with the aardvark, yet the resemblance is convergent evolution rather than kinship. The aardvark is the only living representative of the order Tubulidentata, a name drawn from its tube-like teeth. Its closest living relatives are the elephant shrews, tenrecs, and golden moles. Together with elephants, manatees, hyraxes, and their extinct relatives, they form the superorder Afrotheria. Studies of the brain have also shown similarities with a group called Condylarthra.

  Fossils studied by Bryan Patterson led him to conclude that early relatives of the aardvark appeared in Africa around the end of the Paleocene. The ptolemaiidans, a group of mammals with uncertain affinities, may actually be stem-aardvarks. The first unambiguous tubulidentate was probably Myorycteropus africanus, found in Miocene deposits in Kenya. The earliest member of the genus Orycteropus was Orycteropus mauritanicus, from middle Miocene deposits in Algeria, with an equally old version found in Kenya. Aardvark fossils dated to 5 million years have turned up across Europe and the Near East.

  On Madagascar, an animal called Plesiorycteropus lived in the Pleistocene. It was originally thought to be a tubulidentate whose ancestors reached the island during the Eocene. Subtle anatomical differences and recent molecular evidence now suggest otherwise. Researchers believe it was a relative of golden moles and tenrecs that came to look and live like an aardvark through convergent evolution. The living aardvark is itself called a living fossil, because its chromosomes are highly conserved. They preserve much of the early eutherian arrangement from before the major modern groups diverged. Within this single living species, researchers recognise seventeen poorly defined subspecies, including the Southern, Western, and Eastern aardvarks.

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• 3. Built to Dig

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  An adult aardvark typically weighs between 60 and 80 kg. Its body is usually 105 to 130 cm long, and it can reach 2.2 m once a tail of up to 70 cm is counted. It stands 60 cm tall at the shoulder and has a girth of about 100 cm. Males and females look alike. The animal is vaguely pig-like, with a stout body, a prominently arched back, and sparse coarse hair. That hair is short on the head and tail, longer on the legs, and grows in clusters of three to four. The coat is pale yellowish-grey, often stained reddish-brown by soil. Because the coat is thin, tough skin is the animal's main protection. It is the largest member of the clade Afroinsectiphilia.

  The rear legs are longer than the forelegs. The front feet have lost the thumb and carry four toes, while the rear feet keep all five. Each toe ends in a large, robust nail that is somewhat flattened and shovel-like. The nail looks intermediate between a claw and a hoof. The aardvark is considered digitigrade, yet it sometimes appears plantigrade, because it stands on its soles when it squats. A tissue called compacted coarse cancellous bone gives the skeleton the stress and strain resistance that burrowing demands. The forearm also has an unusually stout ulna and radius.

  Inside the head, each tooth has no pulp cavity. It is a bundle of thin, hexagonal, upright tubes of vasodentin, a modified form of dentine, each with its own pulp canal and all held together by cementum. The largest teeth have about 1,500 of these columns. There is no enamel coating, so the teeth wear away and regrow continuously. A young aardvark is born with conventional incisors and canines, but they fall out and are never replaced. Adults keep only peg-like, rootless cheek teeth, made up of 14 upper and 12 lower molars. Behind the teeth, the stomach has a muscular region that works like a gizzard, so chewing is unnecessary.

  The nose is where the aardvark truly stands apart. It holds between nine and 11 turbinate bones, compared with four to five in dogs. It also holds nine olfactory bulbs, more than any other mammal, and the olfactory lobe of the brain is highly developed. The tip of the snout bears a disc that houses the nostrils, and modified mimetic muscles make it highly mobile. The long, thin, snakelike tongue reaches as much as 30 cm and stays sticky thanks to salivary glands that almost ring the neck. The ears are disproportionately long, about 20 to 25 cm. The eyes, by contrast, are small for the head and contain only rods.

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• 4. Night Foraging

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  When an aardvark leaves its burrow at night, it first waits at the entrance for about ten minutes, sniffing and listening. Then it bounds out to a distance of some 10 m, pauses, pricks its ears, and twists its head before moving off. It emerges in the late afternoon or shortly after sunset and forages over a home range of 10 to 30 km. Its nose stays low and its ears point forward, so smell and hearing both guide the search. It zigzags rather than walking straight, and it usually will not repeat a route for five to eight days. That gap appears to give termite nests time to recover.

  At intervals it stops to dig a V-shaped trench with its forefeet and sniffs it at length to learn about its surroundings. Activity peaks in the first four hours of night, roughly 8:00 p.m. to midnight, and bright or dark nights make no difference. A typical night covers 2 to 5 km, though some studies have found aardvarks travelling as far as 30 km. Studies in the Nama Karoo found that the ant Anoplolepis custodiens was the main prey all year, followed by the termite Trinervitermes trinervoides. In winter, when ant numbers drop, the animals lean more heavily on termites. They often feed on mounds at the moment winged reproductive termites are present, possibly to meet their nutritional needs. They avoid the African driver ant and red ants.

  Once it locates a concentration of insects, the aardvark tears into it with its front legs while keeping its ears upright to listen for predators. Its claws break through the hard crust of a mound quickly, and it seals its nostrils to keep out dust. Termite bites and ant stings are futile against its tough skin. Mounds alone do not supply enough food, so it also hunts termites on the move. Their columns run 10 to 40 m long and are more common where livestock or other hoofed animals have been. Trampled grass and dung attract termites of the genera Odontotermes, Microtermes, and Pseudacanthotermes. After an aardvark has finished with a mound, other animals arrive to collect the leftovers. Such a strict diet is the reason the animal needs a large range to survive.

  One plant has found a way into this insect-eating life. The aardvark cucumber is the only fruit the animal eats, and the arrangement benefits both sides. The aardvark digs up the subterranean fruit and later deposits the seeds near its burrows. There, the loose, fertile soil makes them grow rapidly, and time spent in the aardvark's intestine helps the seeds' fertility. The fruit repays the favour by supplying moisture the animal needs.

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• 5. Burrows and Tenants

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  A main aardvark burrow can reach 13 m in length, with several entrances, and some are large enough for a person to enter. Burrows fall into three categories. Some are dug while foraging, some serve as refuges and resting places, and some are permanent homes. The temporary sites are scattered across the home range, while the main burrow is also used for breeding. The aardvark changes the layout of its home burrow regularly and periodically moves on to dig a new one. It can excavate a yard of tunnel in about five minutes. Only mothers and young share a burrow, although the species is known to live in small family groups or alone.

  The warthog is among the many animals that move into vacated burrows. The list also includes the African wild dog, the ant-eating chat, the bat Nycteris thebaica, hares, mongooses, hyenas, owls, pythons, and lizards. These abandoned holes are described as an important part of the African wildlife scene. Without such refuges, many animals would die during wildfire season.

  The aardvark ranges across sub-Saharan Africa, from Ethiopia all the way to the Cape of Good Hope in South Africa. It lives wherever savanna, grassland, woodland, or bushland offers both suitable habitat and a supply of ants and termites. Individuals have been documented as high as 3200 m in Ethiopia. Coastal areas of Namibia, Ivory Coast, and Ghana are among the few exceptions inside that range, and the animal is not found in Madagascar. The only major habitat it lacks is swamp forest, where a high water table prevents digging to a sufficient depth. It also avoids terrain rocky enough to hinder digging. Daylight hours are spent in dark burrows, away from the heat of the day.

  Lions, leopards, cheetahs, African wild dogs, spotted hyenas, and Southern African rock pythons all prey on the aardvark. Its keen hearing warns it of their approach. It can run in a zigzag, dig fast, or swim even in strong currents. If a predator corners it in a tunnel, it digs out so that fresh fill lies between itself and the attacker. If no burrow is near, it rapidly digs a short new one and later has to back out of it. When every escape fails, it may roll onto its back and lash out with all four feet. It can also strike with its claws, tail, and shoulders, and it is capable of causing substantial damage to an attacker.

  The animal is otherwise rather quiet. It makes soft grunts while foraging, loud grunts as it heads for a tunnel entrance, and a bleating sound if frightened. It has also been known to sleep inside a recently excavated ant nest, which doubles as protection. Some humans hunt it for meat.

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• 6. Raising a Cub

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  During mating, the male secures himself to the female's back with his claws, which can leave noticeable scratches. The aardvark is believed to breed polygamously. The two animals pair only for the breeding season, and the male plays no role in parental care.

  After a gestation of seven months, a single cub weighing around 1.7 to 1.9 kg is born between May and July. The newborn has flaccid ears and many wrinkles, and it nurses from each teat in succession. After two weeks the folds of skin disappear, and after three weeks the ears can be held upright. Body hair begins to grow at five to six weeks. The cub can leave the burrow to accompany its mother after only two weeks. It eats termites at nine weeks and is weaned between three months and 16 weeks.

  At six months old, the young aardvark is able to dig burrows of its own. It often stays with its mother until the next mating season, and it becomes sexually mature at approximately two years of age.

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• 7. A Fragile Future

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  Aardvarks were once thought to be declining, but that impression may simply reflect how rarely anyone sees them. Their nocturnal and secretive habits make definitive counts impossible, and their numbers seem stable overall. They are not common anywhere in Africa, yet their large range keeps populations sufficient. There may be a slight decrease in eastern, northern, and western Africa, while southern African numbers are not falling. The IUCN lists the species as least concern. Even so, the situation is precarious, because the animal depends on such a specific food. A problem with termite abundance would affect the whole species drastically.

  Aardvarks adapt well to captivity, and individuals have lived there for up to 23 years. The first recorded captive was at London Zoo in 1869, an individual that had come from South Africa.

  Recent research suggests aardvarks may be especially vulnerable to temperature changes caused by climate change. Droughts reduce the supply of ants and termites that make up the bulk of the diet. A nocturnal species facing scarcity may become more active by day to save the energy cost of staying warm at night. The price is enduring high daytime temperatures. Aardvarks do shift toward daytime activity when food runs short, which may signal an increased risk of imminent mortality. In a study in the Kalahari Desert, five of the six aardvarks being followed died after a drought.

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• 8. Folklore and Cartoons

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  Across African folklore, the aardvark is admired for its diligent search for food and its fearless response to soldier ants. Hausa magicians make a charm from its heart, skin, forehead, and nails, pounded together with the root of a certain tree. The mixture is wrapped in a piece of skin and worn on the chest. The charm is said to let its owner pass through walls or roofs at night, and burglars are said to use it. It is also said to serve those seeking to visit young girls without their parents' permission. The Margbetu, Ayanda, and Logo peoples make bracelets from aardvark teeth as good luck charms. In the mythology of the Dagbon people of Ghana, the aardvark is believed to possess supernatural powers. Its meat, which resembles pork, is eaten in certain cultures. Scholarship has also noted that the head of the ancient Egyptian god Set, drawn from an unidentified animal, resembles an aardvark.

  On BBC Radio in the 1950s, aardvarks turned up regularly in The Goon Show, in humorous phrases such as "spotted aardvark pudding" and "how to make your aardvark soft again". From 1969 to 1971, the cartoon series The Ant and the Aardvark showed a blue aardvark trying to catch and eat a red ant. It became extremely popular on television once it was paired with NBC's The Pink Panther Show.

  The best-known fictional aardvark is Arthur Read, the hero of Marc Brown's children's book series and of the animated adaptation Arthur. In the first book, Arthur's Nose, published in 1976, he has a long, aardvark-like nose. In later books his face becomes more rounded.

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