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Guinea Pigs and Cavies

Guinea pigs, or cavies, are about 20 species of rodents in the family Caviidae. Guinea pigs are native to South America, occurring from Colombia and Venezuela in the north, to Brazil and northern Argentina. These animals occur in rocky habitats, savannas, forest edges, and swamps, and can be rather common within their preferred habitat.

Guinea pigs have a stout body, with a relatively large head, short limbs and ears, and a vestigial tail that is not visible externally. The molars of guinea pigs grow continuously, an adaptation to the tooth wear associated with their vegetarian diet. Guinea pigs weigh 16-25 oz (450-700 g), and have a body length of 9-14 in (22-36 cm). They have four digits on their fore feet, and three on the hind, with naked soles, and small but sharp nails. Females have a single pair of teats, or mammae. The fur of wild guinea pigs is coarse, long, dense, and generally brown or grayish. However, the fur of domesticated varieties can be quite variable in color and form—the fur can be short or angora-long, dense or thick, straight or curly, and colored white, brown, gray, red, or black, occurring in monotones or in piebald patterns.

These nocturnal animals walk on four legs and are quick but not particularly fast runners. They live in burrows in small groups of several to ten individuals, and are rather vocal, emitting loud squeals, especially when warning the group of danger. Guinea pigs excavate their own dens, or they may take over diggings abandoned by other animals. They are vegetarian, eating a wide variety of plants. They tend to follow well-worn paths when they forage away from their burrows, and will quickly flee to the safety of their den at the first sign of potential danger.

Guinea pigs give birth to one to four babies after a gestation period of 60-70 days. Wild animals can breed as often as twice each year, but pet guinea pigs will breed more frequently than this. The young are mobile within hours of birth, and are sexually mature after about 55-70 days. Guinea pigs have a potential longevity of eight years, but they average less than this in the wild, largely because they are important food for a wide range of predator species, including humans.

The wild cavy (Cavia aperea tschudii) of Chile is believed to be the ancestor of the domestic guinea pig (Cavia aperea porcellus). The wild cavy is a montane and tundra species, living in habitats as high as 13,100 ft (4,000 m). Other relatively common species include the Amazonian wild cavy (C. fulgida), the southern mountain cavy (Microcavia australis), and the rock cavy (Kerodon rupestris). The most widespread species is the aperea (Cavia aperea).

The guinea pig was domesticated by Peruvian Incas in prehistoric times, and cultivated as a source of meat. They are still widely eaten in the highlands of Andean South America. The common name of the domestic guinea pig is likely derived from their piggish squeals, their plump and round body form, and the likelihood that the first animals to arrive in Europe in the late sixteenth century were transported by an indirect route from the coast of West Africa (where Guinea is located), probably in slave-trading ships.

Guinea pigs are widely used in medical and biological research, and are commonly kept as pets. They are gentle animals that are easily tamed, do not bite, and fare well in captivity as long as they are kept warm. Guinea pigs live easily in an open-topped box (because they do not climb), with newspaper or sawdust as bedding and to absorb their feces, a sleeping box, and a feeding bowl. If fed with a variety of grains and vegetables, guinea pigs do not need water to drink. Guinea pigs are social animals, and are happiest when kept with at least one other guinea pig. However, mature males will fight with each other, and are best maintained in separate cages.

Bill Freedman

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Science EncyclopediaScience & Philosophy: Glucagon to Habitat