Pigs

Pigs, also called hogs or swine, are ungulates which have been domesticated as sources of food, leather, and similar products since ancient times. More recently, they have been involved in biomedical research and treatments. Their long association with humans has led to their considerable representation in cultural milieux from paintings to proverbs.

Native to Eurasia, they are collectively grouped under the genus Sus within the Suidae family. Despite pigs' reputation for gluttony, and another reputation for dirtiness, a lesser known quality is their intelligence. The nearest living relatives of the swine family are the peccaries.

Description and behavior
A pig has a snout for a nose, small eyes, and a small tail, which may be curly, kinked, or straight. It has a thick body and short legs. There are four toes on each foot, with the two large middle toes used for walking.[4]

Pigs are omnivores, which means that they consume both plants and animals. Pigs will scavenge and have been known to eat any kind of food, including dead insects, worms, tree bark, rotting carcasses, garbage, and even other pigs. In the wild, they are foraging animals, primarily eating leaves and grasses, roots, fruits and flowers. Occasionally, in captivity, pigs may eat their own young, often if they become severely stressed.

A typical pig has a large head with a long snout which is strengthened by a special bone called the prenasal bone and by a disk of cartilage in the tip. The snout is used to dig into the soil to find food and is a very sensitive sense organ. Pigs have a full set of 44 teeth. The canine teeth, called tusks, grow continually and are sharpened by the lowers and uppers rubbing against each other.[7]

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. Domesticated pigs are commonly raised as livestock by farmers for meat (called pork), as well as for leather. Their bristly hairs are also used for brushes. Some breeds of pigs, such as the Asian pot-bellied pig, are kept as pets.

A female pig can become pregnant at around 8-18 months of age. She will then go into heat every 21 days if not bred. Male pigs become sexually active at 8-10 months of age. A litter of piglets typically contains between 6 and 12 piglets.[5]

Pigs do not have functional sweat glands, so pigs cool themselves using water or mud during hot weather. They also use mud as a form of sunscreen to protect their skin from sunburn. Mud also provides protection against flies and parasites.[5]

Species

 * Sus barbatus
 * Sus bucculentus (possibly extinct).
 * Sus cebifrons
 * Sus celebensis
 * Sus falconeri † (extinct).
 * Sus heureni
 * Sus hysudricus † (extinct).
 * Sus philippensis
 * Sus salvanius
 * Sus scrofa
 * Sus strozzi † (extinct).
 * Sus timoriensis
 * Sus verrucosus

Domestication
Pigs have been domesticated since ancient times in the Old World and, unlike many domestic animals, are known for their intelligence. 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 below).

Pigs can be trained to perform numerous simple tasks and tricks. Recently, they have enjoyed a measure of popularity as house pets, particularly the dwarf breeds.

Cultural references to pigs
Pigs are frequently referenced in culture and are a popular topic for idioms and famous quotes.

Pigs in religion

 * In ancient Egypt pigs were associated with Set, the rival to the sun god Horus. When Set fell into disfavor with the Egyptians, swineherds were forbidden to enter temples.
 * In Hinduism the god Vishnu took the form of a boar in order to save the earth from a demon who had dragged it to the bottom of the sea.
 * In ancient Greece, a sow was an appropriate sacrifice to Demeter and had been her favorite animal since she had been the Great Goddess of archaic times. Initiates at the Eleusinian Mysteries began by sacrificing a pig.
 * The pig is one of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. Believers in Chinese astrology associate each animal with certain personality traits. See: Pig (Zodiac).
 * The dietary laws of Judaism (Kashrut, adj. Kosher) forbid the eating of flesh of swine or pork in any form, considering the pig to be an unclean animal (see taboo food and drink). Seventh-day Adventists and some other fundamental Christian denominations also consider pork unclean as food.
 * Islam also forbids the eating of flesh of swine or pork in any form, because of its uncleanliness and its immodest nature (see Halal).
 * In Catholicism, Eastern Orthodoxy and other older Christian groups, pigs are associated with Saint Anthony, the patron saint of swineherds.
 * [KJV - Lev. 11:7], states "And the swine, though he divide the hoof, and be cloven footed, yet he cheweth not the cud; he is unclean to you."[2]

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. The Invasive Species Specialist Group lists feral pigs on the list of the world's 100 worst invasive species and says about them: Feral pigs like other introduced mammals are major drivers of extinction and ecosystem change. They have been introduced into many parts of the world, and will damage crops and home gardens as well as potentially spreading disease. They uproot large areas of land, eliminating native vegetation and spreading weeds. This results in habitat alteration, a change in plant succession and composition and a decrease in native fauna dependent on the original habitat.

Health issues
Pigs harbour a range of parasites and diseases that can be transmitted to humans. These include trichinosis, cysticercosis, and brucellosis. Pigs are also known to host large concentrations of parasitic ascarid worms in their digestive tract.[1]The presence of these diseases and parasites is one of the reasons why pork meat should always be well cooked or cured before eating. Some religious groups that consider pork unclean refer to these issues as support for their views.[2]

Pigs can be susceptible to pneumonia, usually caused by weather. Pigs have small lungs in relation to body size; for this reason, bronchitis or pneumonia can kill a pig quickly.

Pigs can be aggressive and pig-induced injuries are relatively common in areas where pigs are reared or where they form part of the wild or feral fauna.[3]