Which small mammal, often kept as a pet, is also known as a 'cavy'?

The guinea pig or domestic guinea pig (Cavia porcellus), also known as cavy or domestic 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 Suidae, nor do they come from Guinea in Africa; they originated in the Andes of South America and studies based on biochemistry and hybridization suggest they are domestic, descendants of a closely related species of cavy such as C. tschudii, and therefore do not exist naturally in the wild.

If handled correctly early in life, guinea pigs become amenable to being picked up and carried, and seldom bite or scratch. They are timid explorers and often hesitate to attempt an escape from their cage even when an opportunity presents itself. 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.