Friday, 24 October 2014

The Pig-like Aardvark

A young and an adult Aardvark
Adult and juvenile Aardvarks
Credit: By Scotto Bear from North Beach, MD, USA (aardvarks)
[CC-BY-SA-2.], via Wikimedia Commons
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Superorder: Afrotheria
Order: Tubulidentata
Family: Orycteropodidae
Genus: Orycteropus
Species: Orycteropus afer
Conservation Status: Least Concern (Not Threatened)
Common Name(s): Aardvark, African antbear, Cape anteater

Meet the Aardvark, a medium-sized, burrowing, nocturnal mammal from Africa and the sole living representative of the order Tubulidentata. "Aardvark" derives from South Africa's Afrikaans language and translates to "earth pigs".

As suggest by their common name, they look a bit like pigs, and also have rabbit-like ears and a kangaroo-like tail. Yet, they are not related to any of these animals. Recent genetic studies have placed aardvarks in a taxon called Afrotheria. Their closest surviving relatives are elephants, hyraxes, elephant-shrews, golden moles, and tenrecs.

Distribution & Habitat
Aardvarks live in Africa, in places with a suitable habitat, including savannas, grasslands, woodlands and bushland, and available prey items like ants and termites. The only type of habitat that they can't be found is swamp forest, as the high water table interferes with their digging. They also tend to avoid rocky terrain for the same reason. The species has been recorded in altitudes as high as 3,200 meters (~10,500 ft) in Ethiopia.

Aardvarks occur throughout sub-Saharan Africa all the way to South Africa with few exceptions, the coastal areas of Namibia, Ivory Coast, Ghana and Madagascar. In short, they inhabit about 2/3 of Africa.

They often inhabit temporary holes that are a few meters in length, but are also found in complex and intricate burrows, which can have eight or more entrances and extend as much as 6 meters underground. The entrances are often plugged with a vent left at the top.

Map showing the distribution of Aardavarks
Aardvark Distribution Map

The aardvark has a pig-like appearance although the two are not closely related. The body is stout with a prominently arched back and is sparsely covered with coarse hairs. Adults usually have a weight ranging from 60 to 80 kilograms (132 to 176 lb) and are 105 to 130 cm (3.44–4.27 ft) long. Maximum length is about 2.2 m, when the thick tail (which can be up to 70 cm (28 in) long) is taken into consideration. Aardvarks stand 60 cm (24 in) tall at the shoulder, and have a girth of about 100 cm (40 in.). They have a pale yellowish-gray color that is often stained reddish-brown by the soil as they dig.

They have thin coat, tough skin and no fat layer. The hair is short on the head and tail but a bit longer on the legs. The hair on the most part of the body is grouped in clusters of 3-4 hairs. The hairs surrounding the nostrils are dense and help filter particulate matter out as these strange animals dig the soil.

The species has medium-sized legs, with the rear being longer than the front legs. The front feet have lost the pollex (the first digit of the forelimb), resulting in four toes, while the rear feet retain all five toes. Each toe comes with a large, robust nail which is somewhat flattened and shovel-like. Each nail ends up in a spade-like claw that helps them to dig with great speed and force.

An aardvark walks at the Detroit Zoo, US
An aardvark at Detroit Zoo
Photo By MontageMan
[CC-BY-2.5], via Wikimedia Commons

As you can see on the photos and videos, aardavarks have a greatly elongated head that is set on a short, thick neck. The snout resembles an elongated pig snout, and bears a disc, which houses the nostrils.

The tongue is long, thin and snakelike and can protrude as much as 30 cm (12 in) out of the mouth.

The rabbit-like ears are disproportionately large, about 20–25 cm (7.9–9.8 in) long. The species has a very keen sense of hearing.

The eyes are relatively small and contain only rod cells; cells in the retina that can function in less intense light than the other type of visual photoreceptor, cone cells. The species has relatively poor eyesight.

Aarvarks resting in the London Zoo

The mouth is small and tubular, something expected by an animal that primarily feeds on ants and termites. One of the most distinctive and unique traits of this creature is its dentition. 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. The number of columns is dependent on the size of the tooth, with the largest having about 1,500. 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, which fall out soon later, never to be renewed again.

The aardvark usually moves slowly, however, it can attain speeds of up to 40 km/h when running and dig 1 yard of tunnel in about 5 minutes. It is also an excellent swimmer, capable of swimming even in strong currents.

In the wild, aardvarks are known to live for up to 18 years, and up to 23 years in captivity. They reach sexually maturity approximately at the age of two years old.

Aardvark takes a walk out in the sun
Aardvark out in the sun
Photo By Louise Joubert (Own work)
[CC-BY-SA-3.0], via Wikimedia Commons
Aardvarks are rather quiet animals making very few sounds. The species makes soft grunting sounds while foraging and loud grunts as it moves towards the tunnel entrance. It also makes a bleating sound when frightened or threatened by predators.

O. afer feeds almost exclusively on ants and termites (myrmecophagous). The only fruit eaten by aardvarks is the aardvark cucumber(Cucumis humofructus), Aardvarks eat the fruit for its water content and propagate the seeds through their feces, which are then buried by the animals. Due to the depth of the fruit, the seeds are unable to germinate without assistance, and rely on aardvarks for prepagation. Aardvarks eat the subterranean fruit, then defecate the seeds near the burrows, which then grow rapidly due to the loose soil and fertile nature of the area. The time spent in the intestine of the aardvark helps the fertility of the seed.

Individuals usually emerge from their burrows in the late afternoon or shortly after sunset, and forage over a considerable range, covering distances from 10 to 30 km (6.2 to 18.6 mi). While foraging for food, aardvarks keep their nose to the ground and the ears pointed forward. This suggests that both smell and hearing are involved in the search for food. They use a zig-zag-like movement when foraging. They tend not to repeat the same route for 5–8 days, probably to give ants and termites enough time to recuperate. .

The claws enable them to dig through the extremely hard crust of a termite or ant mound quickly and effortlessly. They avoid inhaling the produced dust by sealing their nostrils.

If ants or termites are detected, the aardvark will keep its long ears upright to listen for predators, and then take up a remarkable number of insects with its long, sticky tongue. Up to as many as 50,000 in one night have been recorded. All bites and stings by their prey are in vain, thanks to their tough skin.

Sometimes, termite and ant mounds alone don't provide enough energy, so they also look for termites on the move. Termites routinely form columns 10 - 40 meters (33–131 ft) long which are quick and easy targets.

Baby aardvark at Jambo Junction at Busch Gardens drinking a bottle of formula

Other than humans, their natural predators are lions, leopards, hunting dogs and pythons. They may not possess many teeth, however they still have a few tricks up their sleeves against them. As aforementioned, they can sprint quite quickly and they will return back to their burrow to elude enemies. When retreating, they use a zig-zag motion making their capture more difficult.

If escape is not an option, they will strike with all their might, using their claws, tail, shoulders and body weight to protect themselves. They will kick, slash and sometimes flip onto their backs lying motionless only to lash out with all four feet. They are capable of causing substantial damage to unprotected areas of a predator while their thick skin protects them from minor and intermediate attacks.

Sometimes they are hunted by humans for their edible flesh and their skin, which is used to make leather clothing and bracelets.

Baby aardvark in Berlin Zoo

Behavior & Reproduction
Aardvarks are solitary creatures that prefer to live alone and have never been found in large numbers. They spend their lives in solidarity, the only exceptions are during courtship and mothers accompanied by their cubs.

They are most active during the first part of the night time (20:00 to 24:00), however, they don't appear to prefer bright or dark nights over the other. During adverse weather or if disturbed (e.g. by a predator) they will retreat or stay inside their burrow systems. Due to their nocturnal lifestyle they are rarely seen out in the wild. Sometimes they come out during the day to sun themselves. When they sleep, they block the entrance of the burrow, leaving only a small opening at the top, and curl into a tight ball.

Little is known about their reproductive patterns in the wild, as most observations have been made on captive individuals. It is believed that they pair exclusively during the breeding season. After a gestation period of about seven months, the females gives birth to one cub weighing around 1.7–1.9 kg (3.7–4.2 lb), from May to July. On rare occasions, a female may give birth to two cubs.

The hairless newborn has flaccid ears, many wrinkles and will nurse off each breast in succession. Two weeks later, the folds of the skin disappear and after three weeks, the ears can be held upright. After 5 to 6 weeks, body hair starts growing.  The cub is able to leave the burrow and follow its mother after just two weeks, starts eating termites at 9 weeks and is weaned by the 16th week. At six months it can dig its own burrows, but it will often remain with the mother until the next mating season.

Aardvark coming out of its burrow
Aardvark in burrow at SanWild, Africa
By Louise Joubert [CC-BY-SA-3.0], via Wikimedia Commons

In Captivity
Aardvarks handle captivity quite well, as you can see on the video down below they may become very friendly with their keepers:

Zookeepers at london zoo handfeed two aardvarks

The first zoo to exhibit this strange animal was the London Zoo, in 1869. Today, some zoos featuring aardavarks are the following:
  • London Zoo, London, UK
  • Colchester Zoo, Colchester, UK
  • Berlin Zoo, Berlin, Germany
  • Bronx Zoo, New York, U.S
  • Brookfield Zoo,  Illinois, U.S
  • Detroit Zoo, Detroit, U.S
  • Lincoln Park Zoo, Chicago, U.S

This is just a quick list I made. Please use google to check if a zoo or park near you has this beautiful animal for exhibition!

Conservation Status
Today, the species is listed under "Least Concern" by the IUCN, due to its abundant and widespread distribution. In southern Africa, there are no indications that the numbers are decreasing or increasing significantly. However, in eastern, central, and western Africa, their numbers have possibly declined as a result of the expansion of human populations, habitat-loss, and hunting for meat. There are no known major threats, except the aforementioned which only affect localized populations.

Other than for its meat, the aardavark is sometimes hunted and killed by humans for its body parts, such as claws and teeth, for charms and medicinal purposes.

The aardvark has seventeen poorly defined subspecies listed:
  • Orycteropus afer afer
  • O a adametzi Grote
  • O a aethiopicus Sundevall
  • O a angolensis Zukowsky & Haltenorth
  • O a erikssoni Lönnberg
  • O a faradjius Hatt
  • O a haussanus Matschie
  • O a kordofanicus Rothschild
  • O a lademanni Grote
  • O a leptodon Hirst
  • O a matschiei Grote
  • O a observandus Grote
  • O a ruvanensis Grote
  • O a senegalensis Lesson
  • O a somalicus Lydekker
  • O a wardi Lydekker
  • O a wertheri Matschie

The skull of an aardvark
Aardvark skull
Photo By Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden (Own work)
[CC-BY-SA-3.0], via Wikimedia Commons

Other Interesting Facts about Aardvarks
- The genus name "Orycteropus" means burrowing foot and comes from the Greek word ορυκτερόπους (orykterópous) meaning "digging footed". The species name "afer" refers to Africa.
- Hausa magicians make a charm from the heart, skin, forehead, and nails of the aardvark, which they then proceed to pound together with the root of a certain tree. The Hausa are one of the largest ethnic groups in Africa. Wrapped in a piece of skin and worn on the chest, the charm is said to give the owner the ability to pass through walls or roofs at night. The charm is said to be used by burglars and those seeking to visit young girls without their parents' permission. Also, some tribes, such as the Margbetu, Ayanda, and Logo, will use the teeth of the aardvark to make bracelets that are regarded as good luck charms.
- The meat is edible and according to some, has a pork-like taste.
- The Egyptian god Seth appears to have the head of an aardvark.

The egyptian god Seth has the head of an aardvark
In Egyptian mythology, Seth appears to have the head of an aardvark

References & Further Reading
- Lehmann, T. (2009). Phylogeny and systematics of the Orycteropodidae (Mammalia, Tubulidentata) Zoological Journal of the Linnean Society, 155 (3), 649-702 DOI: 10.1111/j.1096-3642.2008.00460.x
- Taylor, W., & Skinner, J. (2003). Activity patterns, home ranges and burrow use of aardvarks (Orycteropus afer) in the Karoo Journal of Zoology, 261 (3), 291-297 DOI: 10.1017/S0952836903004217
- Taylor, W., Lindsey, P., & Skinner, J. (2002). The feeding ecology of the aardvark Orycteropus afer Journal of Arid Environments, 50 (1), 135-152 DOI: 10.1006/jare.2001.0854
- Mutlow AG, & Mutlow H (2008). Caesarian section and neonatal care in the aardvark (Orycteropus afer). Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 39 (2), 260-2 PMID: 18634220
- Tabuce, R., Asher, R., & Lehmann, T. (2008). Afrotherian mammals: a review of current data mammalia, 72 (1) DOI: 10.1515/MAMM.2008.004
- White, J., Williams, G., Samour, J., Drury, P., & Cheeseman, P. (1985). The composition of milk from captive aardvark (Orycteropus afer) Zoo Biology, 4 (3), 245-251 DOI: 10.1002/zoo.1430040305
- Lindsey, P.; Cilliers, S.; Griffin, M.; Taylor, A.; Lehmann, T.; Rathbun, G. (2008). "Orycteropus afer". IUCN Red List of Threatened Species.
- Hoiberg, Dale H., ed. (2010). "Aardvark". Encyclopædia Britannica. I: A-ak Bayes (15th ed.). Chicago, IL: Encyclopædia Britannica Inc. ISBN 978-1-59339-837-8.
- Schlitter, D. A. (2005). "Order Tubulidentata". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 86. ISBN 978-0-8018-8221-0. OCLC 62265494.

No comments:

Post a Comment