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Description
An aardvark's weight is typically between 60 and 80 kilograms (130–180 lb).[13] An aardvark's length is usually between 105 and 130 centimetres (3.44–4.27 ft),[5] and can reach lengths of 2.2 metres (7 ft 3 in) when its tail (which can be up to 70 centimetres (28 in)) is taken into account. It is 60 centimetres (24 in) tall at the shoulder, and has a girth of about 100 centimetres (3.3 ft).[14] It is the largestmember of the proposed clade Afroinsectiphilia. The aardvark is pale yellowish-gray in color and often stained reddish-brown by soil. The aardvark's coat is thin, and the animal's primary protection is its tough skin. Its hair is short on its head and tail; however its legs tend to have longer hair.[5] The hair on the majority of its body is grouped in clusters of 3-4 hairs.[14] The hair surrounding its nostrils is dense to help filter particulate matter out as it digs. Its tail is very thick at the base and gradually tapers.The aardvark is vaguely pig-like in appearance. Its body is stout with a prominently arched back[14] and is sparsely covered with coarse hairs. The limbs are of moderate length, with the rear legs being longer than the forelegs.[13] The front feet have lost the pollex (or 'thumb'), resulting in four toes, while 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. Whereas the aardvark is considered digitigrade, it appears at time to be plantigrade. This confusion happens because when it squats it stands on its soles.[14]
Head
The greatly elongated head is set on a short, thick neck, and the end of the snout bears a disc, which houses the nostrils. It contains a thin but complete zygomatic arch.[14] The head of the aardvark contains many unique and different features. One of the most distinctive characteristics of the Tubulidentata is their teeth. Instead of having a pulp cavity, each tooth has a cluster of thin, hexagonal, upright, parallel tubes of vasodentin (a modified form of dentine), with individual pulp canals, held together by cementum.[13] The number of columns is dependent on the size of the tooth, with the largest having about 1,500.[10] The teeth have no enamel coating and are worn away and regrow continuously.[8] The aardvark is born with conventional incisors andcanines at the front of the jaw, which fall out and are not replaced. Adult aardvarks have only cheek teeth at the back of the jaw, and have a dental formula of: 0.0.2-3.30.0.2.3 These remaining teeth are peg-like and rootless and are of unique composition.[15] The teeth consist of 14 upper and 12 lower jaw molars.[1] The nasal area of the aardvark is another unique area, as it contains ten nasal conchae, more than any other placental mammal.[13] The sides of the nostrils are thick with hair.[14] The tip of the snout is highly mobile and is moved by modified mimetic muscles.[13] The fleshy dividing tissue between its nostrils probably has sensory functions,[5] but it is uncertain if it is olfactory or vibration in nature.[16] Its nose is made up of more turbinate bones than any other mammal, with between 9 and 11, compared to dogs with 4 to 5.[8] With a large quantity of turbinate bones, the aardvark has more space for the moist epithelium, which is the location of the olfactory bulb.[8] The nose contains nine olfactory bulbs, more than any other mammal.[14] Its keen sense of smell is not just from the quantity of bulbs in the nose but also in the development of the brain, as its olfactory lobe is very developed.[10] The snout resembles an elongated pig snout. The mouth is small and tubular, typical of species that feed on ants and termites. The aardvark has a long, thin, snakelike, protruding tongue (as much as 30 centimetres (12 in) long)[1] and elaborate structures supporting a keen sense of smell.[17] The ears, which are very effective,[1] are disproportionately long, about 20–25 centimetres (7.9–9.8 in) long.[14] The eyes are small for its head, and consist only of rods.
Habitat and range
Aardvarks live in sub-Saharan Africa, where there is suitable habitat for them to live, such as savannas, grasslands, woodlands and bushland, and available food (i.e., ants and termites).[9] They hide in dark underground burrows to avoid the warm weather.[19] The only major habitat that they are not present in is swamp forest, as the high water table interferes with digging.[2] They have been documented as high as 3,200 metres (10,500 ft) in Ethiopia.[2] They are known to live throughout sub-Saharan Africa all the way to South Africa with few exceptions. These exceptions are coastal areas of Namibia, Ivory Coast, and Ghana.[2] They are also not present in Madagascar.[2] They avoid rocky terrain as it causes problems with digging.[20]
Ecology and behavior
Its keen hearing warns it of predators: lions, leopards, hyenas, and pythons.[1][16] The aardvark's main predators are lions, leopards, hunting dogs and pythons. Some humans also hunt aardvarks for meat.[1] Aardvarks can dig fast or run in zigzag fashion to elude enemies, but if all else fails, they will strike with their claws, tail and shoulders, sometimes flipping onto their backs lying motionless except to lash out with all four feet.[16] They are capable of causing substantial damage to unprotected areas of an attacker.[8] They will also dig to escape as they can, when pressed, dig extremely quickly.[16] Their thick skin also protects them to some extent.[citation needed]Aardvarks live for up to 23 years in captivity.
Movement
The aardvark is known to be a good swimmer and has been witnessed successfully swimming in strong currents. It can dig a yard of tunnel in about five minutes,but otherwise moves fairly slowly.
When leaving the burrow at night, they pause at the entrance for about ten minutes, sniffing and listening. After this period of watchfulness, it will bound out and within seconds it will be 10 metres (33 ft) away. It will then pause, prick its ears, twisting its head to listen, then jump and move off to start foraging.
Aside from digging out ants and termites, the aardvark also excavates burrows in which to live; of which they generally fall into three categories: burrows made while foraging, refuge and resting location, and permanent homes.[5] Temporary sites are scattered around the home range and are used as refuges, while the main burrow is also used for breeding. Main burrows can be deep and extensive, have several entrances and can be as long as 13 metres (43 ft).[5] These burrows can be large enough for a man to enter.[1]The aardvark changes the layout of its home burrow regularly, and periodically moves on and makes a new one. The old burrows are an important part of the African wildlife scene. As they are vacated, then they are inhabited by smaller animals like the African wild dog, ant-eating chat, Nycteris thebaica and warthogs.[21] Other animals that use them are hares, mongooses, hyenas, owls, pythons, and lizards. Without these refuges many animals would die during wildfire season.[21] Only mothers and young share burrows; however, the aardvark is known to live in small family groups or as a solitary creature.[1] If attacked in the tunnel, it will escape by digging out of the tunnel thereby placing the fresh fill between it and its predator, or if it decides to fight it will roll onto its back, and attack with its claws.[1] The aardvark has been known to sleep in a recently excavated antnest, which also serves as protection from its predators.
Conservation
Aardvarks were thought to have declining numbers,[1] however, this is possibly due to the fact that they are not readily seen.[2] There are no definitive counts because of their nocturnal and secretive habits; however, their numbers seem to be stable overall. They are not considered common anywhere in Africa, but due to their large range, they maintain sufficient numbers. There may be a slight decrease in numbers in eastern, northern, and western Africa. Southern African numbers are not decreasing. It receives an official designation from the IUCN as least concern.[2] However, they are a species in a precarious situation, as they are so dependent on such specific food; therefore if a problem arises with the abundance of termites, the species as a whole would be affected drastically.[5]
Aardvarks handle captivity well. The first zoo to have one was London Zoo in 1869, which had an animal from South Africa.
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