It's the largest living rodent (about 70 to 100 pounds) native to Central and South America and the most commonly known animal they are related to and generally associated with is a guinea pig (cavy). www.encyclopedia.com
A capybara is the world's largest species of rodent. It looks like a very large guinea pig and can approach the size of a small pig. It always lives near water in areas of grassland, swamps or forests as it is a semi-aquatic animal. It has developed webbing between the toes of its feet to give it better propulsion in water and can swim very well.
The capybara can stay underwater for several minutes, diving for food. However, it is looking for the most tender shoots of aquatic plants, rather than for fish, as it is totally vegetarian.
The capybara is one of the mammals that lives in the Jau National Park in Brazil, where the flats of the Tiete River provide the perfect habitat for its lifestyle. Like the monkeys, tapirs, and peccaries that also live there, the capybara has to beware of the threatened jaguar that is protected in the park – these small mammals are the big cats main source of food.