出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/10/03 01:01:11」(JST)
| Wild boar Temporal range: Early Pleistocene – Recent |
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|---|---|
| Conservation status | |
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Least Concern (IUCN 3.1)[1] |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Suidae |
| Genus: | Sus |
| Species: | S. scrofa |
| Binomial name | |
| Sus scrofa Linnaeus, 1758 |
|
| Reconstructed range of wild boar (green) and introduced populations (blue). Not shown are smaller introduced populations in the Caribbean, New Zealand, sub-Saharan Africa and elsewhere.[1][2] | |
Wild boar or wild pig (Sus scrofa) is a species of the pig genus Sus, part of the biological family Suidae. The species includes many subspecies. It is the wild ancestor of the domestic pig, an animal with which it freely hybridises.[3] Wild boar are native across much of Northern and Central Europe, the Mediterranean region (including North Africa's Atlas Mountains) and much of Asia, including Japan and as far south as Indonesia. Populations have also been artificially introduced in some parts of the world, most notably the Americas and Australasia, where they are regarded as both an important food resource and an environmental threat.[4] Elsewhere, such as England, populations have reestablished themselves after escapes of wild boar from captivity in areas where they had previously been extirpated.[5]
The term boar is used to denote an adult male of certain species, including domestic pigs. However, for wild boar, it applies to the whole species, including, for example, "wild boar sow" or "wild boar piglet".[6]
Wild boar are also known by various names, including wild hogs or simply boars. In the US, they are more commonly referred to as razorbacks, bush pigs, or European boars.[7]
The body of the wild boar is compact; the head is large, the legs relatively short. The fur consists of stiff bristles and usually finer fur. The colour usually varies from dark grey to black or brown, but there are great regional differences in colour; even whitish animals are known from central Asia.[8] During winter the fur is much more dense.
Wild boars vary considerably in size. In exceptionally large specimens, the species can rival the size of the giant forest hog, the largest extant species of wild suid.[9] Adult boars can measure from 90 to 200 cm (35 to 79 in) in length, not counting a tail of 15 to 40 cm (5.9 to 15.7 in), and have a shoulder height of 55 to 110 cm (22 to 43 in).[10][11] As a whole, their average weight is 50–90 kg (110–200 pounds), though boars show a great deal of weight variation within their geographical ranges.[12] Generally speaking, native Eurasian boars follow Bergmann's rule, with smaller boars nearer the tropics and larger, smaller-eared boars in the North of their range. Mature sows from Southeast Asia and southern India may weigh as little as 44 kg (97 lb).[11] In Great Britain, wild boars typically weigh between 68 and 181 kg (150 and 400 lb).[13] In central Italy, their weight usually ranges from 80 to 100 kg (180 to 220 lb) while boars shot in Tuscany have been recorded to weigh up to 150 kg (331 lb). An unusually large French specimen shot in Negremont forest in Ardenne in 1999 weighed 227 kg (550 lb). Carpathian boars have been recorded to reach weights of 200 kg (441 lb). Romanian and Russian boars can reach weights of 300 kg (661 lb), while unconfirmed giants reported in early Russian hunting journals have reportedly weighed up to 320 kg (710 lb).[10][11]
Adult males develop tusks, continuously growing teeth that protrude from the mouth, from their upper and lower canine teeth. These serve as weapons and tools. The upper tusks are bent upwards in males, and are regularly ground against the lower ones to produce sharp edges. The tusks normally measure about 6 cm (2.4 in), in exceptional cases even 12 cm (4.7 in). Females also have sharp canines, but they are smaller, and not protruding like the males' tusks.[14][15] Tigers hunt boars, but avoid tackling mature male boars. In many cases, boars have gored tigers to death in self-defence.[8] Wild boars can be dangerous to humans, especially when they have piglets.
Wild boar piglets are coloured differently from adults, having marbled chocolate and cream stripes lengthwise over their bodies. The stripes fade by the time the piglet is about 6 months old, when the animal takes on the adult's grizzled grey or brown colour (see photo in Reproduction section to compare adult and juvenile colouring).
Adult males are usually solitary outside of the breeding season, but females and their offspring (both sub-adult males and females) live in groups called sounders. Sounders typically number around 20 animals, although groups of over 50 have been seen, and will consist of 2 to 3 sows; one of which will be the dominant female. Group structure changes with the coming and going of farrowing females, the migration of maturing males (usually when they reach around 20 months) and the arrival of unrelated sexually active males.
Wild boar are situationally crepuscular or nocturnal, foraging in early morning and late afternoon or at night, but resting for periods during both night and day.[1] They are omnivorous scavengers, eating almost anything they come across, including grass, nuts, berries, carrion, nests of ground nesting birds, roots, tubers, refuse,[16] insects and small reptiles. Wild boar in Australia are also known to be predators of young deer and lambs.[17]
If surprised or cornered, a boar (particularly a sow with piglets) can and will defend itself and its young with intense vigour.[18] The male lowers its head, charges, and then slashes upward with its tusks. The female, whose tusks are not visible, charges with head up, mouth wide, and bites.
Sexual activity and testosterone production in males is triggered by decreasing day length, reaching a peak in mid-autumn. The normally solitary males then move into female groups, and rival males fight for dominance, whereupon the largest and most dominant males achieve the most mating. Mating may last over 45 minutes, and is accompanied by pelvic thrusting.[19]
The age of puberty for sows ranges from 6 to 24 months of age depending on environmental and nutritional factors; sexual maturity begins when boars reach a weight of around 30 kg.[4] Pregnancy lasts approximately 115 days and a sow will leave the group to construct a mound-like nest out of vegetation and dirt, 1–3 days before giving birth (farrowing).
The process of giving birth to a litter lasts between 2 and 3 hours, and the sow and piglets remain in, or close to, the nest for 4–6 days. Sows rejoin the group after 4–5 days, and the piglets will cross suckle between other lactating sows.
Litter size is typically four to six piglets but may be smaller for first litter, usually two to three. The largest litters can be up to fourteen piglets. The sex ratio at birth is 1:1. Litter size of wild boars may vary depending on their location. A study in the Great Smoky Mountains National Park in the US reported a mean litter size of 3.3. A similar study on Santa Catalina Island, California reported a mean litter size of 5.[20] Larger litter sizes have been reported in the Middle East.[1] Piglets weigh 750–1,000 g (1.65–2.20 lb) at birth. Rooting behaviour develops in piglets as early as the first few days of life, and piglets are fully weaned after three to four months. They will begin to eat solid foods such as worms and grubs after about two weeks.[21]
Wild boar were originally found in North Africa and much of Eurasia; from the British Isles to Korea and the Sunda Islands. The northern limit of its range extended from southern Scandinavia to southern Siberia and Japan. Within this range it was absent in extremely dry deserts and alpine zones.
A few centuries ago it was found in North Africa along the Nile valley up to Khartum and north of the Sahara. The reconstructed northern boundary of the range in Asia ran from Lake Ladoga (at 60°N) through the area of Novgorod and Moscow into the southern Urals, where it reached 52°N. From there the boundary passed Ishim and farther east the Irtysh at 56°N. In the eastern Baraba steppe (near Novosibirsk) the boundary turned steep south, encircled the Altai Mountains, and went again eastward including the Tannu-Ola Mountains and Lake Baikal. From here the boundary went slightly north of the Amur River eastward to its lower reaches at the Sea of Okhotsk. On Sakhalin there are only fossil reports of wild boar. The southern boundaries in Europe and Asia were almost everywhere identical to the sea shores of these continents. In dry deserts and high mountain ranges, the wild boar is naturally absent. So it is absent in the dry regions of Mongolia from 44–46°N southward, in China westward of Sichuan and in India north of the Himalaya. In high altitudes of Pamir and Tien Shan they are also absent; however, at Tarim basin and on the lower slopes of the Tien Shan they do occur.[8]
In recent centuries, the range of wild boar has changed dramatically, largely due to hunting by humans and more recently because of captive wild boar escaping into the wild. For many years populations dwindled. They probably became extinct in Great Britain in the 13th century.[22] In Denmark the last boar was shot at the beginning of the 19th century, and in 1900 they were absent in Tunisia and Sudan and large areas of Germany, Austria, and Italy. In Russia they were extirpated in wide areas in the 1930s.
A revival of boar populations began in the middle of the 20th century. By 1950 wild boar had once again reached their original northern boundary in many parts of their Asiatic range. By 1960 they reached Saint Petersburg and Moscow, and by 1975 they were to be found in Archangelsk and Astrakhan. In the 1970s they again occurred in Denmark and Sweden, where captive animals escaped and now survive in the wild. (The wild boar population in Sweden was estimated to be around 80,000 in 2006 but grew in excess of 100,000 in a few years). In England, wild boar populations re-established themselves in the 1990s, after escaping from specialist farms that had imported European stock.[22]
Elsewhere, in 1493, Christopher Columbus brought eight hogs to the West Indies. Importation to the American mainland was in the mid-16th century by Hernán Cortés and Hernando de Soto, and in the mid-17th century by Sieur de La Salle. Pure Eurasian boar were also imported there for sport hunting in the early 20th century.[7] Large populations of wild boar also live in Australia, New Zealand and North and South America.[23] In the United States, there are approximately 6 million feral pigs.[24] In the first decade of the 21st century, wild boar escaped from game farms in Alberta and Saskatchewan (Canada) and reproduced rapidly, resulting in bounties offered for pairs of ears. A few years later, population estimates range in the thousands.[25]
Between their medieval extinction and the 1980s, when wild boar farming began, only a handful of captive wild boar, imported from the continent, were present in Britain. Occasional escapes of wild boar from wildlife parks have occurred as early as the 1970s, but since the early 1990s significant populations have re-established themselves after escapes from farms; the number of which has increased as the demand for wild boar meat has grown.
A 1998 MAFF (now DEFRA) study on wild boar living wild in Britain confirmed the presence of two populations of wild boar living in Britain; one in Kent/East Sussex and another in Dorset.[22]
Another DEFRA report, in February 2008,[26] confirmed the existence of these two sites as 'established breeding areas' and identified a third in Gloucestershire/Herefordshire; in the Forest of Dean/Ross on Wye area. A 'new breeding population' was also identified in Devon. There is another significant population in Dumfries and Galloway.
Populations estimates were as follows:
Population estimates for the Forest of Dean are disputed as at the time that the DEFRA estimate was 100 a photo of a group of boar in the forest near Staunton with over 33 animals visible was published and at about the same time over 30 boar were seen in a field near the original escape location of Weston under Penyard many miles away. In early 2010 the Forestry Commission embarked on a cull,[27] with the aim of reducing the boar population from an estimated 150 animals to 100. By August it was stated that efforts were being made to reduce the population from 200 to 90, but that only 25 had been killed.[28] The failure to meet cull targets was confirmed in February 2011.[29]
Wild boar have crossed the River Wye into Monmouthshire Wales. Iolo Williams the BBC Wales wildlife expert attempted to film Welsh boar in late 2012.[30] Many other sightings, across the UK, have also been reported.[31] The effects of wild boar on the UK's woodlands were discussed with Ralph Harmer of the Forestry Commission on the BBC Radio's Farming Today radio programme in 2011. The programme prompted activist writer George Monbiot to propose a thorough population study, followed by the introduction of permit-controlled culling.[32]
Wild boar are known to be competent swimmers, capable of covering long distances. In 2013 one boar was reported to have completed the seven mile swim from France to Alderney in the Channel Islands, before being shot and incinerated.[33]
Recently, Germany has reported a surge in the wild boar population. According to one study, "German wild boar litters have six to eight piglets on average, other countries usually only about four or five."[34] Boar in Germany are also said to be becoming increasingly 'brazen' and intrude further into cities, for example Berlin.[35]
Different subspecies can usually be distinguished by the relative lengths and shapes of their lacrimal bones. S. scrofa cristatus and S. scrofa vittatus have shorter lacrimal bones than European subspecies.[36] Spanish and French boar specimens have 36 chromosomes, as opposed to wild boar in the rest of Europe which possess 38, the same number as domestic pigs. Boars with 36 chromosomes have successfully mated with animals possessing 38, resulting in fertile offspring with 37 chromosomes.[37]
Four subspecies groups are generally recognised:[38]
The domestic pig is usually regarded as a subspecies – Sus scrofa domestica – although this is sometimes classified as a separate species: Sus domestica.
Wild boar are a main food source for tigers in the regions where they coexist. Tigers typically follow boar groups, and pick them off one by one. Tigers have been noted to chase boars for longer distances than with other prey, though they will usually avoid tackling mature male boars. In many cases, boars have gored tigers to death in self-defense.[8] In the Amur region, wild boars are one of the two most important prey species for the Siberian tiger alongside the Manchurian wapiti, with the two species collectively comprising roughly 80% of the prey selected by these tigers.[43] Studies of Bengal tigers indicate that boars are usually secondary in preference to various cervids and bovids.[44] Boars are also probably an important component of the diet of Sumatran tigers, though their specific significance in the tiger's diet there is not known.[45]
Wolves are also major predators of boars in some areas. Wolves mostly feed on piglets, though adults have been recorded to be taken in Italy, the Iberian peninsula, and Russia. Wolves rarely attack boars head on, preferring to tear at their perineum, causing loss of coordination and massive blood loss. In some areas of the former Soviet Union, a single wolf pack can consume an average of 50–80 wild boars annually.[46] In areas of Italy where the two animals are sympatric, the extent to which boars are preyed upon by wolves has led to them developing more aggressive behaviour toward both wolves and domestic dogs.[10]
Striped hyenas occasionally feed on boars, though it has been suggested that only hyenas from the three larger subspecies present in Northwest Africa, the Middle East, and India can successfully kill them.[47]
Young piglets are important prey for several species, including large snakes, such as the reticulated python, large birds of prey, and various wild felids. In Australia many piglets are killed by dingos. Adults, due to their size, strength, and defensive aggression, are generally avoided as prey. However, they have been taken additionally by mature leopards; large bears (mainly brown bears); and mature crocodiles. All predators of boars are opportunistic and would take piglets given the opportunity. Where introduced outside of their natural range, boars may be at the top of the food chain, but it is possible that they can be taken by predators similar to those in their native Eurasia, such as large snakes, raptors, cats, wolves, and other large predators.[12] The Eurasian Eagle-Owl (Bubo bubo) has been caught on video successfully attacking and killing a wild boar piglet.[48]
Although wild boars do not generally pose a threat to people, they occasionally attack humans. Due to the clearing of natural boar habitats, the number of interactions, including aggressive ones, between humans and boars has increased. When dealing aggressively with a human, boars will charge at them. Sometimes, these may be bluff charges but, in other cases, violent contact will be made. While the impact of the large, hard-skulled head may cause considerable damage itself, most damage is inflicted by the boar's tusk. When ramming into a person, the boar will slash the tusks upwards, creating sizeable open lacerations on the skin. Due to the height of the boar relative to a human, most wounds are inflicted to the upper legs. Some attacks are provoked, such as when hunters wound a boar which then counterattacks. Male boars become most aggressive during the mating season and may charge at humans at such times. Occasionally, female boars will attack if they feel their piglets are threatened, especially if a human physically comes between them and their young. Although a majority of boar attack victims recover with medical treatment, fatalities do occasionally occur.[49]
In Medieval hunting the boar, like the hart, was a 'beast of venery', the most prestigious form of quarry. It was normally hunted by being harboured, or found by a 'limer', or bloodhound handled on a leash, before the pack of hounds was released to pursue it on its hot scent. The poem Sir Gawain and the Green Knight[50] contains a description of a boar hunt, depicting how dangerous the boar could be to the pack hounds, or raches, which hunted it.[51] Medieval hunters used special boar spears (along with polearms and various swords) to hunt wild boar. The distinguishing characteristic of the boar spear is a wide cross guard behind the spearhead to prevent the boar from charging up the haft and goring the spearman.
The ancient Lowland Scottish Clan Swinton is said to have acquired the name Swinton for their bravery and clearing their area of wild boar. The chief's coat of arms and the clan crest allude to this legend, as is the name of the village of Swinewood in the county of Berwick which was granted to them in the 11th century.[citation needed]
Wild boar are still occasionally hunted, especially where not legally protected. The minimum safe calibre for shooting wild boar is generally considered to be .243 Winchester with 85 grain or heavier expanding projectiles, with larger calibres being recommended. Repeating action shotguns loaded with solid shot can also be used. Wild boar are strong, solidly built animals with sharp tusks and a willingness to defend themselves vigorously.[52] Boar are known to charge the hunter after a missed shot or a wound that is not immediately lethal; because of this, some of the earliest bayonets were actually used by boar hunters rather than military forces.[53][54]
Captive wild boar in Britain are kept in private or public wildlife collections and in zoos, but exist predominantly on farms. Because wild boar are included in the Dangerous Wild Animals Act 1976, certain legal requirements have to be met prior to setting up a farm. A licence to keep boar is required from the local council, who will appoint a specialist to inspect the premises and report back to the council. Requirements include secure accommodation and fencing, correct drainage, temperature, lighting, hygiene, ventilation and insurance.
The original British wild boar farm stock was mainly of French origin, but from 1987 onwards, farmers have supplemented the original stock with animals of both west European and east European origin. The east European animals were imported from farm stock in Sweden because Sweden, unlike eastern Europe, has a similar health status for pigs to that of Britain. Currently there is no central register listing all the wild boar farms in the UK; the total number of wild boar farms is unknown.[22]
In many countries, boar are farmed for their meat, and in France and Italy, for example, boar (sanglier in French, cinghiale in Italian) may often be found for sale in butcher shops or offered in restaurants (although the consumption of wild boar meat has been linked to transmission of Hepatitis E in Japan).[55] In Germany, boar meat ranks among the highest priced types of meat. In certain countries, such as Laos and parts of China, boar meat is considered an aphrodisiac.[56]
The hair of the boar was often used for the production of the toothbrush until the invention of synthetic materials in the 1930s.[57] The hair for the bristles usually came from the neck area of the boar. While such brushes were popular because the bristles were soft, this was not the best material for oral hygiene as the hairs were slow to dry and usually retained bacteria. Today's toothbrushes are made with plastic bristles.
Boar hair is used in the manufacture of boar-bristle hairbrushes, which are considered to be gentler on hair – and are much more expensive – than common plastic-bristle hairbrushes. However, among shaving brushes, which are almost exclusively made with animal fibres, the cheaper models use boar bristles, while badger hair is used in much more expensive models.[58]
Boar hair is used in the manufacture of paintbrushes, especially those used for oil painting. Boar bristle paintbrushes are stiff enough to spread thick paint well, and the naturally split or "flagged" tip of the untrimmed bristle helps hold more paint.
Despite claims that boar bristles have been used in the manufacture of premium dart boards for use with steel-tipped darts, these boards are, in fact, made of other materials and fibres – the finest ones from sisal rope.
In Celtic mythology the boar was sacred to the Gallic goddess Arduinna,[59][60] and boar hunting features in several stories of Celtic and Irish mythology. One such story is that of how Fionn mac Cumhaill ("Finn McCool") lured his rival Diarmuid Ua Duibhne to his death—gored by a wild boar.[citation needed]
The Calydonian Boar (Greek: ὁ Καλυδώνιος κάπρος[61][62] or ὁ Καλυδώνιος ὗς[63]) is one of the monsters of Greek mythology that had to be overcome by heroes of the Olympian age. Sent by Artemis to ravage the region of Calydon in Aetolia because its king failed to honor her in his rites to the gods, it was killed in the Calydonian Hunt, in which many male heroes took part, but also a powerful woman, Atalanta, who won its hide by first wounding it with an arrow. This outraged some of the men, with tragic results. Strabo was under the impression that the Calydonian Boar was an offspring of the Crommyonian Sow vanquished by Theseus.[64]
In the Asterix comic series set in Gaul, wild boar are the favourite food of Obelix whose immense appetite means that he can eat several roasted boar in a single sitting.[65]
Gullinbursti (meaning "Gold Mane or Golden Bristles") is a boar in Norse mythology. Likewise, in most European pagan traditions, the wild boar is associated with male solar deities, such as Endovelicus, Freyr and Apollon,[66] due to the nature of death and rebirth attached to the boar's connection to the earth and necrophagous behaviour.[67]
In Hindu mythology, the third Avatar of Vishnu was Varaha, a wild boar.[68]
Odysseus, the principal protagonist of Homer's epic The Odyssey carried a distinctive scar inflicted by a boar in his youth.
A story from Nevers, which is reproduced in the Golden Legend, states that one night Charlemagne dreamed he was about to be killed by a wild boar during a hunt, but was saved by the appearance of a child, who had promised to save the emperor if he would give him clothes to cover his nakedness. The bishop of Nevers interpreted this dream to mean that the child was Saint Cyricus and that he wanted the emperor to repair the roof of the Cathédrale Saint-Cyr-et-Sainte-Julitte de Nevers – which Charlemagne duly did.[citation needed]
Folklore, in the Forest of Dean, England, tells of a giant boar, known as the Beast of Dean, which terrorised villagers in the early 19th century.[citation needed]
In the story The Boar by American writer Joe R. Lansdale, a young boy hunts a large boar in East Texas during the Great Depression.
In Tolkien's legendarium of Middle-earth, Folca, the 13th King of Rohan, hunted a great boar and slayed it, but was gored in the process and died of his wounds.[69] The confrontation took place in the woods of Everholt, a name Tolkien derived from Old English eofor, meaning "boar". A more direct application of this Old English in found in Éofor, an early prince of Rohan, although Tolkien knew the name Eofor from the epic of Beowulf.
The wild boar and a boar's head are common charges in heraldry. It represents what are often seen as the positive qualities of the boar, namely courage and fierceness in battle. The arms of the Campbell of Possil family (see Carter-Campbell of Possil) include the head, erect and erased of a wild boar, as does the crest Mackinnon clan. The arms of the Swinton Family also possess wild boar, as does the coat of arms of the Purcell family.[70]
At least three Roman Legions are known to have had a boar as their emblems: Legio I Italica, Legio X Fretensis and Legio XX Valeria Victrix.
A boar is a long-standing symbol of the city of Milan, Italy. In Andrea Alciato's Emblemata (1584), beneath a woodcut of the first raising of Milan's city walls, a boar is seen lifted from the excavation. The foundation of Milan is credited to two Celtic peoples, the Bituriges and the Aedui, having as their emblems a ram and a boar respectively (Bituricis vervex, Heduis dat sucula signum.); therefore "The city's symbol is a wool-bearing boar, an animal of double form, here with sharp bristles, there with sleek wool," (Laniger huic signum sus est, animálque biforme, Acribus hinc setis, lanitio inde levi). Alciato credits the most saintly and learned Ambrose for his account.[71]
Richard III of England (r. 1483–1485) used the white boar as his personal device and badge. It was also passed to his short-lived son, Edward.[citation needed]
Domestic pigs can escape and quite readily become feral, and feral populations are problematic in several ways. They can cause significant amount of damage to trees and other vegetation and may feed on the eggs of ground-nesting birds and turtles.[72] Feral pigs often interbreed with wild boar, producing descendants similar in appearance to wild boar; these can then be difficult to distinguish from natural or introduced true wild boar. The characterisation of populations as feral pig, escaped domestic pig or wild boar is usually decided by where the animals are encountered and what is known of their history. In New Zealand, for example, feral pigs are known as "Captain Cookers" from their supposed descent from liberations and gifts to Māori by explorer Captain James Cook in the 1770s.[73] New Zealand feral pigs are also frequently known as "tuskers", due to their appearance.
One characteristic by which domestic and feral animals are differentiated is their coats. Feral animals almost always have thick, bristly coats ranging in colour from brown through grey to black. A prominent ridge of hair matching the spine is also common, giving rise to the name razorback in the southern United States, where they are common. The tail is usually long and straight. Feral animals tend also to have longer legs than domestic breeds and a longer and narrower head and snout.
A very large swine dubbed Hogzilla was shot in Georgia, United States, in June 2004.[74] Initially thought to be a hoax, the story became something of an internet sensation. National Geographic Explorer investigated the story, sending scientists into the field. After exhuming the animal and performing DNA testing, it was determined that Hogzilla was a hybrid of wild boar and domestic swine.[75] As of 2008[update], the estimated population of 4 million feral pigs caused an estimated US$800 million of property damage per year in the U.S.[76]
The problematic nature of feral hogs has caused several states in the U.S. to declare feral hogs to be an invasive species. Often, these states will have greatly reduced (or even non-existent) hunting regulations regarding feral hogs. In Missouri, no hunting permit is required for the taking of wild boar; hunters may take as many as they like with any weapon. The Missouri Department of Conservation requests that hunters who encounter feral hogs shoot them on sight.[77] Caution is advised, as feral pigs can use their tusks defensively, and hog hunters consider them dangerous when injured or cornered.[78] Similarly, in Texas, the Texas Parks & Wildlife Department allows them to be taken at any time of the year, by any method, with no limit; the only rules are that a person must have a hunting license and permission of the landowner.[79]
At the beginning of the 20th century, wild boar were introduced for hunting in the United States, where they interbred in parts with free roaming domestic pigs. In South America, New Guinea, New Zealand, Australia and other islands, wild boar have also been introduced by humans and have partially interbred with domestic pigs.
In South America, also during the early 20th century, free-ranging boars were introduced in Uruguay for hunting purposes and eventually crossed the border into Brazil sometime during the 1990s, quickly becoming an invasive species, licensed private hunting of both feral boars and hybrids (javaporcos) being allowed from August 2005 on in the Southern Brazilian state of Rio Grande do Sul,[80] although their presence as a pest had been already noticed by the press as early as 1994.[81] Releases and escapes from unlicensed farms (established because of increased demand for boar meat as an alternative to pork), however, continued to bolster feral populations and by mid-2008 licensed hunts had to be expanded to the states of Santa Catarina and São Paulo.[82] Such licensed hunts were, however, forbidden in 2010 by IBAMA, which argued the necessity of additional studies for devising a strategy of pest control for boars. Meanwhile, boars and boar crosses were spotted in the State of Rio de Janeiro, where cases of crop raiding were reported in the municipality of Porciuncula. There was also the danger of an escape from an unlicensed farm in Nova Friburgo, which was closed in December 2011, all 316 animals being sent to an abattoir.[83] In October 2010, a rural worker was killed by a boar in Ibiá, in the State of Minas Gerais.
Recently established Brazilian boar populations are not to be confused with long established populations of feral domestic pigs, which have existed mainly in the Pantanal for more than a hundred years, along with native peccaries. The demographic dynamics of the interaction between feral pigs populations and those of the two native species of peccaries (Collared Peccary and White-lipped Peccary) is obscure and is being studied presently. It has been proposed that the existence of feral pigs could somewhat ease jaguar predation on peccary populations, as jaguars would show a preference for hunting pigs, when these are available.[84]
Feral hogs can rapidly increase their population. Sows can have up to 10 offspring per litter, and are able to have two litters per year. Each piglet reaches sexual maturity at 6 months of age. They have virtually no natural predators.[85]
Feral pigs removal can restore native Hawaiian rain forest in several years.[86]
|date= (help)| Wikisource has the text of the 1911 Encyclopædia Britannica article Boar. |
| Wikispecies has information related to: Sus scrofa |
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| リンク元 | 「イノシシ」「Sus scrofa」 |
| 関連記事 | 「board」「wild」 |