Caplin Rous the Capybara

INSIDE EDITION has found the world's largest pet rodent. His name is Caplin Rous and he's a capybara living outside Austin, Texas, with owner Melanie Typaldos.

Caplin is a very smart animal. Typaldos has trained him walk on hind legs and he can even open doors by himself.

The capybara is a species of giant rodents usually found in South America. They're extremely rare as pets, only 30 or so are sold in the U.S. each year.

Genetically speaking, Caplin is more closely related to the guinea pig than a rat.

"Normally when people see him they have no idea what he is...but they just think he's really cute," says Typaldos.

Caplin weighed just three pounds when Typaldos first got him at the age of 11 days old. Two and a half years later he now tips the scales at more than 100 pounds!

The gentle giant has the run of the house, and Typaldos loves him. He's nothing like the scary giant rodents seen in the film The Princess Bride.

Caplin enjoys taking long walks with his family

Capybaras are semi-aquatic animals and Caplin enjoys swimming in his backyard pool more than anything.

Instead of purring like a house cat, Caplin makes tiny squeaks when he is happy.