Cavy, << KAY vee, >> is a group of South American rodents. Guinea pigs are the best-known cavies. Other cavies include maras, also called Patagonian hares, and mocos. Most cavies have thick bodies, short legs, and short, bristly hair. But maras have long, thin legs. A few kinds of domesticated (tamed) guinea pigs have long hair. All cavies eat plants. Wild cavies live on grassy plains in small groups. They are most active at dawn and dusk. 
