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{{Short description|Domesticated omnivorous even-toed ungulate}}
{{About|the domestic farm animal|other animals known as "swine"|Suina|other uses|Swine (disambiguation)|and|Pig (disambiguation)}}
{{good article}}
{{pp-protected|reason=Restoring per [[Sus (genus)]], which used to reside here.|small=yes}}
{{Use dmy dates|date=February 2022}}
{{Speciesbox
| name          = Pig
| image         = Pig farm Vampula 1.jpg
| image_caption = Domestic pigs
| status        = DOM
| genus         = Sus
| species       = domesticus
| authority     = [[Johann Christian Polycarp Erxleben|Erxleben]], 1777
| synonyms_ref  = <ref name="Groves 1995">{{cite journal |last=Groves |first=Colin P. |year=1995 |title=On the nomenclature of domestic animals |journal=Bulletin of Zoological Nomenclature |volume=52 |issue=2 |pages=137–141 |doi=10.5962/bhl.part.6749 |doi-access=free}} [https://www.biodiversitylibrary.org/page/12338062 Biodiversity Heritage Library]</ref>
| synonyms      = *''Sus domestica''
*''Sus scrofa domesticus'' <small>[[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]</small>
}}

The '''pig''' ('''''Sus domesticus'''''), also called '''swine''' ({{plural form}}: swine) or '''hog''', is an [[Omnivore|omnivorous]], [[Domestication|domesticated]], [[even-toed ungulate|even-toed, hoofed mammal]]. It is named the '''domestic pig''' when distinguishing it from other members of the genus ''[[Sus (genus)|Sus]]''. Some authorities consider it a [[subspecies]] of ''Sus scrofa'' (the [[wild boar]] or Eurasian boar); other authorities consider it a distinct [[species]]. Pigs were domesticated in the [[Neolithic]], both in [[China]] and in the [[Near East]] (around the [[Tigris|Tigris Basin]]). When domesticated pigs arrived in Europe, they extensively interbred with wild boar but retained their domesticated features.

[[Pig farming|Pigs are farmed]] primarily for meat, called [[pork]]. The animal's skin or [[Hide (skin)|hide]] is used for [[leather]]. China is the world's largest pork producer, followed by the European Union and then the United States. Around 1.5 billion pigs are raised each year, producing some 120 million tonnes of meat, often cured as [[bacon]]. Some are kept as [[pet]]s.

Pigs have featured [[Pigs in culture|in human culture]] since Neolithic times, appearing in art and literature for children and adults, and celebrated in cities such as [[Bologna]] for their meat products.

== Description ==

The pig has a large head, with a long snout strengthened by a special prenasal bone and a disk of [[cartilage]] at the tip.<ref name="ADW Sus scrofa">{{cite web |title=Sus scrofa (wild boar) |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Sus_scrofa.html |website=Animal Diversity Web}}</ref> The snout is used to dig into the soil to find food and is an acute sense organ. The [[dental formula]] of adult pigs is {{DentalFormula |upper=3.1.4.3 |lower=3.1.4.3}}, giving a total of 44 [[tooth|teeth]]. The rear teeth are adapted for crushing. In males, the canine teeth can form [[tusk]]s, which grow continuously and are sharpened by grinding against each other.<ref name="ADW Sus scrofa"/> There are four [[hoof]]ed toes on each foot; the two larger central toes bear most of the weight, while the outer two are also used in soft ground.<ref>{{cite web |last=Lockhart |first=Kim |title=American Wild Game / Feral Pigs / Hogs / Pigs / Wild Boar |url=http://www.gunnersden.com/index.htm.shooting-hunting-hogs.html |url-status=dead |archive-url=https://web.archive.org/web/20180823025758/http://gunnersden.com/index.htm.shooting-hunting-hogs.html |archive-date=23 August 2018 |access-date=15 August 2012 |website=gunnersden.com}}</ref> Most pigs have rather sparsely [[bristle]]d hair on their skin, though there are some [[wool]]ly-coated breeds such as the [[Mangalitsa]].<ref>{{cite web |title=Royal visit delights at the Three Counties Show |url=http://www.malverngazette.co.uk/mostpopular.var.1476623.mostviewed.royal_visit_delights_at_the_three_counties_show.php |website=[[Malvern Gazette]] |date=15 June 2007 }}</ref> Adult pigs generally weigh between {{cvt|140|and|300|kg}}, though some breeds can exceed this range. Exceptionally, a pig called Big Bill weighed {{cvt|1157|kg}} and had a shoulder height of {{cvt|1.5|m}}.<ref name="Bradford Dutfield 2018">{{cite web |last1=Bradford |first1=Alina |last2=Dutfield |first2=Scott |title=Pigs, Hogs & Boars: Facts About Swine |url=https://www.livescience.com/50623-pigs-facts.html |website=LiveScience |access-date=4 March 2024 |date=5 October 2018}}</ref>

Pigs possess both [[apocrine sweat gland|apocrine]] and [[eccrine sweat gland]]s, although the latter are limited to the snout.<ref name="Sumena 2010">{{cite journal |last1=Sumena |first1=K. B. |last2=Lucy |first2=K. M. |last3=Chungath |first3=J.J. |last4=Ashok |first4=N. |last5=Harshan |first5=K. R. |year=2010 |title=Regional histology of the subcutaneous tissue and the sweat glands of large white Yorkshire pigs |journal=Tamil Nadu Journal of Veterinary and Animal Sciences |volume=6 |issue=3 |pages=128–135}}</ref> Pigs, like other "hairless" mammals such as elephants, do not use thermal sweat glands in cooling.<ref name="Folk and Semken, (1991)">{{cite journal |last1=Folk |first1=G.E. |last2=Semken |first2=H.A. |year=1991 |title=The evolution of sweat glands |journal=International Journal of Biometeorology |volume=35 |issue=3 |pages=180–186 |bibcode=1991IJBm...35..180F |doi=10.1007/bf01049065 |pmid=1778649 |s2cid=28234765}}</ref> Pigs are less able than many other mammals to dissipate heat from wet [[mucous membrane]]s in the mouth by panting. Their [[Thermal neutral zone|thermoneutral]] zone is {{cvt|16-22|C|F}}.<ref>{{cite web |date=22 April 2008 |title=Sweat like a pig? |url=http://www.abc.net.au/science/articles/2008/04/22/2223974.htm |publisher=Australian Broadcasting Corporation}}</ref> At higher temperatures, pigs lose heat by [[Wallowing in animals|wallowing]] in mud or water via evaporative cooling, although it has been suggested that wallowing may serve other functions, such as protection from sunburn, [[Parasitism|ecto-parasite]] control, and scent-marking.<ref name="Bracke 2011">{{cite journal |last=Bracke |first=M. B. M. |year=2011 |title=Review of wallowing in pigs: Description of the behaviour and its motivational basis |journal=Applied Animal Behaviour Science |volume=132 |issue=1 |pages=1–13 |doi=10.1016/j.applanim.2011.01.002}}</ref> Pigs are among four mammalian species with mutations in the [[nicotinic acetylcholine receptor]] that protect against [[snake venom]]. [[Mongoose]]s, [[honey badger]]s, [[hedgehog]]s, and pigs all have different modifications to the receptor pocket which prevents [[Snake venom#α-neurotoxins|α-neurotoxin]] from binding.<ref>{{cite journal |last1=Drabeck |first1=D. H. |last2=Dean |first2=A. M. |last3=Jansa |first3=S.A. |date=1 June 2015 |title=Why the honey badger don't care: Convergent evolution of venom-targeted nicotinic acetylcholine receptors in mammals that survive venomous snake bites |journal=Toxicon |volume=99 |pages=68–72 |doi=10.1016/j.toxicon.2015.03.007 |pmid=25796346|bibcode=2015Txcn...99...68D }}</ref> Pigs have small lungs for their body size, and are thus more susceptible than other domesticated animals to fatal [[bronchitis]] and [[pneumonia]].<ref>{{cite web |title=Pros and Cons of Potbellied Pigs |url=http://www.pigs.org/article.asp?article_id=3 |url-status=dead |archive-url=https://web.archive.org/web/20140317221208/http://www.pigs.org/article.asp?article_id=3 |archive-date=17 March 2014 |access-date=25 November 2017}}</ref> The [[genome]] of the pig has been sequenced; it contains about 22,342 [[protein]]-coding [[gene]]s.<ref>{{cite journal |last1=Li |first1=Mingzhou |last2=Chen |first2=Lei |last3=Tian |first3=Shilin |last4=Lin |first4=Yu |last5=Tang |first5=Qianzi |last6=Zhou |first6=Xuming |last7=Li |first7=Diyan |last8=Yeung |first8=Carol K. L. |last9=Che |first9=Tiandong |last10=Jin |first10=Long |last11=Fu |first11=Yuhua |date=2017-05-01 |title=Comprehensive variation discovery and recovery of missing sequence in the pig genome using multiple de novo assemblies |url=https://genome.cshlp.org/content/27/5/865 |journal=Genome Research |volume=27 |issue=5 |pages=865–874 |doi=10.1101/gr.207456.116 |pmc=5411780 |pmid=27646534}}</ref><ref>{{cite journal |year=2020 |doi=10.1093/gigascience/giaa051 |pmc=7448572 |pmid=32543654 |last1=Warr |first1=A. |last2=Affara |first2=N. |last3=Aken |first3=B. |last4=Beiki |first4=H. |last5=Bickhart |first5=D. M. |last6=Billis |first6=K. |last7=Chow |first7=W. |last8=Eory |first8=L. |last9=Finlayson |first9=H. A. |last10=Flicek |first10=P. |last11=Girón |first11=C. G. |last12=Griffin |first12=D. K. |display-authors=6 |title=An improved pig reference genome sequence to enable pig genetics and genomics research |journal=GigaScience |volume=9 |issue=6 |pages=giaa051}}</ref><ref>{{cite journal |last1=Karlsson |first1=Max |last2=Sjöstedt |first2=Evelina |last3=Oksvold |first3=Per |last4=Sivertsson |first4=Åsa |last5=Huang |first5=Jinrong |last6=Álvez |first6=María Bueno |last7=Arif |first7=Muhammad |last8=Li |first8=Xiangyu |last9=Lin |first9=Lin |last10=Yu |first10=Jiaying |last11=Ma |first11=Tao |display-authors=6 |date=25 January 2022 |title=Genome-wide annotation of protein-coding genes in pig |journal=BMC Biology |volume=20 |issue=1 |page=25 |doi=10.1186/s12915-022-01229-y |pmid=35073880 |pmc=8788080 |doi-access=free }}</ref>

<gallery class=center mode=nolines widths=220 heights=180>
File:Suíno alta (cropped).jpg|Skeleton
File:Domestic pig skull (cropped).jpeg|Skull
File:Pig hand skeleton (cropped).jpg|Bones of the foot
</gallery>

== Evolution ==

=== Phylogeny ===

Domestic pigs are related to other pig species as shown in the [[cladogram]], based on phylogenetic analysis using [[mitochondrial DNA]].<ref>{{cite journal |last1=Wu |first1=Gui-Sheng |last2=Pang |first2=Jun-feng |last3=Zhang |first3=Ya-Ping |title=Molecular phylogeny and phylogeography of Suidae |journal=Zoological Research |volume=27 |issue=2 |year=2006 |pages=197–201 |url=https://www.researchgate.net/publication/43563862}}</ref>

{{clade
|label1=[[Suidae]]
|1={{clade
   |sublabel1=''Indonesia''
   |1=[[Babirusa]] [[File:Hirscheber1a.jpg|80px]]
   |2={{clade
      |sublabel1=''Africa''
      |1={{clade
         |1=[[Red river hog]] [[File:Red River Hog Smelling (22008101555).jpg|80px]]
         |2=[[Warthog]]s [[File:Southern warthog (Phacochoerus africanus sundevallii) male.jpg|80px]]
         }}
      |sublabel2=''Southeast Asia''
      |2={{clade
         |1=[[Visayan warty pig]] [[File:VisayanWartyPig01 (cropped).jpg|80px]]
         |2={{clade
            |1=[[Philippine warty pig]] [[File:Philippine warty pig (Sus philippensis) in Philippine Eagle Center, Davao, Philippines.jpg|80px]]
            |2={{clade
               |1={{clade
                  |1=[[Bornean bearded pig]] [[File:Bornean bearded pig.jpg|80px]]
                  |2=[[Javan warty pig]] [[File:Sus verrucosus.png|80px]]
                  }}
               |sublabel2=''Eurasia''
               |2={{clade
                  |label1=[[Sus scrofa|Wild boar]]
                  |1=[[File:Wildschwein, Nähe Pulverstampftor (cropped).jpg|80px]]
                  |label2= '''Domestic pig'''
                  |2={{clade
                     |1=East Asian pigs [[File:Meishan pig.JPG|80px]]
                     |2=European pigs<!--inc wild boar--> [[File:Gloucester Old Spot.jpg|80px]]
                     }}
                  }}
               }}
            }}
         }}
      }}
   }}
}}

=== Taxonomy ===

The pig is most often considered to be a [[subspecies]] of the [[wild boar]], which was given the name ''Sus scrofa'' by [[Carl Linnaeus]] in 1758; following from this, the formal name of the pig is ''Sus scrofa domesticus''.<ref>{{cite web |title=Taxonomy Browser |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?name=Sus+scrofa+domestica |website=ncbi.nlm.nih.gov}}</ref><ref name="gentry">{{cite journal |last1=Gentry |first1=Anthea |last2=Clutton-Brock |first2=Juliet |last3=Colin P. Groves |year=2004 |title=The naming of wild animal species and their domestic derivatives |url=http://arts.anu.edu.au/grovco/J%20Arch%20Sci.pdf |url-status=dead |journal=[[Journal of Archaeological Science]] |volume=31 |issue=5 |pages=645–651 |doi=10.1016/j.jas.2003.10.006 |bibcode=2004JArSc..31..645G |archive-url=https://web.archive.org/web/20110408044739/http://arts.anu.edu.au/grovco/J%20Arch%20Sci.pdf |archive-date=8 April 2011}}</ref> However, in 1777, [[Johann Christian Polycarp Erxleben]] classified the pig as a separate [[species]] from the wild boar. He gave it the name ''Sus domesticus'', still used by some taxonomists.<!--<ref>Corbet, G. B.; Hill, J. E., 1992. The mammals of the Indomalayan
Region: a systematic review. Natural History Museum Publications, Oxford University Press. Pp. i-viii, 1-488., cited in {{MSW3|id=14200054}}</ref>--><ref name="gentry2">{{cite journal |last1=Gentry |first1=Anthea |last2=Clutton-Brock |first2=Juliet |last3=Groves |first3=Colin P. |year=1996 |title=Proposed conservation of usage of 15 mammal specific names based on wild species which are antedated by or contemporary with those based on domestic animals |journal=[[Bulletin of Zoological Nomenclature]] |volume=53 |pages=28–37 |doi=10.5962/bhl.part.14102 |doi-access=free}}</ref> The [[American Society of Mammalogists]] considers it a separate species.<ref>{{cite web |title=Explore the Database |url=https://www.mammaldiversity.org/explore.html#species-id=1006374 |access-date=21 August 2021 |website=www.mammaldiversity.org |archive-date=25 December 2022 |archive-url=https://web.archive.org/web/20221225114232/https://www.mammaldiversity.org/explore.html#species-id=1006374 |url-status=dead }}</ref>

=== Domestication in the Neolithic ===

{{further|Domestication}}

[[File:Bosse 2018 pig lineages.png|thumb|upright=1.5|The initial emergence of wild pigs, followed by the genetic divergence between boars and pigs and the domestication of pigs <ref>{{cite book |last=Bosse |first=Mirte |title=Animal Domestication |chapter=A Genomics Perspective on Pig Domestication |publisher=IntechOpen |date=26 December 2018 |doi=10.5772/intechopen.82646 |isbn=978-1-83880-174-8 }}</ref>]]

Archaeological evidence shows that pigs were [[domestication|domesticated]] from wild boar in the [[Near East]] in or around the [[Tigris]] Basin,<ref>{{cite journal |last1=Ottoni |first1=C |last2=Flink |first2=LG. |last3=Evin |first3=A. |last4=Geörg |first4=C. |last5=De Cupere |first5=B. |last6=Van Neer |first6=W. |last7=Bartosiewicz |first7=L. |last8=Linderholm |first8=A. |last9=Barnett |first9=R. |last10=Peters |first10=J |last11=Decorte |first11=R. |display-authors=6 |year=2013 |title=Pig Domestication and Human-Mediated Dispersal in Western Eurasia Revealed through Ancient DNA and Geometric Morphometrics |journal=Molecular Biology and Evolution |volume=30 |issue=4 |pages=824–32 |doi=10.1093/molbev/mss261 |pmc=3603306 |pmid=23180578 |quote=our data suggest a narrative that begins with the domestication of pigs in Southwest Asia, at Upper Tigris sites including Çayönü Tepesi (Ervynck et al. 2001) and possibly Upper Euphrates sites including Cafer Höyük (Helmer 2008) and Nevalı Çori (Peters et al. 2005) }}</ref> being managed in a semi-wild state much as they are managed by some modern New Guineans.<ref>{{cite journal |last1=Rosenberg |first1=M. |last2=Nesbitt |first2=R. |last3=Redding |first3=R. W. |last4=Peasnall |first4=BL |year=1998 |title=Hallan Çemi, pig husbandry, and post-Pleistocene adaptations along the Taurus-Zagros Arc (Turkey) |journal=Paléorient |volume=24 |issue=1 |pages=25–41 |doi=10.3406/paleo.1998.4667 |s2cid=85302206 |url=http://www.persee.fr/web/revues/home/prescript/article/paleo_0153-9345_1998_num_24_1_4667}}</ref> There were pigs in [[Cyprus]] more than 11,400 years ago, introduced from the mainland, implying domestication in the adjacent mainland by then.<ref>{{cite journal |last1=Vigne |first1=J. D. |last2=Zazzo |first2=A. |last3=Saliège |first3=J.F. |last4=Poplin |first4=F. |last5=Guilaine |first5=J. |last6=Simmons |first6=A. |year=2009 |title=Pre-Neolithic wild boar management and introduction to Cyprus more than 11,400 years ago |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=106 |issue=38 |pages=16135–16138 |bibcode=2009PNAS..10616135V |doi=10.1073/pnas.0905015106 |pmc=2752532 |pmid=19706455 |doi-access=free}}</ref> Pigs were separately domesticated in China, starting some 8,000 years ago.<ref>{{cite journal |last1=Lander |first1=Brian |last2=Schneider |first2=Mindi |last3=Brunson |first3=Katherine |title=A History of Pigs in China: From Curious Omnivores to Industrial Pork |journal=Journal of Asian Studies |date=2019 |volume=79 |issue=4 |pages=865–889 |doi=10.1017/S0021911820000054 |doi-access=|s2cid=225700922 }}</ref><ref name="Giuffra">{{cite journal |last1=Giuffra |first1=E. |last2=Kijas |first2=J. M. |last3=Amarger |first3=V. |last4=Carlborg |first4=O. |last5=Jeon |first5=J. T. |last6=Andersson |first6=L. |year=2000 |title=The origin of the domestic pig: independent domestication and subsequent introgression |journal=Genetics |volume=154 |issue=4 |pages=1785–1791 |doi=10.1093/genetics/154.4.1785 |pmc=1461048 |pmid=10747069}}</ref><ref>{{cite speech |date=3 July 2012 |title=History of domestication |author1=Jean-Denis Vigne |author2=Anne Tresset |author3=Jean-Pierre Digard |url=http://www2.mnhn.fr/archeozoo-archeobota/IMG/pdf/Cucchi_ChinaPig_JAS_Online.pdf}}</ref> In the Near East, pig husbandry spread for the next few millennia. It reduced gradually during the [[Bronze Age]], as rural populations instead focused on commodity-producing livestock, but it was sustained in cities.<ref>{{cite web |last=Price |first=Max |date=March 2020 |title=The Genesis of the Near Eastern Pig |url=https://www.asor.org/anetoday/2020/03/near-eastern-pig/ |access-date=8 August 2021 |website=American Society of Overseas Research |archive-date=10 February 2022 |archive-url=https://web.archive.org/web/20220210052924/https://www.asor.org/anetoday/2020/03/near-eastern-pig/ |url-status=dead }}</ref>

Domestication did not involve reproductive isolation with population bottlenecks. Western Asian pigs were introduced into Europe, where they crossed with wild boar. There appears to have been interbreeding with a now extinct [[ghost population]] of wild pigs during the [[Pleistocene]]. The genomes of domestic pigs show strong selection for genes affecting behavior and morphology. Human selection for domestic traits likely counteracted the homogenizing effect of gene flow from wild boars and created [[domestication islands]] in the genome.<ref name="frantz2015">{{cite journal |last=Frantz |first=L |year=2015 |title=Evidence of long-term gene flow and selection during domestication from analyses of Eurasian wild and domestic pig genomes |journal=[[Nature Genetics]] |volume=47 |issue=10 |pages=1141–1148 |doi=10.1038/ng.3394 |pmid=26323058 |s2cid=205350534}}</ref><ref name="pennisi2015">{{cite journal |last=Pennisi |first=E. |author-link=Elizabeth Pennisi |year=2015 |title=The taming of the pig took some wild turns |journal=Science |doi=10.1126/science.aad1692}}</ref> Pigs arrived in Europe from the Near East at least 8,500 years ago. Over the next 3,000 years they interbred with European wild boar until their genome showed less than 5% Near Eastern ancestry, yet retained their domesticated features.<ref>{{cite journal |last1=Frantz |first1=Laurent A. F. |last2=Haile |first2=James |last3=Lin |first3=Audrey T. |last4=Scheu |first4=Amelie |last5=Geörg |first5=Christina |last6=Benecke |first6=Norbert |last7=Alexander |first7=Michelle |last8=Linderholm |first8=Anna |last9=Mullin |first9=Victoria E. |last10=Daly |first10=Kevin G. |last11=Battista |first11=Vincent M. |last12=Price |first12=Max |display-authors=6 |year=2019 |title=Ancient pigs reveal a near-complete genomic turnover following their introduction to Europe |journal=[[Proceedings of the National Academy of Sciences of the United States of America|Proceedings of the National Academy of Sciences]] |volume=116 |issue=35 |pages=17231–17238 |doi=10.1073/pnas.1901169116 |pmc=6717267 |pmid=31405970 |doi-access=free |bibcode=2019PNAS..11617231F }}</ref>

[[DNA]] evidence from subfossil remains of teeth and jawbones of Neolithic pigs shows that the first domestic pigs in Europe were brought from the Near East. This stimulated the domestication of local European wild boar, resulting in a third domestication event with the Near Eastern genes dying out in European pig stock. More recently there have been complex exchanges, with European domesticated lines being exported, in turn, to the ancient Near East.<ref>[http://news.bbc.co.uk/2/hi/science/nature/6978203.stm BBC News, "Pig DNA reveals farming history"] 4 September 2007. The report concerns an article in the journal ''PNAS''</ref><ref>{{cite journal |last1=Larson |first1=G. |last2=Albarella |first2=U. |last3=Dobney |first3=K. |last4=Rowley-Conwy |first4=P. |last5=Schibler |first5=J. |last6=Tresset |first6=A. |last7=Vigne |first7=J.D. |last8=Edwards |first8=C.J. |last9=Schlumbaum |first9=A. |last10=Dinu |first10=A. |last11=Balacsescu |first11=A. |last12=Dolman |first12=G. |display-authors=6 |year=2007 |title=Ancient DNA, pig domestication, and the spread of the Neolithic into Europe |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=104 |issue=39 |pages=15276–15281 |bibcode=2007PNAS..10415276L |doi=10.1073/pnas.0703411104 |pmc=1976408 |pmid=17855556 |doi-access=free |url=https://pure.uva.nl/ws/files/4125719/55285_284894.pdf}}</ref> Historical records indicate that Asian pigs were again introduced into Europe during the 18th and early 19th centuries.<ref name="Giuffra"/>

== History ==

=== Columbian Exchange ===

Among the animals that the Spanish introduced to the [[Chiloé Archipelago]] in the 16th century [[Columbian Exchange]], pigs were the most successful in adapting to local conditions. The pigs benefited from abundant [[shellfish]] and [[algae]] exposed by the large [[tide]]s of the archipelago.<ref name="Torrejonetal2004">{{cite journal |last1=Torrejón |first1=Fernando |last2=Cisternas |first2=Marco |last3=Araneda |first3=Alberto |year=2004 |title=Efectos ambientales de la colonización española desde el río Maullín al archipiélago de Chiloé, sur de Chile |trans-title=Environmental effects of the spanish colonization from de Maullín river to the Chiloé archipelago, southern Chile |journal=[[Revista Chilena de Historia Natural]] |language=es |volume=77 |issue=4 |pages=661–677 |doi=10.4067/s0716-078x2004000400009 |doi-access=free|hdl=10533/175736 |hdl-access=free }}</ref> Pigs were brought to southeastern North America from Europe by [[Hernando de Soto (explorer)|de Soto]] and other early Spanish [[Exploration|explorer]]s. Escaped pigs became [[feral pig|feral]].<ref>[http://www.cambridge.org/us/books/kiple/hogs.htm II.G.13. – Hogs.] {{webarchive|url=https://web.archive.org/web/20071220183225/http://www.cambridge.org/us/books/kiple/hogs.htm |date=20 December 2007 }}</ref>

=== Feral pigs ===

{{main|Feral pig}}

[[File:Wild hogs family (cropped).jpg|thumb|A family of feral pigs]]

Pigs have escaped from farms and gone [[feral]] in many parts of the world. Feral pigs in the southeastern United States have migrated north to the [[Midwestern United States|Midwest]], where many state agencies have programs to remove them.<ref>{{cite web |title=Feral Hogs in Missouri |publisher=Missouri Department of Conservation |url=https://mdc.mo.gov/wildlife/nuisance-problem-species/invasive-species/feral-hogs-missouri |access-date=7 March 2017 |archive-date=8 March 2017 |archive-url=https://web.archive.org/web/20170308143218/https://mdc.mo.gov/wildlife/nuisance-problem-species/invasive-species/feral-hogs-missouri |url-status=dead}}</ref><ref>{{cite web |title=Feral Hog Hunting Regulations |url=http://www.agfc.com/hunting/Pages/HuntingRegulationsFeralHog.aspx |archive-url=https://web.archive.org/web/20170222171722/http://www.agfc.com/hunting/Pages/HuntingRegulationsFeralHog.aspx |archive-date=22 February 2017 |url-status=dead |access-date=7 March 2017 |website=agfc.com}}</ref><ref>{{cite web |title=Feral Hog Management |website=Georgia DNR – Wildlife Resources Division |url=http://georgiawildlife.com/node/3002 |url-status=dead |archive-url=https://web.archive.org/web/20170308133934/http://georgiawildlife.com/node/3002 |archive-date=8 March 2017 |access-date=8 March 2017}}</ref> Feral pigs in New Zealand and northern [[Queensland]] have caused substantial environmental damage.<ref>{{cite news |last=Yoon |first=Carol Kaesuk |date=2 December 1992 |title=Alien Species Threaten Hawaii's Environment |work=The New York Times |url=https://query.nytimes.com/gst/fullpage.html?res=9E0CEED6103CF93AA15751C1A964958260&sec=&spon=&pagewanted=all}}</ref><ref>{{cite web |title=Introduced Birds and Mammals in New Zealand and Their Effect on the Environment – NZETC |url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-Bio27Tuat02-t1-body-d1.html |website=nzetc.org}}</ref> Feral hybrids of the European wild boar with the domestic pig are disruptive to both environment and agriculture, as they destroy crops, spread animal diseases including [[foot-and-mouth disease]], and consume wildlife such as juvenile seabirds and young [[tortoise]]s.<ref>{{cite news |date=21 November 2004 |title=World's 100 most destructive species named |work=[[The Independent]] |url=https://www.independent.co.uk/environment/worlds-100-most-destructive-species-named-534039.html |access-date=7 March 2017}}</ref> Feral pig damage is especially an issue in southeastern South America.<ref>{{cite web |url=http://g1.globo.com/sp/bauru-marilia/noticia/2013/04/autorizacao-para-abate-do-javaporco-tranquiliza-produtores-em-assis-sp.html |title=Autorização para abate do javaporco tranquiliza produtores em Assis, SP |author1=Bauru |author2=Marília |date=12 April 2013 |website=Bauru e Marília}}</ref><ref>{{cite web |title=IBAMA authorizes capture and slaughter of 'javaporcos' – Folha do Sul Gaúcho |url=http://www.jornalfolhadosul.com.br/noticia/2013/02/07/ibama-autoriza-captura-e-abate-de-javaporcos |archiveurl=https://web.archive.org/web/20170703010021/http://www.jornalfolhadosul.com.br/noticia/2013/02/07/ibama-autoriza-captura-e-abate-de-javaporcos|url-status=dead |archivedate=3 July 2017}}</ref>

== Reproduction ==

=== Physiology ===
{{multiple image|perrow=1|image1=The_breeding_of_animals_(1917)_(20385751936).jpg|caption1=[[Reproductive system]] of the boar|image2=The_breeding_of_animals_(1917)_(20412003625).jpg|caption2=Reproductive system of the sow}}
Female pigs reach sexual maturity at 3–12 months of age and come into [[Estrous cycle|estrus]] every 18–24 days if they are not successfully bred. The variation in ovulation rate can be attributed to intrinsic factors such as age and genotype, as well as extrinsic factors like nutrition, environment, and the supplementation of exogenous hormones. The gestation period averages 112–120 days.<ref>{{cite web |date=16 May 2012 |title=Feral Hog Reproductive Biology |url=http://articles.extension.org/pages/63668/feral-hog-reproductive-biology |url-status=dead |archive-url=https://web.archive.org/web/20151122022154/http://articles.extension.org/pages/63668/feral-hog-reproductive-biology#.VlEm2HnP1qY |archive-date=22 November 2015}}</ref>

[[File:Piglets IMG 5523.jpg|thumb|Piglets keeping warm together]]

[[Estrus]] lasts two to three days, and the female's displayed receptiveness to mate is known as standing heat. Standing heat is a reflexive response that is stimulated when the female is in contact with the saliva of a sexually mature boar. [[Androstenol]] is one of the pheromones produced in the submaxillary salivary glands of boars that trigger the female's response.<ref>{{cite web |title=G2312 Artificial Insemination in Swine: Breeding the Female |publisher=University of Missouri Extension |url=http://extension.missouri.edu/publications/DisplayPub.aspx?P=G2312 |access-date=7 March 2017 |archive-date=8 March 2017 |archive-url=https://web.archive.org/web/20170308145924/http://extension.missouri.edu/publications/DisplayPub.aspx?P=G2312 |url-status=dead }}</ref> The female cervix contains a series of five interdigitating pads, or folds, that hold the boar's corkscrew-shaped penis during copulation.<ref>{{cite web |title=The Female – Swine Reproduction |url=http://livestocktrail.illinois.edu/swinerepronet/paperDisplay.cfm?ContentID=6274 |access-date=7 March 2017 |website=livestocktrail.illinois.edu |archive-date=10 February 2022 |archive-url=https://web.archive.org/web/20220210052921/http://livestocktrail.illinois.edu/swinerepronet/paperDisplay.cfm?ContentID=6274 |url-status=dead }}</ref> Females have [[bicornuate uterus]]es and two [[conceptus]]es must be present in both uterine horns to enable pregnancy to proceed.<ref>{{cite journal |last1=Bazer |first1=F. W. |last2=Vallet |first2=J. L. |last3=Roberts |first3=R. M. |last4=Sharp |first4=D. D. |last5=Thatcher |first5=W. W. |year=1986 |title=Role of conceptus secretory products in establishment of pregnancy |journal=J. Reprod. Fertil. |volume=76 |issue=2 |pages=841–850 |doi=10.1530/jrf.0.0760841 |pmid=3517318 |doi-access=free}}</ref> The mother's body recognises that it is pregnant on days 11 to 12 of pregnancy, and is marked by the [[corpus luteum]]'s producing the sex hormone [[progesterone]].<ref>{{cite journal |last1=Bazer |first1=Fuller W. |last2=Song |first2=Gwonhwa |last3=Kim |first3=Jinyoung |last4=Dunlap |first4=Kathrin A. |last5=Satterfield |first5=Michael Carey |last6=Johnson |first6=Gregory A. |last7=Burghardt |first7=Robert C. |last8=Wu |first8=Guoyao |author-link8=Guoyao Wu |date=1 January 2012 |title=Uterine biology in pigs and sheep |journal=Journal of Animal Science and Biotechnology |volume=3 |issue=1 |page=23 |doi=10.1186/2049-1891-3-23 |pmc=3436697 |pmid=22958877 |doi-access=free }}</ref> To sustain the pregnancy, the embryo signals to the corpus luteum with the hormones [[estradiol]] and [[prostaglandin E2]].<ref name="Ziecik, A. J. 2018">{{cite journal |last=Ziecik |first=A. J. |display-authors=etal |year=2018 |title=Regulation of the porcine corpus luteum during pregnancy |journal=Reproduction |volume=156 |issue=3 |pages=R57–R67 |doi=10.1530/rep-17-0662 |pmid=29794023 |doi-access=free}}</ref> This signaling acts on both the endometrium and luteal tissue to prevent the regression of the corpus luteum by activation of genes that are responsible for corpus luteum maintenance.<ref>{{cite journal |last=Waclawik |first=A. |display-authors=etal |year=2017 |title=Embryo-maternal dialogue during pregnancy establishment and implantation in the pig |journal=Molecular Reproduction and Development |volume=84 |issue=9 |pages=842–855 |doi=10.1002/mrd.22835 |pmid=28628266 |doi-access=free}}</ref> During mid to late pregnancy, the corpus luteum relies primarily on [[luteinizing hormone]] for maintenance until birth.<ref name="Ziecik, A. J. 2018"/><!--<ref>{{cite book |last=Farmer |first=Chantal |title=The gestating and lactating sow |publisher=Wageningen Academic Publishers |year=2015 |isbn=9789086868032 |location=The Netherlands |oclc=899008362}}</ref>-->

Archeological evidence indicates that medieval European pigs farrowed, or bore a litter of piglets, once per year.<ref>{{cite journal |last1=Ervynck |first1=Anton |last2=Dobney |first2=Keith |year=2002 |title=A Pig for all Seasons? Approaches to the Assessment of Second Farrowing in Archaeological Pig Populations |journal=Archaeofauna |issue=11 |pages=7–22 |doi=10.15366/archaeofauna2002.11.001 |url=https://revistas.uam.es/archaeofauna/article/download/8489/8868}}</ref> By the nineteenth century, European piglets routinely double-farrowed, or bore two litters of piglets per year. It is unclear when this shift occurred.<ref name="Bintliff Earle Peebles 2008 p. 305">{{cite book |last1=Bintliff |first1=J. |last2=Earle |first2=T. |last3=Peebles |first3=C. |title=A Companion to Archaeology |publisher=Wiley |year=2008 |isbn=978-0-470-99860-1 |url=https://books.google.com/books?id=7w1kGdMiwekC&pg=PA305 |page=305}}</ref> Pigs have a [[maximum life span]] of about 27 years.<ref name="pmid32361879">{{cite journal |last1=Hoffman |first1=J. |last2=Valencak |first2=T. G. |title=A short life on the farm: aging and longevity in agricultural, large-bodied mammals |journal=[[GeroScience]] |volume=42 |issue=3 |pages=909–922 |date=2020 |doi=10.1007/s11357-020-00190-4 |pmc=7286991 |pmid=32361879}}</ref>

=== Nest-building ===

A characteristic of pigs which they share with carnivores is [[nest-building]]. Sows root in the ground to create depressions the size of their body, and then build nest mounds, using twigs and leaves, softer in the middle, in which to give birth.  When the mound reaches the desired height, she places large branches, up to 2 metres in length, on the surface. She enters the mound and roots around to create a depression within the gathered material. She then gives birth in a lying position, unlike other artiodactyls which usually stand while birthing.<ref name="Clutton-Brock 1987"/>

Nest-building occurs during the last 24 hours before the onset of farrowing, and becomes most intense 12 to 6 hours before farrowing.<ref name="Algers 2007"/> The sow separates from the group and seeks a suitable nest site with well-drained soil and shelter from rain and wind. This provides the offspring with shelter, comfort, and thermoregulation. The nest provides protection against weather and predators, while keeping the piglets close to the sow and away from the rest of the herd. This ensures they do not get trampled on, and prevents other piglets from stealing milk from the sow.<ref name="Wischner 2009">{{cite journal |last1=Wischner |first1=D. |last2=Kemper |first2=N. |last3=Krieter |first3=J. |year=2009 |title=Nest-building behaviour in sows and consequences for pig husbandry |journal=Livestock Science |volume=124 |issue=1 |pages=1–8 |doi=10.1016/j.livsci.2009.01.015}}</ref> The onset of nest-building is triggered by a rise in prolactin level, caused by a decrease in progesterone and an increase in prostaglandin; the gathering of nest material seems to be regulated more by external stimuli such as temperature.<ref name="Algers 2007"/>

=== Nursing and suckling ===

Pigs have complex nursing and suckling behaviour.<ref name="Fraser, (1980)">{{cite journal |last=Fraser |first=D. |year=1980 |title=A review of the behavioural mechanisms of milk ejection of the domestic pig |url=https://animalstudiesrepository.org/cgi/viewcontent.cgi?article=1001&context=feebeh |journal=Applied Animal Ethology |volume=6 |issue=3 |pages=247–256 |doi=10.1016/0304-3762(80)90026-7|url-access=subscription }}</ref> Nursing occurs every 50–60 minutes, and the sow requires stimulation from piglets before milk let-down. Sensory inputs (vocalisation, odours from mammary and birth fluids, and hair patterns of the sow) are particularly important immediately post-birth to facilitate teat location by the piglets.<ref name="Rohde Parfet and Gonyou, (1991)">{{cite journal |last1=Rohde Parfet |first1=K.A. |last2=Gonyou |first2=H.W. |year=1991 |title=Attraction of newborn piglets to auditory, visual, olfactory and tactile stimuli |journal=[[Journal of Animal Science]] |volume=69 |issue=1 |pages=125–133 |doi=10.2527/1991.691125x |pmid=2005005 |s2cid=31788525}}</ref> Initially, the piglets compete for position at the udder; then the piglets massage around their respective teats with their snouts, during which time the sow grunts at slow, regular intervals. Each series of grunts varies in frequency, tone and magnitude, indicating the stages of nursing to the piglets.<ref name="Algers, (1993)">{{cite journal |last=Algers |first=B |year=1993 |title=Nursing in pigs: communicating needs and distributing resources |url=https://www.researchgate.net/publication/14973674 |journal=[[Journal of Animal Science]] |volume=71 |issue=10 |pages=2826–2831 |doi=10.2527/1993.71102826x |pmid=8226386}}</ref>

The phase of competition for teats and of nosing the udder lasts for about a minute, ending when milk begins to flow. The piglets then hold the teats in their mouths and suck with slow mouth movements (one per second), and the rate of the sow's grunting increases for approximately 20 seconds. The grunt peak in the third phase of suckling does not coincide with milk ejection, but rather the release of oxytocin from the pituitary into the bloodstream.<ref name="Castren et al., (1989)">{{cite journal |last1=Castren |first1=H. |last2=Algers |first2=B. |last3=Jensen |first3=P. |last4=Saloniemi |first4=H. |year=1989 |title=Suckling behaviour and milk consumption in newborn piglets as a response to sow grunting |journal=Applied Animal Behaviour Science |volume=24 |issue=3 |pages=227–238 |doi=10.1016/0168-1591(89)90069-5}}</ref> Phase four coincides with the period of main milk flow (10–20 seconds) when the piglets suddenly withdraw slightly from the udder and start sucking with rapid mouth movements of about three per second. The sow grunts rapidly, lower in tone and often in quick runs of three or four, during this phase. Finally, the flow stops and so does the grunting of the sow. The piglets may dart from teat to teat and recommence suckling with slow movements, or nosing the udder. Piglets massage and suckle the sow's teats after milk flow ceases as a way of letting the sow know their nutritional status. This helps her to regulate the amount of milk released from that teat in future sucklings. The more intense the post-feed massaging of a teat, the more milk that teat later releases.<ref name="Jensen et al., (1998)">{{cite journal |last1=Jensen |first1=P. |last2=Gustafsson |first2=G. |last3=Augustsson |first3=H. |year=1998 |title=Massaging after milk ejection in domestic pigs – an example of honest begging? |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=55 |issue=4 |pages=779–786 |doi=10.1006/anbe.1997.0651 |pmid=9632466 |s2cid=12493158}}</ref>

<gallery class=center mode=nolines widths=220 heights=220>
File:Pig, Kilcullen.jpg|Sows typically have 12–14 nipples.
File:PigCochon allaitant.jpg|A sow with suckling piglets
</gallery>

=== Teat order ===

In pigs, [[Dominance (ethology)|dominance]] hierarchies are formed at an early age. Piglets are precocious, and attempt to suckle soon after being born. The piglets are born with sharp teeth and fight for the [[anterior]] teats, as these produce more milk. Once established, this teat order remains stable; each piglet tends to feed on a particular teat or group of teats.<ref name="Clutton-Brock 1987"/> Stimulation of the anterior teats appears to be important in causing milk letdown,<ref name="Fraser, (1973)">{{cite journal |last=Fraser |first=D. |year=1973 |title=The nursing and suckling behaviour in pigs. I. The importance of stimulation of the anterior teats |journal=British Veterinary Journal |volume=129 |issue=4 |pages=324–336 |doi=10.1016/s0007-1935(17)36434-5 |pmid=4733757}}</ref> so it might be advantageous to the entire litter to have these teats occupied by healthy piglets. Piglets locate teats by sight and then by olfaction.<ref name="Jeppesen, (1982)">{{cite journal |last=Jeppesen |first=L.E. |year=1982 |title=Teat-order in groups of piglets reared on an artificial sow. II. Maintenance of teat order with some evidence for the use of odour cues |journal=Applied Animal Ethology |volume=8 |issue=4 |pages=347–355 |doi=10.1016/0304-3762(82)90067-0}}</ref>

== Behaviour ==

=== Social ===

[[File:Yorkshire pigs at animal sanctuary.jpg|thumb|[[American Yorkshire]] pigs in a wallow]]

Pig behaviour is intermediate between that of other [[artiodactyls]] and of [[carnivora|carnivores]].<ref name="Clutton-Brock 1987">{{cite book |last=Clutton-Brock |first=Juliet |year=1987 |title=A Natural History of Domesticated Mammals |publisher=[[Cambridge University Press]] |location=Cambridge |pages=73–74}}</ref> Pigs seek out the company of other pigs and often huddle to maintain physical contact, but they do not naturally form large herds. They live in groups of about 8–10 adult sows, some young individuals, and some single males.<ref name="Algers 2007">{{cite journal |last1=Algers |first1=Bo |last2=Uvnäs-Moberg |first2=Kerstin |date=1 June 2007 |title=Maternal behavior in pigs |journal=Hormones and Behavior |series=Reproductive Behavior in Farm and Laboratory Animals: 11th Annual Meeting of the Society for Behavioral Neuroendocrinology |volume=52 |issue=1 |pages=78–85 |doi=10.1016/j.yhbeh.2007.03.022 |pmid=17482189 |s2cid=9742677}}</ref> Pigs confined in a simplified, crowded, or uncomfortable environment may resort to [[Tail biting in pigs|tail-biting]]; farmers sometimes [[Docking (animal)|dock the tails]] of pigs to prevent the problem, or may enrich the environment with toys or other objects to reduce the risk.<ref name="AHDB">{{cite web |title=Tail docking and tail biting in pigs |url=https://ahdb.org.uk/knowledge-library/tail-docking-and-tail-biting-in-pigs |publisher=Animal Husbandry Development Board |access-date=4 March 2024}}</ref><ref name="NADIS">{{Cite web |url=http://www.nadis.org.uk/bulletins/tail-biting.aspx |title=Pig Health- Tail Biting |website=[[National Animal Disease Information Service]] |access-date=4 March 2024 |url-status=dead |archive-url=https://web.archive.org/web/20130113093850/http://www.nadis.org.uk/bulletins/tail-biting.aspx |archive-date=13 January 2013}}</ref>

=== Temperature control ===

Because of their relative lack of sweat glands, pigs often control their body temperature using behavioural thermoregulation. [[Wallowing]], coating the body with mud, is a common behaviour.<ref name="Bracke 2011" /> They do not submerge completely under the mud, but vary the depth and duration of wallowing depending on environmental conditions.<ref name="Bracke 2011"/> Adult pigs start wallowing once the ambient temperature is around {{cvt|17–21|C}}. They cover themselves in mud from head to tail.<ref name="Bracke 2011"/> They may use mud as a sunscreen, or to keep parasites away.<ref name="Bracke 2011"/> Most bristled pigs "blow their coat", meaning that they shed most of the longer, coarser stiff hair once a year, usually in spring or early summer, to prepare for the warmer months ahead.<ref>{{cite web |date=2 April 2016 |title=Blowing Coat – Mini Pig Shedding FAQ |url=http://americanminipigassociation.com/educational/blowing-coat-mini-pig-shedding |website=americanminipigassociation.com}}</ref>

=== Eating, feeding, sleeping ===

[[File:Farm_Pigs_Feeding.jpg|thumb|Pigs around a rotary feeder]]

Where pigs are allowed to roam freely, they walk roughly 4 km daily, [[scavenger|scavenging]] within a home range of around a hectare. Farmers in Africa often choose such a low-input, free-range production system.<ref name="Thomas de Glanville Cook Fèvre 2013">{{cite journal |last1=Thomas |first1=Lian F |last2=de Glanville |first2=William A |last3=Cook |first3=Elizabeth A |last4=Fèvre |first4=Eric M |title=The spatial ecology of free-ranging domestic pigs (Sus scrofa) in western Kenya |journal=BMC Veterinary Research |volume=9 |issue=1 |date=2013 |page=46 |issn=1746-6148 |pmid=23497587 |pmc=3637381 |doi=10.1186/1746-6148-9-46 |doi-access=free}}</ref>

If conditions permit, pigs feed continuously for many hours and then sleep for many hours, in contrast to [[ruminants]], which tend to feed for a short time and then sleep for a short time. Pigs are [[omnivore|omnivorous]] and versatile in their feeding behaviour. They primarily eat leaves, stems, roots, fruits, and flowers.<ref>{{cite journal |last1=Kongsted |first1=A. G. |last2=Horsted |first2=K. |last3=Hermansen |first3=J. E. |year=2013 |title=Free-range pigs foraging on Jerusalem artichokes (Helianthus tuberosus L.) – Effect of feeding strategy on growth, feed conversion and animal behaviour |journal=Acta Agriculturae Scandinavica, Section A |volume=63 |issue=2 |pages=76–83 |doi=10.1080/09064702.2013.787116 |s2cid=84886946}}</ref>

{{Anchor|Rooting}}Rooting is an instinctual comforting behaviour in pigs characterized by nudging the snout into something. It first happens when piglets are born to obtain their mother's milk, and can become a habitual, obsessive behaviour, most prominent in animals [[Weaning|weaned]] too early. Pigs root and dig into the ground to forage for food. Rooting is also a means of communication.<ref name="Minipigassoc 2016">{{cite web |title=Rooting & Nudging Behaviors in Mini Pigs |date=8 June 2016 |url=http://americanminipigassociation.com/educational/rooting-behaviors-in-mini-pigs |website=americanminipigassociation.com}}</ref>

=== Intelligence ===

[[File:Croney 2021 pig using controller.jpg|thumb|A pig using a specifically designed joystick<ref name="Croney2021" />]]

Pigs are relatively intelligent animals, roughly on par with [[dog]]s. They distinguish each other as individuals, spend time in play, and form structured communities. They have good long-term memory and they experience emotions, changing their behaviour in response to the emotional states of other pigs. In terms of experimental tasks, pigs can perform tasks that require them to identify the locations of objects; they can solve mazes; and they can work with a simple language of symbols. They display [[Mirror test|self-recognition in a mirror]]. Pigs have been trained to associate different sorts of music (Bach and a military march) with food and social isolation respectively, and could communicate the resulting positive or negative emotion to untrained pigs.<ref name="Colvin Marino NHM">{{cite web |last1=Colvin |first1=Christina M. |last2=Marino |first2=Lori |title=Signs of Intelligent Life |website=Natural History Magazine |url=http://www.naturalhistorymag.com/features/122899/signs-of-intelligent-life |access-date=3 June 2019 }}</ref><ref name="nytimes2009-11-9">{{cite news |last=Angier |first=Natalie |date=9 November 2009 |title=Pigs Prove to Be Smart, if Not Vain |newspaper=[[The New York Times]] |url=https://www.nytimes.com/2009/11/10/science/10angier.html |access-date=28 July 2010}}</ref> Pigs can be trained to use a [[joystick]] with their snout to select a target on screen.<ref name="Croney2021">{{cite journal |last1=Croney |first1=Candace C. |last2=Boysen |first2=Sarah T. |title=Acquisition of a Joystick-Operated Video Task by Pigs (Sus scrofa) |journal=[[Frontiers in Psychology]] |volume=12 |date=11 February 2021 |doi=10.3389/fpsyg.2021.631755 |doi-access=free |pmid=33679560 |pmc=7928376 }}</ref>

=== Senses ===

[[File:Cochon truffier.JPG|thumb|left|A [[truffle hog|trained pig]] using its sensitive nose to assist the search for wild [[truffle]]s in France]]

Pigs have [[Panorama|panoramic]] vision of approximately 310° and [[binocular vision]] of 35° to 50°. It is thought they have no [[Accommodation (eye)|eye accommodation]].<ref>{{cite web |title=Animalbehaviour.net (Pigs) |url=http://animalbehaviour.net/JudithKBlackshaw/Chapter3e.htm |url-status=dead |archive-url=https://web.archive.org/web/20120317194223/http://animalbehaviour.net/JudithKBlackshaw/Chapter3e.htm |archive-date=17 March 2012 |access-date=9 December 2012}}</ref> Other animals that have no accommodation, e.g. sheep, lift their heads to see distant objects.<ref>{{cite web |title=Animalbehaviour.net (Sheep) |url=http://animalbehaviour.net/JudithKBlackshaw/Chapter3b.htm |url-status=dead |archive-url=https://web.archive.org/web/20121226191014/http://animalbehaviour.net/JudithKBlackshaw/Chapter3b.htm |archive-date=26 December 2012 |access-date=9 December 2012}}</ref> The extent to which pigs have colour vision is still a source of some debate; however, the presence of [[cone cell]]s in the retina with two distinct wavelength sensitivities (blue and green) suggests that at least some colour vision is present.<ref name="Lomas et al., 1998)">{{cite journal |last1=Lomas |first1=C.A. |last2=Piggins |first2=D. |last3=Phillips |first3=C.J.C. |year=1998 |title=Visual awareness |journal=Applied Animal Behaviour Science |volume=57 |issue=3–4 |pages=247–257 |doi=10.1016/s0168-1591(98)00100-2}}</ref>

Pigs have a well-developed sense of smell; this is exploited in Europe where [[truffle hog|trained pigs]] find underground [[truffles]].<ref>{{cite news |last=Sullivan |first=Walter |title=Truffles: Why Pigs Can Sniff Them Out |date=24 March 1982 |url=https://www.nytimes.com/1982/03/24/garden/truffles-why-pigs-can-sniff-them-out.html |work=[[The New York Times]]}}</ref> Pigs have 1,113 genes for smell receptors, compared to 1,094 in dogs; this may indicate an acute sense of smell, but against this, insects have only around 50 to 100 such genes but make extensive use of olfaction.<ref name="McGlone Archer Henderson 2022">{{cite journal |last1=McGlone |first1=John J. |last2=Archer |first2=Courtney |last3=Henderson |first3=Madelyn |title=Interpretive review: Semiochemicals in domestic pigs and dogs |journal=Frontiers in Veterinary Science |volume=9 |date=2022-10-25 |issn=2297-1769 |pmid=36387395 |pmc=9640746 |doi=10.3389/fvets.2022.967980 |doi-access=free}}</ref> Olfactory rather than visual stimuli are used in the identification of other pigs.<ref name="Houpt 2018">{{cite book |last=Houpt |first=Katherine A. |chapter=2. Aggression and Social Structure |title=Domestic Animal Behavior for Veterinarians and Animal Scientists |publisher=John Wiley & Sons |date=2018-03-27 |isbn=978-1-119-23276-6}}</ref> Hearing is well developed; sounds are localised by moving the head. Pigs use auditory stimuli extensively for communication in all social activities.<ref name="Gonyou 2001">{{cite book |last=Gonyou |first=H. W. |chapter=The Social Behaviour of Pigs |pages=147–176 |editor1=Keeling, L. J. |editor2=Gonyou, H. W. |title=Social behaviour in farm animals |publisher=CABI Publishing |year=2001 |isbn=978-0-85199-397-3 |doi=10.1079/9780851993973.0000}}</ref> Alarm or aversive stimuli are transmitted to other pigs not only by auditory cues but also by [[pheromone]]s.<ref name="Vieuille-Thomas and Signoret, (1992)">{{cite journal |last1=Vieuille-Thomas |first1=C. |last2=Signoret |first2=J. P. |year=1992 |title=Pheromonal transmission of an aversive experience in domestic pigs |journal=Journal of Chemical Ecology |volume=18 |issue=9 |pages=1551–1557 |doi=10.1007/bf00993228 |pmid=24254286 |bibcode=1992JCEco..18.1551V |s2cid=4386919}}</ref> Similarly, recognition between the sow and her piglets is by olfactory and vocal cues.<ref name="Jensen and Redbo, (1987)">{{cite journal |last1=Jensen |first1=P. |last2=Redbo |first2=I. |year=1987 |title=Behaviour during nest leaving in free-ranging domestic pigs |journal=[[Applied Animal Behaviour Science]] |volume=18 |issue=3–4 |pages=355–362 |doi=10.1016/0168-1591(87)90229-2}}</ref>

== Pests and diseases ==

[[File:Trichinella spiralis larvae within muscle.jpg|thumb|''[[Trichinella spiralis]]'' larvae in uncooked pig meat]]

Pigs are subject to many pests and diseases which can seriously affect productivity and cause death. These include [[Parasitism|parasite]]s such as ''[[Ascaris]]'' roundworms, [[virus]] diseases such as the [[tick]]-borne [[African swine fever virus|African Swine Fever]], bacterial infections such as ''[[Clostridium]]'', [[arthritis]] caused by ''[[Mycoplasma]]'', and stillbirths caused by [[Parvoviridae|Parvovirus]].<ref>{{cite web |title=Disease A-Z for Pigs |url=https://www.nadis.org.uk/disease-a-z/pigs/ |website=NADIS Animal Health Skills |access-date=15 February 2024}}</ref>

Some parasites of pigs are a [[public health]] risk as they can be transmitted to humans in undercooked pork. These are the pork tapeworm ''[[Taenia solium]]''; a protozoan, ''[[Toxoplasma gondii]]''; and a nematode, ''[[Trichinella spiralis]]''. Transmission can be prevented by thorough sanitation on the farm; by meat inspection and careful commercial processing; and by thorough cooking, or alternatively by sufficient freezing and curing.<ref name="Gamble 1997">{{cite journal |last=Gamble |first=H. R. |title=Parasites associated with pork and pork products |journal=Revue Scientifique et Technique de l'OIE |volume=16 |issue=2 |date=1997-08-01 |doi=10.20506/rst.16.2.1032 |pages=496–506|pmid=9501363 }}</ref>

== In agriculture ==

{{see|Pig farming#Terminology}}

=== Production ===

{{Main|Pig farming}}

Pigs have been raised outdoors, and sometimes allowed to [[foraging|forage]] in woods or pastures. In industrialized nations, pig production has largely switched to large-scale [[intensive pig farming]]. This has lowered production costs but has caused concern about possible [[Cruelty to animals|cruelty]]. As consumers have become concerned with the humane treatment of livestock, demand for pasture-raised pork in these nations has increased.<ref>{{cite news |last=Strom |first=Stephanie |date=2 January 2014 |title=Demand Grows for Hogs That Are Raised Humanely Outdoors |work=[[The New York Times]] |url=https://www.nytimes.com/2014/01/21/business/demand-grows-for-hogs-that-are-raised-humanely.html |access-date=15 April 2015}}</ref> Most pigs in the US receive [[ractopamine]], a [[Beta-adrenergic agonist|beta-agonist drug]], which promotes muscle instead of fat and quicker weight gain, requiring less feed to reach finishing weight, and producing less [[manure]]. China has requested that pork exports be ractopamine-free.<ref>{{cite web |last=Charles |first=Dan |date=14 August 2015 |title=A Muscle Drug For Pigs Comes Out Of The Shadows |publisher=[[NPR]] |url=https://www.npr.org/sections/thesalt/2015/08/14/432102733/a-muscle-drug-for-pigs-comes-out-of-the-shadows}}</ref> With a population of around 1 billion individuals, the domesticated pig is one of the most numerous large mammals on the planet.<ref>{{cite web |title=PSD Online |url=http://www.fas.usda.gov/psdonline/psdQuery.aspx |website=fas.usda.gov}}</ref><ref>[http://www.fas.usda.gov/psdonline/psdReport.aspx?hidReportRetrievalName=Swine+Summary+Selected+Countries&hidReportRetrievalID=1649&hidReportRetrievalTemplateID=7 Swine Summary Selected Countries] {{webarchive |url=https://web.archive.org/web/20120329181120/http://www.fas.usda.gov/psdonline/psdReport.aspx?hidReportRetrievalName=Swine+Summary+Selected+Countries&hidReportRetrievalID=1649&hidReportRetrievalTemplateID=7 |date=29 March 2012}}, United States Department of Agriculture, Foreign Agricultural Service, (total number is Production (Pig Crop) plus Total Beginning Stocks</ref>

Like all animals, pigs are susceptible to adverse impacts from [[climate change]], such as [[heat stress]] from increased annual temperatures and more intense [[heatwave]]s. Heat stress has increased rapidly between 1981 and 2017 on pig farms in Europe. Installing a [[ground-coupled heat exchanger]] is an effective intervention.<ref name="Mikovits2019">{{cite journal |last1=Mikovits |first1=Christian |last2=Zollitsch |first2=Werner |last3=Hörtenhuber |first3=Stefan J. |last4=Baumgartner |first4=Johannes |last5=Niebuhr |first5=Knut |last6=Piringer |first6=Martin |last7=Anders |first7=Ivonne |last8=Andre |first8=Konrad |last9=Hennig-Pauka |first9=Isabel |last10=Schönhart |first10=Martin |last11=Schauberger |first11=Günther |display-authors=6 |date=22 January 2019 |title=Impacts of global warming on confined livestock systems for growing-fattening pigs: simulation of heat stress for 1981 to 2017 in Central Europe |journal=International Journal of Biometeorology |volume=63 |issue=2 |pages=221–230 |doi=10.1007/s00484-018-01655-0 |pmid=30671619 |bibcode=2019IJBm...63..221M |s2cid=58951606|doi-access=free }}</ref>

<gallery mode=packed heights=150>
File:NMA.0063325 Interiör från svinhus, Bjärka-Säby, Östergötland.jpg|Indoor pig farm, Sweden, 1911
File:Bundesarchiv Bild 183-69156-0002, Rhin-Havelluch, Sauenstall mit Ferkelbox.jpg|Sow in stall with separate piglet balcony to prevent crushing, Germany, 1959
Happy Hogs - geograph.org.uk - 279094.jpg|[[Free range]] pigs with field shelters, England, 2006
</gallery>
<gallery class=center mode=nolines widths=220 heights=220 caption="[[FAO]] data for 2021">
File:World Production Of Meat, Main Items.svg|Pork is tied with chicken as the most commonly consumed meat worldwide.
File:Pork_production_1961_2021.png|Pork production has grown substantially over the recent 60 years.
File:Pigmeat-production-tonnes.png|Production of pork worldwide, by country in 2021.
</gallery>

=== Breeds ===

{{Main|List of pig breeds}}

Around 600 [[breed]]s of pig have been created by farmers around the world, mainly in Europe and Asia, differing in coloration, shape, and size.<ref name="Miao Chen Zhang Wang 2023">{{cite journal |last1=Miao |first1=Jian |last2=Chen |first2=Zitao |last3=Zhang |first3=Zhenyang |last4=Wang |first4=Zhen |last5=Wang |first5=Qishan |last6=Zhang |first6=Zhe |last7=Pan |first7=Yuchun |title=A web tool for the global identification of pig breeds |journal=Genetics Selection Evolution |volume=55 |issue=1 |date=2023-03-21 |page=18 |issn=1297-9686 |pmid=36944938 |pmc=10029154 |doi=10.1186/s12711-023-00788-0 |doi-access=free}}</ref> According to [[The Livestock Conservancy]], as of 2016, three breeds of pig are critically rare (having a global population of fewer than 2000). They are the [[Choctaw hog]], the [[Mulefoot]], and the [[Ossabaw Island hog]].<ref>{{cite web |title=The Livestock Conservancy |url=http://livestockconservancy.org/index.php/heritage/internal/conservation-priority-list#Pigs |access-date=7 March 2017 |publisher=livestock Conservancy}}</ref> The smallest known pig breed in the world is the [[Göttingen minipig]], typically weighing about {{convert|26|kg|lb}} as a healthy, full-grown adult.<ref>{{cite web |title=Taking good care of Ellegaard Göttingen Minipigs® |url=https://minipigs.dk/fileadmin/filer/pdf/Taking_good_care_of_Ellegaard_Goettingen_Minipigs_13.03.13.pdf |access-date=2 July 2018 |website=Ellegaard Göttingen Minipigs |archive-date=19 April 2016 |archive-url=https://web.archive.org/web/20160419112736/http://minipigs.dk/fileadmin/filer/pdf/Taking_good_care_of_Ellegaard_Goettingen_Minipigs_13.03.13.pdf |url-status=dead }}</ref>

== As pets ==
[[File:Mini_pig_2.jpg|right|thumb|A mini pet pig]]
[[Vietnamese Pot-bellied]] pigs, a [[Miniature pig|miniature breed of pig]], have been kept as pets in the United States, beginning in the latter half of the 20th century.

Pigs are intelligent, social creatures. They are considered [[hypoallergenic]] and are known to do quite well with people who have the usual animal allergies. Since these animals are known to have a life expectancy of 15 to 20 years, they require a long-term commitment.

Given pigs are bred primarily as livestock and have not been bred as companion animals for very long, selective breeding for a placid or biddable temperament is not well established. Pigs have radically different [[Animal psychology|psychology]] and behaviours compared to dogs, and exhibit [[Fight-or-flight response|fight-or-flight]] instincts, an independent nature, and natural [[assertiveness]].<ref>{{Cite web |title=Info/Resource - Pigs 4 Ever - Gifts, supplies and resources for Pot-Bellied Pigs |url=https://pigs4ever.com/resource.php?recordID=6#:~:text=Pot%20belly%20pigs%20and%20children%20sometimes%20do%20not,see%20small%20children%20as%20something%20they%20can%20dominate. |access-date=11 October 2020 |website=pigs4ever.com}}</ref> Male and female swine that have not been de-sexed may express unwanted aggressive behavior, and are prone to developing serious health issues.<ref>{{Cite web |title=Spay and Neuter – American Mini Pig Association |url=http://americanminipigassociation.com/owners/helpful-owner-articles/spay-and-neuter |website=americanminipigassociation.com|date=18 September 2014 }}</ref> As [[Pig#Rooting|rooting]] is found to be comforting, pigs kept in the house may root household objects, furniture or surfaces. Pet pigs should be let outside to allow them to fulfill their natural desire of rooting around.

== Economy ==

{{Infobox agricultural production|year=2019|amount1=310.4|amount10=12.7|amount9=14.1|amount8=18.4|amount7=19.6|amount6=21.6|amount5=23.7|amount4=40.6|amount3=78.7|amount2=143.1|animal=pig|country1=China (Mainland)|country10=Philippines|country9=Canada|country8=Mexico|country7=Vietnam|country6=Myanmar|country5=Russia|country4=Brazil|country3=United States|country2=European Union|world=850.3}}

Approximately 1.5&nbsp;billion pigs are slaughtered each year for meat.<ref>{{cite web |title=FAOSTAT |url=http://www.fao.org/faostat/en/#data/QL |access-date=25 October 2019 |website=fao.org}}</ref>

The pork belly [[futures contract]] became an icon of [[commodities trading]]. It appears in depictions of the arena in popular entertainment, such as the 1983 film ''[[Trading Places]]''.<ref name="Davey 2011">{{cite news |last=Davey |first=Monica |title=Trade in Pork Bellies Comes to an End, but the Lore Lives |newspaper=[[The New York Times]] |date=30 July 2011 |url=https://www.nytimes.com/2011/07/31/us/31porkbelly.html?_r=0}}</ref> Trade in pork bellies declined, and they were delisted from the [[Chicago Mercantile Exchange]] in 2011.<ref name="Davey 2011"/><ref>{{cite web |url=http://www.ftpress.com/articles/article.aspx?p=1436919&amp;seqNum=8 |title=A Crash Course in Commodities |first=Carley |last=Garner |publisher=[[FT Press]] |date=13 January 2010 |access-date=6 December 2011 |archive-date=21 October 2013 |url-status=dead |archive-url=https://web.archive.org/web/20131021185542/http://www.ftpress.com/articles/article.aspx?p=1436919&amp;seqNum=8}}</ref>

In 2023, China produced more pork than any other country, 55 million tonnes, followed by the European Union with 22.8 million tonnes and the United States with 12.5 million tonnes. Global production in 2023 was 120 million tonnes.<ref>{{cite web |title=Global pork production in 2022 and 2023, by country |url=https://www.statista.com/statistics/273232/net-pork-production-worldwide-by-country/ |website=Statista |access-date=15 February 2024}}</ref> India, despite its large population, consumed under 0.3 million tonnes of pork in 2023.<ref>{{cite web |title=Consumption volume of pork in India from 2013 to 2023 |url=https://www.statista.com/statistics/826720/india-pig-meat-consumption/ |publisher=Statista |access-date=15 February 2024}}</ref> International trade in pork (meat not consumed in the producing country) reached 13 million tonnes in 2020.<ref>{{cite web |last1=Ter Beek |first1=Vincent |title=The remarkable dynamics of global pig meat trade |url=https://www.pigprogress.net/the-industrymarkets/market-trends-analysis-the-industrymarkets-2/the-remarkable-dynamics-of-global-pig-meat-trade/ |website=Pig Progress |access-date=15 February 2024 |date=13 December 2023}}</ref>

== Uses ==

=== Products ===

[[Pig farming|Pigs are farmed]] primarily for meat, called [[pork]]. Pork is eaten in the form of pork chops, loin or rib roasts, shoulder joints, steaks, and loin (also called fillet). The many meat products made from pork include [[ham]], [[bacon]] (mainly from the back and belly), and [[sausage]]s.<ref>{{cite web |title=Pork Cuts |url=https://www.pork.org/cuts/ |publisher=National Pork Board |access-date=15 February 2024}}</ref> Pork is further made into [[charcuterie]] products such as [[Terrine (food)|terrine]]s, [[galantine]]s, [[pâté]]s and [[confit]]s.<ref>{{cite book |last=Davidson |first=Alan |author-link=Alan Davidson (food writer) |chapter=Charcuterie (with links to other chapters: Hams, Sausages, Terrines, Pâtés, Galantines, Crepinettes, Andouille and Andouillette, Blood Sausages, White Pudding, Tripe) |editor-last=Jaine |editor-first=Tom |title=[[The Oxford Companion to Food]] |edition=3rd |location=Oxford |publisher=[[Oxford University Press]] |year=2014 |isbn=978-0-19-967733-7 |page=161}}</ref> Some sausages such as [[salami]] are fermented and air-dried, to be eaten raw. There are many types, the original Italian varieties including Genovese, Milanese, and Cacciatorino, with spicier kinds from the South of Italy including Calabrese, Napoletano, and Peperone.<ref>{{cite book |last=Davidson |first=Alan |author-link=Alan Davidson (food writer) |chapter=Sausages of Italy |editor-last=Jaine |editor-first=Tom |title=The Oxford Companion to Food |edition=3rd |location=Oxford |publisher=[[Oxford University Press]] |year=2014 |isbn=978-0-19-967733-7 |page=719}}</ref>

The hide is made into pigskin [[leather]], which is soft and durable; it can be brushed to form [[suede]] leather. These are used for products such as [[glove]]s, [[wallet]]s, suede shoes, and [[leather jacket]]s.<ref>{{cite web |title=Pig leather |url=https://www.leather-dictionary.com/index.php/Pig_leather#Pig_leather_clothing |website=Leather Dictionary |access-date=15 February 2024}}</ref> In the [[16th century]], pig skin was the most popular book-binding material in [[Germany]], though [[cattle|calf]] skin was more common elsewhere.<ref>{{cite web |title=Cover to Cover: Exposing the Bookbinder's Ancient Craft |url=https://www.adelaide.edu.au/library/special/exhibitions/cover-to-cover/leather/ |publisher=The [[University of Adelaide]] |access-date=6 March 2024}}</ref>

<gallery class=center mode=nolines widths=220 heights=220>
File:Pork chops 167541218.jpg|Pork chops
File:RawBacon.JPG|Streaky or side [[bacon]]
File:Salami aka.jpg|[[Salami]], a fermented and air-dried sausage, originally made in Italy
File:Manuale._Aus_der_Kirchen_Agenda_-_Upper_cover_(c29h6).jpg|A 16th century book bound in pig skin
File:Woman's Gloves (England), ca. 1820 (CH 18564653).jpg|A woman's suede gloves, England, c. 1820
</gallery>

=== In medicine ===

[[File:Gutierrez 2015 pig research.jpg|thumb|The growth in publication of medical research papers using pigs and miniature pigs, and the research done on miniature pigs by organ system<ref name="Gutierrez2015">{{cite journal |last1=Gutierrez |first1=Karina |last2=Dicks |first2=Naomi |last3=Glanzner |first3=Werner G. |last4=Agellon |first4=Luis B. |last5=Bordignon |first5=Vilceu |title=Efficacy of the porcine species in biomedical research |journal=[[Frontiers in Genetics]] |volume=6 |date=16 September 2015 |page=293 |doi=10.3389/fgene.2015.00293 |doi-access=free |pmid=26442109 |pmc=4584988 }}</ref>]]

Pigs, both as live animals and as a source of post-mortem tissues, are valuable animal models because of their biological, physiological, and anatomical similarities to human beings. For instance, human skin is very similar to the pigskin, therefore pigskin has been used in many preclinical studies.<ref name="porcine2018Janu">{{cite web |last=Herron |first=Alan J. |date=5 December 2009 |title=Pigs as Dermatologic Models of Human Skin Disease |url=http://www.ivis.org/proceedings/acvp/2009/Herron.pdf?LA=1 |access-date=27 January 2018 |website=ivis.org |publisher=DVM Center for Comparative Medicine and Department of Pathology Baylor College of Medicine Houston, Texas}}</ref><ref name="porcine2018Janu2">{{cite web |last1=Liu |first1=J. |last2=Kim |first2=L. |last3=Madsen |first3=T. |last4=Bouchard |first4=G. F. |title=Comparison of Human, Porcine and Rodent Wound Healing With New Miniature Swine Study Data |url=http://www.sinclairresearch.com/assets/25_Wound-Healing-AALAS-2009.pdf |access-date=27 January 2018 |website=sinclairresearch.com |publisher=Sinclair Research Centre, Auxvasse, MO, USA; Veterinary Medical Diagnostic Laboratory, Columbia, Missouri |archive-date=27 January 2018 |archive-url=https://web.archive.org/web/20180127084036/http://www.sinclairresearch.com/assets/25_Wound-Healing-AALAS-2009.pdf |url-status=dead }}</ref>

Pigs are good non-human candidates for [[organ donation]] to humans, and in 2021 became the first animal to successfully [[xenotransplantation|donate an organ to a human]] body.<ref>{{cite web |title=Successful pig-to-human kidney transplant a "transformative moment" |url=https://www.yahoo.com/entertainment/successful-pig-human-kidney-transplant-130401356.html |access-date=2 November 2021 |website=www.yahoo.com |date=20 October 2021}}</ref><ref>{{cite news |last=Lapid |first=Nancy |date=20 October 2021 |title=U.S. surgeons successfully test pig kidney transplant in human patient |work=[[Reuters]] |url=https://www.reuters.com/business/healthcare-pharmaceuticals/us-surgeons-successfully-test-pig-kidney-transplant-human-patient-2021-10-19/ |access-date=2 November 2021}}</ref> The procedure used a donor pig genetically engineered not to have a specific carbohydrate that the human body considers a threat–[[Galactose-alpha-1,3-galactose]].<ref>{{cite web |title=Progress in Xenotransplantation Opens Door to New Supply of Critically Needed Organs |url=https://nyulangone.org/news/progress-xenotransplantation-opens-door-new-supply-critically-needed-organs |access-date=2 November 2021 |website=NYU Langone News}}</ref> Pigs are good for human donation as the risk of cross-species disease transmission is reduced by the considerable [[Phylogenetics|phylogenetic]] distance from humans.<ref name="Dooldeniya2003">{{cite journal |last1=Dooldeniya |first1=M. D. |last2=Warrens |first2=A. N. |year=2003 |title=Xenotransplantation: Where are we today? |journal=[[Journal of the Royal Society of Medicine]] |volume=96 |issue=3 |pages=111–117 |doi=10.1177/014107680309600303 |pmc=539416 |pmid=12612110}}</ref> They are readily available, and the danger of creating new human diseases is low as domesticated pigs have been in close contact with humans for thousands of years.<ref name="Taylor2007">Taylor, L. (2007) [http://www.emedicine.com/med/topic3715.htm Xenotransplantation]. Emedicine.com</ref>

== Impact of pig husbandry ==

=== On public health ===

{{further|Zoonotic disease}}

Pig farms can serve as reservoirs of viral diseases that are dangerous to humans and so contribute to their outbreaks in human populations.<ref name="McLean2022" /> The [[2009 swine flu pandemic]] was caused by an [[influenza A]] variant which had first emerged in pigs.<ref>{{cite journal |last1=Mena |first1=Ignacio |last2=Nelson |first2=Martha I. |last3=Quezada-Monroy |first3=Francisco |last4=Dutta |first4=Jayeeta |last5=Cortes-Fernández |first5=Refugio |last6=Lara-Puente |first6=J Horacio |last7=Castro-Peralta |first7=Felipa |last8=Cunha |first8=Luis F. |last9=Trovão |first9=Nídia S. |last10=Lozano-Dubernard |first10=Bernardo |last11=Rambaut |first11=Andrew |last12=van Bakel |first12=Harm |last13=García-Sastre |first13=Adolfo |display-authors=6 |title=Origins of the 2009 H1N1 influenza pandemic in swine in Mexico |journal=eLife |volume=5 |date=28 June 2016 |issn=2050-084X |pmid=27350259 |pmc=4957980 |doi=10.7554/eLife.16777 |doi-access=free}}</ref> Pigs were also essential to the first outbreak of the [[Nipah virus]] in 1999, with 93% of the infected humans having had contact with pigs.<ref name="McLean2022" /> While [[Japanese encephalitis]] is primarily spread by [[mosquito]]es, pigs are a known intermediary host.<ref name="WHO2015">{{cite web |title=Japanese encephalitis |url=https://www.who.int/mediacentre/factsheets/fs386/en/ |website=[[World Health Organization]] |access-date=29 October 2017 |date=December 2015 |url-status=live |archive-url=https://web.archive.org/web/20170713162555/http://www.who.int/mediacentre/factsheets/fs386/en/ |archive-date=13 July 2017 |df=dmy-all}}</ref> There is also a potential for porcine [[coronavirus]]es such as [[porcine epidemic diarrhea virus]] or [[swine acute diarrhea syndrome coronavirus]] to spill over into human populations.<ref name="McLean2022">{{cite journal |last1=McLean |first1=Rebecca |last2=Graham |first2=Simon P. |date=4 April 2022 |title=The pig as an amplifying host for new and emerging zoonotic viruses |journal=One Health |volume=14 |doi=10.1016/j.onehlt.2022.100384 |pmid=35392655 |pmc=8975596 }}</ref>

=== On the environment ===
{{Main|Environmental impact of pig farming}}

[[File:NRCSNC00011_-_North_Carolina_(5131)(NRCS_Photo_Gallery).tif|thumb|A typical waste lagoon in North Carolina]]

As with the other forms of meat, producing pork is more energy-intensive than plant-based foods, and it is associated with more [[greenhouse gas emissions]] per [[calorie]]. However, emissions from pork are many times smaller than those of [[beef]], [[veal]] and [[mutton]], though larger than of [[chicken]] meat.<ref>{{cite report |title=World Food and Agriculture – Statistical Yearbook 2023 |publisher=FAO |year=2023 |doi=10.4060/cc8166en |isbn=978-92-5-138262-2 }}</ref>

Intensive pig production is also associated with [[water pollution]] concerns, as the swine waste is often stored above ground in so-called lagoons. These lagoons typically have high levels of [[nitrogen]] and [[phosphorus]], and can contain [[toxic heavy metal]]s like [[zinc]] and [[copper]], microbial [[pathogen]]s, or hold elevated concentrations of pharmaceuticals from [[subtherapeutic antibiotic use in swine]].<ref name="Burkholder2007" /> This wastewater from lagoons is liable to reach [[groundwater]] on farms, though there is little evidence for it reaching deeper into local [[drinking water]] supplies.<ref>{{cite journal |last1=Fridrich |first1=Beata |last2=Krčmar |first2=Dejan |last3=Dalmacija |first3=Božo |last4=Molnar |first4=Jelena |last5=Pešić |first5=Vesna |last6=Kragulj |first6=Marijana |last7=Varga |first7=Nataša |date=19 January 2014 |title=Impact of wastewater from pig farm lagoons on the quality of local groundwater |journal=Agricultural Water Management |volume=135 |pages=40–53 |doi=10.1016/j.agwat.2013.12.014 |bibcode=2014AgWM..135...40F }}</ref> However, lagoon spills, such as from heavy rains in the wake of a [[hurricane]], can lead to fish kills and algal blooms in local rivers.<ref name="Burkholder2007" /> In the [[United States]], {{cvt|35,000|mi}} of river across over 20 states were estimated to have been contaminated by manure leakage as of 2015.<ref>{{cite web |url=https://www.epa.gov/agriculture |title=Agriculture |website=www.epa.gov |date=19 March 2015 |access-date=2017-04-23}}</ref> There is also evidence that evaporation from lagoons can cause nitrogen and phosphorus to spread through the air as dry particles then reach other water basins when they fall out through [[dry deposition]]. This process then also contributes to water [[eutrophication]].<ref name="Burkholder2007">{{cite journal |last1=Burkholder |first1=JoAnn |last2=Libra |first2=Bob |last3=Weyer |first3=Peter |last4=Heathcote |first4=Susan |last5=Kolpin |first5=Dana |last6=Thorne |first6=Peter S. |last7=Wichman |first7=Michael |date=14 November 2007 |title=Impacts of waste from concentrated animal feeding operations on water quality |journal=Environmental Health Perspectives |volume=115 |issue=2 |pages=308–12 |doi=10.1289/ehp.8839 |pmid=17384784 |pmc=1817674 |bibcode=2007EnvHP.115..308B }}</ref>

=== On animal welfare ===

{{further|Cruelty to animals#Welfare concerns of farm animals|Intensive pig farming}}

[[File:Gestation crates 2.jpg|thumb|left|Sows in [[gestation crate]]s, United States, 2010]]

Intensive pig production involves practices such as [[castration]], [[earmark (agriculture)|earmarking]], tattooing for litter identification, tail [[Docking (animal)|docking]], which are often done without the use of [[anesthetic]].<ref>{{cite web |last1=Cutler |first1=R |last2=Holyoake |first2=P |date=2007 |title=The Structure and Dynamics of the Pig Meat Industry, prepared for Department of Agriculture, Fisheries and Forestry |url=http://www.agriculture.gov.au/SiteCollectionDocuments/animal-plant/animal-health/livestock-movement/pig-movement-ead.pdf |website=agriculture.gov.au}}</ref><ref>{{cite web |url=https://www.aussiepigs.com/gallery/videos |title=Video Gallery |website=aussiepigs.com |access-date=2019-06-02 |archive-date=2019-06-02 |archive-url=https://web.archive.org/web/20190602015527/https://www.aussiepigs.com/gallery/videos |url-status=dead }}</ref> Painful [[teeth clipping]] of piglets is also done to curtail [[cannibalism]], behavioural instability and aggression, and [[Tail biting in pigs|tail biting]], which are induced by the cramped environment.<ref name="Industry Focus" /><ref>{{Cite journal |doi = 10.2903/j.efsa.2007.611|title = The risks associated with tail biting in pigs and possible means to reduce the need for tail docking considering the different housing and husbandry systems - Scientific Opinion of the Panel on Animal Health and Welfare|journal = EFSA Journal|volume = 5|issue = 12|pages = 611|year = 2007|doi-access = free}}</ref> In English indoor farming, young pigs (less than 110kg in weight) are allowed to be kept with less than one square meter of space per pig.<ref>{{Cite web|url=https://pork.ahdb.org.uk/media/276311/keyfiguresbooklet_181001_web.pdf|title=Key figures for pig accommodation in England – legislative requirements|website=AHDB Pork|archive-url=https://web.archive.org/web/20190603062725/https://pork.ahdb.org.uk/media/276311/keyfiguresbooklet_181001_web.pdf|archive-date=3 June 2019}}</ref>

Pigs often begin life in a [[Gestation crate|farrowing or gestation crate]], which is a small pen with a central cage, designed to allow the piglets to feed from their mother while preventing her from attacking or crushing them.<ref name="auto">{{cite web |last1=Cutler |first1=R |last2=Holyoake |first2=P. |date=2007 |title=The Structure and Dynamics of the Pig Meat Industry, prepared for Department of Agriculture, Fisheries and Forestry |url=http://www.agriculture.gov.au/SiteCollectionDocuments/animal-plant/animal-health/livestock-movement/pig-movement-ead.pdf}}</ref> The crates are so small that the mother sows cannot turn around.<ref>{{cite web |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/478588/Opinion_on_Free_Farrowing_Systems.pdf |title=Opinion on Free Farrowing Systems |website=Farm Animal Welfare Committee |archive-url=https://web.archive.org/web/20190403101822/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/478588/Opinion_on_Free_Farrowing_Systems.pdf |archive-date=3 April 2019}}</ref><ref>{{Cite web |url=https://www.viva.org.uk/pigs/farrowing-crate-fact-sheet |title=Farrowing Fact Sheet |date=2016-01-06|website=Viva! - The Vegan Charity |access-date=2019-06-03 |archive-date=1 October 2020 |archive-url=https://web.archive.org/web/20201001234048/https://www.viva.org.uk/pigs/farrowing-crate-fact-sheet |url-status=dead}}</ref> While wild piglets remain with their mothers for around 12 to 14 weeks, farmed piglets are [[wean]]ed and removed from their mothers at between two and five weeks old.<ref name=":0">{{Cite web |url=https://www.ciwf.org.uk/farm-animals/pigs/pig-welfare/ |title=Pig welfare |publisher=[[Compassion in World Farming]] |access-date=3 June 2019}}</ref><ref>{{cite web |url=http://nationalhogfarmer.com/mag/farming_revisiting_weaning_age/ |title=Revisiting Weaning Age Trends, Dynamics |date=15 October 2005 |website=Nationalhogfarmer.com |access-date=28 July 2017}}</ref> Of the piglets born alive, 10% to 18% will not reach weaning age, instead succumbing to disease, starvation, dehydration, or accidental crushing by their mothers.<ref name="Industry Focus">{{cite web |publisher=Australian Pork Limited |title=Industry Focus |url=http://australianpork.com.au/industry-focus/animal-welfare/housing/ |website=australianpork.com.au}}</ref><ref>{{cite web |publisher=Pig Progress |title=Pre-weaning mortality |url=https://www.pigprogress.net/Health/Health-Tool/diseases/Pre-weaning-mortality-/ |website=pigprogress.net |date=13 July 2010 }}</ref> Unusually small [[runt]] piglets are typically killed immediately by staff through blunt trauma to the head.<ref>{{cite book |title=Model code of practice for the welfare of animals: Pigs, Primary Industries Report Series third edition |date=2008 |url=https://www.publish.csiro.au/book/5698 }}</ref><ref>{{cite web |url=https://www.animalaid.org.uk/wp-content/uploads/2016/08/Pigreport.pdf |title=Best of British? The Pig Industry Exposed |publisher=Animal Aid}}</ref> Further, intensive farming involves sows giving birth to large litter sizes at an unnatural frequency, which increases the rate of [[stillborn]] piglets, and causes as many as 25%-50% of sows to die of [[prolapse]].<ref>{{cite web |publisher=Australian Pork Limited |title=Fact Sheet – 'Reproductive Health' |date=2012 |url=https://australianpork.com.au/wp-content/uploads/2013/09/FACT-SHEET-Sectn2-Reproductive-loss__APL-Final_Jan-2012.pdf |website=australianpork.com.au |access-date=2019-06-02 |archive-date=2019-03-30 |archive-url=https://web.archive.org/web/20190330010949/https://australianpork.com.au/wp-content/uploads/2013/09/FACT-SHEET-Sectn2-Reproductive-loss__APL-Final_Jan-2012.pdf |url-status=dead }}</ref><ref>{{cite web |url=https://www.theguardian.com/environment/2018/oct/01/death-rates-surge-female-pigs-us |title='We've bred them to their limit': death rates surge for female pigs in the US |last=Greenaway |first=Twilight |date=2018-10-01 |website=[[The Guardian]] |access-date=17 November 2018}}</ref>

== In culture ==

{{main|Pigs in culture}}

Pigs, widespread in societies around the world since [[Neolithic]] times, have been used for many purposes in art, literature, and other expressions of human [[culture]]. In classical times, the [[Ancient Rome|Romans]] considered [[pork]] the finest of meats, enjoying [[sausage]]s, and depicting them in their art.<ref name="MacKinnon 2001">{{cite journal |last=MacKinnon |first=Michael |title=High on the Hog: Linking Zooarchaeological, Literary, and Artistic Data for Pig Breeds in Roman Italy |journal=American Journal of Archaeology |volume=105 |issue=4 |year=2001 |pages=649–673 |doi=10.2307/507411 |jstor=507411 |s2cid=193116973}}</ref> Across Europe, pigs have been celebrated in [[carnival]]s since the [[Middle Ages]],<ref name="Komins 2001">{{cite journal |last=Komins |first=Benton Jay |title=Western Culture and the Ambiguous Legacies of the Pig |journal=CLCWeb: Comparative Literature and Culture |volume=3 |issue=4 |year=2001 |doi=10.7771/1481-4374.1137 |doi-access=free }}</ref> becoming specially important in [[Medieval Germany]] in cities such as [[Nuremberg]],<ref name="Newey 2014">{{cite news |last=Newey |first=Adam |title=Nuremberg, Germany: celebrating the city's sausage |url=https://www.telegraph.co.uk/travel/destinations/europe/germany/articles/Nuremberg-Germany-In-praise-of-the-citys-sausage/ |work=[[The Daily Telegraph]] |date=8 December 2014}}</ref> and in [[Early modern period|Early Modern]] Italy in cities such as [[Bologna]].<ref>{{cite web |title=Eventi: Pane e salame |date=August 2009 |url=http://www.bibliotechebologna.it/eventi/51430/luogo/51660/date/2017-02-14:2018-03-14/date_from/2017-02-14/date_to/2018-03-14/id/100097 |publisher=Istituzione Biblioteche Bologna |access-date=31 December 2019 |language=it}}</ref><ref name="NYT Mortadella 1988">{{cite news |last1=Virbila |first1=S. Irene |title=Fare of the Country; Mortadella: Bologna's Bologna |url=https://www.nytimes.com/1988/08/07/travel/fare-of-the-country-mortadella-bologna-s-bologna.html |work=[[The New York Times]] |date=7 August 1988}}</ref> Pigs, especially miniature breeds, are occasionally kept as pets.<ref name=cabi>{{cite book |last1=Porter |first1=Valerie |last2=Alderson |first2=Lawrence |last3=Hall |first3=Stephen J.G. |last4=Sponenberg |first4=D. Phillip |chapter=Pig |date=2016 |url=https://books.google.com/books?id=2UEJDAAAQBAJ |title=Mason's World Encyclopedia of Livestock Breeds and Breeding |edition=6 | publisher=CABI |isbn=978-1-7806-4794-4 |page=616}}</ref><ref name=pbs>[https://www.pbs.org/wnet/nature/the-joy-of-pigs-pigs-as-pets/2124/ The Joy of Pigs/ Pigs as Pets]. PBS Nature. Accessed June 2017.</ref>

In literature, both for children<ref>{{cite journal |last=Robinson |first=Robert D. |title=The Three Little Pigs: From Six Directions |journal=Elementary English |date=March 1968 |volume=45 |issue=3 |pages=356–359 |jstor=41386323}}</ref> and adults, pig characters appear in allegories, comic stories, and serious novels.<ref name="Komins 2001"/><ref name="Mullan 2010">{{cite news |last1=Mullan |first1=John |author-link1=John Mullan (academic) |title=Ten of the best pigs in literature |url=https://www.theguardian.com/books/2010/aug/21/ten-best-pigs-in-literature |work=[[The Guardian]] |date=21 August 2010}}</ref><ref name="BBC">{{cite web |last=Bragg |first= Melvyn |author-link=Melvyn Bragg |title=Topics - Pigs in literature |url=https://www.bbc.co.uk/programmes/b006qykl/topics/Pigs_in_literature |publisher=[[BBC]] Radio 4 |access-date=1 January 2020 |quote=Animal Farm ... Sir Gawain and the Green Knight ... The Mabinogion ... The Odyssey ... (''In Our Time'')}}</ref> In art, pigs have been represented in a wide range of media and styles from the earliest times in many cultures.<ref name="MMA">{{cite web |title=Pig |url=https://www.metmuseum.org/search-results#!/search?q=pig |publisher=[[Metropolitan Museum of Art]] |access-date=2 January 2020}}</ref> Pig names are used in idioms and [[animal epithet]]s, often derogatory, since pigs have long been linked with dirtiness and greed,<ref name="Telegraph">{{cite news |title=Fine Swine |date=2 February 2001 |work=[[The Daily Telegraph]] |url=https://www.telegraph.co.uk/comment/4259823/Fine-swine.html}}</ref><ref>{{cite book |author=Horwitz, Richard P. |title=Hog Ties: Pigs, Manure, and Mortality in American Culture |publisher=University of Minnesota Press |date=2002 |isbn=0816641838 |page=23}}</ref> while places such as [[Swindon]] are named for their association with swine.<ref name="Mills 1993">{{cite book |last1=Mills |first1=A. D. |title=A Dictionary of English Place-Names |date=1993 |publisher=Oxford University Press |isbn=0192831313 |pages=150, 318}}</ref> The eating of pork is [[Haram|forbidden in Islam]] and [[Kashrut|Judaism]],<ref>{{cite book|at=Interceding Kashrut|title=Eating Religiously: Food and Faith in the 21st Century|date=2023|isbn=9781000988154|editor1=Fran Markowitz|editor2=Nir Avieli|publisher= Taylor & Francis}}</ref> but pigs are sacred in some other religions.<ref name="Dalal2011">{{cite book |last=Dalal |first=Roshen |title=Hinduism: An Alphabetical Guide |url=https://books.google.com/books?id=DH0vmD8ghdMC&pg=PA444 |date=2011 |publisher=Penguin Books India |isbn=978-0-14-341421-6 |pages=444–445}}</ref><ref>{{cite web |last1=Bonwick |first1=James |title=Sacred Pigs |url=https://www.libraryireland.com/Druids/Sacred-Pigs.php |publisher=Library Ireland |date=1894}}</ref>

<gallery class=center mode=nolines widths=220 heights=220>
File:CapitalMuseum11.jpg|Bronze pig sculpture, [[Zhou dynasty]]
File:Demeter1.jpg|Two men sacrificing a pig to [[Demeter]]. [[Red-figure pottery|Red-figure pot]], [[Ancient Greece]]
File:Piero di Cosimo 025.jpg|Painting of Saint Anthony with a pig in background by [[Piero di Cosimo]] c. 1480
File:Canzone Sopra La Porcellina 1622.jpg|''Canzone Sopra La Porcellina'' ("Song Upon the Piglet") by [[Giulio Cesare Croce]], [[Bologna]], 1622
File:Pigling Bland pg 4 Enh.jpg|[[Pigling Bland]] setting out on his adventures
File:Bologna amazing hams sausages mortadella.jpg|[[Ham]]s, [[pig's trotter]]s, [[sausage]]s, and [[mortadella]] in [[Bologna]], 2019
</gallery>

== References ==

{{reflist|30em}}

== External links ==

{{Commons|Sus domesticus}}

* [https://web.archive.org/web/20100125233320/http://www.accidentalsmallholder.net/articles/pigs/introduction An introduction to pig keeping]
* [http://www.britishpigs.org.uk British Pig Association]
* [https://web.archive.org/web/20091227001050/http://www.pork.org/newsandinformation/quickfacts/SwineCare1.aspx Swine Care]
* [https://web.archive.org/web/20071202060724/http://ucce.ucdavis.edu/files/filelibrary/1385/2027.PDF Swine Study Guide] from [[UC Davis]]

{{Pigs}}
{{Artiodactyla|Suina}}
{{Animal domestication}}
{{Taxonbar|from1=Q787|from2=Q15896091}}
{{Authority control}}

[[Category:Pigs| ]]
[[Category:Mammals described in 1777]]
[[Category:Mammals as pets]]
[[Category:Livestock]]
[[Category:Pork]]
[[Category:Taxa named by Johann Christian Polycarp Erxleben]]
[[Category:Sus (genus)]]
[[Category:Scavengers]]