usa | world | animals | vocabulary | health | science | math | history



Aardvark

The Aardvark (Orycteropus afer) is a large mammal native to Africa. The name comes from the Afrikaans/Dutch for "dirt pig". The Aardvark is the only surviving member of the family Orycteropodidae and of the order Tubulidentata. The Aardvark was originally placed in the same genus as the South American anteaters because of superficial similarities which, it is now known, are the result of convergent evolution, not common ancestry. (For the same reason, Aardvarks bear a striking first-glance resemblance to the marsupial bilbies and bandicoots of Australasia, which are not placental mammals at all.)

The oldest known Tubulidentata fossils have been found in Kenya and date to the early Miocene. Although the relationships of Tubulidentata are unknown, they are probably Ungulates. They spread to Europe and southern Asia during the later Miocene and early Pliocene periods. Three genera of the family Orycteropodidae are known: Leptorycteropus, Myorycteropus, and Orycteropus, the surviving Aardvark. A genus from Madagascar may be related to them, called Plesiorycteropus.

The most distinctive characteristic of the Tubulidentata is (as the name implies) their teeth which, instead of having a pulp cavity, have lots of thin tubes of dentine, each containing pulp and held together by cementum. The teeth have no enamel coating and are worn away and regrow continuously. Aardvarks are born with conventional incisors and canines at the front of the jaw, but these fall out and are not replaced. In adult Aardvarks, the only teeth are the molars at the back of the jaw.

Aardvarks are only vaguely pig-like; the body is stout with an arched back; the limbs are of moderate length. The front feet have lost the pollex (or 'thumb')—resulting in four toes—but the rear feet have all five toes. Each toe bears a large, robust nail which is somewhat flattened and shovel-like, and appears to be intermediate between a claw and a hoof. The ears are disproportionately long and the tail very thick at the base with a gradual taper. The greatly elongated head is set on a short, thick neck, and at the end of the snout is a disk in which the nostrils open. The mouth is typical of species that feed on termites: small and tubular. Aardvarks have long, thin, protrusible tongues and elaborate structures supporting a keen sense of smell. Weight is typically between 40 and 65 kg; length is usually between 1 and 1.3 m. Aardvarks are a pale yellowish gray in color, often stained reddish-brown by soil. The coat is thin and the animal's primary protection is its tough skin; Aardvarks have been known to sleep in a recently excavated ant nest, so well does it protect them.

Aardvarks are nocturnal and solitary creatures that feed almost exclusively on ants and termites. An Aardvark emerges from its burrow in the late afternoon or shortly after sunset, and forages over a considerable home range, swinging its long nose from side to side to pick up the scent of food. When a concentration of ants or termites is found, the Aardvark digs into it with its powerful front legs, keeping its long ears upright to listen for predators, and takes up an astonishing number of insects with its long, sticky tongue—as many as 50,000 in one night has been recorded. They are exceptionally fast diggers, but otherwise move rather slowly.

Aside from digging out ants and termites, aardvarks also excavate burrows to live in: temporary sites scattered around the home range as refuges, and the main burrow which is used for breeding. Main burrows can be deep and extensive, have several entrances, and be 13m long. Aardvarks change the layout of their home burrow regularly, and from time to time move on and make a new one. Only mothers and young share burrows.

After a gestation period of 7 months, a single young weighing around 2 kg is born, and is able to leave the burrow to accompany its mother after only two weeks. At six months of age it is digging its own burrows, but it will often remain with the mother until the next mating season. Aardvarks can grow older than 20 years in captivity.

Aardvarks are distributed across most of sub-Saharan Africa, and although killed by humans both for their flesh and for their teeth (which are used as decorations), do not appear to be threatened.

 

 

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "aardvark".