Domestic guinea pigs (Cavia porcellus) belong to the order Rodentia and family Caviidae, a lineage that diverged from other rodents about 10 million years ago. They are the result of centuries‑long selective breeding from the wild South American cavy, Cavia aperea, which inhabits the Andean foothills, grasslands, and scrub of Brazil, Argentina, and Bolivia. Today C. porcellus is found worldwide as a companion animal, thriving in human homes rather than natural ecosystems. Morphologically, the species is characterized by a compact, stocky body, a short hairless tail less than 2 cm, and continuously growing incisors. Coat colors range from solid white and black to agouti, roan, and speckled patterns, reflecting artificial selection for aesthetic traits. Although fully domesticated, the species retains a herbivorous digestive system adapted to high‑fiber diets and a strong need for vitamin C, which it cannot synthesize. The domestic form is not evaluated by the IUCN, but its wild ancestors are listed as Least Concern. Conservation concerns focus on preserving genetic diversity among heritage breeds and protecting the natural habitats of their wild relatives, which face pressure from agriculture and climate change.

Guinea pigs are highly social mammals that live in stable groups called colonies, typically comprising a dominant male, several females, and their offspring. Within a colony, individuals establish a loose hierarchy through gentle chases, nose‑to‑nose contacts, and scent marking from cheek glands. They are primarily crepuscular, showing peaks of activity at dawn and dusk, but remain alert throughout the day, constantly scanning for predators. Communication relies on a rich vocal repertoire: high‑pitched “wheeks” signal excitement or a desire for food, low “rumblings” convey contentment, and sharp “purrs” indicate mild alarm. Grooming sessions reinforce social bonds, while individuals defend a modest home range of 1–2 m², often overlapping with neighbors. In captivity, providing companions and enrichment mimics their natural social structure and reduces stress‑related behaviors such as excessive bar‑biting or self‑gnawing.

Guinea pigs are strict herbivores with a hindgut fermentation system that extracts nutrients from high‑fiber plant material. Their diet must consist of unlimited access to fresh timothy or orchard grass hay, which supplies the roughage needed for dental wear and gastrointestinal motility. Daily rations include 1–2 cups (≈30–60 g) of a fortified pellet mix containing vitamin C, as they lack the enzyme L‑gulonolactone oxidase required for endogenous synthesis. Fresh vegetables such as bell peppers, kale, and carrots provide additional vitamins, while fruit should be limited to ≤10 % of intake due to sugar content. Water is offered in a sipper bottle and must be changed daily to prevent bacterial growth. In the wild, related cavy species browse on grasses, herbs, and succulent shoots; domestic guinea pigs retain this preference, thriving on a diet of 80 % hay, 15 % pellets, and 5 % fresh produce. Over‑reliance on pellets or lack of vitamin C leads to scurvy, a common health issue in captive populations.

Domestic guinea pigs reach sexual maturity at 4–6 weeks for females and 8–10 weeks for males, though optimal breeding is recommended after 3 months of age to ensure full growth. They are induced ovulators, capable of breeding year‑round under stable temperature and photoperiod conditions. Gestation lasts 59–72 days, averaging 63 days, after which a litter of 1–6 pups (most commonly 2–4) is born altricial but with fur and open eyes. Neonates weigh 70–120 g and are fully furred, allowing immediate thermoregulation. The mother nurses continuously for the first 10 days, providing milk rich in vitamin C, then gradually introduces solid hay and greens. Weaning occurs at 3–4 weeks, and juveniles become independent by 6 weeks. Both parents contribute to nest building, but only the female provides direct care. In well‑managed colonies, inter‑litter intervals can be as short as 30 days, leading to rapid population growth if not controlled.

The domestic guinea pig (Cavia porcellus) is not assessed by the IUCN Red List because it exists solely under human care, and its global population is estimated in the tens of millions as pets and laboratory animals. However, its wild ancestors, particularly Cavia aperea, are classified as Least Concern but face localized threats. Habitat conversion to agriculture and pasture reduces native grassland areas by an estimated 15 % per decade in the Pampas region. Predation by feral dogs, foxes, and raptors further pressures wild populations. In addition, illegal capture for the exotic‑pet trade, though limited, removes individuals from genetic reservoirs. Conservation actions focus on preserving high‑altitude grasslands, establishing protected corridors, and maintaining genetic diversity through breed registries for domestic lines. Community education programs in South America aim to reduce unsustainable trapping, while laboratory guidelines promote the use of alternative models to lessen demand for guinea pig research subjects. Overall, while the domestic form remains abundant, the health of its wild relatives depends on habitat stewardship and responsible breeding practices.

• Guinea pigs cannot synthesize vitamin C and must obtain it from their diet, making scurvy a common risk if fed an improper diet.
• Their teeth grow continuously throughout life; chewing hay and gnawing toys are essential to prevent overgrowth.
• The species was first domesticated by the Inca civilization over 5,000 years ago for food and ritual purposes.
• A single guinea pig can emit over 20 distinct vocalizations, each associated with specific emotions or needs.
• Unlike many rodents, guinea pigs have a relatively long gestation (≈63 days) and give birth to well‑developed, furred pups.