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Sus (genus)

This article is about the genus. For other uses, see Pig (disambiguation).
Pig
A domestic sow suckling her piglet.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Infraclass: Eutheria
Order: Artiodactyla
Family: Suidae
Subfamily: Suinae
Genus: Sus
Linnaeus, 1758
Species
  • See text

A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig and its ancestor, the common Eurasian wild boar (Sus scrofa), along with other species; related creatures outside the genus include the babirusa and the warthog. Pigs, like all suids, are native to the Eurasian and African continents. Juvenile pigs are known as piglets.[1] Pigs are omnivores and are highly social and intelligent animals.[2]

Description and behaviour

A typical pig has a large head with a long snout which is strengthened by a special prenasal bone and by a disk of cartilage at the tip.[3] The snout is used to dig into the soil to find food and is a very acute sense organ. There are four hoofed toes on each trotter (foot), with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.[4]

The dental formula of adult pigs is 3.1.4.33.1.4.3, giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male the canine teeth form tusks, which grow continuously and are sharpened by constantly being ground against each other.[3]

Distribution and evolution

With around 1 billion individuals alive at any time, the domesticated pig is one of the most numerous large mammals on the planet.[5][6]

The ancestor of the domesticated pig is the wild boar, which is one of the most numerous and widespread large mammals. Its many subspecies are native to all but the harshest climates of continental Eurasia and its islands and Africa as well, from Ireland and India to Japan and north to Siberia. Although it has been exterminated in some areas, its numbers are stable, or even increasing rapidly, in most of its native range.

Long isolated from other pigs on the many islands of Indonesia, Malaysia, and the Philippines, pigs have evolved into many different species, including wild boar, bearded pigs, and warty pigs. Humans have introduced pigs into Australia, North and South America, and numerous islands, either accidentally as escaped domestic pigs which have gone feral, or as wild boar. These have typically adapted well, and are increasing in number and broadening their range outside human control.

Habitat and reproduction

The wild pig (Sus scrofa) can take advantage of any forage resources. Therefore, it can live in virtually any productive habitat that can provide enough water to sustain large mammals such as pigs. If there is increased foraging of wild pigs in certain areas, it can cause a nutritional shortage which can cause the pig population to decrease. If the nutritional state returns to normal, the pig population will most likely rise due to the pigs' naturally increased reproduction rate.[7]

Diet and foraging

Pigs are omnivores, which means that they consume both plants and animals. In the wild, they are foraging animals, primarily eating leaves, grasses, roots, fruits and flowers. In confinement[where?] pigs are fed mostly corn and soybean meal with a mixture of vitamins and minerals added to the diet. Because pigs are omnivores they make excellent pasture raised animals.[8] Traditionally they were raised on dairy farms and called "mortgage lifters" due to their ability to use the excess milk as well as whey from cheese and butter making combined with pasture.[9] Older pigs will consume three to five gallons of water per day.[10]

Relationship with humans

Domesticated pigs, called swine, are raised commercially for meat (generally called pork, hams, gammon or bacon), as well as for leather. Their bristly hairs are also used for brushes. Due to their common use as livestock, adult swine have gender specific names: the males are boars (or sometimes "hogs") and the females are sows. Young swine are called piglets or pigs. Pork is one of the most popular forms of meat for human consumption, accounting for 38% of worldwide meat production.[11]

Pigs that are allowed to forage may be watched by swineherds. Because of their foraging abilities and excellent sense of smell, they are used to find truffles in many European countries.

Both wild and feral pigs are commonly hunted. Some breeds of pig, such as the Asian pot-bellied pig, are kept as pets.

Species

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The genus Sus is currently thought to contain ten living species. A number of extinct species () are known from fossils.

  • Sus subtriquetra Xue, 1981
  • Sus strozzi
  • Sus verrucosus Müller, 1840 - Java warty pig
  • Sus xiaozhu Han et al, 1975 - Early Pleistocene of China

The pygmy hog, formerly Sus salvanius is now placed in the monotypic genus Porcula.[12]

Domestic pigs


Main article: Domestic pig

Pigs have been domesticated since ancient times in the Old World. Archaeological evidence suggests that pigs were being managed in the wild in a way similar to the way they are managed by some modern New Guineans from wild boar as early as 13,000–12,700 BP in the Near East in the Tigris Basin.[13] Remains of pigs have been dated to earlier than 11,400 BP in Cyprus that must have been introduced from the mainland which suggests domestication in the adjacent mainland by then.[14] A separate domestication also occurred in China.[15]

In India, pigs have been domesticated for a long time mostly in Goa and some rural areas for pig toilets. This was also done in China. Though ecologically logical as well as economical, pig toilets are waning in popularity as use of septic tanks and/or sewerage systems is increasing in rural areas.

Pigs were brought to southeastern North America from Europe by Hernando de Soto and other early Spanish explorers. Pigs are particularly valued in China and on certain oceanic islands, where their self-sufficiency allows them to be turned loose, although the practice is not without its drawbacks (see environmental impact). With managed rotational grazing techniques pigs can be raised in an environmentally sound manner on pasture much like grazing sheep, goats and cows without high grain inputs.[16]

The domestic pig (Sus scrofa domesticus) is usually given the scientific name Sus scrofa, although some authors call it S. domesticus, reserving S. scrofa for the wild boar. It was domesticated approximately 5,000 to 7,000 years ago. Their coats are coarse and bristly. They are born brownish coloured and tend to turn more grayish coloured with age. The upper canines form sharp distinctive tusks that curve outward and upward. Compared to other artiodactyles, their head is relatively long, pointed, and free of warts. Their head and body length ranges from 0.9 to 1.8 m (35 to 71 in) and they can weigh between 50 and 350 kg (110 and 770 lb).

Pigs are intelligent[17] and can be trained to perform numerous tasks and tricks.[18] Recently, they have enjoyed a measure of popularity as house pets, particularly the dwarf breeds.

Cultural and religious reference to pigs

Pigs appear in the traditional art and literature of many societies, where they sometimes carry religious symbolism. In Asia the wild boar is one of twelve animal images comprising the Chinese zodiac, while in Europe the boar represents a standard charge in heraldry. Pigs are frequently alluded to in proverbs, metaphors, idioms, and folk art.

Environmental impacts

Domestic pigs that have escaped from farms or were allowed to forage in the wild, and in some cases wild boars which were introduced as prey for hunting, have given rise to large populations of feral pigs in North and South America, Australia, New Zealand, Hawaii, and other areas where pigs are not native. Accidental or deliberate releases of pigs into countries or environments where they are an alien species have caused extensive environmental change. Their omnivorous diet, aggressive behaviour, and their feeding method of rooting in the ground all combine to severely alter ecosystems unused to pigs. Pigs will even eat small animals and destroy nests of ground nesting birds.[3] The Invasive Species Specialist Group lists feral pigs on the list of the world's 100 worst invasive species and says:[19]

Health issues

Pigs can harbour a range of parasites and diseases that can be transmitted to humans. These include trichinosis, Taenia solium, cysticercosis, and brucellosis. Pigs are also known to host large concentrations of parasitic ascarid worms in their digestive tract.[20] The presence of these diseases and parasites is one reason pork meat should always be well cooked or cured before eating. Today trichinellosis infections from eating undercooked pork are rare in more technologically developed countries due to refrigeration, health laws, and public awareness.[21] Some religious groups have dietary laws that make pork an "unclean" meat, and adherents sometimes interpret these health issues as validation of their views.[22]

Pigs have health issues of their own, of course. Pigs have small lungs in relation to their body size and are thus more susceptible than other domesticated animals to fatal bronchitis and pneumonia.[23] Some strains of influenza are endemic in pigs (see swine influenza). Pigs also can acquire human influenza.

Pigs can be aggressive in defending themselves and their young. Pig-induced injuries are thus not unusual in areas where pigs are raised or where they form part of the wild or feral fauna.[24]

See also

References

External links

  • Pig genome resources
  • Swine breeds, with pictures
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