The Uakari is a species of monkey that inhabits the tropical forests of South America. Soon after the ancestors reached the area it became isolated by a sea barrier, and the monkeys developed along slightly different lines from their Old World relatives. All very agile forest dwellings and many, but not the uakari , are helped in climbing by the prehensile tail, which can be used as an extra hand. Some carry obvious tufts of hair. Others have bald and often brightly coloured skin on their hands.