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, especially for their eyes and hearts, which closely resemble those of humans. Their long association with humans has led to their considerable representation in cultural milieux from paintings to proverbs. There are 2 billion pigs on the planet.

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, short legs, and coarse hair. There are four toes on each foot, with the two large middle toes used for walking.

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, grasses, roots, fruits and flowers. Occasionally while in captivity, pigs may eat their own young 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.Fact: date=July 2008 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.

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.

Breeding occurs throughout the year in the tropics, but births peak around rainy seasons. A female pig can become pregnant at around 8-18 months of age. She will then go into estrus 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. After the young are weaned, two or more families may come together until the next mating season.

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.