Pigs are mammals with stocky bodies, flat snouts that can move independently of their heads, small eyes and large ears. They are highly intelligent, social animals, and are found all over the world.
Pigs are in the Suidae family, which includes eight genera and 16 species. Among those species are wild boars, warthogs and pygmy hogs and domestic pigs. Pig, hog and boar essentially describe the same animal, but there are some distinctions. A boar is an uncastrated male domestic pig, but it also means a wild pig of any gender. A hog often means a domestic pig that weighs more than 120 lbs. (54 kilograms). Pigs are also called swine.
Pigs were among the first animals to be domesticated — about 9,000 years ago — in China and in a region in what is now Turkey. Asian farmers first brought domesticated pigs to Europe around 7,500 years ago, according to Smithsonian magazine.
Domestic pigs are descended mainly from the wild boar (Sus scrofa) and the Sulawesi warty pig (Sus celebensis), diverging from their closest ancestors about 500,000 years ago according to the Encyclopedia of Life. Today, there are an estimated 2 billion domesticated pigs on the planet, mostly classified as a subspecies of wild boars, Sus scrofa domesticus or Sus scrofa scrofa, according to the Integrated Taxonomic Information System (ITIS).
Pigs usually weigh between 300 and 700 lbs. (140 and 300 kilograms), but domestic pigs are often bred to be heavier. In 2012, a hog named Reggie set a weight record of 1,335 lbs. (605.5 kg) in the Iowa State Fair’s "Biggest Boar" contest, Radio Iowa reported.
But even massive Reggie is outweighed by the largest domestic pig of all time. That title goes to a porker named Big Norm of Hubbardsville, New York, who topped the scales at a whopping 1,600 lbs. (726 kg) when he died in 2009, according to the Syracuse Post-Standard.
Wild pigs vary greatly in size and weight. The largest boar is the giant forest hog (Hylochoerus meinertzhageni). Native to more than a dozen countries across Africa, it grows up to 6.9 feet (2.1 meters) long and measures 3.6 feet (1.1 m) tall, according to the Encyclopedia of Life. Though it is rarely seen, video of the elusive beast was captured in June 2018 by ecologists in Uganda, National Geographic reported.
The heaviest boar is the Eurasian wild pig (Sus scrofa), which grows to 710 lbs. (320 kg), and the smallest boar is the pygmy hog (Sus salvanius). This delicate swine grows to a length between 1.8 and 2.4 feet (55 to 71 centimeters) and stands 9.8 inches (25 cm) tall from hoof to shoulder. The pygmy hog only weighs 14.5 to 21 lbs. (6.6 to 9.7 kg), according to the San Diego Zoo.
Boars, pigs and hogs live all over the world, except for Antarctica, northern Africa and far northern Eurasia, according to the Encyclopedia of Life. For example, red river hogs (Potamochoerus porcus), also called bush pigs, are found in Africa; babirusas (Babyrousa babyrussa), or pig deer, are found in Indonesia; and Visayan warty pigs (Sus cebifrons) come from the Philippines.
Wild pigs typically live in grasslands, wetlands, rain forests, savannas, scrublands and temperate forests. All pigs wallow in mud whenever they have the chance, as it helps them to regulate their body temperature and discourages parasites.
Pigs are very intelligent animals. According to a review published in 2015 in the International Journal of Comparative Psychology, pigs are "cognitively complex," sharing many traits with animals that are typically considered to be highly intelligent. The review analyzed findings from a number of studies, suggesting that pigs were capable of remembering objects, perceiving time, and making use of learned information to navigate their environment. Pigs are also playful and have a wide range of play behaviors — another indication of intelligence in animals, the researchers reported.
Pigs communicate with a variety of grunts and squeaks. A short grunt, a longer growl and a loud roar will warn other pigs of approaching danger, according to the San Diego Zoo. The pigs' primary defense is speed, but when cornered, their tusks can be formidable weapons. Their lower tusks can get to be about 3 inches long (7 cm) and are razor sharp.
Pigs, boars and hogs are omnivores and will eat just about anything. Wild boars eat roots, fruit, rodents and small reptiles, National Geographic reported. Domestic pigs and hogs are fed feed that is made from corn, wheat, soy or barley. On small farms, pigs are often fed "slop,” which consists of vegetable peels, fruit rinds and other leftover food items. Most species of pigs process plants in their hindguts; however, their digestion of cellulose in inefficient, requiring them to feed often, according to the Encyclopedia of Life.
Female pigs, called cows or sows, give birth to offspring twice a year to a litter of around 12 young. Baby pigs are called piglets. At birth, piglets weigh around 2.5 lbs. (1.1 kg), according to National Geographic. Within a week, most piglets will double their weight. When they are two to four weeks old, the piglets are weaned.
Wild pigs can give birth to six for 14 piglets at a time. These piglets will stay in a nest for their first 10 days and are weaned after three months. Wild pigs live five to 20 years.
Wild boars are not endangered, according to the International Union for Conservation of Nature’s Red List of Threatened Species. They are listed as "least concern" due to the wild pig's "wide range, abundance, tolerance to habitat disturbance and presence in many protected areas."
Sulawesi warty pigs are listed as “near threatened”; bearded pigs, Palawan bearded pigs and Philippine warty pigs are “vulnerable”; Javan warty pigs are “endangered”; and Visayan warty pigs are “critically endangered.” Hunting and habitat loss are cited as the causes of declining populations in these species.
This article was updated on Oct. 5, 2018 by Live Science Senior Writer, Mindy Weisberger.
Editor's Note: This article was updated at 4:16 PM EDT on Oct. 10, 2018 to reflect a correction. A previous version incorrectly stated that pigs are not found in Australia.