Pigs

pig is any of the animals in the genus Sus, within the even-toed ungulate family Suidae. Pigs include domestic pigs and their ancestor, the common Eurasian wild boar (Sus scrofa), along with other species. Pigs, like all suids, are native to the Eurasian and African continents, ranging from Europe to the Pacific islands. Suids other than the pig are the babirusa of Indonesia, the pygmy hog of Asia, the warthog of Africa, and another genus of pigs from Africa. The suids are a sister clade to peccaries.

Juvenile pigs are known as piglets.[1] Pigs are highly social and intelligent animals.[2]

With around 1 billion individuals alive at any time, the domestic pig is among the most populous large mammals in the world.[3][4] Pigs are omnivores and can consume a wide range of food.[5] Pigs are biologically similar to humans and are thus frequently used for human medical research.[6]

Contents

 * 1Etymology
 * 2Description and behaviour
 * 3Distribution and evolution
 * 4Habitat and reproduction
 * 5Diet and foraging
 * 6Relationship with humans
 * 6.1Use in human healthcare
 * 7Species
 * 8Domestic pigs
 * 9In culture
 * 10Environmental impacts
 * 11Health issues
 * 12See also
 * 13References
 * 14External links

Etymology
The Online Etymology Dictionary provides anecdotal evidence as well as linguistic, saying that the term derives

The Online Etymology Dictionary also traces the evolution of sow, the term for a female pig, through various historical languages:

An adjectival form is porcine. Another adjectival form (technically for the subfamily rather than genus name) is suine (comparable to bovine, canine, etc.); for the family, it is suid (as with bovid, canid).

Description and behaviour
Skull of a domestic pig (Sus scrofa domesticus)

A typical pig has a large head with a long snout that is strengthened by a special prenasal bone and by a disk of cartilage at the tip.[8] 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 foot, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.[9]

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.[8]

Occasionally, captive mother pigs may savage their own piglets, often if they become severely stressed.[10] Some attacks on newborn piglets are non-fatal. Others may cause the death of the piglets and sometimes, the mother may eat the piglets. It is estimated that 50% of piglet fatalities are due to the mother attacking, or unintentionally crushing, the newborn pre-weaned animals.[11]

Distribution and evolution
With around 1 billion individuals alive at any time, the domestic pig is one of the most numerous large mammals on the planet.[3][4]

The ancestor of the domestic 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.

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.

Habitat and reproduction
The wild boar (Sus scrofa) can take advantage of any forage resources. Therefore, they 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 boars in certain areas, they 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.[12]

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, roots, fruits, and flowers, in addition to some insects and fish. As livestock, pigs are fed mostly corn and soybean meal[13] with a mixture of vitamins and minerals added to the diet. 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.[14] Older pigs will consume three to five gallons of water per day.[15] When kept as pets, the optimal healthy diet consists mainly of a balanced diet of raw vegetables, although some may give their pigs conventional mini pig pellet feed.[16]

Relationship with humans
A pig trained to find truffles

Further information: Pig farming

Domesticated pigs, especially miniature breeds, are commonly kept as pets.[17] Domestic pigs are raised commercially as livestock; materials that are garnered include their meat (known as pork), leather, and their bristly hairs which are used to make brushes. 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.

The relatively short, stiff, coarse hairs of the pig are called bristles, and were once so commonly used in paintbrushes that in 1946 the Australian Government launched Operation Pig Bristle. In May 1946, in response to a shortage of pig bristles for paintbrushes to paint houses in the post-World War II construction boom, the Royal Australian Air Force (RAAF) flew in 28 short tons of pig bristles from China, their only commercially available source at the time.[18]