Guinea pig



The guinea pig (Cavia porcellus), also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea. They originated in the Andes, and earlier studies based on biochemistry and hybridization suggested they are domesticated descendants of a closely related species of cavy such as Cavia aperea, C. fulgida, or C. tschudii and, therefore, do not exist naturally in the wild.[1] [2] Recent studies applying molecular markers,[3] [4] in addition to studying the skull and skeletal morphology of current and mummified animals,[5] revealed that the ancestor is most likely Cavia tschudii.

The guinea pig plays an important role in the folk culture of many Indigenous South American groups, especially as a food source, but also in folk medicine and in community religious ceremonies.[6] Since the 1960s, efforts have been made to increase consumption of the animal outside South America.[7]

In Western societies, the guinea pig has enjoyed widespread popularity as a household pet since its introduction by European traders in the 16th century. Their docile nature, their responsiveness to handling and feeding, and the relative ease of caring for them, continue to make the guinea pig a popular pet. Organizations devoted to competitive breeding of guinea pigs have been formed worldwide, and many specialized breeds of guinea pig, with varying coat colors and compositions, are cultivated by breeders.

Biological experimentation on guinea pigs has been carried out since the 17th century. The animals were frequently used as a model organism in the 19th and 20th centuries, resulting in the epithet "guinea pig" for a test subject, but have since been largely replaced by other rodents such as mice and rats. They are still used in research, primarily as models for human medical conditions such as juvenile diabetes, tuberculosis, scurvy, and pregnancy complications.

History
The common guinea pig was first domesticated as early as 5000 BC for food by tribes in the Andean region of South America (present-day the southern part of Colombia, Ecuador, Peru, and Bolivia),[8] some thousands of years after the domestication of the South American camelids.[9] Statues dating from ca. 500 BC to 500 AD that depict guinea pigs have been unearthed in archaeological digs in Peru and Ecuador.[10] The Moche people of ancient Peru worshipped animals and often depicted the guinea pig in their art.[11] From ca. 1200 AD to the Spanish conquest in 1532, selective breeding resulted in many varieties of domestic guinea pigs, which form the basis for some of the modern domestic breeds.[12] They continue to be a food source in the region; many households in the Andean highlands raise the animal, which subsists off the family's vegetable scraps.[13] Folklore traditions involving guinea pigs are numerous; they are exchanged as gifts, used in customary social and religious ceremonies, and frequently referenced in spoken metaphors.[14] They also play a role in traditional healing rituals by folk doctors, or curanderos, who use the animals to diagnose diseases such as jaundice, rheumatism, arthritis, and typhus.[15] They are rubbed against the bodies of the sick, and are seen as a supernatural medium.[16] Black guinea pigs are considered especially useful for diagnoses.<sup class="reference" id="cite_ref-16">[17] The animal also may be cut open and its entrails examined to determine whether the cure was effective.<sup class="reference" id="cite_ref-17">[18] These methods are widely accepted in many parts of the Andes, where Western medicine is either unavailable or distrusted.<sup class="reference" id="cite_ref-18">[19]

Spanish, Dutch, and English traders brought guinea pigs to Europe, where they quickly became popular as exotic pets among the upper classes and royalty, including Queen Elizabeth I.<sup class="reference" id="cite_ref-Morales.2C_p._3_7-1">[8] The earliest known written account of the guinea pig dates from 1547, in a description of the animal from Santo Domingo; because cavies are not native to Hispaniola, it was earlier believed that the animal was likely introduced there by Spanish travelers.<sup class="reference" id="cite_ref-weir_0-1">[1] However, based on more recent excavations on West Indian islands, it has become known that the animal must have been introduced by ceramic-making horticulturalists from South America to the Caribbean around 2500 BP,<sup class="reference" id="cite_ref-19">[20] and it was present in the Ostionoid period, for example, on Puerto Rico,<sup class="reference" id="cite_ref-20">[21] long before the advent of the Spaniards. The guinea pig was first described in the West in 1554 by the Swiss naturalist Conrad Gessner.<sup class="reference" id="cite_ref-21">[22] Its binomial scientific name was first used by Erxleben in 1777; it is an amalgam of Pallas' generic designation (1766) and Linnaeus' specific conferral (1758).<sup class="reference" id="cite_ref-weir_0-2">[1]

Name
The scientific name of the common species is Cavia porcellus, with porcellus being Latin for "little pig". Cavia is New Latin; it is derived from cabiai, the animal's name in the language of the Galibi tribes once native to French Guiana.<sup class="reference" id="cite_ref-22">[23] Cabiai may be an adaptation of the Portuguese çavia (now savia), which is itself derived from the Tupi word saujá, meaning rat.<sup class="reference" id="cite_ref-23">[24] Guinea pigs are called quwi or jaca in Quechua and cuy or cuyo (pl. cuyes, cuyos) in the Spanish of Ecuador, Peru, and Bolivia.<sup class="reference" id="cite_ref-diccionario_24-0">[25] Ironically, breeders tend to use the more formal "cavy" to describe the animal, while in scientific and laboratory contexts it is far more commonly referred to by the more colloquial "guinea pig".<sup class="reference" id="cite_ref-wagner_25-0">[26]

How the animals came to be called "pigs" is not clear. They are built somewhat like pigs, with large heads relative to their bodies, stout necks, and rounded rumps with no tail of any consequence; some of the sounds they emit are very similar to those made by pigs, and they also spend a large amount of time eating.<sup class="reference" id="cite_ref-26">[27] They can survive for long periods in small quarters, like a 'pig pen', and were thus easily transported on ships to Europe.<sup class="reference" id="cite_ref-27">[28]

The animal's name carries porcine connotations in many European languages. The German word for them is Meerschweinchen, literally "sea piglet", which has been translated into Polish as świnka morska, into Hungarian as tengerimalac and into Russian as морская свинка. This derives from the Middle High German name "merswin". This originally meant "dolphin" and was used because of the animals' grunting sounds (which were felt to be similar).<sup class="reference" id="cite_ref-28">[29] There are however many other, possibly less scientifically based explanations of the German name. For example, sailing ships stopping to reprovision in the New World would pick up stores of guinea pigs, which provided an easily transportable source of fresh meat. The French term is Cochon d'Inde (Indian pig) or cobaye; the Dutch call it Guinees biggetje (Guinean piglet) or cavia (while in some Dutch dialects it is called Spaanse rat); and in Portuguese the guinea pig is variously referred to as cobaia, from the Tupi word via its Latinization, or as porquinho da Índia (little Indian pig). This is not universal; for example, the common word in Spanish is conejillo de Indias (little rabbit of the Indies).<sup class="reference" id="cite_ref-diccionario_24-1">[25] The Chinese refer to them as Holland pigs (荷蘭豬, hélánzhū). The Japanese word for guinea pig is "モルモット"(morumotto), which derives from the name of another mountain-dwelling rodent, the marmot; this is what guinea pigs were called by the Dutch traders who first brought them to Nagasaki in 1843.

The origin of "guinea" in "guinea pig" is harder to explain. One theory is that the animals were brought to Europe by way of Guinea, leading people to think they had originated there.<sup class="reference" id="cite_ref-wagner_25-1">[26] "Guinea" was also frequently used in English to refer generally to any far-off, unknown country, and so the name may simply be a colorful reference to the animal's foreignness.<sup class="reference" id="cite_ref-dictionary_29-0">[30] <sup class="reference" id="cite_ref-30">[31] Another theory suggests the "guinea" in the name is a corruption of "Guiana", an area in South America, though the animals are not native to that region.<sup class="reference" id="cite_ref-dictionary_29-1">[30] <sup class="reference" id="cite_ref-31">[32] A common misconception is that they were so named because they were sold for the price of a guinea coin; this theory is untenable, because the guinea was first struck in England in 1663, and William Harvey used the term "Ginny-pig" as early as 1653.<sup class="reference" id="cite_ref-32">[33] Others believe "guinea" may be an alteration of the word coney (rabbit); guinea pigs were referred to as "pig coneys" in Edward Topsell's 1607 treatise on quadrupeds.<sup class="reference" id="cite_ref-wagner_25-2">[26]

Traits and environment
Two parti-colored Abyssinian guinea pigsGuinea pigs are large for rodents, weighing between 700 and 1200 g (1.5–2.5 pounds), and measuring between 20 and 25 cm (8–10 inches) in length.<sup class="reference" id="cite_ref-vanderlip_33-0">[34] They typically live an average of four to five years, but may live as long as eight years.<sup class="reference" id="cite_ref-richardson_34-0">[35] According to the 2006 Guinness Book of Records the longest living guinea pig survived 14 years, 10.5 months.<sup class="reference" id="cite_ref-35">[36]

In the 1990s, a minority scientific opinion emerged proposing that caviomorphs, such as guinea pigs, chinchillas, and degus, are not rodents and should be reclassified as a separate order of mammals (similar to lagomorphs).<sup class="reference" id="cite_ref-36">[37] <sup class="reference" id="cite_ref-37">[38] Subsequent research using wider sampling has restored consensus among mammalian biologists that the current classification of rodents as monophyletic is justified.<sup class="reference" id="cite_ref-38">[39] <sup class="reference" id="cite_ref-39">[40]

Domestic habitat
Domesticated guinea pigs thrive in groups of two or more; groups of sows, or groups of one or more sows and a neutered boar are common combinations. Guinea pigs learn to recognize and bond with other individual guinea pigs, and testing of boars shows that their neuroendocrine stress response is significantly lowered in the presence of a bonded female when compared to the presence of unfamiliar females.<sup class="reference" id="cite_ref-42">[43] Groups of boars may also get along, provided that their cage has enough space, they are introduced at an early age, and no females are present.<sup class="reference" id="cite_ref-43">[44] Domestic guinea pigs have developed a different biological rhythm from their wild counterparts, and have longer periods of activity followed by short periods of sleep in between.<sup class="reference" id="cite_ref-terril_41-1">[42] Activity is scattered randomly over the 24 hours of the day; aside from avoidance of intense light, no regular circadian patterns are apparent.<sup class="reference" id="cite_ref-terril_41-2">[42] This cat has accepted this pair of guinea pigs. The success of this type of interspecies interaction varies according to the individual animals involvedDomestic guinea pigs generally live in cages, although some owners of large numbers of guinea pigs will dedicate entire rooms to their pets. Cages with solid or wire mesh floors are used, although wire mesh floors can cause injury and may be associated with an infection commonly known as bumblefoot (ulcerative pododermatitis).<sup class="reference" id="cite_ref-44">[45] "Cubes and Coroplast" (or C&C) style cages are now a common choice.<sup class="reference" id="cite_ref-ygph_45-0">[46] Cages are often lined with wood shavings or a similar material. Bedding made from red cedar (Eastern or Western) and pine, both softwoods, were commonly used in the past, however these materials are now believed to contain harmful phenols (aromatic hydrocarbons) and oils.<sup class="reference" id="cite_ref-terril2_46-0">[47] Safer beddings include those made from hardwoods (such as aspen), paper products, and corn cob materials are other alternatives.<sup class="reference" id="cite_ref-terril2_46-1">[47] Guinea pigs tend to be messy within their cages; they often jump into their food bowls or kick bedding and feces into them, and their urine sometimes crystallizes on cage surfaces, making it difficult to remove.<sup class="reference" id="cite_ref-47">[48] After its cage has been cleaned, a guinea pig will typically urinate and drag the lower body across the floor of the cage to mark its territory.<sup class="reference" id="cite_ref-nrc_48-0">[49] Male guinea pigs may also mark their territory in this way when they are taken out of their cages.

Guinea pigs do not generally thrive when housed with other species. Cohousing of guinea pigs with other rodents such as gerbils and hamsters may increase instances of respiratory and other infections,<sup class="reference" id="cite_ref-49">[50] and such rodents may act aggressively toward the guinea pig.<sup class="reference" id="cite_ref-50">[51] Larger animals may regard guinea pigs as prey, though some (such as dogs) can be trained to accept them.<sup class="reference" id="cite_ref-behrend_51-0">[52] Opinion is divided over the cohousing of guinea pigs and domestic rabbits. Some published sources say that guinea pigs and rabbits complement each other well when sharing a cage.<sup class="reference" id="cite_ref-behrend_51-1">[52] <sup class="reference" id="cite_ref-Vanderlip.2C_p._20_52-0">[53] However, as lagomorphs, rabbits have different nutritional requirements, and so the two species cannot be fed the same food.<sup class="reference" id="cite_ref-terril3_53-0">[54] Rabbits may also harbor diseases (such as the respiratory infections Bordetella and Pasteurella), to which guinea pigs are susceptible.<sup class="reference" id="cite_ref-54">[55] Even the dwarf rabbit is much stronger than the guinea pig and may cause intentional or inadvertent injury.<sup class="reference" id="cite_ref-gpc_55-0">[56]

Behavior
Guinea pigs can learn complex paths to food, and can accurately remember a learned path for months. Their strongest problem solving strategy is motion.<sup class="reference" id="cite_ref-56">[57] While guinea pigs can jump small obstacles, they are poor climbers, and are not particularly agile. They startle extremely easily, and will either freeze in place for long periods or run for cover with rapid, darting motions when they sense danger.<sup class="reference" id="cite_ref-terril_41-3">[42] Larger groups of startled guinea pigs will "stampede", running in haphazard directions as a means of confusing predators.<sup class="reference" id="cite_ref-57">[58] When excited, guinea pigs may repeatedly perform little hops in the air (known as "popcorning"), a movement analogous to the ferret's war dance.<sup class="reference" id="cite_ref-58">[59] They are also exceedingly good swimmers.<sup class="reference" id="cite_ref-harkness_59-0">[60] Guinea pigs "social groom"Like many rodents, guinea pigs sometimes participate in social grooming, and they regularly self-groom.<sup class="reference" id="cite_ref-60">[61] A milky-white substance is secreted from their eyes and rubbed into the hair during the grooming process.<sup class="reference" id="cite_ref-61">[62] Groups of boars will often chew each other's hair, but this is a method of establishing hierarchy within a group, rather than a social gesture.<sup class="reference" id="cite_ref-harkness_59-1">[60] Dominance is also established through biting (especially of the ears), piloerection, aggressive noises, head thrusts, and leaping attacks.<sup class="reference" id="cite_ref-62">[63] Non-sexual simulated mounting for dominance is also common among same-sex groups.

Guinea pig sight is not as good as a human, but they have a wider range of vision (about 340°) and see in partial color (dichromacy). They have well-developed senses of hearing, smell, and touch.<sup class="reference" id="cite_ref-63">[64] Vocalization is the primary means of communication between members of the species.<sup class="reference" id="cite_ref-64">[65] Some sounds are:<sup class="reference" id="cite_ref-65">[66] <sup class="reference" id="cite_ref-jackie_66-0">[67]
 * Wheek – A loud noise, the name of which is onomatopoeic, also known as a whistle. An expression of general excitement, it may occur in response to the presence of its owner or to 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. listen (help·info)
 * Bubbling or purring – This sound is made when the guinea pig is enjoying itself, such as when being petted or held. They may also make this sound when grooming, crawling around to investigate a new place, or when given food. listen (help·info)
 * Rumbling – This sound is normally related to dominance within a group, though it can also come as a response being scared or angry. In these cases the rumble often sounds higher and the body vibrates shortly. While courting, a male usually purrs deeply, swaying and circling the female<sup class="reference" id="cite_ref-67">[68] in a behavior called "rumblestrutting". A low rumble while walking away reluctantly shows passive resistance. listen (help·info)
 * Chutting and whining – These are sounds made in pursuit situations, by the pursuer and pursuee, respectively. listen (help·info)
 * Chattering – This sound is made by rapidly gnashing the teeth, and is generally a sign of warning. Guinea pigs tend to raise their heads when making this sound.
 * Squealing or shrieking – A high-pitched sound of discontent, in response to pain or danger. listen (help·info)
 * Chirping – This less-common sound, likened to bird song, seems to be related to stress, or when a baby guinea pig wants to be fed. Very rarely, the chirping will last for several minutes. listen (help·info)

Breeding
Main article: List of guinea pig breedsPregnant sow one week before delivering three pupsThe guinea pig is able to breed year-round, with birth peaks usually coming in the spring; as many as five litters can be produced per year.<sup class="reference" id="cite_ref-walker_11-2">[12] The gestation period lasts from 59–72 days, with an average of 63–68 days.<sup class="reference" id="cite_ref-nrc_48-1">[49] Because of the long gestation period and the large size of the pups, pregnant females may become large and eggplant-shaped, although the change in size and shape varies. Unlike the offspring of most other rodents, which are altricial at birth, newborn pups are well-developed with hair, teeth, claws, and partial eyesight;<sup class="reference" id="cite_ref-harkness_59-2">[60] they are immediately mobile, and begin eating solid food immediately, though they continue to suckle. Litters yield 1–6 pups, with an average of three;<sup class="reference" id="cite_ref-richardson_34-1">[35] the largest recorded litter size is 17.<sup class="reference" id="cite_ref-68">[69]

In smaller litters, difficulties may occur during labour due to over-sized 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.<sup class="reference" id="cite_ref-69">[70] Cohabitating females assist in mothering duties if lactating.<sup class="reference" id="cite_ref-percy_70-0">[71]

Male and female guinea pigs do not differ in external appearance apart from general size. The position of the anus is very close to the genitals in both sexes. Female genitals are distinguished by a Y-shaped configuration formed from a vulvar flap; while the male genitals may look similar with the penis and anus forming a like shape, the penis will protrude if pressure is applied to the surrounding hair.<sup class="reference" id="cite_ref-71">[72] The male's testes may also be visible externally from scrotal swelling. Guinea pig pup at eight hours oldMales reach sexual maturity at 3–5 weeks; females can be fertile as early as four weeks and can carry litters before they are adults.<sup class="reference" id="cite_ref-72">[73] Females that have never given birth commonly develop irreversible fusing of the pubic symphysis, a joint in the pelvis, after six months of age.<sup class="reference" id="cite_ref-nrc_48-2">[49] <sup class="reference" style="white-space:nowrap;">:73 If they become pregnant after this has happened, the birth canal will not widen sufficiently; this may lead to dystocia and death as they attempt to give birth.<sup class="reference" id="cite_ref-73">[74] Females can become pregnant 6–48 hours after giving birth, but it is not healthy for a female to be thus constantly pregnant.<sup class="reference" id="cite_ref-74">[75]

Toxemia of pregnancy is common and kills many pregnant females. Signs of toxemia include anorexia, lack of energy, excessive salivation, a sweet or fruity breath odor due to ketones, and seizures in advanced cases.<sup class="reference" id="cite_ref-75">[76] Pregnancy toxemia appears to be most common in hot climates.<sup class="reference" id="cite_ref-76">[77] Other serious complications of pregnancy can include a prolapsed uterus,

Diet
A silver agouti guinea pig eating grassGrass is the guinea pig's natural diet. Their molars are particularly suited for grinding plant matter, and grow continuously throughout the animal's life.<sup class="reference" id="cite_ref-78">[79] Most grass-eating mammals are quite large and have a long digestive tract; while guinea pigs have much longer colons than most rodents, they must also supplement their diet by coprophagy, the eating of their own feces.<sup class="reference" id="cite_ref-79">[80] However, they do not consume all their feces indiscriminately, but produce special soft pellets, called cecotropes, which recycle B vitamins, fiber, and bacteria required for proper digestion.<sup class="reference" id="cite_ref-80">[81] The cecotropes (or caecal pellets) are eaten directly from the anus, unless the guinea pig is pregnant or obese.<sup class="reference" id="cite_ref-terril3_53-1">[54] They share this behaviour with rabbits. In geriatric boars or sows (the condition is rarer in young ones), the muscles which allow the softer pellets to be expelled from the anus for consumption can become weak. This creates a condition known as anal impaction, which prevents the boar from redigesting cecotropes, though harder pellets may pass through the impacted mass.<sup class="reference" id="cite_ref-81">[82] The condition may be temporarily alleviated by carefully expelling the impacted feces.

Guinea pigs benefit from feeding on fresh grass hay, such as timothy hay, in addition to food pellets which are often based from timothy. Alfalfa is also a popular food choice; most guinea pigs will eat large amounts of alfalfa when offered it,<sup class="reference" id="cite_ref-82">[83] though there exists some controversy over the feeding of alfalfa to adult guinea pigs. Some pet owners and veterinary organizations have advised that, as a legume rather than a grass hay, alfalfa consumed in large amounts may lead to obesity, as well as bladder stones due to excess calcium, in any but pregnant and very young guinea pigs.<sup class="reference" id="cite_ref-83">[84] <sup class="reference" id="cite_ref-84">[85] However, published scientific sources mention alfalfa as a source for replenishment of protein, amino acids, and fiber.<sup class="reference" id="cite_ref-85">[86] <sup class="reference" id="cite_ref-86">[87]

Like humans, but unlike most other mammals, guinea pigs cannot synthesize their own vitamin C and must obtain this vital nutrient from food. If guinea pigs do not ingest enough vitamin C, they can suffer from potentially fatal scurvy. Guinea pigs require about 10 mg of vitamin C daily (20 mg if pregnant), which can be obtained through fresh, raw fruits and vegetables (such as broccoli, apple, cabbage, carrot, celery, and spinach) or through dietary supplements.<sup class="reference" id="cite_ref-87">[88] Healthy diets for guinea pigs require a complex balance of calcium, magnesium, phosphorus, potassium, and hydrogen ions; adequate amounts of vitamins E, A, and D are also necessary.<sup class="reference" id="cite_ref-88">[89] Imbalanced diets have been associated with muscular dystrophy, metastatic calcification, difficulties with pregnancy, vitamin deficiencies, and teeth problems.<sup class="reference" id="cite_ref-89">[90] Guinea pigs tend to be fickle eaters when it comes to fresh fruits and vegetables, having learned early in life what is and is not appropriate to consume, and their habits are difficult to change after maturity.<sup class="reference" id="cite_ref-90">[91] They do not respond well to sudden changes in diet; they may stop eating and starve rather than accepting new food types.<sup class="reference" id="cite_ref-harkness_59-3">[60] A constant supply of hay or other food is generally recommended, as guinea pigs feed continuously and may develop habits such as chewing on their own hair if food is not present.<sup class="reference" id="cite_ref-91">[92] Because guinea pigs' teeth grow constantly, they routinely gnaw, lest their teeth become too large for their mouth, a common problem in rodents.<sup class="reference" id="cite_ref-ygph_45-1">[46] Guinea pigs will also chew on cloth, paper, plastic, and rubber.

A number of plants are poisonous to guinea pigs, including bracken, bryony, buttercup, charlock, deadly nightshade, foxglove, hellebore, hemlock, Lily of the Valley, mayweed<sup class="plainlinks noprint Inline-Template" style="vertical-align:text-top;white-space:nowrap;">[disambiguation needed], monkshood, privet, ragwort, rhubarb, speedwell, toadflax<sup class="plainlinks noprint Inline-Template" style="vertical-align:text-top;white-space:nowrap;">[disambiguation needed] , and wild celery.<sup class="reference" id="cite_ref-richardson3_92-0">[93] Additionally, any plant which grows from a bulb (e.g., tulip and onion) is normally considered poisonous.<sup class="reference" id="cite_ref-richardson3_92-1">[93] also Ivy and oak tree leaves.

Health
A parti-colored guinea pig suffering from torticollis, or wry neckCommon ailments in domestic guinea pigs include respiratory tract infections, diarrhea, scurvy (vitamin C deficiency, typically characterized by sluggishness), abscesses due to infection (often in the neck, due to hay embedded in the throat, or from external scratches), and infections by lice, mites, or fungus.<sup class="reference" id="cite_ref-93">[94]

Mange mites (Trixacarus caviae) are a common cause of hair loss, and other symptoms may also include excessive scratching, unusually aggressive behavior when touched (due to pain), and, in some instances, seizures.<sup class="reference" id="cite_ref-94">[95] Guinea pigs may also suffer from "running lice" (Gliricola porcelli), a small white insect which can be seen moving through the hair; the eggs of these lice, which appear as black or white specks attached to the hair, are sometimes referred to as "static lice". Other causes of hair loss can be due to hormonal upsets caused by underlying medical conditions such as ovarian cysts.<sup class="reference" id="cite_ref-95">[96]

Foreign bodies, especially small pieces of hay or straw, can become lodged in the eyes of guinea pigs, resulting in excessive blinking, tearing, and in some cases an opaque film over the eye due to corneal ulcer.<sup class="reference" id="cite_ref-96">[97] Hay or straw dust can also cause sneezing. While it is normal for guinea pigs to sneeze periodically, frequent sneezing may be a symptom of pneumonia, especially in response to atmospheric changes. Pneumonia may also be accompanied by torticollis and can be fatal.<sup class="reference" id="cite_ref-97">[98]

Because the guinea pig has a stout, compact body, the animal more easily tolerates excessive cold than excessive heat.<sup class="reference" id="cite_ref-wagner3_98-0">[99] Its normal body temperature is 101–104 °F (38–40 °C),<sup class="reference" id="cite_ref-99">[100] and so its ideal ambient air temperature range is similar to the human's, about 65–75 °F (18–24 °C).<sup class="reference" id="cite_ref-wagner3_98-1">[99] Consistent ambient temperatures in excess of 90 °F (32 °C) have been linked to hyperthermia and death, especially among pregnant sows.<sup class="reference" id="cite_ref-wagner3_98-2">[99] Guinea pigs are not well suited to environments that feature wind or frequent drafts,<sup class="reference" id="cite_ref-100">[101] and respond poorly to extremes of humidity outside of the range of 30–70%.<sup class="reference" id="cite_ref-101">[102]

Guinea pigs are prey animals whose survival instinct is to mask pain and signs of illness, and many times health problems may not be apparent until a condition is severe or in its advanced stages. Treatment of disease is made more difficult by the extreme sensitivity guinea pigs have to most antibiotics, including penicillin, which kill off the intestinal flora and quickly bring on episodes of diarrhea and in some cases, death.<sup class="reference" id="cite_ref-102">[103]

Similar to the inherited genetic diseases of other breeds of animal (such as hip dysplasia in canines), a number of genetic abnormalities of guinea pigs have been reported. Most commonly, the roan coloration of Abyssinian guinea pigs is associated with congenital eye disorders and problems with the digestive system.<sup class="reference" id="cite_ref-103">[104] Other genetic disorders include "waltzing disease" (deafness coupled with a tendency to run in circles), palsy, and tremor conditions.<sup class="reference" id="cite_ref-robinson_104-0">[105]

Pets
Main article: List of guinea pig breedsA guinea pig being heldIf handled correctly early in their life, guinea pigs become amenable to being picked up and carried, and seldom bite or scratch.<sup class="reference" id="cite_ref-harkness_59-4">[60] They are timid explorers and often hesitate to attempt an escape from their cage even when an opportunity presents itself.<sup class="reference" id="cite_ref-Vanderlip.2C_p._20_52-1">[53] Still, they show considerable curiosity when allowed to walk freely, especially in familiar and safe terrain. Guinea pigs that become familiar with their owner will whistle on the owner's approach; they will also learn to whistle in response to the rustling of plastic bags or the opening of refrigerator doors, where their food is most commonly stored.

Guinea pigs should be kept in pairs or, preferably groups, unless there is a specific medical condition that requires isolation. Lone guinea pigs are more likely to suffer from stress and depression.<sup class="reference" id="cite_ref-105">[106] Domesticated guinea pigs come in many breeds, which have been developed since their introduction to Europe and North America. These varieties vary in hair and color composition. The most common varieties found in pet stores are the English shorthair (also known as the American), which have a short, smooth coat, and the Abyssinian, whose coat is ruffled with cowlicks, or rosettes. Also popular among breeders are the Peruvian and the Sheltie (or Silkie), both straight longhair breeds, and the Texel, a curly longhair.

Cavy Clubs and Associations dedicated to the showing and breeding of guinea pigs have been established worldwide. The American Cavy Breeders Association, an adjunct to the American Rabbit Breeders' Association, is the governing body in the United States and Canada.<sup class="reference" id="cite_ref-106">[107] The British Cavy Council governs cavy clubs in the United Kingdom. Similar organizations exist in Australia (Australian National Cavy Council)<sup class="reference" id="cite_ref-107">[108] and New Zealand (New Zealand Cavy Club).<sup class="reference" id="cite_ref-108">[109] Each club publishes its own Standard of Perfection and determines which breeds are eligible for showing.