Guinea pig

Appearance

Guinea pigs are large for rodents, weighing between 700 and 1200 g, and measuring between 20 and 25 cm in length. They typically live an average of four to five years, but may live as long as eight years.

Naming

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. ''Cabiai'' may be an adaptation of the Portuguese ''çavia'', which is itself derived from the Tupi word ''saujá'', meaning rat.

Guinea pigs are called ''quwi'' or ''jaca'' in Quechua and ''cuy'' or ''cuyo'' in the Spanish of Ecuador, Peru, and Bolivia. 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".

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. They can survive for long periods in small quarters, like a 'pig pen', and were thus easily transported on ships to Europe.

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. 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.

Larger groups of startled guinea pigs will "stampede", running in haphazard directions as a means of confusing predators. When excited, guinea pigs may repeatedly perform little hops in the air , a movement analogous to the ferret's war dance. They are also exceedingly good swimmers.

Like many rodents, guinea pigs sometimes participate in social grooming, and they regularly self-groom. A milky-white substance is secreted from their eyes and rubbed into the hair during the grooming process. 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. Dominance is also established through biting , piloerection, aggressive noises, head thrusts, and leaping attacks. 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 and see in partial color. They have well-developed senses of hearing, smell, and touch. Vocalization is the primary means of communication between members of the species.

Reproduction

The 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.

The gestation period lasts from 59–72 days, with an average of 63–68 days. 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; 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; the largest recorded litter size is 17.

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. Cohabitating females assist in mothering duties if lactating.

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. The male's testes may also be visible externally from scrotal swelling.

Males reach sexual maturity at 3 - 5 weeks; females can be fertile as early as four weeks and can carry litters before they are adults.

Females that have never given birth commonly develop irreversible fusing of the pubic symphysis, a joint in the pelvis, after six months of age. 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. Females can become pregnant 6-48 hours after giving birth, but it is not healthy for a female to be thus constantly pregnant.

Food

Grass is the guinea pig's natural diet. Their molars are particularly suited for grinding plant matter, and grow continuously throughout the animal's life.

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. 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.

Uses

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. Since the 1960s, efforts have been made to increase consumption of the animal outside South America.

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.