The guinea pig is the domesticated variety of the wild or Peruvian cavy, a rodent that lives in the mountain regions of Chile and Peru. Domesticated by the Peruvian Indians, the wild cavy has been used for food and religious purposes.

Guinea pigs have short legs and cylindrical bodies. Their short, thick necks support large heads. Adult guinea pigs weigh approximately two pounds and are about 10 to 12 inches long. Their tiny tails curl under their bodies, giving the impression that they have no tails at all. Guinea pigs' teeth grow continuously throughout their lives.

The gestation period for guinea pigs is nine weeks. A litter size ranges from two to three pups. Guinea pigs are a precocial species, which means that pups are born fully furred and with their eyes open. They can eat solid food at two to three days of age. The life span for guinea pigs is about five years.

Guinea pigs are herbivores. They eat a variety of dry cereals such as crushed oats, barley, and maize as well as hay, carrots, celery, broccoli, apples, and grapes. Guinea pigs communicate by making high-pitched squeaks or grinding their teeth to produce chattering sounds.