Pigs are members of the Suidae family, which includes eight genera and 16 species. Among those species are wild boars, warthogs, pygmy hogs and domestic pigs.
Archaeological evidence suggests that pigs were domesticated around 10,500 years ago in the Near East, before farmers first brought them to Europe around 8,500 years ago, according to research published in the journal Proceedings of the National Academy of Sciences.
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. Currently there are approximately 752 million domestic pigs worldwide, 406 million of which can be found in China, according to Statista.
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How big are pigs?
Pigs usually weigh between 300 and 700 lbs. (140 and 300 kilograms), but domestic pigs are often bred to be heavier. The largest pig in history was a swine called Big Bill, who stood at 5 feet (1.52m) tall and weighed an impressive 2,552 lbs (1,157 kilograms), according to Guinness World Records.
Wild pigs on the other hand 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 6.6 feet (2 meters) long and measures 3.6 feet (1.1 metres) 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.
Where do boars live?
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. Whenever they have the chance, all pigs wallow in mud as it helps them to regulate their body temperature and discourages parasites.
Swine behaviour
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.
In 2020, researchers at Pennsylvania State University put pig intelligence to the test in a series of joystick-operated video tasks. Two Panepinto micro pigs and two Yorkshire pigs (Sus scrofa) were trained to control the movements of the computer cursor via a joystick, a test used to assess the cognitive abilities of other animals, such as monkeys and pigeons. The pigs were tasked with making contact between the cursor and a randomly placed target on the screen. On successful contact an automatic dispenser released a food pellet reward. All pigs were "significantly above chance on first attempts to contact one-walled target", the authors of the study wrote. This suggests that these pigs were able to make the association between the joystick and the cursor.
They are also very social. Feral pigs often travel in close-knit groups called sounders, which typically consist of two females and their young, according to Texas Parks and Wildlife.
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.
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What do pigs eat?
Pigs, boars and hogs are omnivores and will eat just about anything. Wild boars, for example, fill the majority of their diet with roots, seeds, bulbs and green plants, according to the Woodland Trust, however as opportunistic feeders they will also chow down on invertebrates, carrion (decaying flesh) and even small mammals found on the forest floor.
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 is inefficient, requiring them to feed often, according to the Encyclopedia of Life.
How many offspring do pigs have?
Domestic pigs can breed throughout the year without any seasonal constraints. Once pregnant, female pigs, commonly called sows, carry a litter of around 10 piglets for approximately 114 days before giving birth, according to the animal welfare organisation Compassion in World Farming.
Within the first six hours piglets suckle the "first milk", also known as colostrum, which is jam-packed with nutrients and essential antibodies to build the piglet's immune system. If the piglet drinks the first milk after 25 hours of being born their intestines will not be able to successfully absorb the antibodies in the milk, according to the Agriculture and Horticulture Development Board.
Wild pigs mate during the winter season, when solitary males seek out a potential mate. Once impregnated, wild sows will also give birth to around 10 piglets and will share the responsibility of raising them until they reach 1 year old. At which point the sounder will return to his solitary life-style, according to the Woodland Trust.
Conservation status
Wild boars are not endangered, according to the International Union for Conservation of Nature’s (IUCN) 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."
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Historically wild boar have been driven to extinction in various countries around the world, for example in England by 1260, boar had been hunted to complete eradication, Countryside has previously reported. However, through introduction programmes there are currently over 4,000 wild boar throughout the United Kingdom, BBC Countryfile has previously reported.
Although wild boar populations are generally not considered endangered, there are several species under threat. Sulawesi warty pigs (Sus celebensis) and Palawan bearded pigs (Sus ahoenobarbus) are listed as "near threatened"; Philippine warty pigs (Sus philippensis) are "vulnerable"; Javan warty pigs (Sus verrucosus) are "endangered"; and Visayan warty pigs are "critically endangered." Hunting and habitat loss are cited as the causes of declining populations in these species, according to the IUCN.
Additional resources:
- Discover different breeds of pigs with The Illustrated Guide to Pigs by Celia Lewis
- Learn more about the origins of pigs by reading The Pig: A Natural History by Richard Lutwyche
- For more information about pig farming head to The Countryside Charity
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.
