Wild boar

• 1. Introduction

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  In 1749, in Hachinohe, Japan, 3,000 people died in what became known as the wild boar famine. The animal behind that name is the wild boar, Sus scrofa, also called the wild swine or the Eurasian wild pig. Its native range covers much of Eurasia and North Africa, and people later carried it to the Americas and Oceania. The IUCN Red List rates it least concern, because it is numerous, widespread, and adaptable.

  Questions follow this animal everywhere it goes. Why did people spend thousands of years both hunting the boar and revering it? How did a creature that gave the world its farmyard pigs become a pest in lands it never evolved in? And what lets one species outlast almost every rival, even after humans wiped it out of entire countries?

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• 2. Built to Dig

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  Up to one-third of a wild boar's body length is head, and that head works like a plough. The body is bulky, with a short, robust trunk and short, relatively thin legs. A hump rises behind the shoulder blades, and the neck is so short and thick that it is nearly immobile. Powerful neck muscles let the animal dig 8-10 cm into frozen ground and heave up rocks weighing 40-50 kg.

  For all that bulk, a boar can run at up to 40 km/h, or 25 mph. It can also jump 140-150 cm. Its medial hooves are larger and more elongated than the outer ones, and they are capable of quick movements.

  Males are typically 5-10% larger and 20-30% heavier than females, and the difference shows in their weapons. The canine teeth of males keep growing for life. The lower canines are sharper and longer, with 10-12 cm of each one exposed. The upper canines start out short and growing sideways, then slowly curve upward. During the breeding period, a male grows a layer of subcutaneous tissue 2-3 cm thick from the shoulder blades to the rump. This armour protects his vital organs in fights. A mane along the back is especially visible in autumn and winter.

  Adult size depends on food and water. In most of Europe, males average 75-100 kg and females 60-80 kg. In dry Mediterranean areas, males may average as little as 50 kg. In the richer lands of Eastern Europe, males average 110-130 kg, and in Western and Central Europe the largest males reach 200 kg. In Northeastern Asia, large males can reach 270 kg, a size compared to brown bears. Some adults in Primorsky Krai and Manchuria have been recorded at 300-350 kg, standing 125 cm at the shoulder. Animals that big are generally safe from wolves. Giants like these are now rare, because past overhunting kept animals from reaching full growth.

  The boar's sense of smell is so keen that the animal is used for drug detection in Germany. Its hearing is sharp, but its eyesight is poor. It cannot see colour, and it fails to recognise a standing human at 10-15 m.

  Pigs also belong to a tiny group of four mammal types with mutations in the nicotinic acetylcholine receptor that protect against snake venom. The others are mongooses, honey badgers, and hedgehogs. Each group evolved the change independently, altering the receptor pocket so the venom's α-neurotoxin cannot bind.

  Boar voices fall into three categories: contact calls, alarm calls, and combat calls. Females grunt often, adult males are usually silent, and piglets whine. Studies show that piglets imitate their mother's sounds, so different litters may each have their own distinct voices.

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• 3. Life in the Sounder

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  Young males leave their birth group at 8-15 months, while young females stay with their mothers or set up territories nearby. What remains is a female-run society called a sounder, led by an old matriarch and made up of mothers with young plus barren sows. Subadult males may roam in loose groups. Adult and elderly males mostly live alone outside the breeding season.

  The rut in most areas runs from November to January, though mating itself lasts only about a month and a half. Beforehand, males build up their armour of subcutaneous tissue. Their testicles double in size, and their glands secrete a foamy yellowish liquid. They then travel long distances in search of a sounder of sows, eating little on the way. Once a male finds one, he drives off all the young animals and chases the sows relentlessly. He also fights rivals fiercely. A single male can mate with 5-10 sows. By the end of the rut, males are often badly mauled and have lost 20% of their body weight. Young males are shut out for years, because older males do not let them mate. They begin taking part in the rut only after 4-5 years.

  Gestation lasts 114-130 days for first-time mothers and 133-140 days for older sows. Farrowing happens between March and May. The average litter is 4-6 piglets, and the maximum is 10-12. The mother builds a nest of twigs, grasses, and leaves for the birth. If she dies early, the other sows in the sounder adopt her piglets.

  Newborn piglets weigh around 600-1,000 grams. They have no underfur, and each half of the jaw holds one milk incisor and one canine. Competition is intense over the most milk-rich nipples, since the best-fed piglets grow faster and end up with stronger constitutions. For the first week, the piglets stay in the lair. If the mother is away, they lie pressed tightly together. At two weeks they start following her on her travels. When danger appears, they take cover or freeze, trusting their camouflage. Their early coat is light brown or rusty-brown with pale bands, and it fades after three months. Adult colouring arrives at eight months.

  Nursing lasts 2.5-3.5 months, but piglets start showing adult feeding habits at only 2-3 weeks old. Sows reach sexual maturity at one year and males a year later, though a sow's first estrus usually comes after two years. The maximum lifespan in the wild is 10-14 years, yet few animals survive past 4-5. Boars in captivity have lived for 20 years.

  Between times of activity, the whole family rests in a shelter lined with insulating material such as spruce branches and dry hay. Males lie separately. The animals never defecate in the shelter, and they cover themselves in soil and pine needles when insects irritate them.

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• 4. Origins and Pigs

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  Studies of mitochondrial DNA point to islands in Southeast Asia, such as Indonesia and the Philippines, as the wild boar's birthplace. From there it spread onto mainland Eurasia and North Africa. The earliest fossils come from both Europe and Asia and date to the Early Pleistocene. By the late Villafranchian, it had largely displaced a large relative called S. strozzii, pushing that animal back to insular Asia. Its closest living wild relative is the bearded pig of Malacca and the surrounding islands.

  Up to 16 subspecies are recognised, sorted into four regional groupings by skull height and the length of the lacrimal bone. The Ussuri boar of eastern China, Korea, and the Amur region is the largest subspecies. The Trans-Baikal boar is the smallest in the former Soviet region. The Indonesian group, represented only by S. s. vittatus, is the most basal of the four. It has the smallest relative brain size, more primitive teeth, and an unspecialised skull.

  Archaeological evidence suggests that pigs were domesticated from wild boar as early as 13,000-12,700 BCE in the Tigris Basin of the Near East. Pig remains on Cyprus date to before 11,400 BCE. Because those animals must have been brought from the mainland, domestication probably took place there by then. A separate domestication occurred in China about 8,000 years ago.

  In Europe, DNA from the teeth and jawbones of Neolithic pigs shows that the first domestic pigs came from the Near East. Their arrival stimulated the domestication of local European boars. This was a third domestication event, and the Near Eastern genes eventually died out in European stock. Later exchanges were complex, and historical records show Asian pigs reaching Europe in the 18th and early 19th centuries. The pigs of Timor and Papua New Guinea are exceptions, since they appear to descend from the Sulawesi warty pig.

  Domestication reshaped the body. In domestic pigs, 70% of the weight sits in the hindquarters. In the wild boar, the muscle is concentrated on the head and shoulders.

  The boar's family tree has its own mystery. Heude's pig, also called the Indochinese warty pig, was an alleged species from Laos and Vietnam. It was virtually unknown and feared extinct until 1995, when a skull from a recently killed animal turned up in the Annamite Range in Laos. Later studies concluded that it was not a valid species, and as of 2022 the Mammal Diversity Database counts it within Sus scrofa.

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• 5. Habitat and Food Chain

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  Wild boars live in habitats ranging from boreal taigas to deserts. In the mountains they reach up to 1900 m in the Carpathians and 2600 m in the Caucasus. In Central Asia and Kazakhstan, they climb to 3600-4000 m. A boar needs only three things: thick cover to hide from predators, water for drinking and bathing, and a place without regular snowfall.

  In Europe, the favoured ground is deciduous and mixed forest, best of all oak and beech woods around marshes and meadows. In Tajikistan and Turkmenistan, boars visit pistachio groves in winter and move out to open desert in spring. On the islands of Komodo and Rinca, they live in savanna and open monsoon forest. Boars are also competent swimmers. In 2013, one was reported to have swum 7 mi from France to Alderney in the Channel Islands. Because of disease concerns, it was shot and incinerated.

  A 50 kg boar needs around 4,000-4,500 calories a day, and the variety in its diet rivals that of humans. It digs up roots, tubers, and bulbs all year. In temperate zones, acorns and beechnuts are its most important foods, because their carbohydrates build the fat reserves that carry it through lean periods. It also eats earthworms, insects, fish, eggs, frogs, snakes, and carrion. It can eat poisonous plants such as Aconitum and Pteridium without ill effect.

  Some populations have unusual menus. In Ujung Kulon National Park on Java, boars of the vittatus subspecies live mainly on fruit from 50 different species, especially figs, which makes them important seed dispersers. Along the Volga Delta and some Kazakh rivers, boars feed heavily on carp and Caspian roach. In the Volga Delta, they also take cormorant and heron chicks. There is at least one record from India's Bandipur National Park of a boar killing and eating a bonnet macaque. In another case, a group of boars killed and ate a healthy adult female axis deer.

  Piglets fall prey to Eurasian lynx, jungle cats, snow leopards, brown bears, and yellow-throated martens. For adults, the wolf is the main threat across most of the range. A single wolf can kill around 50-80 boars of differing ages in a year. In Italy and in Belarus's Belovezhskaya Pushcha National Park, boars are the wolf's primary prey. Deep snow makes wolves especially dangerous. In the Baltic regions, heavy snowfall can let them nearly eliminate boars from an area. Wolves mostly take piglets and subadults and avoid adult males. Dholes keep boar numbers down in northwestern Bhutan, and leopards in Iran's Sarigol National Park take boars second most often after mouflon.

  Tigers once ranked as the boar's chief predator in Transcaucasia, Kazakhstan, Middle Asia, and the Far East until the late 19th century. A single tiger can destroy a whole sounder one animal at a time, and tigers chase boars over longer distances than other prey. The fights do not always go one way. In two rare cases, boars reportedly gored a small tiger and a tigress to death in self-defense. Another account tells of a "large male tiger" that died of wounds from an old boar it had killed in "a battle royal." In the Amur region today, boars and Manchurian wapiti make up roughly 80% of Siberian tiger prey. In Sikhote Alin, one tiger can kill 30-34 boars a year.

  On Komodo, Rinca, and Flores, the tiger's role belongs to the Komodo dragon.

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• 6. Vanishing and Return

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  At its fullest, the wild boar's range stretched from the British Isles to Korea and the Sunda Islands. In Africa it followed the Nile valley as far as Khartoum and lived north of the Sahara. The northern limit ran from southern Scandinavia to southern Siberia and Japan. In Asia, the reconstructed boundary started at Lake Ladoga, at 60°N, and crossed the Moscow region to the southern Urals. Only extreme deserts and high alpine zones were off limits.

  In 1087, a forestry law under William the Conqueror punished the unlawful killing of a boar with blinding. Even then, wild boars were apparently growing rare in Britain. Populations there probably died out in the 13th century. Charles I tried to reintroduce the species in the New Forest, but that group was exterminated in the 17th century during the English Civil War.

  The retreat was widespread. Denmark's last boar was shot at the start of the 19th century. By 1900, boars had vanished from Tunisia, Sudan, and large areas of Germany, Austria, and Italy. In Russia, they were extirpated across wide areas by the 1930s. Egypt's last boar reportedly died in the Giza Zoo on the 20th of December 1912, and wild populations had disappeared there by 1894-1902. Prince Kamal el Dine Hussein tried to repopulate Wadi El Natrun with boars of Hungarian stock, but poachers quickly exterminated them.

  Some absences were older than anyone knew. Scientists long believed that boars never lived in Finland in prehistory, because no ancient boar bones had been found there. That changed in 2013, when a bone discovered in Askola showed the animal lived in Finland more than 8,000 years ago. Hunting by people probably kept it from establishing itself.

  A revival began in the middle of the 20th century. By 1950, boars had again reached their original northern boundary in many parts of Asia. By 1960 they had reached Leningrad and Moscow, and by 1975 they were in Arkhangelsk and Astrakhan. Animals that escaped from captivity re-established populations in Denmark and Sweden in the 1970s. Boars later spread into Norway, and by the 2020s they had breeding populations in the southeast of the country.

  In England, boars re-established themselves in the 1990s after escaping from specialist farms that had imported European stock. A 1998 study confirmed two wild populations, one in Kent and East Sussex and another in Dorset. A DEFRA report in February 2008 added a third in the Forest of Dean and Ross on Wye area and a new population in Devon. Counts there are disputed. In early 2010 the Forestry Commission began a cull in the Forest of Dean, aiming to cut an estimated 150 animals to 100. By August only 25 had been killed, and the failure to meet targets was confirmed in February 2011.

  In Scotland, officials call the animals feral pigs, since their genes may be a mix of wild boar and domestic pig. They live in Dumfries and Galloway and in the Highlands, mainly around Loch Ness. Farmers there reported that boars had killed and eaten several lambs.

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• 7. A Pest Abroad

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  The first pure wild boars reached North America in 1890, when Austin Corbin bought 13 animals from Carl Hagenbeck in Germany. He released them into a 9500 ha game preserve in Sullivan County, New Hampshire. Several escaped, and some were seen crossing into Vermont. Domestic pigs and feral "razorbacks" had been in North America since early European colonization, and Europeans had brought pigs to the Americas for food in the 16th century. Wealthy landowners were the ones who released pure boars, as big game animals.

  In 1902-15-20 boars from Germany were set loose on a 3200 ha estate in Hamilton County, New York. The most extensive introduction came in 1912, when 13 boars of undetermined European origin went into two fenced enclosures at Hooper Bald in Graham County, North Carolina. A large hunt a decade later drove the survivors through the fences. In 1924, a dozen Hooper Bald animals were shipped to California, and their hybrid descendants were later used as breeding stock in several states. Boars were released at the Powder Horn Ranch in Calhoun County, Texas, in 1939. In the mid-1980s, animals from the San Diego Zoo and Tierpark Berlin were let loose, and later releases used stock from Canadian farms and Białowieża Forest. Wild pigs have now been reported in 44 US states, most of them probably hybrids of boar and feral hog.

  In Brazil, wild boar and hybrids were bred on a large scale from the mid-1990s. Boars crossed into Rio Grande do Sul around 1989. After IBAMA ruled against importing and breeding boars in 1998, breeders let animals escape or released them on purpose. A growing feral population now advances across Brazilian territory.

  The damage is long. Introduced boars compete with native species for food, destroy ground-nesting birds' nests, and kill fawns and young livestock. They ruin crops, eat tree seeds and seedlings, and wreck wetlands by wallowing. Their activity in streams and pools clouds the water and can push fecal coliform to dangerous levels. They also carry brucellosis, trichinosis, and pseudorabies. Boars have caused a great decrease in over 300 animal or plant species, 250 of them endangered or threatened.

  Control can reverse the damage quickly. In a study of feral swine control, turtle nests jumped from 57 to 143 within two years, and nest predation dropped from 74% to 15%. In the United States, damage is estimated at $800 million yearly in environmental and financial costs. Hunting is the most common tool for private landowners, but alone it is often not effective enough.

  Problems also arise within the native range. In the Belovezh forest, 34-47% of local boars enter fields in years of moderate natural food. Research shows that hunting is the only strategy that significantly reduces crop damage. Growing cities have also pushed habituated boars into human areas. As of 2010, at least 44 cities in 15 countries had faced problems with them. Peri-urban adults can weigh up to 35% more than forest boars. A 2023 study found that pigs feeding in large regional landfills grow heavier, have larger litters, and cause more vehicle collisions. Landfill feeding has also been identified as a way for African swine fever virus to spread.

  Media tone shapes the response. Every 10 negative articles increases wild boar policy activity by 6.7%. And the animals' soil disturbance releases carbon dioxide equal to about 1.1 million passenger vehicles each year, or 4.9 Mt.

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• 8. Myth and the Hunt

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  About 11,600 years ago, Neolithic hunter-gatherers carved ferocious wild boars into temple pillars at Göbekli Tepe. For many Indo-European peoples, killing a boar proved a person's valor and strength. In Greek myth, almost every hero fights a boar at some point. Herakles's third labour is to capture the Erymanthian Boar, and Theseus kills the wild sow Phaea. Odysseus carries boar scars, and his handmaiden Eurycleia recognises him by them. Adonis is killed by a boar, and Zeus allows him to leave Hades only in spring and summer.

  The boar's dark colour, solitary habits, and appetite for crops tied it to night and evil in several traditions. Ephesus was said to have been founded where Prince Androklos of Athens killed a boar. On Greek funerary monuments, boars appear beside lions as gallant losers who finally met their match. The Hittites sacrificed a boar alongside a dog and a prisoner of war after a military defeat.

  Germanic peoples engraved boars on shields and swords and set them on helmets, such as the Benty Grange helmet. The boar was closely linked to the god Freyr and may have been a totem of the Swedes' Yngling dynasty. Tacitus wrote that the Baltic Aesti wore boars on their helmets. The Celts held the boar to be their most important sacred animal, but the image of Celts feasting on boar owes much to the Asterix series. Boar bones are rare at Celtic sites, and the few found show no butchery marks.

  In Hindu tradition, the boar becomes Varaha, an avatar of Vishnu, who raised the Earth from the primeval waters. In Japan, the boar stands for recklessness, and several expressions for rashness include it. It is the last animal of the Oriental zodiac, and hunters sometimes name their sons after it, using the word inoshishi. The boar also symbolises fertility and prosperity. It appeared on the ¥10 note of the Meiji period, and people believed that a clump of boar hair kept in a wallet could make a man rich. Yet Japanese culture also calls the animal the "king of pests," and rural young men are told, "When you get married, choose a place with no wild boar." The Kyrgyz, before converting to Islam, believed they descended from boars and avoided pork. Richard III of England used the white boar as his badge while Duke of Gloucester.

  Hunters have pursued the boar for millennia, and the oldest artistic depictions date to the Upper Paleolithic. At some Chinese sites from the Holocene Climatic Optimum, boar made up as many as 73% of medium and large mammal remains. Boar hunting spread among young Roman nobles in the 3rd century BC, with Scipio Aemilianus among its first practitioners. Romans netted off an area, flushed the boar with dogs, and finished it with a venabulum, a short spear with a crossguard. The cookbook of Apicius devotes a chapter to boar meat, with 10 recipes. In medieval times, a boar's head was the centrepiece of most noble Christmas feasts. During the Renaissance, boar hunting became the nobility's sole prerogative, and the German Peasants' War and the French Revolution counted it among the charges against the rich.

  Boars can fight back. A 2012 study compiled records of attacks from 1825 to 2012 and found 665 human victims of wild boars and feral pigs. The United States accounted for 24% of the attacks and India for 19%. Most happened in rural areas during winter, outside hunting, and were committed by solitary males. A boar typically charges with its tusks pointed forward, and most injuries land on the thigh.

  Hunting language has its own ladder for the animal's age. A boar is a squeaker for its first 10 months and a pig of the sounder in its second year. Boars in their third to fifth years have year-numbered names. The top rung, the grand old boar, is reserved for animals past their sixth year.

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