Pig

Quick Take

• One body part instantly reveals whether a pig is wild or domesticated, and it is not the part you would expect. See the tail difference →
• Pigs share a rare genetic mutation with only three other mammals that gives them a surprising survival edge in the wild. Explore the venom resistance →
• Wild pigs outlive their domestic counterparts by years, and the gap is far wider than most people assume. Compare wild vs. domestic lifespans →
• Pig anatomy has found its way into human operating rooms, and the biological reason behind it is stranger than it sounds. Discover the human connection →

Among the first animals to be domesticated by humans, the pig is found everywhere in the world except in Antarctica, North Africa, and far-northern Eurasia. These highly social and intelligent creatures are among the most populous large mammals in the world and are very biologically similar to humans.

The domestic pig is a major food source for humans. Approximately 70 to 80 million pigs are found on farms in the U.S. alone, and nearly 1.5 billion are slaughtered annually worldwide. Some pig species are classified at various levels of endangerment, and examples of many of these species can be found in zoos around the world.

An Incredible Animal: 5 Pig Facts

• Mud wallowers: Pigs lack sufficient sweat glands to effectively regulate their body temperatures, so they often wallow in mud to cool down on hot days. The mud is also used as a sunscreen and as a way to protect their skin from parasites.
• Highly intelligent: The pig is among the most intelligent animals on the planet. It can perceive time, remember objects, use learned information to navigate environments, and engage in a range of playful behaviors.
• Unique among hoofed animals: Unlike most hoofed mammals, pigs do not have multichambered ruminating stomachs, so they can’t subsist on grass and leaves alone. Also, unlike most hoofed creatures, pigs build nests for their young.
• It’s in the tail: The easiest way to tell whether a pig is domesticated or wild is by looking at its tail. Domestic pigs have curly tails, while wild pigs have straight tails.
• Hundreds of breeds: In 2007, the Food and Agriculture Organization of the UN reported that there were more than 740 classifications, or breeds, of the domesticated pig; 137 are listed as extinct, and 130 are classified as endangered.

Classification and Scientific Name

The pig is a mammal belonging to the order Artiodactyla and the family Suidae, which is also known as the even-toed ungulate family. That family is further subdivided into four to eight genera, with domesticated pigs and wild boars belonging to the genus Sus. Species belonging to that genus are regarded as suids or swine; eight living species currently exist.

The scientific name for pig is Sus scrofa, a name which applies to the wild boar, the Eurasian wild pig, as well as the domesticated mammal.

Evolution

The domestic pig originates from the Eurasian wild boar. Evidence suggests domestication of this species occurred multiple times and in multiple locations across Asia, Southeast Asia, India, Europe, and Africa. Domestication began approximately 9,000 years ago in Eastern Turkey. In 1539, Hernando de Soto brought domestic pigs to North America, which eventually established the initial populations of “feral hogs.” In the early 1930s, Eurasian boar were released onto hunting preserves in Texas, where some interbred with the feral hogs. Today, there are potentially three types of wild pigs in Texas and North America: feral hogs, hybrids between Eurasian boar and feral hogs, and Eurasian boar. There are also hundreds of breeds of domestic pigs of all sizes and colors.

Appearance and Behavior

Pigs span many breeds, so they vary a bit in appearance. In general, however, they are known for their stout bodies, short legs, and prominent snouts. On average, they grow to a size of between 300 and 700 pounds. The largest pig of all time, Big Norm of Hubbardsville, New York, weighed 1,600 pounds at his death in 2008. In 2012, a hog named Reggie set the weight record at the Iowa State Fair for Biggest Boar, weighing in at 1,335 pounds.

Most of them have sparse patches of bristles covering their skin. Some have patterns of spots, while others are more uniform in color. They have four hoofed toes on each foot, and their large heads contain a total of 44 teeth. These animals have scent glands covering their faces, and they rub their faces against objects to spread their scent and claim their territory. Their snouts are highly sensitive, and they dig into the soil to root around for food.

Today, there are more than 500 breeds of domesticated pigs in the world. The most popular include the Yorkshire, also known as the large white, which can grow up to 850 pounds in size. The Chester White is known for its all-white appearance and medium floppy ears. The Landrace pig, another all-white breed, is particularly prized for its bacon.

Highly social animals, pigs gather in groups, called sounders, in the wild. These groups typically consist of two or more females and their young. Males tend to be more solitary. These animals communicate using a variety of sounds, including squeaks and grunts. They also use various body postures to get their point across. For example, they might raise the crest of hair on their backs, grind their teeth, jerk their head, or cock their ears.

Pigs are biologically very similar to humans. As a result, they are often used in medical research and experimentation. Their heart valves are sometimes transplanted into human hearts, saving human lives.

Habitat

These animals have thrived so well because they can survive in a variety of habitats. They are found in grasslands, rainforests, wetlands, scrublands, temperate forests, and savannas everywhere in the world except for Antarctica, Northern Africa, and far northern Eurasia. They are also omnivores and will consume just about anything.

In the wild, their ranges vary in size. The pygmy hog, for example, has a range of approximately 60 acres; the Eurasian wild hog, on the other hand, has a range that can extend to more than 7 square miles in size.

Physiology

Although pigs have sweat glands, they don’t rely on perspiration to regulate their body temperature (a trait they share with elephants and rhinos). They prefer a cooling dip in a mud pool, which also helps keep parasites at bay and serves as a sunscreen.

Due to an evolutionary mutation, pigs are believed to enjoy a degree of resistance to snake venom. They are one of only four mammals that scientists have found to have such immunity formed from mutation. This puts the pig in the special category with the hedgehog, mongoose, and honey badger when it comes to resisting snake venom. These mutations appear to have evolved independently of each other.

Unlike ruminants, which have multichambered stomachs, pigs are monogastric. In other words, they have only a single-chambered stomach. As a result, they are omnivorous and will eat almost anything.

Diet

True omnivores, these animals subsist on both plants and animals. In the wild, wild boars primarily subsist on roots, fruit, rodents, and small reptiles. On the other hand, domesticated swine are fed diets that typically consist of grains like soy, wheat, corn, and barley. They are often given “slop,” which is made up of things like fruit rinds, vegetable peels, and other food scraps. As a result, they are useful on farms because they will eat human leftovers and are not picky eaters.

These animals use their snouts to root around in the soil for food. They are famous for being able to find truffles. Their rooting behavior helps the environment by clearing away dead animals, controlling insects, spreading seeds, and breaking up soil, which promotes new plant growth. At the same time, this behavior can be highly destructive to local environments.

Predators and Threats

Wild pigs are highly adaptable and can survive in a variety of ecosystems, but they do have their predators. Juveniles may fall prey to small mammals such as coyotes, bobcats, foxes, and others. However, humans and mountain lions are the primary predators of wild pigs in North America. In some areas, hunting is used to control populations, while other regions rely on fences or trapping programs to reduce numbers. These methods help reduce damage caused by wild pig populations, but it is worth noting that these animals play an important role in the natural ecosystem as well.

Reproduction, Babies, and Lifespan

Female pigs, called sows, go into heat every 21 days throughout the year; each heat lasts for eight to 36 hours. Males follow females and nudge them repeatedly to show interest. The female then allows the male to taste and smell her urine. Males usually stay with females for several days before moving on to new ones. The gestation period lasts approximately three months, three weeks, and three days (about 114 days). Sows make nests for their young within 24 hours of giving birth. A baby pig is called a piglet, and anywhere from 10 to 14 piglets are born per litter, on average. A female may have up to two litters per year.

Newborn baby pigs, or piglets, start feeding within one hour of birth. They are typically weaned after about two to three weeks. At birth, piglets weigh around 2.5 pounds, and they usually double in size within about a week.

Wild pigs and wild boars live for an average of 10 to 14 years in the wild, with maximum recorded lifespans of around 20 years. Domesticated pigs have an average lifespan of 6 to 10 years.

Population

Large populations of feral pigs are still found across the world, including in areas of North America, South America, Australia, New Zealand, and Hawaii. Exact figures for the total wild pig population are unknown. However, it is believed that there are approximately 2 billion domesticated pigs on the planet at any given time. Roughly 1 billion pigs are slaughtered every year, but intensive farming practices make it easy for farmers to keep up with demand.

Conservation

The biggest threat faced by pigs is exploitation by humans. Pork and pork products account for more than 40% of all meat and poultry consumed worldwide (as of 2017). Every year, China alone processes more than 500 million pigs for food. The U.S. processes around 64 million per year, Brazil processes around 40 million per year, and Germany processes around 27 million per year.

In the Zoo

Pigs of all species are found in zoos around the world. Domesticated pigs are often found in the petting zoo sections of larger zoos, where they are used to let people enjoy close-up experiences. Various species of wild pigs are also found in zoos around the globe. For example, the San Diego Zoo has a population of Visayan warty pigs, the most endangered pig species in the world. It was the first zoo outside of the Philippines to breed them, and more than 60 have been born there since 2002. Like many prominent zoos, the San Diego Zoo also boasts red river hogs and pig deer, or babirusa pigs, which are natives of Indonesia.