Editing Guinea pig (section)

==Biology==
{{Main|List of guinea pig breeds}}

[[File:Nibbles and strips 2.jpg|thumb|[[Parti-colored]] [[Abyssinian guinea pig]]s]]

Guinea pigs are relatively large for rodents. In pet breeds, adults typically weigh between {{convert|700|and|1200|g|lb|abbr=on}} and measure between {{convert|20|and|25|cm|in|round=0.5|abbr=on}} in length.{{sfn|Vanderlip|2003|p=13}} Some livestock breeds weigh {{Convert|3|kg|lb|abbr=on}} when full grown.<ref name="yamamoto2">{{Cite book |last=Yamamoto |first=Dorothy |title=Guinea Pig |publisher=Reaktion Books |year=2015 |isbn=978-1-78023-467-0 |location=London |chapter=Section 4: On The Menu |chapter-url=https://books.google.com/books?id=ooGiCgAAQBAJ&q=breeding+program+guinea+pig&pg=PT81}}</ref> Pet breeds live an average of four to five years but may live as long as eight years.{{sfn|Richardson|2000|pages=132–133}} According to ''[[Guinness World Records]]'', {{As of|2006||lc=y}}, the longest-lived guinea pig was 14&nbsp;years, 10&nbsp;months, and 2 weeks old.<ref>{{Cite book |title=Guinness Book of World Records |publisher=Guinness World Records Ltd. |year=2006 |isbn=978-1-904994-02-2 |editor-last=Glenday |editor-first=Craig |page=[https://archive.org/details/guinnessworldrec00glen/page/60 60] |title-link=Guinness Book of World Records }}</ref> Most guinea pigs have fur, but one laboratory breed adopted by some pet owners, the [[skinny pig]], is mostly furless. In contrast, several breeds have long fur, such as the [[Peruvian guinea pig|Peruvian]], the [[Silkie guinea pig|Silkie]], and the [[Texel Guinea Pig|Texel]]. They have four front teeth and small back teeth. Their front teeth grow continuously, so guinea pigs chew on materials such as wood to wear them down to prevent them from becoming too long.<ref>{{cite book|last=Petrylak |first=Ashley |date=2009|title=Guinea Pigs (Great Pets)|url=|publisher=Cavendish Square Publishing|page=13|isbn=978-0-7614-4148-9}}</ref> In the 1990s, a minority scientific opinion emerged proposing that [[caviomorpha|caviomorphs]] such as guinea pigs, [[chinchilla]]s, and [[Octodon|degu]]s are not actually rodents, and should be [[Taxonomy (biology)|reclassified]] as a separate [[order (biology)|order]] of mammals (similar to the rodent-like [[lagomorpha|lagomorphs]] which includes rabbits and hares).<ref>{{cite journal|last1 = Graur|first1 = D.|title = Is the Guinea-Pig a Rodent?|year = 1991|journal = [[Nature (journal)|Nature]]|volume = 351|pages = 649–652|doi = 10.1038/351649a0|last2 = Hide|first2 = Winston A.|last3 = Li|first3 = Wen-Hsiung|pmid = 2052090|issue = 6328|display-authors = 1|bibcode = 1991Natur.351..649G|s2cid = 4344039}}</ref><ref>{{cite journal|last1 = D'Erchia|first1 = A.|title = The Guinea Pig is Not a Rodent|year = 1996|journal = [[Nature (journal)|Nature]]|volume = 381|pages = 597–600|doi = 10.1038/381597a0|last2 = Gissi|first2 = Carmela|last3 = Pesole|first3 = Graziano|last4 = Saccone|first4 = Cecilia|last5 = Arnason|first5 = Ulfur|pmid = 8637593|issue = 6583|display-authors = 1|bibcode = 1996Natur.381..597D|s2cid = 4336262}}</ref><ref name="rodent">{{Cite journal |title=Is the guinea-pig (''Cavia porcellus'') a rodent? |journal=Comparative Biochemistry and Physiology Part B: Comparative Biochemistry |volume=107 |issue=2 |date=February 1994 |pages=179–182 |doi=10.1016/0305-0491(94)90037-X |last1=Noguchi |first1=Tomoo |last2=Fujiwara |first2=Satoko |last3=Hayashi |first3=Sucko |last4=Sakuraba |first4=Haruhiko}}</ref> Subsequent research using [[Sampling (statistics)|wider sampling]] restored the consensus among mammalian biologists regarding the current classification of rodents, including guinea pigs, as [[monophyly|monophyletic]].<ref>{{Cite book|last1 = Carleton|first1 = Michael D.|last2 = Musser|first2 = Guy G.|contribution = Order Rodentia|editor1-last = Wilson|editor1-first = Don E.|title = Mammal Species of the World|edition = 3rd|year = 2005|volume = 2|page = 745|publisher = Johns Hopkins University Press|isbn = 978-0-8018-8221-0|editor2-last = Reeder|editor2-first = DeeAnn M.}}</ref><ref>{{Cite journal |last1=Huchon |first1=Dorothée |last2=Chevret |first2=Pascale |last3=Jordan |first3=Ursula |last4=Kilpatrick |first4=C. William |last5=Ranwez |first5=Vincent |last6=Jenkins |first6=Paulina D. |last7=Brosius |first7=Jürgen |last8=Schmitz |first8=Jürgen |date=May 1, 2007 |title=Multiple molecular evidences for a living mammalian fossil |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=104 |issue=18 |pages=7495–7499 |bibcode=2007PNAS..104.7495H |doi=10.1073/pnas.0701289104 |pmc=1863447 |pmid=17452635|doi-access=free }}</ref>

Wild cavies are found on grassy plains and occupy an [[ecological niche]] similar to that of [[cattle]]. They are social animals, living in the wild in small groups ("[[herd]]s") that consist of several females ("sows"), a male ("boar"), and their young ("pups" not "piglets", a break with the preceding [[pig|porcine]] nomenclature). Herds of animals move together, eating grass or other vegetation, yet do not store food.{{sfn|Wagner|Manning|1976|pp=31–32}} While they do not [[burrow]] themselves or build nests, they frequently seek shelter in the burrows of other animals, as well as in crevices and tunnels formed by vegetation.{{sfn|Wagner|Manning|1976|pp=31–32}} They are [[crepuscular]] and tend to be most active during dawn and dusk when it is harder for predators to spot them.{{sfn|Terril|Clemons|1998|p=6}}<!-- Male vs. female -->

Male and female guinea pigs do not significantly [[sexual dimorphism|differ in appearance]] apart from general size. The position of the [[anus]] is very close to the [[genitals]] in both sexes. [[Sexing|Sexing animals]] at a young age must be done by someone trained in the differences. Female genitals are distinguished by a Y-shaped configuration formed from a [[Vulva|vulvar flap]]. While male genitals may look similar, with the [[penis]] and anus forming a similar shape, the penis will protrude if pressure is applied to the surrounding hair anterior to the genital region.{{sfn|Richardson|2000|pages=14, 17}} The male's [[testes]] may also be visible externally from [[scrotal]] swelling.

[[File:Guinea pigs - Japanese petting zoo - 2018 6 26.webm|thumb|Guinea pigs in a petting zoo]]

===Behavior===
[[File:Three guinea pigs (Cavia porcellus) at Keswick Public Library.jpg|thumb|Guinea pigs "social groom" each other.|alt=|left]]

Guinea pigs can learn complex paths to food and can accurately remember a learned path for months. Their most robust [[problem-solving]] strategy is motion.<ref>{{cite journal|last = Charters|first = Jessie Blount Allen|title = The associative processes of the guinea pig: A study of the psychical development of an animal with a nervous system well medullated at birth|journal = Journal of Comparative Neurology and Psychology|volume = XIV|issue = 4|pages = 300–337|date=July 1904|url = https://books.google.com/books?id=dWcKAAAAMAAJ&q=guinea+pigs&pg=RA2-PA300|access-date = 2006-12-27|doi=10.1002/cne.920140402| hdl=2027/mdp.39015031094876 }}</ref> While guinea pigs can jump small obstacles, they cannot jump very high. Most of them are poor climbers and are not particularly agile. They startle easily, and when they sense danger, they either freeze in place for long periods or run for cover with rapid, darting motions.{{sfn|Terril|Clemons|1998|p=6}} Larger groups of startled guinea pigs "[[stampede]]", running in haphazard directions as a means of confusing predators.{{sfn|Wagner|Manning|1976|p=34}} When happily excited, guinea pigs may (often repeatedly) perform little hops in the air (a movement known as "popcorning"), analogous to the [[ferret]]'s [[weasel war dance|war dance]]<ref>{{cite web|title = Guinea Pigs|publisher = Canadian Federation of Humane Societies|url = http://cfhs.ca/athome/guinea_pigs|access-date = 2007-03-21|archive-url = https://web.archive.org/web/20070402223933/http://cfhs.ca/athome/guinea_pigs/|archive-date = 2007-04-02}}</ref> or rabbit happy hops (binkies). Guinea pigs are also good swimmers,<ref name="harkness">{{cite book|last1 = Harkness|first1 = John E.|last2 = Wagner|first2 = Joseph E.|title = The Biology and Medicine of Rabbits and Rodents|publisher = Williams & Wilkins|year = 1995|pages = 30–39|isbn = 978-0-683-03919-1}}</ref> although they do not like being wet and infrequently need bathing.

Like many rodents, guinea pigs sometimes participate in [[social grooming]] and regularly self-groom.{{sfn|Vanderlip|2003|p=79}} A milky-white substance is secreted from their eyes and rubbed into the hair during the grooming process.{{sfn|Richardson|2000|page=72}} Groups of boars often chew each other's hair, but this is a method of establishing hierarchy within a group, rather than a social gesture.<ref name="harkness" /> Dominance is also established through biting (especially of the ears), [[Goose bumps|piloerection]], aggressive noises, head thrusts, and leaping attacks.{{sfn|Wagner|Manning|1976|p=38}} Non-sexual simulated [[wikt:mount#Verb|mounting]] for dominance is also common among same-sex groups.{{citation needed|date=November 2020}}

Guinea pig eyesight is not as good as that of a human in terms of distance and color, but they have a wider angle of vision (about 340°) and see in partial color ([[dichromacy]]). They have well-developed senses of hearing, [[olfaction|smell]], and touch.{{sfn|Wagner|Manning|1976|pp=32–33}}{{sfn|Vanderlip|2003|p=14}}

Guinea pigs have developed a different [[biological rhythm]] from their wild counterparts and have longer periods of activity followed by short sleep in between.{{sfn|Terril|Clemons|1998|p=6}} Activity is scattered randomly throughout the day; aside from an avoidance of intense light, no regular [[circadian rhythm|circadian patterns]] are apparent.{{sfn|Terril|Clemons|1998|p=6}}[[File:Cat with guinea pigs.jpg|alt=|thumb|300x300px|Although this cat has accepted these guinea pigs, the success of interspecies interaction depends on the individual animals.]]Guinea pigs do not generally thrive when housed with other species. Larger animals may regard guinea pigs as [[predation|prey]], though some [[dog]]s and [[cat]]s can be trained to accept them.<ref name="behrend">{{cite book|last=Behrend|first=Katrin|url=https://archive.org/details/guineapigseveryt00behr/page/22|title=Guinea Pigs: A Complete Pet Owner's Manual|publisher=Barron's|year=1998|isbn=978-0-7641-0670-5|pages=[https://archive.org/details/guineapigseveryt00behr/page/22 22–23]}}</ref> Opinion is divided over the cohousing of guinea pigs and [[domestic rabbit|rabbit]]s. Some published sources say that guinea pigs and rabbits complement each other well when sharing a cage.<ref name="behrend" />{{sfn|Vanderlip|2003|p=20}} However, rabbits have different nutritional requirements; as [[Lagomorpha|lagomorphs]], they synthesize their own [[vitamin C]], so the two species will not thrive if fed the same food when housed together.{{sfn|Terril|Clemons|1998|p=41}} Rabbits may also harbor diseases (such as respiratory infections from ''[[Bordetella]]'' and ''[[Pasteurella]]''), to which guinea pigs are susceptible.{{sfn|Wagner|Manning|1976|pp=126–128}} Housing guinea pigs with other rodents such as [[gerbil]]s and [[hamster]]s may increase instances of respiratory and other infections,{{sfn|Wagner|Manning|1976|p=122}} and such rodents may act aggressively toward guinea pigs.{{sfn|Vanderlip|2003|p=19}}

===Vocalization===
Vocalization is the primary means of communication between members of the species.{{sfn|Terril|Clemons|1998|p=7}} These are the most common sounds made by the guinea pig:{{sfn|Terril|Clemons|1998|pp=7–8}}
*A "''wheek''" is a loud noise, the name of which is [[onomatopoeia|onomatopoeic]], also known as a whistle. An expression of general excitement may occur in response to the presence of its owner or feeding. It is sometimes used to find other guinea pigs if they are running. If a guinea pig is lost, it may wheek for assistance. {{Audio|Guinea Pig Feeding Wheek.ogg|listen}}
*A bubbling or purring sound is made when the guinea pig enjoys itself, such as when petting and holding. It may also make this sound when grooming, crawling around to investigate a new place, or when given food. {{Audio|Guinea Pig Happy.ogg|listen}}
*A rumbling sound is normally related to dominance within a group, though it can also come as a response to being scared or angry. In the case of being scared, the rumble often sounds higher, and the body vibrates shortly. While courting, a male usually purrs deeply, swaying and circling the female{{sfn|Wagner|Manning|1976|p=39}} in a behavior called ''rumblestrutting''. A low rumble while walking away reluctantly shows [[Passive aggressive|passive]] resistance. {{Audio|Guinea Pig Keep Away.ogg|listen}}
*Chutting and whining are sounds made in pursuit situations by the pursuer and pursuee, respectively. {{Audio|Guinea Pig Angry.ogg|listen}}
*A chattering sound is made by rapidly gnashing the [[tooth|teeth]], and is generally a sign of warning. Guinea pigs tend to raise their heads when making this sound.
*Squealing or shrieking is a high-pitched sound of discontent in response to pain or danger. {{Audio|Guinea Pig In Distress.ogg|listen}}
*Chirping, a less common sound likened to [[bird vocalization|bird song]], seems to be related to stress or discomfort or when a baby guinea pig wants to be fed. Very rarely, the chirping will last for several minutes. {{Audio|Guinea Pig Chirping.ogg|listen}}

=== Reproduction ===
[[File:Fat Adie pictures 001.jpg|thumb|right|[[Pregnant]] sow one week before delivering three pups]]

Males (boars) reach [[sexual maturity]] in 3–5 weeks. Similarly, females (sows) can be fertile as early as four weeks old and carry litters before becoming fully grown adults.{{sfn|Richardson|2000|pages=15–16}} A sow can breed year-round (with spring being the peak). A sow can have as many as five litters in a year, but six is theoretically possible<!-- 360/60 -->.<ref name="walker" /> Unlike the offspring of most [[rodents]], which are [[altricial]] at birth, newborn cavy pups are [[Precociality|precocial]], and are well-developed with hair, teeth, claws, and partial eyesight.<ref name="harkness" /> The pups are immediately mobile and capable of eating solid food, though they continue to [[breastfeeding|suckle]]. Sows can once again become pregnant 6–48 hours after giving birth, but it is not healthy for a female to be constantly pregnant.{{sfn|Richardson|2000|pages=17–18}}

The [[gestation]] period lasts from {{convert|59|-|72|day|month}}, with an average of {{convert|63|-|68|day|month}}.<ref name="nrc" /> Because of the long gestation period and the large size of the pups, pregnant sows may become large and [[eggplant]]-shaped, although the change in size and shape varies depending upon the size of the litter. [[Litter (animal)|Litter]] size ranges from one to six, with three being the average;{{sfn|Richardson|2000|pages=}} the largest recorded litter size is 9.<ref>{{Cite web |title=Largest litter of guinea pigs |url=https://www.guinnessworldrecords.com/world-records/69437-largest-guinea-pig-litter |access-date=2021-03-15 |website=Guinness World Records |language=en-GB}}</ref> The guinea pig mother only has two nipples, but she can readily raise the more average-sized litters of 2 to 4 pups.<ref name="Merck Veterinarian Manual, 2016">[http://www.merckvetmanual.com/all-other-pets/guinea-pigs/breeding-and-reproduction-of-guinea-pigs Breeding and Reproduction of Guinea Pigs], Merck Veterinarian Manual, Katherine E. Quesenberry, DVM, MPH, DABVP (Avian); Kenneth R. Boschert, DVM, DACLAM, 2016.</ref><ref name="Harkness and Wagner's Biology and Medicine of Rabbits and Rodents, 2010">[https://books.google.com/books?id=SFSXqsWvsMQC&dq=%22despite+having+only+two+nipples%2C+guinea+pigs+can+raise+litters+of+3%2C+4%2C+and+more+young%22&pg=PA55 Harkness and Wagner's Biology and Medicine of Rabbits and Rodents, 5th Edition], John E. Harkness, Patricia V. Turner, Susan VandeWoude, Colette L. Wheler, Iowa, USA: Wiley & Sons, "Ch. 2 Biology and Husbandry," 2010.</ref> In smaller litters, difficulties may occur during [[Childbirth|labour]] due to oversized pups. Large litters result in higher incidences of [[stillbirth]], but because the pups are delivered at an advanced stage of development, lack of access to the mother's milk has little effect on the mortality rate of newborns.{{sfn|Wagner|Manning|1976|p=88}}[[File:Guinea baby 1.jpg|thumb|Guinea pig pup at eight hours old|alt=|left]]

Cohabitating females assist in mothering duties if [[Lactation|lactating]];<ref name="percy">{{cite book |last1=Percy |first1=Dean H. |title=Pathology of Laboratory Rodents and Rabbits |last2=Barthold |first2=Stephen W. |publisher=Iowa State University Press |year=2001 |isbn=978-0-8138-2551-9 |edition=2nd |pages=209–247}}</ref> guinea pigs practice [[Alloparenting|alloparental care]], in which a sow may adopt the pups of another. This might take place if the original parents die or are, for some reason, separated from them. This behavior is common and is seen in many other animal species, such as the elephant.<ref>{{cite journal |last1=Riedman |first1=Marianne L. |year=1982 |title=The Evolution of Alloparental Care in Mammals and Birds |journal=The Quarterly Review of Biology |volume=57 |issue=4 |pages=405–435 |doi=10.1086/412936 |s2cid=85378202}}</ref>

<!-- Complications -->[[pre-eclampsia|Toxemia of pregnancy]] (hypertension) is a common problem and kills many pregnant females. Signs of toxemia include anorexia (loss of appetite), [[Lethargy|lack of energy]], [[Salivation|excessive salivation]], a [[Bad breath|sweet or fruity breath odor]] due to [[ketone]]s, and [[seizure]]s in advanced cases.{{sfn|Richardson|2000|pages=20–21}} Pregnancy toxemia appears to be most common in hot climates.{{sfn|Richardson|2000|page=20}} Other serious complications during pregnancy can include a [[prolapse|prolapsed uterus]], [[hypocalcaemia]], and [[mastitis]].{{sfn|Richardson|2000|pages=25–29}}

Females that do not give birth may develop an irreversible fusing or calcified cartilage of the [[pubic symphysis]], a joint in the [[pelvis]], which may occur after six months of age.<ref name="nrc" />{{rp|72–73|date=November 2012}} If they become pregnant after this has happened, the birth canal may not widen sufficiently, which may lead to [[dystocia]] and death as they attempt to give birth.{{sfn|Richardson|2000|pages=25–26}}